[Federal Register Volume 79, Number 82 (Tuesday, April 29, 2014)]
[Rules and Regulations]
[Pages 24255-24310]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2014-09488]



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Vol. 79

Tuesday,

No. 82

April 29, 2014

Part IV





Department of the Interior





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Fish and Wildlife Service





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50 CFR Part 17





Endangered and Threatened Wildlife and Plants; Endangered Species 
Status for Sierra Nevada Yellow-Legged Frog and Northern Distinct 
Population Segment of the Mountain Yellow-Legged Frog, and Threatened 
Species Status for Yosemite Toad; Final Rule

Federal Register / Vol. 79 , No. 82 / Tuesday, April 29, 2014 / Rules 
and Regulations

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R8-ES-2012-0100; 4500030113]
RIN 1018-AZ21


Endangered and Threatened Wildlife and Plants; Endangered Species 
Status for Sierra Nevada Yellow-Legged Frog and Northern Distinct 
Population Segment of the Mountain Yellow-Legged Frog, and Threatened 
Species Status for Yosemite Toad

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Final rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), determine 
endangered species status under the Endangered Species Act of 1973 
(Act), as amended, for the Sierra Nevada yellow-legged frog and the 
northern distinct population segment (DPS) of the mountain yellow-
legged frog (mountain yellow-legged frog populations that occur north 
of the Tehachapi Mountains), and determine threatened species status 
under the Act for the Yosemite toad. The effect of this regulation will 
be to add these species to the List of Endangered and Threatened 
Wildlife.

DATES: This rule becomes effective June 30, 2014.

ADDRESSES: This final rule is available on the Internet at http://www.regulations.gov and at the Sacramento Fish and Wildlife Office. 
Comments and materials we received, as well as supporting documentation 
used in preparing this rule, are available for public inspection at 
http://www.regulations.gov. All of the comments, materials, and 
documentation that we considered in this rulemaking are available by 
appointment, during normal business hours at: U.S. Fish and Wildlife 
Service, Sacramento Fish and Wildlife Office, 2800 Cottage Way, Room W-
2605, Sacramento, CA 95825; 916-414-6600 (telephone); 916-414-6712 
(facsimile).

FOR FURTHER INFORMATION CONTACT: Jennifer Norris, Field Supervisor, 
U.S. Fish and Wildlife Service, Sacramento Fish and Wildlife Office, 
2800 Cottage Way, Room W-2605, Sacramento, CA 95825; 916-414-6600 
(telephone); 916-414-6712 (facsimile). Persons who use a 
telecommunications device for the deaf (TDD) may call the Federal 
Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION: 

Executive Summary

    Why we need to publish a rule. Under the Endangered Species Act, a 
species may warrant protection through listing if it is endangered or 
threatened throughout all or a significant portion of its range. 
Listing a species as an endangered or threatened species can be only 
completed by issuing a rule.
    This rule will finalize the listing of the Sierra Nevada yellow-
legged frog (Rana sierrae) as an endangered species, the northern DPS 
of the mountain yellow-legged frog (Rana muscosa) as an endangered 
species, and the Yosemite toad (Anaxyrus canorus) as a threatened 
species.
    The basis for our action. Under the Endangered Species Act, we can 
determine that a species is an endangered or threatened species based 
on any of five factors: (A) The present or threatened destruction, 
modification, or curtailment of its habitat or range; (B) 
Overutilization for commercial, recreational, scientific, or 
educational purposes; (C) Disease or predation; (D) The inadequacy of 
existing regulatory mechanisms; or (E) Other natural or manmade factors 
affecting its continued existence.
    We have determined that both the Sierra Nevada yellow-legged frog 
and the northern DPS of the mountain yellow-legged frog are presently 
in danger of extinction throughout their entire ranges, based on the 
immediacy, severity, and scope of the threats to their continued 
existence. These include habitat degradation and fragmentation, 
predation and disease, climate change, inadequate regulatory 
protections, and the interaction of these various stressors impacting 
small remnant populations. A rangewide reduction in abundance and 
geographic extent of surviving populations of frogs has occurred 
following decades of fish stocking, habitat fragmentation, and most 
recently a disease epidemic. Surviving populations are smaller and more 
isolated, and recruitment in diseased populations is much reduced 
relative to historic norms. This combination of population stressors 
makes persistence of these species precarious throughout the currently 
occupied range in the Sierra Nevada.
    We have also determined that the Yosemite toad is likely to become 
endangered throughout its range within the foreseeable future, based on 
the immediacy, severity, and scope of the threats to its continued 
existence. These include habitat loss associated with degradation of 
meadow hydrology following stream incision consequent to the cumulative 
effects of historical land management activities, notably livestock 
grazing, and also the anticipated hydrologic effects upon habitat from 
climate change. We also find that the Yosemite toad is likely to become 
endangered through the direct effects of climate change impacting small 
remnant populations, likely compounded with the cumulative effect of 
other threat factors (such as disease).
    Peer review and public comment. We sought comments from independent 
specialists to ensure that our designations are based on scientifically 
sound data, assumptions, and analyses. We invited these peer reviewers 
to comment on our listing proposal. We also considered all comments and 
information received during the comment period.

Previous Federal Actions

    Please refer to the proposed listing rule for the Sierra Nevada 
yellow-legged frog, the northern DPS of the mountain yellow-legged 
frog, and the Yosemite toad (78 FR 24472, April 25, 2013) for a 
detailed description of previous Federal actions concerning these 
species.
    We will also be finalizing critical habitat designations for the 
Sierra Nevada yellow-legged frog, the northern DPS of the mountain 
yellow-legged, and the Yosemite toad under the Act in the near future.

Summary of Biological Status and Threats for the Sierra Nevada Yellow-
Legged Frog and the Northern DPS of the Mountain Yellow-Legged Frog

Background

    Please refer to the proposed listing rule for the Sierra Nevada 
yellow-legged frog and the northern DPS of the mountain yellow-legged 
frog under the Act (16 U.S.C. 1531 et seq.) for additional species 
information. In the proposed rule, we described two separate species of 
yellow-legged frogs, Rana sierrae and Rana muscosa, that resulted from 
the recent taxonomic split (see Taxonomy section below) of the 
previously known Rana muscosa, which we referred to in our proposed 
rule as the mountain yellow-legged frog ``species complex.'' For 
clarity and in order to maintain consistency with our previous 
treatment of the southern DPS of the mountain yellow legged frog in 
southern California (67 FR 44382, July 2, 2002) as well as with our 
proposed rule, and for the purposes of this document, we retain the 
common name of mountain yellow-legged frog for Rana muscosa, as opposed 
to the new common name, southern mountain yellow-legged frog, as 
published by

[[Page 24257]]

Crother et al. (2008, p. 11). We also note that the California 
Department of Fish and Game (CDFG) was recently renamed the California 
Department of Fish and Wildlife (CDFW). We refer to the California 
Department of Fish and Wildlife in all cases when discussing the agency 
in the text. Where citations are from CDFG documents, we include CDFW 
in parentheses for clarification.

Taxonomy

    Please refer to the proposed listing rule for the Sierra Nevada 
yellow-legged frog and the northern DPS of the mountain yellow-legged 
frog under the Act (16 U.S.C. 1531 et seq.) for detailed species 
information on taxonomy (78 FR 24472, April 25, 2013).
    Vredenburg et al. (2007, p. 371) determined that Rana sierrae 
occurs in the Sierra Nevada north of the South Fork Kings River 
watershed, along the east slope of the Sierra Nevada south into Inyo 
County at the southern extent of its range, and in the Glass Mountains 
just south of Mono Lake; and that R. muscosa occurs in the southern 
portion of the Sierra Nevada within and south of the South Fork Kings 
River watershed to the west of the Sierra Nevada crest (along with 
those populations inhabiting southern California) (Vredenburg et al. 
2007, pp. 370-371). The Monarch Divide separates these species in the 
western Sierra Nevada, while they are separated by the Cirque Crest to 
the east (Knapp 2013, unpaginated).
    For purposes of this rule, we recognize the species differentiation 
as presented in Vredenburg et al. (2007, p. 371) and adopted by the 
official societies mentioned above (Crother et al. 2008, p. 11), and in 
this final rule we refer to Rana sierrae as the Sierra Nevada yellow-
legged frog, and we refer to the Sierra Nevada populations of R. 
muscosa as the northern DPS of the mountain yellow-legged frog. In 
California and Nevada, the Sierra Nevada yellow-legged frogs occupy the 
western Sierra Nevada north of the Monarch Divide (in Fresno County) 
and the eastern slope of the Sierra Nevada (east of the crest) from 
Inyo County through Mono County (including the Glass Mountains), to 
areas north of Lake Tahoe. The northern DPS of the mountain yellow-
legged frog occurs only in California in the western Sierra Nevada and 
extends from south of the Monarch Divide in Fresno County through 
portions of the Kern River drainage. Figure 1 shows the approximate 
species boundaries within their historical ranges as determined by 
Knapp (unpubl. data).
BILLING CODE 4310-55-P

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[GRAPHIC] [TIFF OMITTED] TR29AP14.001

BILLING CODE 4310-55-C
    Many studies cited in the rest of this document include articles 
and reports that were published prior to the official species 
reclassification, where the researchers may reference either one or 
both species. Where possible and appropriate, information will be 
referenced specifically (either as Sierra Nevada yellow-legged frog or 
the northern DPS of the mountain yellow-legged frog) to reflect the 
split of the species. Where information applies to both species, the 
two species will be referred to collectively as mountain yellow-legged 
frog or mountain yellow-legged frog species complex.

Species Description

    Please refer to the proposed listing rule for the Sierra Nevada 
yellow-legged frog and the northern DPS of the mountain yellow-legged 
frog under the Act (16 U.S.C. 1531 et seq.) for additional information 
about species descriptions (78 FR 24472, April 25, 2013). The body 
lengths (snout to vent) of the mountain yellow-legged frogs range from 
40 to 80 millimeters (mm) (1.5 to 3.25 inches (in)) (Jennings and Hayes 
1994, p. 74). Females average slightly larger than males, and males 
have a swollen, darkened thumb base (Wright and Wright 1949, pp. 424-
430; Stebbins 1951, pp. 330-335; Zweifel 1955, p. 235; Zweifel 1968, p. 
65.1). Dorsal (upper) coloration in adults is variable, exhibiting a 
mix of brown and yellow, but also can be grey, red, or green-brown, and 
is usually patterned with dark spots (Jennings and Hayes 1994, p. 74; 
Stebbins 2003, p. 233). These spots may be large (6 mm (0.25 in)) and 
few, smaller and more numerous, or a mixture of both (Zweifel 1955, p. 
230). Irregular lichen- or moss-like patches (to which the name muscosa 
refers) may also be present on the dorsal surface (Zweifel 1955, pp. 
230, 235; Stebbins 2003, p. 233).

[[Page 24259]]

    The belly and undersurfaces of the hind limbs are yellow or orange, 
and this pigmentation may extend forward from the abdomen to the 
forelimbs (Wright and Wright 1949, pp. 424-429; Stebbins 2003, p. 233). 
Mountain yellow-legged frogs may produce a distinctive mink or garlic-
like odor when disturbed (Wright and Wright 1949, p. 432; Stebbins 
2003, p. 233). Although these species lack vocal sacs, they can 
vocalize in or out of water, producing what has been described as a 
faint clicking sound (Zweifel 1955, p. 234; Ziesmer 1997, pp. 46-47; 
Stebbins 2003, p. 233). Mountain yellow-legged frogs have smoother 
skin, generally with heavier spotting and mottling dorsally, darker toe 
tips (Zweifel 1955, p. 234), and more opaque ventral coloration 
(Stebbins 2003, p. 233) than the foothill yellow-legged frog.
    The Sierra Nevada yellow-legged frog and the northern DPS of the 
mountain yellow-legged frog are similar morphologically and 
behaviorally (hence their shared taxonomic designation until recently). 
However, these two species can be distinguished from each other 
physically by the ratio of the lower leg (fibulotibia) length to snout 
vent length. The northern DPS of the mountain yellow-legged frog has 
longer limbs (Vredenburg et al. 2007, p. 368). Typically, this ratio is 
greater than or equal to 0.55 in the northern DPS of the mountain 
yellow-legged frog and less than 0.55 in the Sierra Nevada yellow-
legged frog.
    Mountain yellow-legged frogs deposit their eggs in globular clumps, 
which are often somewhat flattened and roughly 2.5 to 5 centimeters 
(cm) (1 to 2 in) in diameter (Stebbins 2003, p. 444). When eggs are 
close to hatching, egg mass volume averages 198 cubic cm (78 cubic in) 
(Pope 1999, p. 30). Eggs have three firm, jelly-like, transparent 
envelopes surrounding a grey-tan or black vitelline (egg yolk) capsule 
(Wright and Wright 1949, pp. 431-433). Clutch size varies from 15 to 
350 eggs per egg mass (Livezey and Wright 1945, p. 703; Vredenburg et 
al. 2005, p. 565). Egg development is temperature dependent. In 
laboratory breeding experiments, egg hatching time ranged from 18 to 21 
days at temperatures of 5 to 13.5 degrees Celsius ([deg]C) (41 to 56 
degrees Fahrenheit ([deg]F)) (Zweifel 1955, pp. 262-264). Field 
observations show similar results (Pope 1999, p. 31).
    The tadpoles of mountain yellow-legged frogs generally are mottled 
brown on the dorsal side with a faintly yellow venter (underside) 
(Zweifel 1955, p. 231; Stebbins 2003, p. 460). Total tadpole length 
reaches 72 mm (2.8 in), the body is flattened, and the tail musculature 
is wide (about 2.5 cm (1 in) or more) before tapering into a rounded 
tip (Wright and Wright 1949, p. 431). The mouth has a maximum of eight 
labial (lip) tooth rows (two to four upper and four lower) (Stebbins 
2003, p. 460). Tadpoles may take more than 1 year (Wright and Wright 
1949, p. 431), and often require 2 to 4 years, to reach metamorphosis 
(transformation from tadpoles to frogs) (Cory 1962b, p. 515; Bradford 
1983, pp. 1171, 1182; Bradford et al. 1993, p. 883; Knapp and Matthews 
2000, p. 435), depending on local climate conditions and site-specific 
variables.
    The time required to reach reproductive maturity in mountain 
yellow-legged frogs is thought to vary between 3 and 4 years post 
metamorphosis (Zweifel 1955, p. 254). This information, in combination 
with the extended amount of time as a tadpole before metamorphosis, 
means that it may take 5 to 8 years for mountain yellow-legged frogs to 
begin reproducing. While the typical lifespan of mountain yellow-legged 
frogs is largely unknown, Matthews and Miaud (2007, p. 991) estimated 
that the total lifespan (including tadpole and adult life stages) 
ranges up to 14 years, with other documented estimates of up to 16 
years of age for the Sierra Nevada yellow-legged frog (Fellers et al. 
2013, p. 155), suggesting that mountain yellow-legged frogs are long-
lived amphibians.

Habitat and Life History

    Mountain yellow-legged frogs currently exist in montane regions of 
the Sierra Nevada of California. Throughout their range, these species 
historically inhabited lakes, ponds, marshes, meadows, and streams at 
elevations typically ranging from 1,370 to 3,660 meters (m) (4,500 to 
12,000 feet (ft)) ((CDFG (CDFW)) 2011, pp. A-1-A-5), but can occur as 
low as 1,067 m (3,500 ft) in the northern portions of their range (USFS 
2011, geospatial data; USFS 2013, p. 4). Mountain yellow-legged frogs 
are highly aquatic; they are generally not found more than 1 m (3.3 ft) 
from water (Stebbins 1951, p. 340; Mullally and Cunningham 1956a, p. 
191; Bradford et al. 1993, p. 886). Mullally and Cunningham (1956a, p. 
191) found adults sitting on rocks along the shoreline, where there was 
little or no vegetation. Although mountain yellow-legged frogs may use 
a variety of shoreline habitats, both tadpoles and adults are observed 
less frequently at shorelines that drop abruptly to a depth of 60 cm (2 
ft) than at open shorelines that gently slope up to shallow waters of 
only 5 to 8 cm (2 to 3 in) in depth (Mullally and Cunningham 1956a, p. 
191; Jennings and Hayes 1994, p. 77).
    At lower elevations within their historical range, these species 
have been associated with rocky streambeds and wet meadows surrounded 
by coniferous forest (Zweifel 1955, p. 237; Zeiner et al. 1988, p. 88), 
although, in general, little is known about the ecology of mountain 
yellow-legged frogs in Sierra Nevada stream habitats (Brown 2013, 
unpaginated). Zweifel (1955, p. 237) found that streams utilized by 
adults varied from streams having high gradients and numerous pools, 
rapids, and small waterfalls, to streams with low gradients and slow 
flows, marshy edges, and sod banks, while aquatic substrates varied 
from bedrock to fine sand, rubble (rock fragments), and boulders. 
Jennings and Hayes (1994, p. 77) have indicated that mountain yellow-
legged frogs appear absent from the smallest creeks, and suggest that 
it is probably because these creeks have insufficient depth for 
adequate refuge and overwintering habitat. However, Brown (2013, 
unpaginated) reports that the frogs are found in small creeks, although 
she notes that the extent to which these are remnant populations now 
excluded from preferred habitat is not known. In the northern portion 
of the Sierra Nevada yellow-legged frog range, the remnant populations 
primarily occur in stream habitats.
    At higher elevations, these species occupy lakes, ponds, tarns 
(small steep-banked mountain lakes or pools, generally of glacial 
origin), and streams (Zweifel 1955, p. 237; Mullally and Cunningham 
1956a, p. 191). Mountain yellow-legged frogs in the Sierra Nevada are 
most abundant in high-elevation lakes and slow-moving portions of 
streams (Zweifel 1955, p. 237; Mullally and Cunningham 1956a, p. 191). 
The borders of alpine (above the tree line) lakes and mountain meadow 
streams used by mountain yellow-legged frogs are frequently grassy or 
muddy, although many are bordered by exposed glaciated bedrock. Zweifel 
(1955, pp. 237-238) suggested that alpine lakeshores differ from the 
sandy or rocky shores inhabited by mountain yellow-legged frogs in 
lower elevation streams.
    Adult mountain yellow-legged frogs breed in a variety of habitats 
including the shallows of stillwater habitat (lakes or ponds) and 
flowing inlet streams (Zweifel 1955, p. 243; Pope 1999, p. 30). Adults 
emerge from overwintering sites immediately following snowmelt, and 
will even move over ice to reach breeding sites (Pope 1999, pp. 46-47; 
Vredenburg et al. 2005, p. 565). Mountain yellow-legged frogs deposit

[[Page 24260]]

their eggs underwater in clusters, which they attach to rocks, gravel, 
or vegetation, or which they deposit under banks (Wright and Wright 
1949, p. 431; Stebbins 1951, p. 341; Zweifel 1955, p. 243; Pope 1999, 
p. 30).
    Lake depth is an important attribute defining habitat suitability 
for mountain yellow-legged frogs. At high elevations, both frogs and 
tadpoles overwinter under ice in lakes and streams. As tadpoles must 
overwinter multiple years before metamorphosis, successful breeding 
sites are located in (or connected to) lakes and ponds that do not dry 
out in the summer, and also are deep enough that they do not completely 
freeze or become oxygen-depleted (anoxic) in winter. Both adults and 
tadpole mountain yellow-legged frogs overwinter for up to 9 months in 
the bottoms of lakes that are at least 1.7 m (5.6 ft) deep; however, 
overwinter survival may be greater in lakes that are at least 2.5 m 
(8.2 ft) deep (Bradford 1983, p. 1179; Vredenburg et al. 2005, p. 565).
    Bradford (1983, pp. 1173, 1178-1179) found that, in years with 
exceptional precipitation (61 percent above average) and greater than 
normal ice-depths, mountain yellow-legged frog die-offs sometimes 
result from oxygen depletion during winter in lakes less than 4 m (13 
ft) in depth, finding that in ice-covered lakes, oxygen depletion 
occurs most rapidly in shallow lakes relative to deeper lakes. However, 
tadpoles may survive for months in nearly anoxic conditions when 
shallow lakes are frozen to the bottom. More recent work reported 
populations of mountain yellow-legged frogs overwintering in lakes less 
than 1.5 m (5 ft) deep that were assumed to have frozen to the bottom, 
and yet healthy frogs emerged the following July (Matthews and Pope 
1999, pp. 622-623; Pope 1999, pp. 42-43). Matthews and Pope 1999, p. 
619) used radio telemetry to find that, when lakes had begun to freeze 
over, the frogs were utilizing rock crevices, holes, and ledges near 
shore, where water depths ranged from 0.2 m (0.7 ft) to 1.5 m (5 ft). 
Vredenburg et al. (2005, p. 565) noted that such behavior may be a 
response to presence of introduced fish. Matthews and Pope (1999, p. 
622) suggested that the granite surrounding these overwintering 
habitats probably insulates mountain yellow-legged frogs from extreme 
winter temperatures, and that they can survive, provided there is an 
adequate supply of oxygen.
    Mountain yellow-legged frog tadpoles maintain a relatively high 
body temperature by selecting warmer microhabitats (Bradford 1984, p. 
973). During winter, tadpoles remain in warmer water below the 
thermocline (the transition layer between thermally stratified water). 
After spring overturn (thaw and thermal mixing of the water), they 
behaviorally modulate their body temperature by moving to shallow, 
near-shore water when warmer days raise surface water temperatures. 
During the late afternoon and evening, mountain yellow-legged frogs 
retreat to offshore waters that are less subject to night cooling 
(Bradford 1984, p. 974).
    Available evidence suggests that adult mountain yellow-legged frogs 
display strong site fidelity and return to the same overwintering and 
summer habitats from year to year (Pope 1999, p. 45; Matthews and 
Preisler 2010, p. 252). Matthews and Pope (1999, pp. 618-623) observed 
that the frogs' movement patterns and habitat associations shifted 
seasonally. Frogs were well-distributed in most lakes, ponds, and 
creeks during August, but moved to only a few lakes by October. 
Matthews and Pope (1999, pp. 618-623) established home-range areas for 
10 frogs and found that frogs remained through August in the lake or 
creek where they'd been captured, with movement confined to areas 
ranging from 19.4 to 1,028 square meters (m\2\) (23.20 to 1,229 square 
yards (y\2\)). In September, movements increased, with home-ranges 
varying from 53 to 9,807 m\2\ in size (63.4 to 11,729 y\2\); six of 
nine frogs tagged in September moved from that lake by the end of the 
month, suggesting a pattern in which adult mountain yellow-legged frogs 
move among overwintering, breeding, and feeding sites during the year, 
with narrow distributions in early spring and late fall due to 
restricted overwintering habitat (Pope and Matthews 2001, p. 791). 
Although terrestrial movements of more than two or three hops from 
water were previously undocumented, overland movements exceeding 66 m 
(217 ft) were observed in 17 percent of tagged frogs, demonstrating 
that mountain yellow-legged frogs move overland as well as along 
aquatic pathways (Pope and Matthews 2001, p. 791). Pope and Matthews 
(2001, p. 791) also recorded a movement distance of over 1 km 
(including a minimum of 420 m (0.26 miles) overland movement and 
movement through a stream course). The farthest reported distance of a 
mountain yellow-legged frog from water is 400 m (1,300 ft) (Vredenburg 
2002, p. 4).
    Within stream systems, Sierra Nevada yellow-legged frogs have been 
documented to move 1,032 m (3,385 ft) over a 29-day period (Fellers et 
al. 2013, p. 159). Wengert (2008, p. 18) conducted a telemetry study 
that documented single-season movement distances for Sierra Nevada 
yellow-legged frog of up to 3.3 kilometers (km) (2.05 miles (mi)) along 
streams. Along stream habitats, adults have been observed greater than 
22 m (71 ft) from the water during the overwintering period (Wengert 
2008, p. 20). Additionally, during the duration of the study, Wengert 
(2008, p. 13) found that 14 percent of the documented frog locations 
occurred greater than 0.2 m (0.66 ft) from the stream edge. While 
recent information suggests that the frogs in the Wengert study may 
have actually been foothill yellow-legged frog (Rana boylii) (Poorten 
et al., 2013, p. 4), we expect that the movement distances recorded are 
applicable to the Sierra Nevada yellow-legged frog within a stream-
based system, as the ecology is comparable between the two sister taxa 
in regard to stream systems.
    Almost no data exist on the dispersal of juvenile mountain yellow-
legged frogs away from breeding sites; however, juveniles that may be 
dispersing have been observed in small intermittent streams (Bradford 
1991, p. 176). Regionally, mountain yellow-legged frogs are thought to 
exhibit a metapopulation structure (Bradford et al. 1993, p. 886; Drost 
and Fellers 1996, p. 424). Metapopulations are spatially separated 
population subunits within migratory distance of one another such that 
individuals may interbreed among subunits and populations may become 
reestablished if they are extirpated (Hanski and Simberloff 1997, p. 
6).

Historical Range and Distribution

    Mountain yellow-legged frogs were historically abundant and 
ubiquitous across many of the higher elevations within the Sierra 
Nevada. Grinnell and Storer (1924, p. 664) reported the Sierra Nevada 
yellow-legged frog to be the most common amphibian surveyed in the 
Yosemite area. It is difficult to know the precise historical ranges of 
the Sierra Nevada yellow-legged frog and the northern DPS of the 
mountain yellow-legged frog, because projections must be inferred from 
museum collections that do not reflect systematic surveys, and survey 
information predating significant rangewide reduction is very limited. 
However, projections of historical ranges are available using 
predictive habitat modeling based on recent research (Knapp, unpubl. 
data).
    Historically, the range of the Sierra Nevada yellow-legged frog 
extended in California from north of the Feather River, in Butte and 
Plumas Counties, south to the Monarch Divide on the west side of the 
Sierra Nevada crest in Fresno County. East of the Sierra Nevada crest 
in California, the historical

[[Page 24261]]

range of the Sierra Nevada yellow-legged frog extends from areas north 
of Lake Tahoe, through Mono County (including the Glass Mountains) to 
Inyo County. Historical records indicate that the Sierra Nevada yellow-
legged frog also occurred at locations within the Carson Range of 
Nevada, including Mount Rose in Washoe County, and also occurred in the 
vicinity of Lake Tahoe in Douglas County, Nevada (Linsdale 1940, pp. 
208-210; Zweifel 1955, p. 231; Jennings 1984, p. 52; Knapp 2013, 
unpaginated).
    Historically, the northern DPS of the mountain yellow-legged frog 
ranged from the Monarch Divide in Fresno County as far southward as 
Breckenridge Mountain, in Kern County (Vredenburg et al. 2007, p. 371). 
The historical ranges of the two frog species within the mountain 
yellow-legged complex, therefore, meet each other roughly along the 
Monarch Divide to the north, and along the crest of the Sierra Nevada 
to the east. Because we have determined that the historic range of R. 
muscosa is entirely within the State of California, in this final rule 
we correct the listing for the southern DPS of the mountain yellow-
legged frog to remove Nevada from its historic range.

Current Range and Distribution

    Since the time of the mountain yellow-legged frog observations of 
Grinnell and Storer (1924, pp. 664-665), a number of researchers have 
reported disappearances of these species from a large fraction of their 
historical ranges in the Sierra Nevada (Hayes and Jennings 1986, p. 
490; Bradford 1989, p. 775; Bradford et al. 1994, pp. 323-327; Jennings 
and Hayes 1994, p. 78; Jennings 1995, p. 133; Stebbins and Cohen 1995, 
pp. 225-226; Drost and Fellers 1996, p. 414; Jennings 1996, pp. 934-
935; Knapp and Matthews 2000, p. 428; Vredenburg et al. 2005, p. 564).
    The current distributions of the Sierra Nevada yellow-legged frog 
and the northern DPS of the mountain yellow-legged frog are restricted 
primarily to publicly managed lands at high elevations, including 
streams, lakes, ponds, and meadow wetlands located within National 
Forests and National Parks. National Forests with extant (surviving) 
populations of mountain yellow-legged frogs include the Plumas National 
Forest, Tahoe National Forest, Humboldt-Toiyabe National Forest, Lake 
Tahoe Basin Management Unit, Eldorado National Forest, Stanislaus 
National Forest, Sierra National Forest, Sequoia National Forest, and 
Inyo National Forest. National Parks with extant populations of 
mountain yellow-legged frogs include Yosemite National Park, Kings 
Canyon National Park, and Sequoia National Park.
    The most pronounced declines within the mountain yellow-legged frog 
complex have occurred north of Lake Tahoe in the northernmost 125-km 
(78-mi) portion of the range (Sierra Nevada yellow-legged frog) and 
south of Kings Canyon National Park in Tulare County (the northern DPS 
of the mountain yellow-legged frog). In the southernmost 50-km (31-mi) 
portion of the range, only a few populations of the northern DPS of the 
mountain yellow-legged frog remain (Fellers 1994, p. 5; Jennings and 
Hayes 1994, pp. 74-78); except for a few small populations in the Kern 
River drainage, the northern DPS of the mountain yellow-legged frog is 
entirely extirpated from all of Sequoia National Park (Knapp 2013, 
unpaginated). As of 2000, mountain yellow-legged frog populations were 
known to have persisted in greater density in the National Parks of the 
Sierra Nevada as compared to the surrounding U.S. Forest Service (USFS) 
lands, and the populations that did occur in the National Parks 
generally exhibited higher abundances than those on USFS lands 
(Bradford et al. 1994, p. 323; Knapp and Matthews 2000, p. 430).

Population Estimates and Status

    Monitoring efforts and research studies have documented substantial 
declines of mountain yellow-legged frog populations in the Sierra 
Nevada. The number of extant populations has declined greatly over the 
last few decades. Remaining populations are patchily scattered 
throughout the historical range (Jennings and Hayes 1994, pp. 74-78; 
Jennings 1995, p. 133; Jennings 1996, p. 936). In the northernmost 
portion of the range (Butte and Plumas Counties), only a few Sierra 
Nevada yellow-legged frog populations have been documented since 1970 
(Jennings and Hayes 1994, pp. 74-78; CDFG (CDFW) et al., unpubl. data). 
Declines of both species have also been noted in the central and 
southern Sierra Nevada (Drost and Fellers 1996, p. 420; Knapp and 
Matthews 2001, pp. 433-437; Knapp 2013, unpaginated). In the southern 
Sierra Nevada (Sierra, Sequoia, and Inyo National Forests; and Kings 
Canyon and Yosemite National Parks), modest to relatively large 
populations (for example, breeding populations of approximately 40 to 
more than 200 adults) of mountain yellow-legged frogs do remain; 
however, in recent years some large populations have been extirpated in 
this area (Bradford 1991, p. 176; Bradford et al. 1994, pp. 325-326; 
Knapp 2002a, p. 10, Wake and Vredenburg 2009, pp. 11467-11470).
    Davidson et al. (2002, p. 1591) reviewed 255 previously documented 
mountain yellow-legged frog locations (based on Jennings and Hayes 
1994, pp. 74-78) throughout the historical range and concluded that 83 
percent of these sites no longer support frog populations. Vredenburg 
et al. (2007, pp. 369-371) compared recent survey records (1995-2004) 
with museum records from 1899-1994 and reported that 92.5 percent of 
historical Sierra Nevada yellow-legged frog populations and 92.3 
percent of populations of the northern DPS of mountain yellow-legged 
frog are now extirpated.
    CDFW (CDFG (CDFW) 2011, pp. 17-20) used historical localities from 
museum records covering the same time interval (1899-1994), but updated 
recent locality information with additional survey data (1995-2010) to 
significantly increase proportional coverage from the Vredenburg et al. 
(2007) study. These more recent surveys failed to detect any extant 
frog populations (within 1 km (0.63 mi), a metric used to capture 
interbreeding individuals within metapopulations) at 220 of 318 
historical Sierra Nevada yellow-legged frog localities and 94 of 109 
historical northern DPS of the mountain yellow-legged frog localities 
(in the Sierran portion of their range). This calculates to an 
estimated loss of 69 percent of Sierra Nevada yellow-legged frog 
metapopulations and 86 percent of northern DPS of the mountain yellow-
legged frog metapopulations from historical occurrences.
    In addition to comparisons based on individual localities, CDFW 
(CDFG 2011, pp. 20-25) compared historical and recent population status 
at the watershed scale. This is a rough index of the geographic extent 
of the species through their respective ranges. Within the Sierra 
Nevada, 44 percent of watersheds historically utilized by Sierra Nevada 
yellow-legged frogs, and 59 percent of watersheds historically utilized 
by northern DPS mountain yellow-legged frogs, no longer support extant 
populations. However, this watershed-level survey methodology is not a 
good indicator of population changes because a watershed is counted as 
recently occupied if a single individual (at any life stage) is 
observed within the entire watershed even though several individual 
populations may have been lost (CDFG (CDFW) 2011b, p. 20). Therefore, 
these surveys likely underestimate population declines. Many watersheds 
support only a single extant metapopulation, which occupies one to 
several adjacent water bodies

[[Page 24262]]

(CDFG (CDFW) 2011, p. 20). Remaining populations are generally very 
small.
    Rangewide, declines of mountain yellow-legged frog populations were 
estimated at around one-half of historical populations by the end of 
the 1980s (Bradford et al. 1994, p. 323). Between 1988 and 1991, 
Bradford et al. (1994a, pp. 323-327) resurveyed sites known 
historically (1955 through 1979 surveys) to support mountain yellow-
legged frogs. They did not detect frogs at 27 historical sites on the 
Kaweah River, and they detected frogs at 52 percent of historical sites 
within Sequoia and Kings Canyon National Parks and 12.5 percent of 
historical sites outside of Sequoia and Kings Canyon National Parks. 
Because this work was completed before the taxonomic division of 
mountain yellow-legged frogs, we have not differentiated between the 
two species here. When both species are combined, this resurvey effort 
detected mountain yellow-legged frogs at 19.4 percent of historical 
sites (Bradford et al. 1994, pp. 324-325).
    Available information discussed below indicates that the rates of 
population decline have not abated, and they have likely accelerated 
during the 1990s into the 2000s. Drost and Fellers (1996, p. 417) 
repeated Grinnell and Storer's early 20th century surveys in Yosemite 
National Park, and reported frog presence at 2 of 14 historical sites 
where what is now known as Sierra Nevada yellow-legged frogs occurred. 
The two positive sightings consisted of a single tadpole at one site 
and a single adult female at another. They identified 17 additional 
sites with suitable mountain yellow-legged frog habitat, and in those 
surveys, they detected 3 additional populations. In 2002, Knapp (2002a, 
p. 10) resurveyed 302 water bodies known to be occupied by mountain 
yellow-legged frogs between 1995 and 1997, and 744 sites where frogs 
were not previously detected. Knapp found frogs at 59 percent of the 
previously occupied sites, whereas 8 percent of previously unoccupied 
sites were colonized. These data suggest an extirpation rate five to 
six times higher than the colonization rate within this study area. The 
documented extirpations appeared to occur non-randomly across the 
landscape, were typically spatially clumped, and involved the 
disappearance of all or nearly all of the mountain yellow-legged frog 
populations in a watershed (Knapp 2002a, p. 9). CDFW (CDFG 2011, p. 20) 
assessed data from sites where multiple surveys were completed after 
1995 (at least 5 years apart). They found that the Sierra Nevada 
yellow-legged frog was not detected at 45 percent of sites where they 
previously had been confirmed, while the mountain yellow-legged frog 
(rangewide, including southern California) was no longer detectable at 
81 percent of historically occupied sites.
    The USFS has been conducting a rangewide, long-term monitoring 
program for the Sierra Nevada yellow-legged frog and the northern DPS 
of the mountain yellow-legged frog on National Forest lands in the 
Sierra Nevada, known as the Sierra Nevada Amphibian Monitoring Program 
(SNAMPH). This monitoring effort provides unbiased estimates by using 
an integrated unequal probability design, and it provides numbers for 
robust statistical comparisons across 5-year monitoring cycles spanning 
208 watersheds (Brown et al. 2011, pp. 3-4). The results of this 
assessment indicate that the species have declined in both distribution 
and abundance. Based on surveys conducted from 2002 through 2009, 
breeding activity was found in about half (48 percent) of the 
watersheds where the species were found in the decade prior to SNAMPH 
monitoring (1990 and 2001) (Brown et al. 2011, p. 4). Breeding was 
found in 3 percent of watersheds where species had been found prior to 
1990. Rangewide, breeding was found in 4 percent of watersheds. 
Moreover, relative abundances were low; an estimated 9 percent of 
populations were large (numbering more than 100 frogs or 500 tadpoles); 
about 90 percent of the watersheds had fewer than 10 adults, while 80 
percent had fewer than 10 subadults and 100 tadpoles (Brown et al. 
2011, p. 24).
    To summarize population trends over the available historical 
record, estimates range from losses between 69 to 93 percent of Sierra 
Nevada yellow-legged frog populations and 86 to 92 percent of the 
northern DPS of the mountain yellow-legged frog. Rangewide reduction 
has diminished the number of watersheds that support mountain yellow-
legged frogs somewhere between the conservative estimates of 44 percent 
in the case of Sierra Nevada yellow-legged frogs and at least 59 
percent in the case of the northern DPS of the mountain yellow-legged 
frogs, to as high as 97 percent of watersheds for the mountain yellow-
legged frog complex across the Sierra Nevada. Remaining populations are 
much smaller than historical norms, and the density of populations per 
watershed has declined substantially; as a result, many watersheds 
currently support single metapopulations at low abundances.

Distinct Vertebrate Population Segment Analysis

    Under the Act, we must consider for listing any species, 
subspecies, or, for vertebrates, any DPS of these taxa if there is 
sufficient information to indicate that such action may be warranted. 
To implement the measures prescribed by the Act, we, along with the 
National Marine Fisheries Service (National Oceanic and Atmospheric 
Administration-Fisheries), developed a joint policy that addresses the 
recognition of DPSs for potential listing actions (61 FR 4722). The 
policy allows for a more refined application of the Act that better 
reflects the biological needs of the taxon being considered and avoids 
the inclusion of entities that do not require the Act's protective 
measures.
    Under our DPS policy, three elements are considered in a decision 
regarding the status of a possible DPS as endangered or threatened 
under the Act. The elements are: (1) Discreteness of the population 
segment in relation to the remainder of the species to which it 
belongs; (2) the significance of the population segment to the species 
to which it belongs; and (3) the population segment's conservation 
status in relation to the Act's standards for listing. In other words, 
if we determine that a population segment of a vertebrate species being 
considered for listing is both discrete and significant, we would 
conclude that it represents a DPS, and thus a ``species'' under section 
3(16) of the Act, whereupon we would evaluate the level of threat to 
the DPS based on the five listing factors established under section 
4(a)(1) of the Act to determine whether listing the DPS as an 
``endangered species'' or a ``threatened species'' is warranted.
    Please refer to the proposed listing rule for detailed information 
about the distinct vertebrate population segment analysis for the 
northern DPS of the mountain yellow-legged frog (78 FR 24472, April 25, 
2013). We previously confirmed the status of the southern California 
population of the mountain yellow-legged frog as a DPS at the time that 
it was listed as endangered under the Act (67 FR 44382, pp. 44384-
44385). We summarize below the analysis for discreteness and 
significance for the northern California population of the mountain 
yellow-legged frog (in the Sierra Nevada); this summary includes 
changes from the proposed rule to address comments received from the 
public (78 FR 24472, April 25, 2013).

[[Page 24263]]

Discreteness

    Under our DPS Policy, a population segment of a vertebrate species 
may be considered discrete if it satisfies either of the following two 
conditions: (1) It is markedly separated from other populations of the 
same taxon as a consequence of physical, physiological, ecological, or 
behavioral factors (quantitative measures of genetic or morphological 
discontinuity may provide evidence of this separation); or (2) it is 
delimited by international governmental boundaries within which 
significant differences in control of exploitation, management of 
habitat, conservation, status, or regulatory mechanisms exist.
    The analysis of the northern population segment of the mountain 
yellow-legged frog (Rana muscosa) (in the Sierra Nevada) is based on 
the marked separation from other populations. The range of the mountain 
yellow-legged frog is divided by a natural geographic barrier, the 
Tehachapi Mountains, which physically isolates the populations in the 
southern Sierra Nevada from those in the mountains of southern 
California. The distance of the geographic separation is about 225 km 
(140 mi). The geographic separation of the Sierra Nevada and southern 
California frogs was recognized in the earliest description of the 
species by Camp (1917), who treated frogs from the two areas as 
separate subspecies within the R. boylii group (see more on 
classification of the mountain yellow-legged frogs in Taxonomy). There 
is no contiguous habitat that provides connectivity between the two 
populations that is sufficient for the migration, growth, rearing, or 
reproduction of dispersing frogs. Genetic differences well-supported in 
the scientific literature also provide evidence of this separation (see 
Taxonomy). Therefore, we find that the northern population segment of 
the mountain yellow-legged frog (Rana muscosa) (in the Sierra Nevada) 
is discrete from the remainder of the species.

Significance

    Under our DPS Policy, once we have determined that a population 
segment is discrete, we consider its biological and ecological 
significance to the larger taxon to which it belongs. Our DPS policy 
provides several potential considerations that may demonstrate the 
significance of a population segment to the remainder of its taxon, 
including: (1) Evidence of the persistence of the discrete population 
segment in an ecological setting unusual or unique for the taxon, (2) 
evidence that loss of the discrete population segment would result in a 
significant gap in the range of the taxon, (3) evidence that the 
population segment represents the only surviving natural occurrence of 
a taxon that may be more abundant elsewhere as an introduced population 
outside its historic range, or (4) evidence that the discrete 
population segment differs markedly from the remainder of the species 
in its genetic characteristics.
    We have found substantial evidence that three of the four 
significance criteria are met by the discrete northern population 
segment of the mountain yellow-legged frog that occurs in the Sierra 
Nevada. These include its persistence in an ecological setting that is 
unique for the taxon, evidence that its loss would result in a 
significant gap in the range of the taxon, and its genetic uniqueness 
(reflecting significant reproductive isolation over time). To establish 
the significance of the discrete northern population segment, we rely 
on the effect that the loss of this population segment would have on 
the range of the taxon, and supplement that with evidence that the 
population segment persists in an ecological setting unusual or unique 
for the taxon and also differs from other population segments in its 
genetic characteristics. There are no introduced populations of the 
northern DPS of the mountain yellow-legged frog outside of the species' 
historical range.
    Evidence indicates that loss of the northern population segment of 
the mountain yellow-legged frog (in the Sierra Nevada) would result in 
a significant gap in the range of the taxon. The Sierran mountain 
yellow-legged frogs comprise the entire distribution of the species in 
approximately the northern half of the species' range, and loss of the 
distinct population segment in the northern portion of the range could 
have significant conservation implications for the species. 
Furthermore, loss of the northern population segment of the mountain 
yellow-legged frog (in the Sierra Nevada) would reduce the species to 
the remaining small, isolated sites in the streams of southern 
California (USFWS, Jul 2012, pp. 11-12). Loss of the northern 
population segment of the mountain yellow-legged frog would leave an 
area of the southern Sierra Nevada over 150 km (93 mi) in length 
without any ranid (frogs in the genus Ranidae) frogs, which were once 
abundant and widespread in the higher elevation Sierra Nevada (Cory 
1962b, p. 515; Fellers 1994, p. 5). The potential loss of the northern 
population segment of the mountain yellow-legged frog would constitute 
a significant gap in the range of the species.
    One of the most striking differences between the northern 
population segment and the southern population segment of the mountain 
yellow-legged frogs is the difference in the ecological setting in 
which they each persist. Zweifel (1955, pp. 237-241) observed that the 
frogs in southern California are typically found in steep-gradient 
streams in the chaparral belt at low elevations (370 m (1,220 ft)), 
even though they may range into small meadow streams at higher 
elevations up to 2,290 m (7,560 ft). In contrast, frogs from the 
northern population segment of mountain yellow-legged frogs are most 
abundant in high-elevation lakes and slow-moving portions of streams 
where winter conditions are extreme. David Bradford's (1989) southern 
Sierra Nevada study of mountain yellow-legged frogs, for example, was 
conducted in Sequoia and Kings Canyon National Parks at high elevations 
between 2,910 and 3,430 m (9,600 to 11,319 ft). The rugged canyons of 
the arid mountain ranges of southern California, where waters seldom 
freeze, bear little resemblance to the alpine lakes and streams of the 
Sierra Nevada where adult frogs and tadpoles must overwinter at the 
bottoms of ice and snow-covered lakes for up to 9 months of the year. 
The significantly different ecological settings between mountain 
yellow-legged frogs in southern California and those in the northern 
population segment (in the Sierra Nevada) distinguish these populations 
from each other.
    Finally, the northern population segment of the mountain yellow-
legged frog is biologically significant based on genetic differences. 
Vredenburg et al. (2007, p. 361) identified that two of three distinct 
genetic clades (groups of distinct lineage) constitute the northern 
range of the mountain yellow-legged frog found in the Sierra Nevada, 
with the remaining clade represented by the endangered southern 
California DPS of the mountain yellow-legged frog. Macey et al. (2001, 
p. 141) estimated the genetic divergence between the northern 
population of mountain yellow-legged frogs (in the Sierra Nevada) and 
the southern population of mountain yellow-legged frogs (in southern 
California) to have occurred 1.4 million years before present (mybp), 
thereby indicating functional isolation.
    The loss of the northern population of the mountain yellow-legged 
frog would result in a significant gap in the range of the mountain 
yellow-legged frog species. The differences between the ecological 
settings for the southern

[[Page 24264]]

population of mountain yellow-legged frogs (steep-gradient streams that 
seldom freeze) and the northern population of mountain yellow-legged 
frogs (high-elevation lakes and slow-moving portions of streams where 
frogs overwinter under ice and snow for up to 75 percent of the year) 
are significant. Additionally, the genetic distinction between these 
two populations reflects isolation for over a million years. Therefore 
based on the information discussed above, we find that northern 
population of the mountain yellow-legged frog (in the Sierra Nevada 
mountains) meets the significance criteria under our Policy Regarding 
the Recognition of Distinct Vertebrate Population Segments (61 FR 
4722).
DPS Conclusion
    Based on the best scientific and commercial data available on 
distribution as well as ecological setting and genetic characteristics 
of the species, we have determined that the northern population segment 
of the mountain yellow-legged frog (in the Sierra Nevada) is both 
discrete and significant per our DPS policy. Therefore, we conclude 
that the northern discrete population segment of the mountain yellow-
legged frog is a DPS, and thus a ``species'' under section 3(16) of the 
Act. Our determination of biological and ecological significance is 
appropriate because the population segment has a geographical 
distribution that is biologically meaningful.

Summary of Changes From the Proposed Rule for the Sierra Nevada Yellow-
Legged Frog and the Northern DPS of the Mountain Yellow-Legged Frog

    Based on peer review, Federal and State, and public comments (see 
comments in the Summary of Comments and Recommendations section below), 
we have clarified information in the sections provided for the Sierra 
Nevada yellow-legged frog and the northern DPS of the mountain yellow-
legged frog to better characterize our knowledge of the species' 
habitat requirements, correcting some information based on peer review 
(vocalizations (Species Description), species ranges (Taxonomy and 
Historic and Current Ranges and Distribution sections), current 
distribution in Sequoia National Park (Historic and Current Ranges and 
Distribution), and clarifying the basis for our determination of 
significance for the northern population of the mountain yellow-legged 
frog in response to public comments (Distinct Vertebrate Population 
Segment)), occasionally adding additional information where needed. In 
the Summary of Factors Affecting the Species section, we have re-
ordered threats in Factor A so that the primary activity that has 
modified the habitat of the mountain yellow-legged frog complex is 
addressed first, while activities with potential only for localized 
effects are addressed later. Based on peer review, and Federal, State, 
county, and public comments, we have added information where needed and 
clarified our findings on the role of current activities, such as 
grazing, recreation, packstock use, etc., in species declines. We 
reviewed the analysis of dams and diversions that we presented in the 
proposed rule and determined that most large reservoir facilities are 
below the current range of the mountain yellow-legged frogs. We revised 
the dams and water diversions threat magnitude from moderate prevalent 
in the proposed rule to minor localized where such structures occur in 
this final rule.
    In the proposed rule, we stated that grazing presented a minor 
prevalent threat. We reworded this final rule to more accurately 
reflect the contribution of legacy effects of past grazing levels to 
this threat assessment. We found that current livestock grazing that 
complies with forest standards and guidelines is not expected to 
negatively affect mountain yellow-legged frog populations in most 
cases, although limited exceptions could occur (where extant habitat is 
limited and legacy effects to meadows still require restoration, where 
habitat is limited such as in stream riparian zones or small meadows, 
or where grazing standards are exceeded). Rangewide, livestock grazing 
is not a substantial threat to the species.
    In response to information provided during the public comment 
period, we added a discussion of mining activities in the Factor A 
discussion. In this final rule, we determine that, while most mining 
activities take place below the extant ranges of the species, where 
some types of mining activities occur, localized habitat-related 
effects may result.
    We added new information available on packstock grazing, retaining 
our finding that packstock grazing is only likely to be a threat to 
mountain yellow-legged frogs in limited situations. We also added more 
information on roads and timber harvests, and we clarified that these 
activities primarily do not occur where there are extant populations 
(except where frogs occur in the northern or lower elevation portions 
of the range), and that USFS standards are generally designed to limit 
potential effects of such activities. We clarified the threat magnitude 
for roads and timber harvest from minor prevalence rangewide to not a 
threat to extant populations across much of the species' ranges 
(although they may pose important habitat-related effects to the 
species in localized areas). We reviewed information provided by the 
U.S. Forest Service (USFS), the National Park Service (NPS), CDFW, and 
others on recreation activities, and we changed our conclusion on the 
recreation threat magnitude from low significance to the species 
overall to not considered a threat to populations over much of their 
range. However, we recognize that there may be localized effects, 
especially outside of backcountry areas where use is high or where 
motorized and mechanical use occurs in extant frog habitat.
    We added a brief discussion of bullfrogs (Lithobates catesbeiana) 
under Factor C for mountain yellow-legged frogs noting that bullfrog 
predation and competition is expected to have population-level effects 
to mountain yellow-legged frog populations in those low elevation 
areas, or in the Lake Tahoe Basin, where the two species may co-occur. 
We slightly revised our characterization of the recent population 
declines of the mountain yellow-legged frogs due to Batrachochytrium 
dendrobatidis (Bd), identifying the fungus as one of the primary 
drivers of recent declines, and adding information provided by peer 
reviewers and agencies. We also added information to our discussion 
under Factor D, including information about the National Park Service 
Organic Act, information on the provision in the Wilderness Act about 
withdrawing minerals, and information on the status of the Sierra 
Nevada yellow-legged frog and the mountain yellow-legged frog under the 
California Endangered Species Act (CESA). We also moved discussion of 
current CDFW fisheries management to the ``Habitat Modification Due to 
Introduction of Trout to Historically Fishless Areas'' section under 
Factor A.
    We removed the discussion of contaminants under Factor E and refer 
readers to the proposed rule. Although we received additional 
information that clarified some text and provided additional references 
regarding contaminants, the clarifications supported our conclusions in 
the proposed rule that the best available information indicates that 
contaminants do not pose a current or continuing threat to the species. 
We also added additional information either available in our files, or 
provided by commenters,

[[Page 24265]]

to clarify and support our finding on the threat of climate change. We 
revised the explanation in the determinations for each species to 
reflect the above changes.

Summary of Factors Affecting the Species

    Section 4 of the Act (16 U.S.C. 1533), and its implementing 
regulations at 50 CFR part 424, set forth the procedures for adding 
species to the Federal Lists of Endangered and Threatened Wildlife and 
Plants. Under section 4(a)(1) of the Act, we may list a species based 
on any of the following five factors: (A) The present or threatened 
destruction, modification, or curtailment of its habitat or range; (B) 
overutilization for commercial, recreational, scientific, or 
educational purposes; (C) disease or predation; (D) the inadequacy of 
existing regulatory mechanisms; and (E) other natural or manmade 
factors affecting its continued existence. Listing actions may be 
warranted based on any of the above threat factors, singly or in 
combination. Each of these factors is discussed below, and changes from 
the proposed rule (78 FR 24472, April 25, 2013) are reflected in these 
discussions. The following analysis is applicable to both the Sierra 
Nevada yellow-legged frog (Rana sierrae) and the northern distinct 
population segment of the mountain yellow-legged frog (Rana muscosa).

Factor A. The Present or Threatened Destruction, Modification, or 
Curtailment of Its Habitat or Range

    A number of hypotheses, including habitat modification (including 
loss of vegetation, loss of wetlands, habitat modification for urban 
development, and degradation of upland habitats) have been proposed for 
recent global amphibian declines (Bradford et al. 1993, p. 883; Corn 
1994, p. 62; Alford and Richards 1999, p. 134). However, physical 
habitat modification has not been associated with the rangewide decline 
of mountain yellow-legged frogs. Mountain yellow-legged frogs occur 
primarily at high elevations in the Sierra Nevada, which have not had 
the types or extent of large-scale habitat conversion and physical 
disturbance that have occurred at lower elevations (Knapp and Matthews 
2000, p. 429). Thus, direct habitat destruction or modification 
associated with intensive human activities has not been implicated in 
the decline of this species (Davidson et al. 2002, p. 1597).
    However, other human activities may have played a role in the 
modification of mountain yellow-legged frog habitat. We have identified 
the following habitat-related activities as potentially relevant to the 
conservation status of the mountain yellow-legged frog complex: Fish 
introductions (see also Factor C, below), dams and water diversions, 
livestock grazing, timber management, road construction and 
maintenance, packstock use, recreational activities, and fire 
management activities. Such activities may have degraded habitat in 
ways that have reduced its capacity to sustain viable populations and 
may have fragmented and isolated mountain yellow-legged frog 
populations from each other.
Habitat Modification Due to Introduction of Trout to Historically 
Fishless Areas
    One habitat feature that is documented to have a significant 
detrimental impact to mountain yellow-legged frog populations is the 
presence of introduced trout resulting from stocking programs for the 
creation and maintenance of a recreational fishery. To further angling 
success and opportunity, trout stocking programs in the Sierra Nevada 
started in the late 19th century (Bahls 1992, p. 185; Pister 2001, p. 
280). This anthropogenic activity has community-level effects and is 
one of the primary threats to mountain yellow-legged frog habitat and 
species viability.
    Prior to extensive trout planting programs, almost all streams and 
lakes in the Sierra Nevada at elevations above 1,800 m (6,000 ft) were 
fishless. Several native fish species occur naturally in aquatic 
habitats below this elevation in the Sierra Nevada (Knapp 1996, pp. 12-
14; Moyle et al. 1996, p. 354; Moyle 2002, p. 25), but natural barriers 
prevented fish from colonizing the higher-elevation waters of the 
Sierra Nevada watershed (Moyle et al. 1996, p. 354). The upper reaches 
of the Kern River, where native fish such as the Little Kern golden 
trout (Oncorhynchus mykiss whitei) and California golden trout (O. m. 
aguabonita) evolved, represent the only major exception to the 1,800-m 
(6,000-ft) elevation limit for fishes within the range of the mountain 
yellow-legged frog in the Sierra Nevada (Moyle 2002, p. 25). 
Additionally, prior to extensive planting, native Paiute cutthroat (O. 
clarki seleneris) and Lahontan cutthroat (O. c. henshawi) were limited 
in their distribution to several rivers, streams, and limited large 
lakes in the eastern Sierra Nevada (Knapp 1996, p. 369; Moyle 1996 et 
al., pp. 954-958), indicating some overlap with the range of the Sierra 
Nevada yellow-legged frog.
    Some of the first practitioners of trout stocking in the Sierra 
Nevada were the Sierra Club, local sportsmen's clubs, private citizens, 
and the U.S. military (Knapp 1996, p. 8; Pister 2001, p. 280). As more 
hatcheries were built and the management of the trout fishery became 
better organized, fish planting continued for the purpose of increased 
angler opportunities and success (Pister 2001, p. 281). After World War 
II, the method of transporting trout to high-elevation areas changed 
from packstock to aircraft, which allowed stocking in more remote lakes 
and in greater numbers. With the advent of aerial stocking, trout 
planting expanded to new areas, with higher efficiency.
    Brook trout (Salvelinus fontinalis), brown trout (Salmo trutta), 
rainbow trout (Oncorhynchus mykiss), and other trout species 
assemblages have been planted in most streams and lakes of the Sierra 
Nevada (Knapp 1996, p. 8; Moyle 2002, p. 25). Since the advent of 
aerial stocking, backcountry areas not accessible by truck are stocked 
by air (Pert 2002, pers. comm.), which limits stocking to lakes. 
National Forests in the Sierra Nevada have a higher proportion of lakes 
with fish occupancy than do National Parks (Knapp 1996, p. 3), 
primarily because the National Park Service (NPS) began phasing out 
fish stocking within their jurisdictional boundaries in 1969, with 
limited stocking occurring until it was terminated altogether in Sierra 
Nevada National Parks in 1991 (Knapp 1996, p. 9). California Department 
of Fish and Wildlife (CDFW) continues to stock trout in National Forest 
water bodies, but in 2001 reduced the number of stocked water bodies to 
reduce impacts to native amphibians (ICF Jones & Stokes 2010, pp. ES-1-
ES-16). Current stocking decisions are based on criteria outlined in 
the Environmental Impact Report for the Hatchery and Stocking Program 
(ICF Jones & Stokes 2010, Appendix K).
    Fish stocking as a practice has been widespread throughout the 
range of both species of mountain yellow-legged frogs. Knapp and 
Matthews (2000, p. 428) indicated that 65 percent of the water bodies 
that were 1 ha (2.5 ac) or larger in National Forests they studied were 
stocked with fish on a regular basis. Over 90 percent of the total 
water body surface area in the John Muir Wilderness was occupied by 
nonnative trout (Knapp and Matthews 2000, p. 434).
    Another detrimental feature of fish stocking is that, in the Sierra 
Nevada, fish often persist in water bodies even after stocking ceases. 
Thirty-five to 50 percent of lakes larger than 1 ha (2.5 ac) within 
Sierra Nevada National Parks are occupied by nonnative fish, which is

[[Page 24266]]

only a 29 to 44 percent decrease in fish occupancy since fish stocking 
was terminated around 2 decades before the estimate was made (Knapp 
1996, p. 1). Though data on fish occupancy in streams are lacking 
throughout the Sierra Nevada, Knapp (1996, pp. 9-11) estimated that 60 
percent of the streams in Yosemite National Park were still occupied by 
introduced trout because trout readily move out of lakes to colonize 
both inlet and outlet streams. The presence of trout in these once 
fishless waters has modified the habitat at a landscape scale.
    Thus, the frog's habitat has been modified due to the introduction 
of a nonnative predator that both competes for limited food resources 
and directly preys on mountain yellow-legged frog tadpoles and adults 
(see Factor C below). Presence of nonnative trout in naturally fishless 
ecosystems has had profound effects on the structure and composition of 
faunal assemblages, severely reducing not only amphibians, but also 
zooplankton and large invertebrate species (see Knapp 1996, p. 6; 
Bradford et al. 1998, p. 2489; Finlay and Vredenburg 2007, pp. 2194-
2197). Within the frog's historical range, past trout introductions and 
the continuing presence of fish in most lakes resulted in the 
elimination of frogs from most waters that were suitable for fish. 
Across the range of these species in the Sierra Nevada, the presence of 
fish in most of the deeper lakes has altered the aquatic habitat that 
mountain yellow-legged frogs rely on for overwintering and breeding, 
and has also reduced connectivity among frog populations. Fish now 
populate the deeper lakes and connecting streams and largely separate 
and increase the distance between the current sites inhabited by the 
highly-aquatic frogs (the connectivity of occupied sites in present 
versus former fishless conditions differs by approximately 10-fold) 
(Bradford et al. 1993, pp. 884-887; Knapp 1996, pp. 373-379). Where 
reservoirs harbor introduced fish, successful reproduction of mountain 
yellow-legged frogs may be reduced if there are no shallow side 
channels or separate pools (Jennings 1996, p. 939). Most reservoirs do 
not overlap significantly with the current extant range of the species 
(CDFW 2013, p. 3) (see Dams and Water Diversions below); however, a 
number of reservoirs were constructed in the mid-1900s at mid-
elevations within lower edges of the species' historic range (for 
example, Sierra Nevada yellow-legged frogs were taken from Bear River 
Reservoir (Eldorado National Forest), Union Reservoir (Stanislaus 
National Forest), and several others). With the exception of one 1999 
record from Faggs Reservoir on the Plumas National Forest, all of 
several dozen records of the species from reservoirs are pre-1975, and 
at least half pre-date the water development projects at those 
locations (Brown et al. 2009, p. 78). All of these reservoirs now 
harbor introduced fish species, and at least two also harbor bullfrogs, 
suggesting that subsequent introductions may have played a role in past 
declines in those areas (see Brown et al. 2009, p. 78).
    The body of scientific research has demonstrated that introduced 
trout have negatively impacted mountain yellow-legged frogs over much 
of the Sierra Nevada (Grinnell and Storer 1924, p. 664; Bradford 1989, 
pp. 775-778; Bradford et al. 1993, pp. 882-888; Knapp 1994, p. 3; Drost 
and Fellers 1996, p. 422; Knapp 1996, pp. 13-15; Bradford et al. 1998, 
pp. 2482, 2489; Knapp and Matthews 2000, p. 428; Knapp et al. 2001, p. 
401). Fish stocking programs have negative ecological implications 
because fish eat aquatic fauna, including amphibians and invertebrates 
(Bahls 1992, p. 191; Erman 1996, p. 992; Jennings 1996, p. 939; Knapp 
1996, pp. 373-379; Matthews et al. 2001, pp. 1135-1136; Pilliod and 
Peterson 2001, p. 329; Schindler et al. 2001, p. 309; Moyle 2002, p. 
58; Epanchin et al. 2010, p. 2406). Finlay and Vredenburg (2007, p. 
2187) documented that the same benthic (bottom-dwelling) invertebrate 
resource base sustains the growth of both frogs and trout, suggesting 
that competition with trout for prey is an important factor that may 
contribute to the decline of the mountain yellow-legged frog. 
Introductions of salmonids to fishless lakes have also been associated 
with alteration of nutrient cycles and primary productivity in mountain 
lakes, including those in the Sierra Nevada (Schindler et al. 2001, pp. 
308, 313-319).
    Knapp and Matthews (2000, p. 428) surveyed more than 1,700 water 
bodies, and concluded that a strong negative correlation exists between 
introduced trout and mountain yellow-legged frogs (Knapp and Matthews 
2000, p. 435). Consistent with this finding are the results of an 
analysis of the distribution of mountain yellow-legged frog tadpoles, 
which indicate that the presence and abundance of this life stage are 
reduced dramatically in fish-stocked lakes (Knapp et al. 2001, p. 408). 
Knapp (2005a, pp. 265-279) also compared the distribution of nonnative 
trout with the distributions of several amphibian and reptile species 
in 2,239 lakes and ponds in Yosemite National Park, and found that 
mountain yellow-legged frogs were five times less likely to be detected 
in waters where trout were present. Even though stocking within the 
National Park ceased in 1991, more than 50 percent of water bodies 
deeper than 4 m (13 ft) and 75 percent deeper than 16 m (52 ft) still 
contained trout populations in 2000-2002 (Knapp 2005a, p. 270). Both 
trout and mountain yellow-legged frogs utilize deeper water bodies. 
Based on the results from Knapp (2005a), the reduced detection of frogs 
in trout-occupied waters indicates that trout are excluding mountain 
yellow-legged frogs from some of the best aquatic habitat.
    Several aspects of the mountain yellow-legged frog's life history 
are thought to exacerbate its vulnerability to extirpation by trout 
(Bradford 1989, pp. 777-778; Bradford et al. 1993, pp. 886-888; Knapp 
1996, p. 14; Knapp and Matthews 2000, p. 435). Mountain yellow-legged 
frogs are highly aquatic and are found primarily in lakes, most of 
which now contain trout (Knapp 1996, p. 14). In comparison to other 
Sierran frogs, mountain yellow-legged frog tadpoles generally need at 
least 2 years to reach metamorphosis, which restricts breeding to 
waters that are deep enough to avoid depletion of oxygen when ice-
covered (Knapp 1996, p.14). Overwintering adults must also avoid oxygen 
depletion when the water is covered by ice, generally limiting 
overwintering to deeper waters that do not become anoxic (Mullally and 
Cunningham 1956a, p. 194; Bradford 1983, p. 1179; Knapp and Matthews 
2000, pp. 435-436). At high elevations, both tadpoles and adults 
overwinter under ice for up to 9 months (Bradford 1983, p. 1171). These 
habitat requirements appear to restrict successful breeding and 
overwintering to the deeper water bodies where the chances of summer 
drying and winter freezing are reduced, the same water bodies that are 
most suitable for fishes; fishes also need deeper water bodies where 
the chances of summer drying and winter freezing are reduced (Bradford 
1983, pp. 1172-1179; Knapp 1996, p. 14; Knapp and Matthews 2000, pp. 
429, 435-436). Past fish-stocking practices targeted the deeper lakes, 
so the percentage of water bodies containing fish has increased with 
water depth, resulting in elimination of mountain yellow-legged frogs 
from once suitable habitats in which they were historically most 
common, and thereby generally isolating populations to the shallower, 
marginal habitats that do not have fish (Bradford 1983, pp. 1172-1179; 
Bradford et al. 1993, pp. 884, 886-

[[Page 24267]]

887; Knapp and Matthews 2000, pp. 435-436).
    Mountain yellow-legged frogs and trout (native and nonnative) do 
co-occur at some sites, but these co-occurrences are generally thought 
to represent mountain yellow-legged frog ``sink'' populations (areas 
with negative population growth rates in the absence of immigration) 
(Bradford et al. 1998, p. 2489; Knapp and Matthews 2000, p. 436). 
Mountain yellow-legged frogs have also been extirpated at some fishless 
bodies of water (Bradford 1991, p. 176; Drost and Fellers 1996, p. 
422). A possible explanation is the isolation and fragmentation of 
remaining populations due to introduced fishes in the streams that once 
provided mountain yellow-legged frogs with dispersal and recolonization 
routes; these remote populations are now non-functional as 
metapopulations (Bradford 1991, p. 176; Bradford et al. 1993, p. 887). 
Based on a survey of 95 basins within Sequoia and Kings Canyon National 
Parks, Bradford et al. (1993, pp. 885-886) estimated that the 
introduction of fishes into the study area resulted in an approximately 
10-fold increase in habitat fragmentation between populations of 
mountain yellow-legged frogs. Knapp and Matthews (2000, p. 436) believe 
that this fragmentation has further isolated mountain yellow-legged 
frogs within the already marginal habitat left unused by fishes.
    Fragmentation of mountain yellow-legged frog habitat renders 
populations more vulnerable to extirpation from random events (such as 
disease) (Wilcox 1980, pp. 114-115; Bradford et al. 1993, p. 887; 
Hanski and Simberloff 1997, p. 21; Knapp and Matthews 2000, p. 436). 
Isolated population locations may have higher extinction rates because 
trout prevent successful recolonization and dispersal to and from these 
sites (Bradford et al. 1993, p. 887; Blaustein et al. 1994a, p. 7; 
Knapp and Matthews 2000, p. 436). If the distance between sites is too 
great, amphibians may not readily recolonize unoccupied sites following 
local extinctions because of physiological constraints, the tendency to 
move only short distances, and high site fidelity. Finally, frogs that 
do attempt recolonization may emigrate into fish-occupied habitat and 
perish, rendering sites with such metapopulation dynamics less able to 
sustain frog populations.
    In 2001, CDFW revised fish stocking practices and implemented an 
informal policy on fish stocking in the range of the Sierra Nevada 
yellow-legged frog and northern DPS of the mountain yellow-legged frog. 
This policy directs that: (1) Fish will not be stocked in lakes with 
known populations of mountain yellow-legged frogs, nor in lakes that 
have not yet been surveyed for mountain yellow-legged frog presence; 
(2) waters will be stocked only with a fisheries management 
justification; and (3) the number of stocked lakes will be reduced over 
time. In 2001, the number of lakes stocked with fish within the range 
of the mountain yellow-legged frog in the Sierra Nevada was reduced by 
75 percent (Milliron 2002, pp. 6-7; Pert et al. 2002, pers. comm.). 
Current CDFW guidelines stipulate that water bodies within the same 
basin and 2 km (1.25 mi) from a known mountain yellow-legged frog 
population will not be stocked with fish unless stocking is justified 
through a management plan that considers all the aquatic resources in 
the basin, or unless there is heavy angler use and no opportunity to 
improve the mountain yellow-legged frog habitat (Milliron 2002a, p. 5). 
The Hatchery and Stocking Program Environmental Impact Report/
Environmental Impact Statement, finalized in 2010 (ICF Jones & Stokes 
2010, Appendix K), outlines a decision approach to mitigate fish 
stocking effects on Sierra amphibians that prohibits fish stocking in 
lakes with confirmed presence of a limited number of designated 
species, including the mountain yellow-legged frogs (see ICF Jones & 
Stokes 2010, Appendix E) using recognized survey protocols. Large 
reservoirs generally continue to be stocked to provide a put-and-take 
fishery for recreational angling.
    As part of the High Mountain Lakes Project, CDFW is in the process 
of developing management plans for basins within the range of the 
Sierra Nevada yellow-legged frog and the northern DPS of mountain 
yellow-legged frog (CDFG (CDFW) 2001, p. 1; Lockhart 2011, pers. 
comm.). CDFW states that objectives of the basin plans specific to the 
mountain yellow-legged frog include management in a manner that 
maintains or restores native biodiversity and habitat quality, supports 
viable populations of native species, and provides for recreational 
opportunities that consider historical use patterns (CDFG (CDFW) 2001, 
p. 3). They state that, under this approach, lakes that support 
mountain yellow-legged populations in breeding, foraging, or dispersal, 
and/or present opportunities to restore or expand habitat, are managed 
for the conservation of the species. Lakes that do not support mountain 
yellow-legged frogs are not viable restoration opportunities, and lakes 
that support trout populations are managed primarily for recreational 
angling (CDFG (CDFW) 2001, p. 3). They further note that lakes managed 
for recreational angling may be stocked if CDFW determines that 
stocking the lake will achieve a desirable fisheries management 
objective and is not otherwise precluded by stocking decision 
guidelines and agreements (for stocking decision documents, see CDFW 
2013, pp. 1, 2).
    Since the mid-1990s, various parties, including researchers, CDFW, 
NPS, and the USFS, have implemented a variety of projects to actively 
restore habitat for the mountain yellow-legged frog via the removal of 
nonnative trout (USFS 2011, pp. 128-130; NPS 2013, pp. 3-5).
    Although fish stocking has been curtailed within many occupied 
basins, the impacts to frog populations persist due to the presence of 
self-sustaining fish populations in some of the best habitat that 
normally would have sustained mountain yellow-legged frogs. The 
fragmentation that persists across the range of these frog species 
renders them more vulnerable to other population stressors, and 
recovery is slow, if not impossible, without costly and physically 
difficult direct human intervention (such as physical and chemical 
trout removal) (see Knapp et al. 2007a, pp. 11-19). While most of the 
impacts occurred historically, the impact upon the biogeographic 
(population/metapopulation) integrity of the species will be long-
lasting. Currently, habitat degradation and fragmentation by fish is 
considered a highly significant and prevalent threat to persistence and 
recovery of the species.
Dams and Water Diversions
    While a majority of dams and water diversions within the Sierra 
Nevada are located at lower elevations (USFS 2011, p. 83), some large 
reservoirs have been constructed within the historic range of the 
mountain yellow-legged frog complex. These large reservoirs include, 
but are not limited to Huntington Lake, Florence Lake, Lake Thomas A. 
Edison, Saddlebag Lake, Cherry Lake, Hetch Hetchy, Upper and Lower Blue 
Lakes, Lake Aloha, Silver Lake, Hell Hole Reservoir, French Meadow 
Reservoir, Lake Spaulding, Alpine Lake, Loon Lake, and Ice House 
Reservoir. A number of these occur at elevations below the current 
range of the species, indicating that the network of large water and 
power projects found at lower elevations does not overlap significantly 
with the current accepted distribution of the mountain yellow-legged 
frogs in the Sierra Nevada (CDFW 2013, p. 3).
    Kondolf et al. (1996, p. 1014) report that dams can have direct 
effects to

[[Page 24268]]

riparian habitat through permanent removal of habitat to construct 
roads, penstocks, powerhouses, canals, and dams. Impacts of reservoirs 
include flooding of riparian vegetation and impediments to 
establishment of new shoreline vegetation by fluctuating water levels. 
Dams can alter the temperature and sediment load of the rivers they 
impound (Cole and Landres 1996, p. 175). Dams, water diversions, and 
their associated structures can also alter the natural flow regime with 
unseasonal and fluctuating releases of water (Kondolf et al. 1996, p. 
1014). We expect most such effects to occur in stream systems below the 
extant range of the mountain yellow-legged frogs, although it is 
possible that stream localities at the northern extent of the range or 
at low elevations may be affected (see also CDFW 2013, pp. 2-4).
    The extent of past impacts to mountain yellow-legged frog 
populations from habitat loss or modification due to reservoir projects 
has not been quantified. CDFW (2013, p. 3) has noted that there are 
locations where the habitat inundated as the result of dam construction 
(for example, Lake Aloha in the Desolation Wilderness) may have been of 
higher quality for mountain yellow-legged frogs than the created 
impoundment. Reservoirs can provide habitat for introduced predators, 
including fish, bullfrogs, and crayfish, and in some cases, the past 
construction of reservoirs has facilitated the spread of nonnative fish 
(CDFW 2013, pp. 3, 4). In such cases, reservoirs may function as 
barriers to movement of mountain yellow-legged frogs. However, CDFW 
reported observing mountain yellow-legged frogs dispersing through 
fishless reservoirs (CDFW 2013, p. 4). (For a complete discussion of 
the impacts of fish stocking see Habitat Modification Due to 
Introduction of Trout to Historically Fishless Areas above and the 
discussion under Factor C.).
    Most of the dams constructed within the historic range of the 
mountain yellow-legged frogs are small streamflow-maintenance dams 
(CDFW 2013, p. 13) at the outflows of high-elevation lakes. These small 
dams may create additional habitat for the species and can act as 
barriers to fish migration from downstream tributaries into fishless 
habitats, although they do not impede frog movement (CDFW 2013, p. 3). 
CDFW staff (2013, p. 13) have observed that extant frog populations may 
have persisted where such dams have helped to preserve a fishless 
environment behind the dam.
    Based on comments from CDFW and others and the provision of 
additional information, we have reviewed the analysis of dams and 
diversions that we presented in the proposed rule. We find that most 
large facilities are below the current range of the mountain yellow-
legged frogs and have revised our finding. In the proposed rule, we 
stated that dams and diversions presented a moderate, prevalent threat 
to persistence and recovery of the species. In this final rule, we find 
that dams and water diversions present a minor, localized threat to 
persistence and recovery of the species where structures occur.
Livestock Use (Grazing)
    The combined effect of legacy conditions from historically 
excessive grazing use and current livestock grazing activities has the 
potential to impact habitat in the range of the mountain yellow-legged 
frog. The following subsections discuss the effects of excessive 
historical grazing, current extent of grazing, and current grazing 
management practices. As discussed below, grazing has the potential to 
reduce the suitability of habitat for mountain yellow-legged frogs by 
reducing its capability to sustain frogs and facilitate dispersal and 
migration, especially in stream areas.
    Grazing of livestock in riparian areas impacts the function of the 
aquatic system in multiple ways, including soil compaction, which 
increases runoff and decreases water availability to plants; vegetation 
removal, which promotes increased soil temperatures and evaporation 
rates at the soil surface; and direct physical damage to the vegetation 
(Kauffman and Krueger 1984, pp. 433-434; Cole and Landres 1996, pp. 
171-172; Knapp and Matthews 1996, pp. 816-817). Streamside vegetation 
protects and stabilizes streambanks by binding soils to resist erosion 
and trap sediment (Kauffman et al. 1983, p. 683; Chaney et al. 1990, p. 
2). Grazing within mountain yellow-legged frog habitat has been 
observed to remove vegetative cover, potentially exposing frogs to 
predation and increased desiccation (Knapp 1993b, p. 1; Jennings 1996, 
p. 539), and to lead to erosion which may silt in ponds and thereby 
reduce the water depth needed for overwinter survival (Knapp 1993b, p. 
1). However, an appropriately managed grazing regime (including timing 
and intensity) can enhance primary riparian vegetation attributes that 
are strongly correlated to stream channel and riparian soil stability 
conditions necessary to maintain a functioning riparian system (George 
et al. 2011, p. 227). Although, where highly degraded conditions such 
as downcut channels exist, grazing management alone may not be 
sufficient to restore former riparian conditions (George et al. 2011, 
p. 227).
    Aquatic habitat can also be degraded by grazing. Mass erosion from 
trampling and hoof slide causes streambank collapse and an accelerated 
rate of soil transport to streams (Meehan and Platts 1978, p. 274). 
Accelerated rates of erosion lead to elevated instream sediment loads 
and depositions, and changes in stream-channel morphology (Meehan and 
Platts 1978, pp. 275-276; Kauffman and Krueger 1984, p. 432). Livestock 
grazing may lead to diminished perennial streamflows (Armour et al. 
1994, p. 10). Livestock can increase nutrient-loading in water bodies 
due to urination and defecation in or near the water, and can cause 
elevated bacteria levels in areas where cattle are concentrated (Meehan 
and Platts 1978, p. 276; Stephenson and Street 1978, p. 156; Kauffman 
and Krueger 1984, p. 432). With increased grazing intensity, these 
adverse effects to the aquatic ecosystem increase proportionately 
(Meehan and Platts 1978, p. 275; Clary and Kinney 2000, p. 294).
    Observational data indicate that livestock can negatively impact 
mountain yellow-legged frogs by altering riparian habitat (Knapp 1993a, 
p. 1; 1993b, p. 1; 1994, p. 3; Jennings 1996, p. 938; Carlson 2002, 
pers. comm.; Knapp 2002a, p. 29). Livestock tend to concentrate along 
streams and wet areas where there is water and herbaceous vegetation; 
grazing impacts are, therefore, most pronounced in these habitats 
(Meehan and Platts 1978, p. 274; U.S. Government Accounting Office 
(GAO) 1988, pp. 10-11; Fleischner 1994, p. 635; Menke et al. 1996, p. 
17). This concentration of livestock contributes to the destabilization 
of streambanks, causing undercuts and bank failures (Kauffman et al. 
1983, p. 684; Marlow and Pogacnik 1985, pp. 282-283; Knapp and Matthews 
1996, p. 816; Moyle 2002, p. 55). Grazing activity can contribute to 
the downcutting of streambeds and lower the water table. The degree of 
erosion caused by livestock grazing can vary with slope gradient, 
aspect, soil condition, vegetation density, and accessibility to 
livestock, with soil disturbance greater in areas overused by livestock 
(Meehan and Platts 1978, pp. 275-276; Kauffman et al. 1983, p. 685; 
Kauffman and Krueger 1984, p. 432; Bohn and Buckhouse 1985, p. 378; GAO 
1988, p. 11; Armour et al. 1994, pp. 9-11; Moyle 2002, p. 55).
    Livestock grazing may impact other wetland systems, including ponds 
that can serve as mountain yellow-legged

[[Page 24269]]

frog habitat. Grazing can modify shoreline habitats by removing 
overhanging banks that provide shelter, and grazing contributes to the 
siltation of breeding ponds. Bradford (1983, p. 1179) and Pope (1999, 
pp. 43-44) have documented the importance of deep lakes to overwinter 
survival of these species. We expect that pond siltation due to grazing 
may reduce the depth of breeding ponds and cover underwater crevices in 
some circumstances where grazing is heavy and where soils are highly 
erodable, thereby making the ponds less suitable, or unsuitable, as 
overwintering habitat for tadpoles and adult mountain yellow-legged 
frogs.

Effects of Excessive Historical Grazing

    In general, historical livestock grazing within the range of the 
mountain yellow-legged frog was at a high (although undocumented), 
unregulated and unsustainable level until the establishment of National 
Parks (beginning in 1890) and National Forests (beginning in 1905) (UC 
1996a, p. 114; Menke et al. 1996, p. 14). Historical evidence indicates 
that heavy livestock use in the Sierra Nevada has resulted in 
widespread damage to rangelands and riparian systems due to sod 
destruction in meadows, vegetation destruction, and gully erosion (see 
review in Brown et al. 2009, pp. 56-58). Within the newly established 
National Parks, grazing by cattle and sheep was eliminated, although 
grazing by packstock, such as horses and mules, continued. Within the 
National Forests, the amount of livestock grazing was gradually 
reduced, and the types of animals shifted away from sheep and toward 
cattle and packstock, with cattle becoming the dominant livestock. 
During World Wars I and II, increased livestock use occurred on 
National Forests in the west, causing overuse in the periods 1914-1920 
and 1939-1946. Between 1950 and 1970 livestock numbers were permanently 
reduced due to allotment closures and uneconomical operations, with 
increased emphasis on resource protection and riparian enhancement. 
Further reductions in livestock use began again in the 1990s, due in 
part to USFS reductions in permitted livestock numbers, seasons of use, 
implementation of rest-rotation grazing systems, and to responses to 
drought (Menke et al. 1996, pp. 7, 8). Between 1981 and 1998, livestock 
numbers on National Forests in the Sierra Nevada decreased from 163,000 
to approximately 97,000 head, concurrent with Forest Service 
implementation of standards and guidelines for grazing and other 
resource management (USFS 2001, pp. 399-416).

Effects of Current Grazing

    Yosemite, Sequoia, and Kings Canyon National Parks remain closed to 
livestock grazing. On USFS-administered lands that overlap the 
historical ranges of the mountain yellow-legged frog in the Sierra 
Nevada, there are currently 161 active Rangeland Management Unit 
Allotments for livestock grazing. However, based on frog surveys 
performed since 2005, only 27 of these allotments have extant mountain 
yellow-legged frog populations, while some allotments that were located 
in sensitive areas have been closed (USFS 2008, unpubl. data; CDFW 
(CDFG) unpubl. data). As of 2009, USFS data indicated that grazing 
occurs on about 65 percent of National Forest lands within the range of 
the mountain yellow-legged frog; that livestock numbers remain greatly 
reduced from historical levels; and that numerous watershed restoration 
projects have been implemented, although grazing may still impact many 
meadows above mid-elevation and restoration efforts are far from 
complete (Brown et al. 2009, pp. 56, 57). However, Brown et al. (2009, 
p. 56) report that livestock grazing is more likely to occur in certain 
habitat types used by mountain yellow-legged frogs than others, 
indicating that populations found in meadows, stream riparian zones, 
and lakes in meadows are more likely to encounter habitat effects of 
grazing than populations found in the deeper alpine lakes that the 
species more likely inhabit (Brown et al. 2009, p. 56).
    USFS standards and guidelines in forest land and resource 
management plans have been implemented to protect water quality, 
sensitive species, vegetation, and stream morphology. Further, USFS 
standards have been implemented in remaining allotments to protect 
aquatic habitats (see discussion of the aquatic management strategy 
under Factor D for examples). USFS data from long-term meadow 
monitoring collected from 1999 to 2006 indicate that most meadows 
appear to be in an intermediate quality condition class, with seeming 
limited change in condition class over the first 6 years of monitoring. 
In addition, USFS grazing standards and guidelines are based on current 
science and are designed to improve or maintain range ecological 
conditions, and standards for managing habitat for threatened, 
endangered, and sensitive species have also been incorporated (Brown et 
al. 2009, pp. 56-58). The seasonal turn-out dates (dates at which 
livestock are permitted to move onto USFS allotments) are set yearly 
based on factors such as elevation, annual precipitation, soil 
moisture, and forage plant phenology, and meadow readiness dates are 
also set for montane meadows. However, animals turned out to graze on 
low-elevation range (until higher elevation meadows are ready) may 
reach upper portions of allotments before the meadows have reached 
range readiness (Brown et al. 2009, p. 58).
    Menke et al. (1996) have reported that grazing livestock in numbers 
that are consistent with grazing capacity and use of sustainable 
methods led to better range management in the Sierra Nevada over the 20 
years prior to development of the report. They also noted that moderate 
livestock grazing has the potential to increase native species 
diversity in wet and mesic meadows by allowing native plant cover to 
increase on site. Brown et al. (2009, p. 58) expect proper livestock 
management, such as proper timing, intensity, and duration, to result 
in a trend towards increased riparian species and a trend towards 
restored wet and mesic meadows on National Forests. To date, the 
scientific and commercial information available to us does not include 
descriptive or cause-effect research that establishes a causal link 
between habitat effects of livestock grazing and mountain yellow-legged 
frog populations; however, anecdotal information of specific habitat 
effects suggests that, in specific locations, the current grazing 
levels may have population-level effects (see Knapp 1993b, p. 1; Brown 
et al. 2009, p. 56). In addition, where low-elevation populations occur 
in meadows, additional conservation measures may be required for 
recovery (USFS 2013, p. 5).
    In summary, the legacy effects to habitat from historical grazing 
levels, such as increased erosion, stream downcutting and headcutting, 
lowered water tables, and increased siltation, are a threat to mountain 
yellow-legged frogs in those areas where such conditions still occur 
and may need active restoration. In the proposed rule, we stated that 
grazing presented a minor prevalent threat. Based on USFS and public 
comments, we have reevaluated our analysis of grazing to clarify 
effects of past versus current grazing. We have reworded the finding to 
more accurately reflect the contribution of legacy effects of past 
grazing levels to this threat assessment, as follows: Current livestock 
grazing activities may present an ongoing, localized threat to 
individual populations in locations where the populations occur in 
stream

[[Page 24270]]

riparian zones and in small waters within meadow systems, where active 
grazing co-occurs with extant frog populations. Livestock grazing that 
complies with forest standards and guidelines is not expected to 
negatively affect mountain yellow-legged frog populations in most 
cases, although limited exceptions could occur, especially where extant 
habitat is limited. In addition, mountain yellow-legged frogs may be 
negatively affected where grazing standards are exceeded. Rangewide, 
current livestock grazing is not a substantial threat to the species.
Mining
    Several types of mining activities have occurred, or may currently 
occur, on National Forests, including aggregate mining (the extraction 
of materials from streams or stream terraces for use in construction), 
hardrock mining (the extraction of minerals by drilling or digging into 
solid rock), hydraulic mining (a historical practice using pressurized 
water to erode hillsides, outlawed in 1884), placer mining (mining in 
sand or gravel, or on the surface, without resorting to mechanically 
assisted means or explosives), and suction-dredge mining (the 
extraction of gold from riverine materials, in which water, sediment, 
and rocks are vacuumed from portions of streams and rivers, sorted to 
obtain gold, and the spoils redeposited in the stream (see review in 
Brown et al. 2009, pp. 62-64).
    Aggregate mining can alter sediment transport in streams, altering 
and incising stream channels, and can cause downstream deposition of 
sediment, altering or eliminating habitat. Aggregate mining typically 
occurs in large riverine channels that are downstream of much of the 
range of the mountain yellow-legged frog complex (see review in Brown 
et al. 2009, pp. 62-64). However, Brown et al. (2009, pp. 62-64) note 
that effects of aggregate mining may occur in some portions of the 
Feather River system where such operations occur within the historic 
range of the Sierra Nevada yellow-legged frog, and potentially in 
localized areas within the range of both species, where the USFS 
maintains small quarries for road work. They note that, although 
effects of aggregate mining on mountain yellow-legged frogs are 
unstudied, impacts are probably slight.
    Hardrock mining can be a source of pollution where potentially 
toxic metals are solubilized by waters that are slightly acidic. Past 
mining activities have resulted in the existence of many shaft or 
tunnel mines on the forest in the Sierra Nevada, although most are 
thought to occur below the range of the species. Most operations that 
are thought to have the potential to impact the mountain yellow-legged 
frogs occur in the lower elevation portions of the Sierra Nevada 
yellow-legged frog range on the Plumas National Forest and in the 
ranges of both species on the Inyo National Forest (see review in Brown 
et al. 2009, pp. 62-64).
    Hydraulic mining has exposed previously concealed rocks that can 
increase pollutants such as acid, cadmium, mercury, and asbestos, and 
its effect on water pollution may still be apparent on the Feather 
River. However, most of the area that was mined in this way is below 
the elevation where Sierra Nevada yellow-legged frogs are present, so 
effects are likely highly localized (see review in Brown et al. 2009, 
pp. 63, 64). Although placer mining was dominant historically, today 
it's almost exclusively recreational and is not expected to have 
habitat-related effects.
    Brown et al. (2009, p. 64) report that suction-dredge mining is 
also primarily recreational noting that, because nozzles are currently 
restricted to 6 inches or smaller, CDFW (CDFG, 1994) expects disturbed 
areas to recover quickly (although CDFW notes that such dredging may 
increase suspended sediments, change stream geomorphology, and bury or 
suffocate larvae). Suction dredge mining occurs primarily in the 
foothills of the Sierra Nevada, thus presenting a risk primarily to 
mountain yellow-legged frog populations at the lower elevations of the 
species' range. Suction dredging is highly regulated by the CDFW, and 
in the past, many streams have been seasonally or permanently closed 
(see review in Brown et al. 2009, p. 64). Currently CDFW has imposed a 
moratorium on suction dredging.
    The high-elevation areas where most Sierra Nevada yellow-legged 
frogs and mountain yellow-legged frogs occur are within designated 
wilderness, where mechanical uses are prohibited by the Wilderness Act. 
Designated wilderness was withdrawn for new mining claims on January 1, 
1984, although a limited number of active mines that predated the 
withdrawal still occur within wilderness (see Wilderness Act under 
Factor D, below). Therefore, we expect that mining activities may pose 
local habitat-related impacts to the species at specific localities 
where mining occurs.
Packstock Use
    Similar to cattle, horses and mules may significantly overgraze, 
trample, or pollute riparian and aquatic habitat if too many are 
concentrated in riparian areas too often or for too long. Commercial 
packstock trips are permitted in National Forests and National Parks 
within the Sierra Nevada, often providing transport services into 
wilderness areas through the use of horses or mules. Use of packstock 
in the Sierra Nevada increased after World War II as road access, 
leisure time, and disposable income increased (Menke et al. 1996, p. 
919). Packstock grazing is the only grazing currently permitted in the 
National Parks of the Sierra Nevada. Since the mid-1970s, National 
Forests and National Parks have generally implemented regulations to 
manage visitor use and group sizes, including measures to reduce 
packstock impacts to vegetation and soils in order to protect 
wilderness resources. For example, Sequoia and Kings Canyon National 
Parks have the backcountry area with the longest history of research 
and management of packstock impacts (Hendee et al. 1990, p. 461). 
Hendee et al. (1990, p. 461) report that the extensive and long-term 
monitoring for Sequoia, Kings Canyon, and Yosemite National Parks makes 
it possible to quantify impacts of packstock use, showing that the vast 
majority of Sierra Nevada yellow-legged frog and mountain yellow-legged 
frog populations in the Parks show no to negligible impacts from 
packstock use (National Park Service 2013, p. 3). In the Sixty-Lakes 
Basin of Kings Canyon National Park, packstock use is regulated in wet 
meadows to protect mountain yellow-legged frog breeding habitat in bogs 
and along lake shores from trampling and associated degradation 
(Vredenburg 2002, p. 11; Werner 2002, p. 2; National Park Service 2013, 
p. 3). Packstock use is also regulated in designated wilderness in 
National Forests within the Sierra Nevada.
    Packstock use is likely a threat of low significance to mountain 
yellow-legged frogs at the current time, except on a limited, site-
specific basis. As California's human population increases, the impact 
of recreational activities, including packstock use and riding on the 
National Forests in the Sierra Nevada, are projected to increase (USDA 
2001a, pp. 473-474). However, on the Inyo National Forest, current 
commercial packstock use is approximately 27 percent of the level of 
use in the 1980s reflecting a decline in the public's need and demand 
for packstock trips. From 2001 to 2005, commercial packstock outfitters 
within the Golden Trout and South Sierra Wilderness Areas averaged 28 
percent of their current authorized use (USFS

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2006, p. 3-18). Similarly, long-term permitting data for 
administrative, commercial, and recreational packstock use in the three 
National Parks indicates that packstock use is declining in the Parks, 
providing no evidence to suggest that packstock use will increase in 
the future in the Parks (National Park Service 2013, pp. 3, 4). Habitat 
changes due to packstock grazing may pose a risk to some remnant 
populations of frogs and, in certain circumstances, a hindrance to 
recovery of populations in heavily used areas.
Roads and Timber Harvest
    Activities that alter the terrestrial environment (such as road 
construction and timber harvest) may impact amphibian populations in 
the Sierra Nevada (Jennings 1996, p. 938) at locations where these 
activities occur. Historically, road construction and timber harvest 
may have acted to reduce the species' range prior to the more recent 
detailed studies and systematic monitoring that have quantified and 
documented species losses. Prior to the formation of National Parks in 
1890 and National Forests in 1905, timber harvest was widespread and 
unregulated, but primarily took place at elevations on the western 
slope of the Sierra Nevada below the range of the mountain yellow-
legged frog (University of California (UC) 1996b, pp. 24-25). Between 
1900 and 1950, the majority of timber harvest occurred in old-growth 
forests on private land (UC 1996b, p. 25). Between 1950 and the early 
1990s, timber harvest on National Forests increased, and the majority 
of timber harvest-associated impacts on mountain yellow-legged frogs 
may therefore have taken place during this period in lower elevation 
locations where timber harvest and species occurrences overlapped. 
Currently, these activities are expected to occur outside National 
Parks or National Forest wilderness areas, with limited exceptions.
    Timber harvest activities (including vegetation management and 
fuels management) remove vegetation and cause ground disturbance and 
compaction, making the ground more susceptible to erosion (Helms and 
Tappeiner 1996, p. 446). This erosion can increase siltation downstream 
and potentially damage mountain yellow-legged frog breeding habitat. 
Timber harvest may alter the annual hydrograph (timing and volume of 
surface flows) in areas where harvests occur. The majority of erosion 
caused by timber harvests is from logging roads (Helms and Tappeiner 
1996, p. 447). A recent monitoring effort, which was conducted by the 
USFS in stream habitats in the northern part of the Sierra Nevada 
yellow-legged frog's range, attempted to assess the impact of 
vegetation management activities, which would include activities 
similar to timber harvest, on mountain yellow-legged frog populations 
(Foote et al. 2013, p. 2). However, given the timing of project 
implementation, the results were limited to the impacts of these 
management activities on mountain yellow-legged frog habitat. The 
results of the monitoring suggest these activities did not 
significantly impact perennial stream habitat for the mountain yellow-
legged frog, although there were instances of habitat degradation 
attributed to sedimentation resulting from road decommissioning and 
culvert replacement (Foote et al. 2013, p. 32).
    Roadways have the potential to affect riparian habitat by altering 
the physical and chemical environment, including alteration of surface-
water run-off, with potential changes to hydrology in high-mountain 
lake and stream systems (Brown et al. 2009, pp. 71-72). Roads, 
including those associated with timber harvests, have also been found 
to contribute to habitat fragmentation and limit amphibian movement, 
thus having a negative effect on amphibian species richness. Therefore, 
road construction could fragment mountain yellow-legged frog habitat if 
a road bisects habitat consisting of water bodies in close proximity. 
In the prairies and forests of Minnesota, Lehtinen et al. (1999, pp. 8-
9) found that increased road density reduced amphibian species 
richness. DeMaynadier and Hunter (2000, p. 56) found similar results in 
a study of eight amphibian species in Maine, although results varied 
with road type and width. Results showed that anuran (true frogs, the 
group of frogs that includes the mountain yellow-legged frogs) habitat 
use and movement were not affected even by a wide, heavily used logging 
road (deMaynadier and Hunter 2000, p. 56); this finding suggests that 
forest roads may not fragment populations where such roads occur.
    Currently, most of the mountain yellow-legged frog populations 
occur in National Parks or designated wilderness areas where timber is 
not harvested (Bradford et al. 1994, p. 323; Drost and Fellers 1996, p. 
421; Knapp and Matthews 2000, p. 430) and where motorized access (and 
roads) does not occur. Mountain yellow-legged frog populations outside 
of these areas are most often located above the timberline, so timber 
harvest activity is not expected to affect the majority of extant 
mountain yellow-legged frog populations. There is a higher potential 
overlap of timber harvest activities with the species in the northern 
and lower elevation portions of the species' ranges where the frogs 
occur in streams and meadows in forested environments; in these areas, 
populations are very small and fragmented (Brown 2013, unpaginated). 
Likewise, at lower elevations of the Sierra Nevada, forest roads and 
logging roads are more common (Brown et al. 2009, p. 71). Habitat 
effects associated with roads are most likely to occur where existing 
roadways occur (for example, see Knapp 1993b, unpaginated). Although 
additional roads may be constructed within the range of the mountain 
yellow-legged frogs, we are not aware of any proposals to build new 
roads at this time.
    In riparian areas, the USFS generally maintains standards and 
guidelines for land management activities, such as timber harvests, 
that are designed to maintain the hydrologic, geomorphic, and ecologic 
processes that directly affect streams, stream processes, and aquatic 
habitats, and which can limit potential effects of such activities 
(Foote et al. 2013, pp. 4, 32). In general, we expect the standards to 
be effective in preventing habitat-related effects to these species. 
Additionally, neither timber harvests nor roads have been implicated as 
important contributors to the decline of this species (Jennings 1996, 
pp. 921-941), although habitat alterations due to these activities may, 
in site-specific, localized cases, have population-level effects to 
mountain yellow-legged frogs. We expect that such cases would be more 
likely at lower elevations or in the more northern portion of the 
species' range where limited extant populations occur in close 
proximity to timber harvest, or where populations occur in drainages 
adjacent to roadways. In the proposed rule, we stated that roads and 
timber harvest likely present minor prevalent threats to the mountain 
yellow-legged frogs factored across the range of the species. We are 
clarifying that language, noting that they may pose important habitat-
related effects to the species in localized areas, but are not likely 
threats across most of the species' ranges.
Fire and Fire Management Activities
    Mountain yellow-legged frogs are generally found at high elevations 
in wilderness areas and National Parks where vegetation is sparse and 
where fire may have historically played a limited role in the 
ecosystem. However, at lower elevations and in the northern portion of 
the range, mountain yellow-legged frogs occur in stream or lake 
environments within areas that are

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forested to various extents. In some areas within the current range of 
the mountain yellow-legged frog, long-term fire suppression has changed 
the forest structure and created conditions that increase fire severity 
and intensity (McKelvey et al. 1996, pp. 1934-1935). Excessive erosion 
and siltation of mountain yellow-legged frog habitats following 
wildfire is a concern where shallow, lower elevation aquatic areas 
occur below forested stands. However, prescribed fire has been used by 
land managers to achieve various silvicultural objectives, including 
fuel load reduction. In some systems, fire is thought to be important 
in maintaining open aquatic and riparian habitats for amphibians 
(Russell et al. 1999, p. 378), although severe and intense wildfires 
may reduce amphibian survival, as the moist and permeable skin of 
amphibians increases their susceptibility to heat and desiccation 
(Russell et al. 1999, p. 374). Amphibians may avoid direct mortality 
from fire by retreating to wet habitats or sheltering in subterranean 
burrows.
    The effects of past fire and fire management activities on 
historical populations of mountain yellow-legged frogs are not known. 
Neither the direct nor indirect effects of prescribed fire or wildfire 
on the mountain yellow-legged frog have been studied. Hossack et al. 
(2012, pp. 221, 226), in a study of the effects of six stand-replacing 
fires on three amphibians that breed in temporary ponds in low-
elevation dense coniferous forests or in high-elevation open, subalpine 
forests in Glacier National Park, found that effects of wildfire on 
amphibians may not be evident for several years post-fire with time-
lagged declines. The decline in populations was presumably due to the 
proximity of high-severity fires to important breeding habitats, which 
resulted in low recruitment of juveniles into the breeding population. 
They cautioned, however, that amphibian responses to fire are context 
specific and cannot be generalized too broadly; they found no change in 
occupancy after wildfire at high elevations where wetlands were in 
sparse forest or open meadows where there was less change in canopy 
cover and insolation after wildfire. Where fire has occurred in the 
steep canyons of southern California where the southern DPS of the 
mountain yellow-legged frog occurs, the character of the habitat has 
been significantly altered, leading to erosive scouring and flooding of 
creeks after surface vegetation is denuded (North 2012, pers. comm.). 
North (2012, pers. comm.) reported that at least one population of the 
federally endangered southern DPS of the mountain yellow-legged frog, 
which occurs in streams, declined substantially after fire on the East 
Fork City Creek (San Bernardino Mountains) in 2003 and, by 2012, was 
approaching extirpation. Although most populations of mountain yellow-
legged frogs are in alpine habitat that differs from the habitat in 
southern California, when they occur in lower-elevation stream 
habitats, they could be similarly affected by large wildfires. When a 
large fire does occur in occupied habitat, mountain yellow-legged frogs 
can be susceptible to both direct mortality (leading to significantly 
reduced population sizes) and indirect effects (habitat alteration and 
reduced breeding habitat). It is possible that fire has caused 
localized extirpations in the past. However, because these species 
generally occupy high-elevation habitat, we have determined that fire 
is not a significant threat to the mountain yellow-legged frog complex 
over much of its current range, although where the species occur at 
lower elevations or in the most northerly portion of their ranges, 
fire-related changes to habitat may have population-level effects to 
the species.
Recreation
    Recreational activities that include hiking, camping, and 
backpacking take place throughout the Sierra Nevada, whereas off-road 
vehicle (ORV) use takes place in areas outside of designated 
wilderness. These activities can have significant negative impacts on 
many plant and animal species and their habitats (U.S. Department of 
Agriculture (USDA) 2001a, pp. 483-493). Extant populations of the 
mountain yellow-legged frog complex are primarily located at high 
elevations in sub-alpine and alpine habitat within designated 
wilderness. High-elevation wilderness areas are ecosystems that are 
subject to intense solar exposure; extremes in temperatures, 
precipitation levels, and wind; short growing seasons; and shallow, 
nutrient-poor soil. Such habitats are typically not resilient to 
disturbance (Schoenherr 1992, p. 167; Cole and Landres 1996, p. 170).
    In easily accessible areas, heavy foot traffic in riparian areas 
can trample vegetation, compact soils, and physically damage stream 
banks (Kondolf et al. 1996, pp. 1014, 1019). Human foot, horse, 
bicycle, or off-highway motor vehicle trails can replace riparian 
habitat with compacted soil (Kondolph et al. 1996, pp. 1014, 1017, 
1019), lower the water table, and cause increased erosion where such 
activities occur. Bahls (1992, p. 190) reported that the recreational 
activity of anglers at high mountain lakes can be locally intense in 
western wilderness areas, with most regions reporting a level of use 
greater than the fragile lakeshore environments can withstand. Heavy 
recreation use has been associated with changes in the basic ecology of 
lakes. In the 1970s, Silverman and Erman (1979) found that the most 
heavily used back-country lakes in their study had less nitrate and 
more iron and aquatic plants than other lakes. These researchers 
suggested that erosion at trails and campsites, improper waste 
disposal, destruction of vegetation, and campsites might cause an 
increase in elements that formerly limited plant growth (Hendee et al. 
1990, pp. 435, 436). The NPS considers hiking and backpacking to be a 
negligible risk for the mountain yellow-legged frogs within the Parks, 
noting that, while hiking and backpacking occur adjacent to many 
populations, evidence indicates that risk to habitat is slight to none. 
For example, monitoring of a high-use trail that allows thousands of 
hikers annually to come into close contact with several populations of 
mountain yellow-legged frogs, whose habitat is immediately adjacent to 
the trail, shows that the populations have grown substantially over the 
last decade (NPS 2013, p. 6). In one location where high hiking levels 
may be having an impact due to access via an adjacent road, Yosemite 
National Park personnel have restricted access (NPS 2013, p. 6). 
Although recreation was noted in 1998 as the fastest growing use of 
National Forests (USFS 2001a, p. 453), to our knowledge, no studies to 
date have identified a correlation between such recreation-related 
impacts to habitat and effects to populations of the mountain yellow-
legged frog complex.
    Because of demand for wilderness recreational experiences and 
concern about wilderness resource conditions, wilderness land 
management now includes standards for wilderness conditions, 
implementing permit systems and group-size limits for visitors and 
packstock, prohibitions on camping and packstock use close to water, 
and other visitor management techniques to reduce impacts to habitat, 
including riparian habitat (Cole 2001, pp. 4-5). These wilderness land 
management techniques are currently being used in National Forest 
Wilderness areas in the Sierra Nevada and in backcountry areas of 
Yosemite, Sequoia, and Kings Canyon National Parks. In the proposed 
rule, we stated that current recreation activities were considered a 
threat of low significance to the species' habitat overall. Based on

[[Page 24273]]

comments from the National Park Service, the USFS, CDFW, and the 
public, we have reevaluated the previous analysis and have revised our 
finding. Therefore, current habitat effects of recreational activities 
are not considered to have population-level effects to mountain yellow-
legged frogs over much of their respective ranges, although there may 
be localized effects especially outside of backcountry areas where use 
levels are not limited, or where motorized use occurs in extant frog 
habitat.
    In summary, based on the best available scientific and commercial 
information, we consider the modification of habitat and curtailment of 
the species' ranges to be a significant and ongoing threat to the 
Sierra Nevada yellow-legged frog and northern DPS of the mountain 
yellow-legged frog. Habitat fragmentation and degradation (loss of 
habitat through competitive exclusion) from stocking and the continued 
presence of introduced trout across the majority of the species' range 
is a threat of high prevalence. This threat is a significant limiting 
factor to persistence and recovery of the species rangewide. Threats of 
low prevalence (threats that may be important limiting factors in some 
areas, but not across a large part of the mountain yellow-legged frog 
complex's range) include dams and water diversions, grazing, packstock 
use, timber harvest and roads, recreation, and fire management 
activities.

Factor B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    No commercial market for mountain yellow-legged frogs exists, nor 
any documented recreational or educational uses for these species. 
Scientific research may cause stress to mountain yellow-legged frogs 
through disturbance, including disruption of the species' behavior, 
handling of individual frogs, and injuries associated with marking and 
tracking individuals. However, this is a relatively minor nuisance and 
not likely a negative impact to the survival and reproduction of 
individuals or the viability of the populations.
    Based on the best available scientific and commercial information, 
we do not consider overutilization for commercial, recreational, 
scientific, or educational purposes to be a threat to the mountain 
yellow-legged frog complex now or in the future.

Factor C. Disease or Predation

Predation
    Researchers have observed predation of mountain yellow-legged frogs 
by the mountain garter snake (Thamnophis elegans elegans), Brewer's 
blackbird (Euphagus cyanocephalus), Clark's nutcracker (Nucifraga 
columbiana), coyote (Canis latrans), and black bear (Ursus americanus) 
(Mullally and Cunningham 1956a, p. 193; Bradford 1991, pp. 176-177; 
Jennings et al. 1992, p. 505; Feldman and Wilkinson 2000, p. 102; 
Vredenburg et al. 2005, p. 565). However, none of these has been 
implicated as a driver of population dynamics, and we expect that such 
predation events do not generally have population-level impacts except 
where so few individuals remain that such predation is associated with 
loss of a population (Bradford 1991, pp 174-177; Jennings 1996, p. 
938).
    The American bullfrog (Lithobates catesbeiana) is native to the 
United States east of the Rocky Mountains, but was introduced to 
California about a century ago. The American bullfrog has become common 
in California in most permanent lakes and ponds below 1,829 m (6,000 
ft) and is implicated in the declines of a number of native frog 
species (Jennings 1996, p. 931). Mountain yellow-legged frogs are 
thought to be particularly vulnerable to bullfrogs and introduced 
crayfish, potentially because the frogs did not evolve with a predator 
(Jennings 1996, p. 939). In addition, research indicates that bullfrogs 
may outcompete other species of amphibians where fish are present 
because bullfrogs are both unpalatable to fish and are naturally 
vulnerable to invertebrate predators such as dragonfly (Anisoptera) 
nymphs, which fish preferentially consume. Bullfrogs may co-occur with 
mountain yellow-legged frogs at lower elevations. On the Plumas 
National Forest, sites created as a result of restoration activities 
have been invaded by bullfrogs (Brown et al. 2009, pp. 48, 49). 
Bullfrogs also occur in the Lake Tahoe Basin (USFS 2000, pp. 530, G-12) 
in the vicinity of Fallen Leaf Lake. Bullfrog predation and competition 
is expected to have population-level effects where bullfrog populations 
occupy the same areas as extant mountain yellow-legged frog 
populations.
    The most prominent predator of mountain yellow-legged frogs is 
introduced trout, whose significance is well-established because it has 
been repeatedly observed that the frogs rarely coexist with fish, and 
it is known that introduced trout can and do prey on all frog life 
stages except for eggs (Grinnell and Storer 1924, p. 664; Mullally and 
Cunningham 1956a, p. 190; Cory 1962a, p. 401; 1963, p. 172; Bradford 
1989, pp. 775-778; Bradford and Gordon 1992, p. 65; Bradford et al. 
1993, pp. 882-888; 1994a, p. 326; Drost and Fellers 1996, p. 422; 
Jennings 1996, p. 940; Knapp 1996, p. 14; Knapp and Matthews 2000, p. 
428; Knapp et al. 2001, p. 401; Vredenburg 2004, p. 7649; Knapp 2013, 
unpaginated). Knapp (1996, pp. 1-44) estimated that 63 percent of lakes 
larger than 1 ha (2.5 ac) in the Sierra Nevada contain one or more 
nonnative trout species, and that greater than 60 percent of streams 
contain nonnative trout. In some areas, trout-occupied waters comprise 
greater than 90 percent of total water body surface area (Knapp and 
Matthews 2000, p. 434).
    The multiple-year tadpole stage of the mountain yellow-legged frog 
requires submersion in the aquatic habitat year-round until 
metamorphosis. Moreover, all life stages are highly aquatic, increasing 
the frog's susceptibility to predation by trout (where they co-occur) 
throughout its lifespan. Overwinter mortality due to predation is 
especially significant because, when water bodies ice over in winter, 
adults and tadpoles move from shallow margins of lakes and ponds into 
deeper unfrozen water where they are more vulnerable to predation; fish 
encounters in such areas increase, while refuge is less available.
    The predation of mountain yellow-legged frogs by fishes observed in 
the early 20th century by Grinnell and Storer and the documented 
population declines of the 1970s (Bradford 1991, pp. 174-177; Bradford 
et al. 1994, pp. 323-327; Stebbins and Cohen 1995, pp. 226-227) were 
not the beginning of the mountain yellow-legged frog's decline, but 
rather the continuation of a long decline that started soon after fish 
introductions to the Sierra Nevada began in the mid-1800s (Knapp and 
Matthews 2000, p. 436). Metapopulation theory (Hanski 1997, pp. 85-86) 
predicts this type of time lag from habitat modification to population 
extinction (Knapp and Matthews 2000, p. 436). In 2004, Vredenburg 
(2004, p. 7647) concluded that introduced trout are effective predators 
on mountain yellow-legged frog tadpoles and suggested that the 
introduction of trout is the most likely reason for the decline of the 
mountain yellow-legged frog complex. This threat due to predation by 
introduced trout is a significant, prevalent (rangewide) risk to 
mountain yellow-legged frogs, and it will persist into the future in 
those locations where fish are present. The effect of introduced 
bullfrogs is expected to be a substantial continuing threat in those 
locations

[[Page 24274]]

where bullfrogs are known to occur presently, but may present more of a 
future threat if bullfrogs expand their elevational range as a result 
of climate change.
Disease
    Over roughly the last 2 decades, pathogens have been associated 
with amphibian population declines, mass die-offs, and even extinctions 
worldwide (Bradford 1991, pp. 174-177; Blaustein et al. 1994b, pp. 251-
254; Alford and Richards 1999, pp. 506; Muths et al. 2003, p. 357; 
Weldon et al. 2004, p. 2100; Rachowicz et al. 2005, p. 1446; Fisher et 
al. 2009, p. 292). One pathogen strongly associated with dramatic 
declines on all continents that harbor amphibians (all continents 
except Antarctica) is the chytrid fungus, Batrachochytrium 
dendrobatidis (Bd) (Rachowicz et al. 2005, p. 1442). This chytrid 
fungus has now been reported in amphibian species worldwide (Fellers et 
al. 2001, p. 945; Rachowicz et al. 2005, p. 1442). Early doubt that 
this particular pathogen was responsible for worldwide die-offs has 
largely been overcome by the weight of evidence documenting the 
appearance, spread, and detrimental effects to affected populations 
(Vredenburg et al. 2010, p. 9689). The correlation of notable recent 
amphibian declines with reports of outbreaks of fatal chytridiomycosis 
(the disease caused by Bd) in montane areas has led to a general 
association between high altitude, cooler climates, and population 
extirpations associated with Bd (Fisher et al. 2009, p. 298).
    Bd affects the mouth parts and epidermal (skin) tissue of tadpoles 
and metamorphosed frogs (Fellers et al. 2001, pp. 950-951). The fungus 
can reproduce asexually, and can generally withstand adverse conditions 
such as freezing or drought (Briggs et al. 2002, p. 38). It also may 
reproduce sexually, leading to thick-walled sporangia that would be 
capable of long-term survival (for distant transport and persistence in 
sites even after all susceptible host animal populations are 
extirpated) (Morgan et al. 2007, p. 13849). Adult frogs can acquire 
this fungus from tadpoles, and it can also be transmitted between 
tadpoles (Rachowicz and Vredenburg 2004, p. 80).
    In California, chytridiomycosis has been detected in many amphibian 
species, including mountain yellow-legged frogs (Briggs et al. 2002, p. 
38; Knapp 2002b, p. 1). The earliest documented case in the mountain 
yellow-legged frog complex was in 1998, at Yosemite National Park 
(Fellers et al. 2001, p. 945); however, more recent literature shows Bd 
occurring in mountain yellow-legged frogs as early as 1975 (Ouellet et 
al. (2005, p. 1436; Vredenberg et al. 2010, p. 9689). It is unclear how 
Bd was originally transmitted to the frogs (Briggs et al. 2002, p. 39). 
Visual examination of 43 tadpole specimens collected between 1955 and 
1976 revealed no evidence of Bd infection, yet 14 of 36 specimens 
preserved between 1993 and 1999 did have abnormalities attributable to 
Bd (Fellers et al. 2001, p. 947). The earliest recorded case of Bd in 
mountain yellow-legged frogs is from 1975, and Bd was also identified 
on two adult Yosemite toads among over 50 dead, dying, or healthy 
Yosemite toads collected during a die-off in 1976 (Green and Kagarise 
Sherman 2001, p. 92), although it was not thought to be the cause of 
the die-off in the population. Given these records, it is possible that 
this pathogen has affected all three amphibian species covered in this 
final rule since at least the mid-1970s. Mountain yellow-legged frogs 
may be especially vulnerable to Bd infections because all life stages 
share the same aquatic habitat nearly year round, facilitating the 
transmission of this fungus among individuals at different life stages 
(Fellers et al. 2001, p. 951).
    During the epidemic phase of chytrid infection into unexposed 
populations, rapid die-offs of adult and subadult lifestages are 
observed (Vredenburg et al. 2010, p. 9691), with metamorphs being 
extremely sensitive to Bd infection (Kilpatrick et al. 2009, p. 113; 
Vredenburg et al. 2010, p. 9691; see also Vredenburg 2013, 
unpaginated). Field and laboratory experiments indicate that Bd 
infection is generally lethal to mountain yellow-legged frogs (Knapp 
2005b; Rachowicz 2005, pers. comm.), and is likely responsible for 
declines in sites that were occupied as recently as 2002, but where 
frogs were absent by 2005 (Knapp 2005b). Rachowicz et al. (2006, p. 
1671) monitored several infected and uninfected populations in Sequoia 
and Kings Canyon National Parks over multiple years, documenting 
dramatic declines and extirpations in only the infected populations. 
Rapid die-offs of mountain yellow-legged frogs from chytridiomycosis 
have been observed in more than 50 water bodies in the southern Sierra 
Nevada in recent years (Briggs et al. 2005, p. 3151). Studies of the 
microscopic structure of tissue and other evidence suggests Bd caused 
many of the recent extinctions in the Sierra National Forest's John 
Muir Wilderness Area and in Kings Canyon National Park, where 41 
percent of the populations went extinct between 1995 and 2002 (Knapp 
2002a, p. 10).
    In several areas where detailed studies of the effects of Bd on the 
mountain yellow-legged frog are ongoing, substantial declines have been 
observed following the course of the disease infection and spread. 
Survey results from 2000 in Yosemite and Sequoia and Kings Canyon 
National Parks indicated that 17 percent of frog populations in 
Yosemite and 27 percent of the mountain yellow-legged frog populations 
sampled across both Sequoia and Kings Canyon National Parks showed 
evidence of Bd infection, although the proportion of infected frogs at 
each site varied greatly and disease incidence varied within each Park 
(Briggs et al. 2002, p. 40) (In the proposed rule, these two figures 
were averaged across all three parks; these numbers reflect the text 
presented in Briggs et al. 2002). In both 2003 and 2004, 19 percent of 
the populations that were sampled in Sequoia and Kings Canyon National 
Parks were infected with Bd (Rachowicz 2005, pp. 2-3). By 2005, 91 
percent of assayed populations in Yosemite National Park showed 
evidence of Bd infection (Knapp 2005b, pp. 1-2), and the number of 
occupied sites in Sequoia and Kings Canyon National Parks had decreased 
by 47 percent from those known to be occupied 3 to 8 years previously 
(Knapp 2005b, pers. comm). Currently, it is believed that all 
populations in Yosemite Park are infected with Bd (Knapp et al. 2011, 
p. 9).
    The effects of Bd on host populations of the mountain yellow-legged 
frog are variable, ranging from extirpation to persistence with a low 
level of infection (Briggs et al. 2002, pp. 40-41). When Bd infection 
first occurs in a population, the most common outcome is epidemic 
spread of the disease and population extirpation (Briggs et al. 2010, 
p. 9699). Die-offs are characterized by rapid onset of high-level Bd 
infections, followed by death due to chytridiomycosis. Although most 
populations that are newly exposed to Bd are driven to extirpation 
following the arrival of Bd, some populations that experience Bd-caused 
population crashes are not extirpated, and some may even recover 
despite ongoing chytridiomycosis (Briggs et al. 2010, pp. 9695-9696). 
However, it is apparent that even at sites exhibiting population 
persistence with Bd, high mortality of metamorphosing frogs persists, 
and this phenomenon may explain the lower abundances observed in such 
populations (Briggs et al. 2010, p. 9699).
    Vredenburg et al. (2010a, pp. 2-4) studied frog populations before, 
during, and after the infection and spread of Bd in three study basins 
constituting 13, 33,

[[Page 24275]]

and 42 frog populations, respectively, then comprising the most intact 
metapopulations remaining for these species throughout their range. The 
spread of Bd averaged 688 m/year (yr) (2,257 ft/yr), reaching all areas 
of the smaller basin in 1 year, and taking 3 to 5 years to completely 
infect the larger basins, progressing like a wave across the landscape. 
The researchers documented die-offs following the spread of Bd, with 
decreased population growth rates evident within the first year of 
infection. Basinwide, metapopulations crashed from 1,680 to 22 
individuals (northern DPS of the mountain yellow-legged frog) in 
Milestone Basin, with 9 of 13 populations extirpated; from 2,193 to 47 
individuals (northern DPS of the mountain yellow-legged frog) in Sixty 
Lakes Basin, with 27 of 33 populations extirpated; and from 5,588 to 
436 individuals (Sierra Nevada yellow-legged frog) in Barrett Lakes 
Basin, with 33 of 42 populations extirpated. The evidence is clear that 
Bd can and does decimate newly infected frog populations. Moreover, 
this rangewide population threat is acting upon a landscape already 
impacted by habitat modification and degradation by introduced fishes 
(see Factor A discussion, above). As a result, remnant populations in 
fishless lakes are now affected by Bd.
    Vredenburg et al. (2010a, p. 3) projected that, at current 
extinction rates, and given the disease dynamics of Bd (infected 
tadpoles succumb to chytridiomycosis at metamorphosis), most if not 
all, extant populations within the recently infected basins they 
studied would go extinct within the next 3 years. Available data (CDFW, 
unpubl. data; Knapp 2005b; Rachowicz 2005, pers. comm.; Rachowicz et 
al. 2006, p. 1671) indicate that Bd is now widespread throughout the 
Sierra Nevada and, although it has not infected all populations at this 
time, it is a serious and substantial threat rangewide to the mountain 
yellow-legged frog complex.
    Other diseases have also been reported as adversely affecting 
amphibian species, and these may be present within the range of the 
mountain yellow-legged frog. Bradford (1991, pp. 174-177) reported an 
outbreak of red-leg disease in Kings Canyon National Park, and 
suggested this was a result of overcrowding within a mountain yellow-
legged frog population. Red-leg disease is caused by the bacterial 
pathogen Aeromonas hydrophila, along with other pathogens. Red-leg 
disease is opportunistic and successfully attacks immune-suppressed 
individuals, and this pathogen appears to be highly contagious, 
affecting the epidermis and digestive tract of otherwise healthy 
amphibians (Shotts 1984, pp. 51-52; Carey 1993, p. 358; Carey and 
Bryant 1995, pp. 14-15). Although it has been correlated with decline 
of a frog population in at least one case, red-leg disease is not 
thought to be a significant contributor to observed frog population 
declines rangewide, based on the available literature.
    Saprolegnia is a globally distributed fungus that commonly attacks 
all life stages of fishes (especially hatchery-reared fishes), and has 
recently been documented to attack and kill egg masses of western toads 
(Bufo boreas) (Blaustein et al. 1994b, p. 252). This pathogen may be 
introduced through fish stocking, or it may already be established in 
the aquatic ecosystem. Fishes and migrating or dispersing amphibians 
may be vectors for this fungus (Blaustein et al. 1994b, p. 253; 
Kiesecker et al. 2001, p. 1068). Saprolegnia has been reported in the 
southern DPS of the mountain yellow-legged frog (North 2012, pers. 
comm.); however, its occurrence within the Sierran range of the 
mountain yellow-legged frog complex and associated influence on 
population dynamics (if any) are unknown.
    Other pathogens of concern for amphibian species include 
ranaviruses (Family Iridoviridae). Mao et al. (1999, pp. 49-50) 
isolated identical iridoviruses from co-occurring populations of the 
threespine stickleback (Gasterosteus aculeatus) and the red-legged frog 
(Rana aurora), indicating that infection by a given virus is not 
limited to a single species, and that iridoviruses can infect animals 
of different taxonomic classes. This suggests that virus-hosting trout 
introduced into mountain yellow-legged frog habitat may be a vector for 
amphibian viruses. However, definitive mechanisms for the transmission 
to the mountain yellow-legged frog remain unknown. No viruses were 
detected in the mountain yellow-legged frogs that Fellers et al. (2001, 
p. 950) analyzed for Bd. In Kings Canyon National Park, Knapp (2002a, 
p. 20) found mountain yellow-legged frogs showing symptoms attributed 
to a ranavirus (Knapp 2013, unpaginated). To date, ranaviruses remain a 
concern for the mountain yellow-legged frog complex, but the available 
information does not indicate they are negatively affecting 
populations.
    It is unknown whether amphibian pathogens in the high Sierra Nevada 
have always coexisted with amphibian populations or if the presence of 
such pathogens is a recent phenomenon. However, it has been suggested 
that the susceptibility of amphibians to pathogens may have recently 
increased in response to anthropogenic environmental disruption (Carey 
1993, pp. 355-360; Blaustein et al. 1994b, p. 253; Carey et al. 1999, 
p. 7). This hypothesis suggests that environmental changes may be 
indirectly responsible for certain amphibian die-offs due to immune 
system suppression of tadpoles or post-metamorphic amphibians (Carey 
1993, p. 358; Blaustein et al. 1994b, p. 253; Carey et al. 1999, pp. 7-
8). Pathogens such as Aeromonas hydrophila, which are present in fresh 
water and in healthy organisms, may become more of a threat, 
potentially causing localized amphibian population die-offs when the 
immune systems of individuals within the host population are suppressed 
(Carey 1993, p. 358; Carey and Bryant 1995, p. 14).
    The contribution of Bd as an environmental stressor and limiting 
factor on mountain yellow-legged frog population dynamics is currently 
extremely high, and it poses a significant current and continuing 
threat to remnant uninfected populations in the southern Sierra Nevada. 
Its effects are most dramatic following the epidemic stage as it 
spreads across newly infected habitats; massive die-off events follow 
the spread of the fungus, and it is likely that survival of mountain 
yellow-legged frogs through the metamorphosis stage is substantially 
reduced even years after the initial epidemic (Rachowicz et al. 2006, 
pp. 1679-1680). The relative impact from other diseases and the 
interaction of other stressors and disease on the immune systems of 
mountain yellow-legged frogs remains poorly documented to date.
    In summary, based on the best available scientific and commercial 
information, we consider the threats of predation and disease to be 
significant, ongoing threats to the Sierra Nevada yellow-legged frog 
and the northern DPS of the mountain yellow-legged frog. These threats 
include predation by bullfrogs and introduced fishes, and amphibian 
pathogens (most specifically, the chytrid fungus), two primary driving 
forces leading to population declines in the mountain yellow-legged 
frog complex. These are highly prevalent threats, and they are 
predominant limiting factors hindering population viability and 
precluding recovery across the ranges of the mountain yellow-legged 
frog complex.

[[Page 24276]]

Factor D. The Inadequacy of Existing Regulatory Mechanisms

    In determining whether the inadequacy of regulatory mechanisms 
constitutes a threat to the mountain yellow-legged frog complex, we 
analyzed the existing Federal and State laws and regulations that may 
address the threats to these species or contain relevant protective 
measures. Regulatory mechanisms are typically nondiscretionary and 
enforceable, and may preclude the need for listing if such mechanisms 
are judged to adequately address the threat(s) to the species such that 
listing is not warranted. Conversely, threats on the landscape are not 
ameliorated where existing regulatory mechanisms are not adequate (or 
when existing mechanisms are not adequately implemented or enforced).
Federal Wilderness Act
    The Wilderness Act of 1964 (16 U.S.C. 1131 et seq.) established a 
National Wilderness Preservation System made up of federally owned 
areas designated by Congress as ``wilderness'' for the purpose of 
preserving and protecting designated areas in their natural condition. 
The Wilderness Act states the use of these areas with limited exception 
are subject to the following restrictions: (1) New or temporary roads 
cannot be built; (2) motor vehicles, motorized equipment, or motorboats 
cannot be used; (3) aircraft cannot land; (4) no form of mechanical 
transport can occur; and (5) no structure or installation may be built. 
In addition, a special provision within the Wilderness Act stipulated 
that, except for valid existing rights, effective January 1, 1984, the 
minerals within designated wilderness areas would be withdrawn from all 
forms of appropriation under mining laws, precluding new mining claims 
within designated wilderness after that date (see Hendee et al. 1990, 
p. 508). A large number of mountain yellow-legged frog locations occur 
within wilderness areas managed by the USFS and NPS and, therefore, are 
afforded protection from direct loss or degradation of habitat by some 
human activities (such as development, commercial timber harvest, road 
construction, and some fire management actions). Livestock grazing and 
fish stocking both occur within designated wilderness areas on lands 
within the National Forest System.
National Forest Management Act of 1976
    Under the National Forest Management Act of 1976, as amended (NFMA) 
(16 U.S.C. 1600 et seq.), the USFS is tasked with managing National 
Forest lands based on multiple-use, sustained-yield principles, and 
with implementing land and resource management plans (LRMP) on each 
National Forest to provide for a diversity of plant and animal 
communities. The purpose of an LRMP is to guide and set standards for 
all natural resource management activities for the life of the plan (10 
to 15 years). NFMA requires the USFS to incorporate standards and 
guidelines into LRMPs. The 1982 planning regulations for implementing 
NFMA (47 FR 43026; September 30, 1982), under which all existing forest 
plans in the Sierra Nevada were prepared until recently, guided 
management of National Forests and required that fish and wildlife 
habitat on National Forest system lands be managed to maintain viable 
populations of existing native and desired nonnative vertebrate species 
in the planning area. A viable population is defined as a population of 
a species that continues to persist over the long term with sufficient 
distribution to be resilient and adaptable to stressors and likely 
future environments. In order to insure that viable populations would 
be maintained, the 1982 planning regulations directed that habitat must 
be provided to support, at least, a minimum number of reproductive 
individuals and that habitat must be well-distributed so that those 
individuals could interact with others in the planning area.
    On April 9, 2012, the USFS published a final rule (77 FR 21162) 
amending 36 CFR 219 to adopt new National Forest System land management 
regulations that guide the development, amendment, and revision of 
LRMPs for all Forest System lands. These revised regulations, which 
became effective on May 9, 2012, replaced the 1982 planning rule. The 
2012 planning rule requires that the USFS maintain viable populations 
of species of conservation concern at the discretion of regional 
foresters. This rule could thereby result in removal of the limited 
protections that are currently in place for mountain yellow-legged 
frogs under the Sierra Nevada Forest Plan Amendment (SNFPA), as 
described below.
Sierra Nevada Forest Plan Amendment
    In 2001, a record of decision was signed by the USFS for the Sierra 
Nevada Forest Plan Amendment (SNFPA), based on the final environmental 
impact statement for the SNFPA effort and prepared under the 1982 NFMA 
planning regulations. The Record of Decision amends the USFS Pacific 
Southwest Regional Guide, the Intermountain Regional Guide, and the 
LRMPs for National Forests in the Sierra Nevada and Modoc Plateau. This 
document affects land management on all National Forests throughout the 
range of the mountain yellow-legged frog complex. The SNFPA addresses 
and gives management direction on issues pertaining to old forest 
ecosystems; aquatic, riparian, and meadow ecosystems; fire and fuels; 
noxious weeds; and lower west-side hardwood ecosystems of the Sierra 
Nevada. In January 2004, the USFS amended the SNFPA, based on the final 
supplemental environmental impact statement, following a review of fire 
and fuels treatments, compatibility with the National Fire Plan, 
compatibility with the Herger-Feinstein Quincy Library Group Forest 
Recovery Pilot Project, and effects of the SNFPA on grazing, 
recreation, and local communities (USDA 2004, pp. 26-30).
    Relevant to the mountain yellow-legged frog complex, the Record of 
Decision for SNFPA aims to protect and restore aquatic, riparian, and 
meadow ecosystems, and to provide for the viability of associated 
native species through implementation of an aquatic management 
strategy. The aquatic management strategy is a general framework with 
broad policy direction. Implementation of this strategy was intended to 
take place at the landscape and project levels. Nine goals are 
associated with the aquatic management strategy:
    (1) The maintenance and restoration of water quality to comply with 
the Clean Water Act (CWA) and the Safe Drinking Water Act;
    (2) The maintenance and restoration of habitat to support viable 
populations of native and desired nonnative riparian-dependent species, 
and to reduce negative impacts of nonnative species on native 
populations;
    (3) The maintenance and restoration of species diversity in 
riparian areas, wetlands, and meadows to provide desired habitats and 
ecological functions;
    (4) The maintenance and restoration of the distribution and 
function of biotic communities and biological diversity in special 
aquatic habitats (such as springs, seeps, vernal pools, fens, bogs, and 
marshes);
    (5) The maintenance and restoration of spatial and temporal 
connectivity for aquatic and riparian species within and between 
watersheds to provide physically, chemically, and biologically 
unobstructed movement for their survival, migration, and reproduction;
    (6) The maintenance and restoration of hydrologic connectivity 
between

[[Page 24277]]

floodplains, channels, and water tables to distribute flood flows and 
to sustain diverse habitats;
    (7) The maintenance and restoration of watershed conditions as 
measured by favorable infiltration characteristics of soils and diverse 
vegetation cover to absorb and filter precipitation, and to sustain 
favorable conditions of streamflows;
    (8) The maintenance and restoration of instream flows sufficient to 
sustain desired conditions of riparian, aquatic, wetland, and meadow 
habitats, and to keep sediment regimes within the natural range of 
variability; and
    (9) The maintenance and restoration of the physical structure and 
condition of streambanks and shorelines to minimize erosion and sustain 
desired habitat diversity.
    If these goals of the aquatic management strategy are pursued and 
met, threats to the mountain yellow-legged frog complex resulting from 
habitat alterations could be reduced. However, the aquatic management 
strategy is a generalized approach that does not contain specific 
implementation timeframes or objectives, and it does not provide direct 
protections for the mountain yellow-legged frog. Additionally, as 
described above, the April 9, 2012, final rule (77 FR 21162) that 
amended 36 CFR 219 to adopt new National Forest System land management 
planning regulations could result in removal of the limited protections 
that are currently in place for mountain yellow-legged frogs under the 
SNFPA.
National Park Service Organic Act
    The statute establishing the National Park Service, commonly 
referred to as the National Park Service Organic Act (39 Stat. 535; 16 
U.S.C. 1, 2, 3, and 4), states that the NPS will administer areas under 
their jurisdiction ``. . . by such means and measures as conform to the 
fundamental purpose of said parks, monuments, and reservations, which 
purpose is to conserve the scenery and the natural and historic objects 
and the wildlife therein and to provide for the enjoyment of the same 
in such manner and by such means as will leave them unimpaired for the 
enjoyment of future generations.'' Park managers must take action to 
ensure that ongoing NPS activities do not cause impairment. In cases of 
doubt as to the impact of activities on park natural resource, the Park 
Service is to decide in favor of protecting the natural resources. 
Sequoia, Kings Canyon, and Yosemite National Parks began phasing out 
fish stocking by the State in 1969 and terminated this practice 
entirely in 1991 (Knapp 1996, p. 9).
Federal Power Act
    The Federal Power Act of 1920, as amended (FPA) (16 U.S.C. 791 et 
seq.) was enacted to regulate non-federal hydroelectric projects to 
support the development of rivers for energy generation and other 
beneficial uses. The FPA provides for cooperation between the Federal 
Energy Regulatory Commission (Commission) and other Federal agencies in 
licensing and relicensing power projects. The FPA mandates that each 
license includes conditions to protect, mitigate, and enhance fish and 
wildlife and their habitat affected by the project. However, the FPA 
also requires that the Commission give equal consideration to competing 
priorities, such as power and development, energy conservation, 
protection of recreational opportunities, and preservation of other 
aspects of environmental quality. Further, the FPA does not mandate 
protections of habitat or enhancements for fish and wildlife species, 
but provides a mechanism for resource agency recommendations that are 
incorporated into a license at the discretion of the Commission. 
Additionally, the FPA provides for the issuance of a license for the 
duration of up to 50 years, and the FPA contains no provision for 
modification of the project for the benefit of species, such as 
mountain yellow-legged frogs, before a current license expires.
    Although most reservoirs and water diversions are located at lower 
elevations than those at which extant mountain yellow-legged frog 
populations occur, numerous extant populations occur within watersheds 
that feed into developed and managed aquatic systems (such as 
reservoirs and water diversions) operated for the purpose of power 
generation and regulated by the FPA and may be considered during 
project relicensing.
State
California Endangered Species Act
    This section has been updated from the information presented in the 
proposed rule, and discussion of CDFW's current fish-stocking practices 
has been moved to the Factor A discussion of Habitat Modification Due 
to Introduction of Trout to Historically Fishless Areas.
    The California Endangered Species Act (CESA) (California Fish and 
Game Code, section 2080 et seq.) prohibits the unauthorized take of 
State-listed endangered or threatened species. CESA requires State 
agencies to consult with CDFW on activities that may affect a State-
listed species, and mitigate for any adverse impacts to the species or 
its habitat. Pursuant to CESA, it is unlawful to import or export, 
take, possess, purchase, or sell any species or part or product of any 
species listed as endangered or threatened. The State may authorize 
permits for scientific, educational, or management purposes, and allow 
take that is incidental to otherwise lawful activities. On April 1, 
2013, the Sierra Nevada yellow-legged frog was listed as a threatened 
species and the mountain yellow-legged frog (Statewide) was listed as 
an endangered species under CESA (CDFW 2013, p. 1).
    While the listing of the Sierra Nevada yellow-legged frog and the 
mountain yellow-legged frog under CESA provide some protections to 
these species, as State regulation prohibits the unauthorized take of 
State-listed species, the definition of take under CESA does not 
include habitat modification or degradation. Additionally, the majority 
of the lands occupied by these species are federally managed lands, so 
there is limited jurisdiction in which to regulate land management 
activities that may affect these species.
    Overall, existing Federal and State laws and regulatory mechanisms 
currently offer some level of protection for the mountain yellow-legged 
frog complex. While not the intent of the Wilderness Act, the mountain 
yellow-legged frogs receive ancillary protection from the Wilderness 
Act due to its prohibitions on development, road construction, and 
timber harvest, and associated standards and guidelines that limit 
visitor and packstock group sizes and use. With the exception of the 
National Park Service Organic Act, the existing regulatory mechanisms 
have not been effective in reducing threats to mountain yellow-legged 
frogs and their habitat from fish stocking and the continuing presence 
of nonnative fish. Nor have these mechanisms been effective in 
protecting populations from infection by diseases, although Forest 
Service standards and guidelines have likely reduced threats associated 
with grazing, timber harvest, and recreation use. Although State 
regulations under CESA provide some protection against take of the 
mountain yellow-legged frogs, the definition of take under CESA does 
not include habitat modification or degradation.

Factor E. Other Natural or Manmade Factors Affecting Its Continued 
Existence

    The mountain yellow-legged frog is sensitive to environmental 
change or

[[Page 24278]]

degradation because it has an aquatic and terrestrial life history and 
highly permeable skin that increases exposure of individuals to 
substances in the water, air, and terrestrial substrates (Blaustein and 
Wake 1990, p. 203; Bradford and Gordon 1992. p. 9; Blaustein and Wake 
1995, p. 52; Stebbins and Cohen 1995, pp. 227-228). Several natural or 
anthropogenically influenced changes, including contaminant deposition, 
acid precipitation, increases in ambient ultraviolet radiation, and 
climate change, have been implicated as contributing to amphibian 
declines (Corn 1994, pp. 62-63; Alford and Richards 1999, pp. 2-7). 
There are also documented incidences of direct mortality of, or the 
potential for direct disturbance to, individuals from some activities 
already discussed; in severe instances, these actions may have 
population-level consequences. As presented in the proposed rule (78 FR 
24472, April 25, 2013), contaminants, acid precipitation, and ambient 
ultraviolet radiation are not known to pose a threat (current or 
historical) to the mountain yellow-legged frog and, therefore, are not 
discussed further. Please refer to the proposed listing rule for the 
Sierra Nevada yellow-legged frog, the northern DPS of the mountain 
yellow-legged frog, and the Yosemite toad (78 FR 24472, April 25, 2013) 
for a detailed discussion of contaminants, acid precipitation, and 
ambient ultraviolet radiation.
Climate Change
    Our analysis under the Act includes consideration of ongoing and 
projected changes in climate. The terms ``climate'' and ``climate 
change'' are defined by the Intergovernmental Panel on Climate Change 
(IPCC). The term ``climate'' refers to the mean and variability of 
different types of weather conditions over time, with 30 years being a 
typical period for such measurements, although shorter or longer 
periods also may be used (IPCC 2007a, p. 1450; IPCC 2013a, Annex III). 
The term ``climate change'' thus refers to a change in the mean or 
variability of one or more measures of climate (for example, 
temperature or precipitation) that persists for an extended period, 
typically decades or longer, whether the change is due to natural 
variability, human activity, or both (IPCC 2007a, p. 1450; IPCC 2013a, 
Annex III). A recent compilation of climate change and its effects is 
available from reports of the Intergovernmental Panel on Climate Change 
(IPCC) (IPCC 2013b, entire).
    Global climate projections are informative and, in some cases, the 
only or the best scientific information available for us to use. 
However, projected changes in climate and related impacts can vary 
substantially across and within different regions of the world (for 
example, IPCC 2007a, pp. 8-12). Therefore, we use downscaled 
projections when they are available and have been developed through 
appropriate scientific procedures, because such projections provide 
higher resolution information that is more relevant to the spatial 
scales used for analyses of a given species (see Glick et al. 2011, pp. 
58-61, for a discussion of downscaling). With regard to our analysis 
for the Sierra Nevada of California (and western United States), 
downscaled projections are available, yet even downscaled climate 
models contain some uncertainty.
    Variability exists in outputs from different climate models, and 
uncertainty regarding future GHG emissions is also a factor in modeling 
(PRBO 2011, p. 3). A general pattern that holds for many predictive 
models indicates northern areas of the United States will become 
wetter, and southern areas (particularly the Southwest) will become 
drier. These models also predict that extreme events, such as heavier 
storms, heat waves, and regional droughts, may become more frequent 
(Glick et al. 2011, p. 7). Moreover, it is generally expected that the 
duration and intensity of droughts will increase in the future (Glick 
et al. 2011, p. 45; PRBO 2011, p. 21).
    The last century has included some of the most variable climate 
reversals documented, at both the annual and near-decadal scales, 
including a high frequency of El Ni[ntilde]o (associated with more 
severe winters) and La Ni[ntilde]a (associated with milder winters) 
events (reflecting drought periods of 5 to 8 years alternating with wet 
periods) (USDA 2001b, p. 33). Scientists have confirmed a longer 
duration climate cycle termed the Pacific Decadal Oscillation (PDO), 
which operates on cycles between 2 to 3 decades, and generally is 
characterized by warm and dry (PDO positive) followed by cool and wet 
cycles (PDO negative) (Mantua et al. 1997, pp. 1069-1079; Zhang et al. 
1997, pp. 1004-1018). Snowpack is seen to follow this pattern--heavier 
in the PDO negative phase in California, and lighter in the positive 
phase (Mantua et al. 1997, p. 14; Cayan et al. 1998, p. 3148; McCabe 
and Dettinger 2002, p. 24).
    For the Sierra Nevada ecoregion, climate models predict that mean 
annual temperatures will increase by 1.8 to 2.4 [deg]C (3.2 to 
4.3[emsp14][deg]F) by 2070, including warmer winters with earlier 
spring snowmelt and higher summer temperatures. However, it is expected 
that temperature and climate variability will vary based on topographic 
diversity (for example, wind intensity will determine east versus west 
slope variability) (PRBO 2011, p. 18). Mean annual rainfall is 
projected to decrease from 9.2-33.9 cm (3.6-13.3 in) by 2070; however, 
projections have high uncertainty and one study predicts the opposite 
effect (PRBO 2011, p. 18). Given the varied outputs from differing 
modeling assumptions, and the influence of complex topography on 
microclimate patterns, it is difficult to draw general conclusions 
about the effects of climate change on precipitation patterns in the 
Sierra Nevada (PRBO 2011, p. 18). Snowpack is, by all projections, 
going to decrease dramatically (following the temperature rise and more 
precipitation falling as rain) (Kadir et al. 2013, pp. 76-80). Higher 
winter streamflows, earlier runoff, and reduced spring and summer 
streamflows are projected, with increasing severity in the southern 
Sierra Nevada (PRBO 2011, pp. 20-22); (Kadir et al. 2013, pp. 71-75).
    Snow-dominated elevations of 2,000-2,800 m (6,560-9,190 ft) will be 
the most sensitive to temperature increases, and a warming of 5 [deg]C 
(9[emsp14][deg]F) is projected to shift center timing (the measure when 
half a stream's annual flow has passed a given point in time) to more 
than 45 days earlier in the year as compared to the 1961-1990 baseline 
(PRBO 2011, p. 23). Lakes, ponds, and other standing waters fed by 
snowmelt or streams are likely to dry out or be more ephemeral during 
the non-winter months (Lacan et al. 2008, pp. 216-222; PRBO 2011, p. 
24). This pattern could influence ground water transport, and springs 
may be similarly depleted, leading to lower lake levels.
    Blaustein et al. (2010, pp. 285-300) provide an exhaustive review 
of potential direct and indirect and habitat-related effects of climate 
change to amphibian species, with documentation of effects in a number 
of species where such effects have been studied. Altitudinal range 
shifts with changes in climate have been reported in some regions. They 
note that temperature can influence the concentration of dissolved 
oxygen in aquatic habitats, with warmer water generally having lower 
concentrations of dissolved oxygen, and that water balance heavily 
influences amphibian physiology and behavior. They predict that 
projected changes in temperature and precipitation are likely to 
increase habitat loss and alteration for those species living in 
sensitive habitats, such

[[Page 24279]]

as ephemeral ponds and alpine habitats (Blaustein et al. 2010, pp. 285-
287).
    Because environmental cues such as temperature and precipitation 
are clearly linked to onset of reproduction in many species, climate 
change will likely affect the timing of reproduction in many species, 
potentially with different sexes responding differently to climate 
change. For example, males of two newt species (Triturus spp.) showed a 
greater degree of change in arrival date at breeding ponds (Blaustein 
et al. 2010, p. 288). Lower concentrations of dissolved oxygen in 
aquatic habitats may negatively affect developing embryos and larvae, 
in part because increases in temperature increase the oxygen 
consumption rate in amphibians. Reduced oxygen concentrations have also 
been shown to result in accelerated hatching in ranid frogs, but at a 
smaller size, while larval development and behavior may also be 
affected and may be mediated by larval density and food availability 
(Blaustein et al. 2010, pp. 288-289).
    Increased temperatures can reduce time to metamorphosis, which can 
increase chances of survival where ponds dry, but also result in 
metamorphosis at a smaller size, suggesting a likely trade-off between 
development and growth, which may be exacerbated by climate change and 
have fitness consequences for adults (Blaustein et al. 2010, pp. 289-
290). Changes in terrestrial habitat, such as changed soil moisture and 
vegetation, can also directly affect adult and juvenile amphibians, 
especially those adapted to moist forest floors and cool, highly 
oxygenated water that characterizes montane regions. Climate change may 
also interact with other stressors that may be acting on a particular 
species, such as disease and contaminants (Blaustein et al. 2010, pp. 
290-299).
    A recent paper (Kadir et al. 2013, entire) provides specific 
information on the effects of climate change in the Sierra Nevada. The 
report found that glaciers in the Sierra Nevada have decreased in area 
over the past century, and glacier shrinkage results in earlier peak 
water runoff and drier summer conditions. Another result from the 
report is that the lower edge of the conifer-dominated forests in the 
Sierra Nevada has been retreating upslope over the past 60 years. 
Regarding wildfire, since 1950, annual acreage burned in wildfires 
statewide has been increasing in California, and in the western United 
States, large wildfires have become more frequent, increasing in tandem 
with rising spring and summer temperatures. Finally, the report found 
that today's subalpine forests in the Sierra Nevada are much denser--
that is, comprise more small-diameter trees--than they were over 70 
years ago. During this time period, warmer temperatures, earlier 
snowmelt, and more rain than snow occurred in this region. Many of 
these changes in the Sierra Nevada of California due to climate are 
likely to influence mountain yellow-legged frogs because both mountain 
yellow-legged frog species in the Sierra Nevada are highly vulnerable 
to climate change because changing hydrology and habitat in the Sierra 
Nevada will likely have impacts on remaining populations (Viers et al. 
2013, pp. 55, 56).
    Vulnerability of species to climate change is a function of three 
factors: Sensitivity of a species or its habitat to climate change, 
exposure of individuals to such physical changes in the environment, 
and their capacity to adapt to those changes (Glick et al. 2011, pp. 
19-22). Critical sensitivity elements broadly applicable across 
organizational levels (from species through habitats to ecosystems) are 
associated with physical variables, such as hydrology (timing, 
magnitude, and volume of waterflows), fire regime (frequency, extent, 
and severity of fires), and wind (Glick et al. 2011, pp. 39-40). 
Species-level sensitivities generally include physiological factors, 
such as changes in temperature, moisture, or pH as they influence 
individuals; these also include dependence on sensitive habitats, 
ecological linkages to other species, and changes in phenology (timing 
of key life-history events) (Glick et al. 2011, pp. 40-41).
    Exposure to environmental stressors renders species vulnerable to 
climate change impacts, either through direct mechanisms (for example, 
physical temperature extremes or changes in solar radiation), or 
indirectly through impacts upon habitat (hydrology; fire regime; or 
abundance and distribution of prey, competitors, or predator species). 
A species' capacity to adapt to climate change is increased by 
behavioral plasticity (the ability to modify behavior to mitigate the 
impacts of the stressor), dispersal ability (the ability to relocate to 
meet shifting conditions), and evolutionary potential (for example, 
shorter lived species with multiple generations have more capacity to 
adapt through evolution) (Glick et al. 2011, pp. 48-49).
    The International Union for Conservation of Nature describes five 
categories of life-history traits that render species more vulnerable 
to climate change (Foden et al. 2008 in Glick et al. 2011, p. 33): (1) 
Specialized habitat or microhabitat requirements, (2) narrow 
environmental tolerances or thresholds that are likely to be exceeded 
under climate change, (3) dependence on specific triggers or cues that 
are likely to be disrupted (for example, rainfall or temperature cues 
for breeding, migration, or hibernation), (4) dependence on 
interactions between species that are likely to be disrupted, and (5) 
inability or poor ability to disperse quickly or to colonize more 
suitable range. We apply these criteria in this final rule to assess 
the vulnerability of mountain yellow-legged frogs to climate change.
    At high elevations, where most extant populations occur, mountain 
yellow-legged frogs depend on high mountain lakes where both adult and 
larval frogs overwinter under ice for up to 9 months of the year. 
Overwintering under ice poses physiological problems for the frogs, 
most notably the depletion of oxygen in the water during the winter 
(Bradford 1983, p. 1171). Bradford (1983, pp. 1174-1182) has found, 
based on lab and field results, that tadpoles are more resistant to low 
dissolved oxygen levels than adult frogs; after two drought years that 
were followed by a severe winter, all frogs in 21 of 26 study lakes 
were lost (with the exception of one 2.1-m (6.9-ft) deep lake that 
contained only one individual), while tadpoles survived in all but one 
of the shallowest lakes. Losses were apparently due to oxygen depletion 
in a year when there was exceptional precipitation, ice depths that 
were thicker than usual, and lake thawing was 5 to 6 weeks later than 
the previous year. The survival of adults in substantial numbers was 
significantly correlated with lake depth and confined to lakes deeper 
than 4 m (13.1 ft).
    Bradford (1983, pp. 1174-1179) found that mean oxygen concentration 
in lakes was directly related to maximum lake depth, with dissolved 
oxygen levels declining throughout the winter. He also found that a 
thickened ice layer on a lake causes the lake to become effectively 
more shallow, leading to an increased rate of oxygen depletion 
(Bradford 1983, p. 1178). Studies of winterkill of fish due to oxygen 
depletion also show that oxygen depletion is inversely related to lake 
depth and occurs most rapidly in shallow lakes relative to deeper lakes 
(See review in Bradford 1983, p. 1179). Bradford (1983, p. 1179) 
considered the possibility that winterkill of the frogs was due to 
freezing, but dismissed the potential because some of the lakes where 
winterkill occurred were deeper than the probable maximum ice depth in 
that year. Because the deeper lakes

[[Page 24280]]

that once supported frog populations now harbor introduced trout 
populations and are generally no longer available as refugia for frogs, 
the shallower lakes where frogs currently occur may be more vulnerable 
to weather extremes in a climate with increased variability, including 
drought years and years with exceptional severe cold winters. Such 
episodic stressors may have been infrequent in the past, but appear to 
be increasing, and they are important to long-lived species with small 
populations.
    In summer, reduced snowpack and enhanced evapotranspiration 
following higher temperatures can dry out ponds that otherwise would 
have sustained rearing tadpoles (Lacan et al. 2008, p. 220), and may 
also reduce fecundity (egg production) (Lacan et al. 2008, p. 222). 
Lacan et al. (2008, p. 211) observed that most frog breeding occurred 
in the smaller, fishless lakes of Kings Canyon National Park that are 
shallow and prone to summer drying. Thus, climate change will likely 
reduce available breeding habitat for mountain yellow-legged frogs and 
lead to greater frequency of stranding and death of tadpoles as such 
lakes dry out earlier in the year (Corn 2005, p. 64; Lacan et al. 2008, 
p. 222).
    Earlier snowmelt is expected to cue breeding earlier in the year. 
The advance of this primary signal for breeding phenology in montane 
and boreal habitats (Corn 2005, p. 61) may have both positive and 
negative effects. Additional time for growth and development may render 
larger individuals more fit to overwinter; however, earlier breeding 
may also expose young tadpoles (or eggs) to killing frosts in more 
variable conditions of early spring (Corn 2005, p. 60).
    Whether mountain yellow-legged frogs depend on other species that 
may be affected either positively or negatively by climate change is 
unclear. Climate change may alter invertebrate communities (PRBO 2011 
p. 24). In one study, an experimental increase in stream temperature 
was shown to decrease density and biomass of invertebrates (Hogg and 
Williams 1996, p. 401). Thus, climate change might have a negative 
impact on the mountain yellow-legged frog prey base.
    Indirect effects from climate change may lead to greater risk to 
mountain yellow-legged frog population persistence. For example, fire 
intensity and magnitude are projected to increase (PRBO 2011, pp. 24-
25), and, therefore, the contribution and influence of this stressor 
upon frog habitat and populations will increase. Climate change may 
alter lake productivity through changes in water chemistry, the extent 
and timing of mixing, and nutrient inputs from increased fires, all of 
which may influence community dynamics and composition (Melack et al. 
1997, p. 971; Parker et al. 2008, p. 12927). These changes may not all 
be negative; for example, water chemistry and nutrient inputs, along 
with warmer summer temperatures, could increase net primary 
productivity in high mountain lakes to enhance frog food sources, 
although changes in net primary productivity may also negatively affect 
invertebrate prey species endemic to oligotrophic lakes (low nutrient, 
low productivity).
    Carey (1993, p. 359) has suggested that, where environmental 
changes cause sufficient stress to cause immunological suppression, 
cold body temperatures that montane amphibians experience over winter 
could play a synergistic role in reducing further immunological 
responses to disease. Thus, such conditions might make mountain yellow-
legged frogs more susceptible to disease. Additionally, Blaustein et 
al. (2001, p. 1808) have suggested that climate change could also 
affect the distribution of pathogens and their vectors, exposing 
amphibians to new pathogens. Climate change (warming) has been 
hypothesized as a driver for the range shift of Bd (Pounds et al. 2006, 
p. 161; Bosch et al. 2007, p. 253). However, other work has indicated 
that survival and transmission of Bd is more likely facilitated by 
cooler and wetter conditions (Corn 2005, p. 63). Fisher et al. (2009, 
p. 299) present a review of information available to date and evaluate 
the competing hypotheses regarding Bd dynamics, and they present some 
cases that suggest a changing climate can change the host-pathogen 
dynamic to a more virulent state.
    The key risk factor for climate change impacts on mountain yellow-
legged frogs is likely the combined effect of reduced water levels in 
high mountain lakes and ponds and the relative inability of individuals 
to disperse and colonize across longer distances in order to occupy 
more favorable habitat conditions (if they exist). Although such 
adaptive range shifts have been observed in some plant and animal 
species, they have not been reported in amphibians. The changes 
observed in amphibians to date have been more associated with changes 
in timing of breeding (phenology) (Corn 2005, p. 60). This limited 
adaptive capacity for mountain yellow-legged frogs is a function of 
high site fidelity and the extensive habitat fragmentation due to the 
introduction of fishes in many of the more productive and persistent 
high mountain lake habitats and streams that constitute critical 
dispersal corridors throughout much of the frogs' range (see Factor C 
discussion above).
    An increase in the frequency, intensity, and duration of droughts 
caused by climate change may have compounding effects on populations of 
mountain yellow-legged frogs already in decline. In situations where 
other stressors (such as introduced fish) have resulted in the 
isolation of mountain yellow-legged frogs in marginal habitats, 
localized mountain yellow-legged frog population crashes or 
extirpations resulting from drought may exacerbate their isolation and 
preclude natural recolonization (Bradford et al. 1993, p. 887; Drost 
and Fellers 1996, p. 424; Lacan et al. 2008, p. 222). Viers et al. 
(2013, pp. 55, 56) have used a variety of risk metrics to determine 
that both mountain yellow-legged frog species in the Sierra Nevada are 
highly vulnerable to climate change, and that changing hydrology and 
habitat in the Sierra Nevada will likely have drastic impacts on 
remaining populations. Climate change represents a substantial future 
threat to the persistence of mountain yellow-legged frog populations.
Direct and Indirect Mortality
    Other risk factors include direct and indirect mortality as an 
unintentional consequence of activities within mountain yellow-legged 
frog habitat. Mortality due to trampling by grazing livestock has been 
noted in a limited number of situations, with expected mortality risk 
thought to be greatest if livestock concentrate in prime breeding 
habitat early in the season when adults are breeding and egg masses are 
present (Brown et al. 2009, p. 59). Brown et al. (2009, p. 59) note 
that standards in the SNFPA are intended to mitigate this risk. 
Recreational uses also have the potential to result in direct or 
indirect mortality of mountain yellow-legged frog individuals at all 
life stages. The Forest Service has identified activities, including 
recreational activities that occur in the frogs' breeding sites as 
being risk factors for the frogs, while noting that recreation use is a 
risk that USFS management can change (USDA 2001a, pp. 213-214). Brown 
et al. (2009, pp. 65-66) note that tadpoles and juveniles, in 
particular, may be injured or killed by trampling, crushing, etc., by 
hikers, bikers, anglers, pets, packstock, or off-highway vehicles, 
although the number of documented situations appears limited. 
Recreational activities, such as hiking and camping, are associated 
primarily with physical site

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alteration (changes to soil and vegetation conditions), and such 
effects are found to be highly localized. For example, estimates in a 
heavily-used portion of the Eagle Cap Wilderness in Oregon indicated 
that no more than 2 percent of the area had been altered by 
recreational use (Cole and Landres 1996, p. 170). However, where 
impacts of recreational use are highly localized, species impacts due 
to trampling have been identified, especially for rare plant species 
(Cole and Landres 1996, p. 170). Fire management activities (i.e. fuels 
reduction and prescribed fire) lead to some direct mortality and have 
the potential to disrupt behavior. Please refer to the proposed listing 
rule for the Sierra Nevada yellow-legged frog and the northern DPS of 
the mountain yellow-legged frog under the Act (16 U.S.C. 1531 et seq.) 
for information about effects of fire retardants on mountain yellow-
legged frogs. Roads create the potential for direct mortality of 
amphibians by vehicle strikes (deMaynadier and Hunter 2000, p. 56) and 
the possible introduction of contaminants into new areas; however, most 
extant populations are not located near roads. Collectively, direct 
mortality risks to mountain yellow-legged frogs are likely of sporadic 
significance. They may be important on occasion on a site-specific 
basis, but are likely of low prevalence across the range of the 
species.
Small Population Size
    In many localities, remaining populations for both the Sierra 
Nevada yellow-legged frog and the mountain yellow-legged frog are small 
(CDFW, unpubl. data). Brown et al. (2011, p. 24) reported that about 90 
percent of watersheds have fewer than 10 adults and 80 percent have 
fewer than 10 subadults and 100 tadpoles. Remnant populations in the 
northern portion of the range for the Sierra Nevada yellow-legged frog 
(from Lake Tahoe north) and the southern portion of the populations of 
the northern DPS of the mountain yellow-legged frog (south of Kings 
Canyon National Park) currently also exhibit very low abundances (CDFW, 
unpubl. data).
    Compared to large populations, small populations are more 
vulnerable to extirpation from environmental, demographic, and genetic 
stochasticity (random natural occurrences), and unforeseen (natural or 
unnatural) catastrophes (Shaffer 1981, p. 131).
    Environmental stochasticity refers to annual variation in birth and 
death rates in response to weather, disease, competition, predation, or 
other factors external to the population (Shaffer 1981, p. 131). Small 
populations may be less able to respond to natural environmental 
changes (K[eacute]ry et al. 2000, p. 28), such as a prolonged drought 
or even a significant natural predation event. Periods of prolonged 
drought are more likely to have a significant effect on mountain 
yellow-legged frogs because drought conditions occur on a landscape 
scale and all life stages are dependent on habitat with suitable 
perennial water. Demographic stochasticity is random variability in 
survival or reproduction among individuals within a population (Shaffer 
1981, p. 131) and could increase the risk of extirpation of the smaller 
remaining populations. Genetic stochasticity results from changes in 
gene frequencies due to the founder effect (loss of genetic variation 
that occurs when a new population is established by a small number of 
individuals) (Reiger 1968, p. 163); random fixation (the complete loss 
of one of two alleles in a population, the other allele reaching a 
frequency of 100 percent) (Reiger 1968, p. 371); or inbreeding 
depression (loss of fitness or vigor due to mating among relatives) 
(Soul[eacute] 1980, p. 96). Additionally, small populations generally 
have an increased chance of genetic drift (random changes in gene 
frequencies from generation to generation that can lead to a loss of 
variation) and inbreeding (Ellstrand and Elam 1993, p. 225).
    Allee effects (Dennis 1989, pp. 481-538) occur when a population 
loses its positive stock-recruitment relationship (when population is 
in decline). In a declining population, an extinction threshold or 
``Allee threshold'' (Berec et al. 2006, pp. 185-191) may be crossed, 
where adults in the population either cease to breed or the population 
becomes so compromised that breeding does not contribute to population 
growth. Allee effects typically fall into three broad categories 
(Courchamp et al. 1999, pp. 405-410): lack of facilitation (including 
low mate detection and loss of breeding cues), demographic 
stochasticity, and loss of heterozygosity (a measure of genetic 
variability). Environmental stochasticity amplifies Allee effects 
(Dennis 1989, pp. 481-538; Dennis 2002, pp, 389-401). The Allee effects 
of demographic stochasticity and loss of heterozygosity are likely as 
mountain yellow-legged frog populations continue to diminish.
    The extinction risk for a species represented by few small 
populations is magnified when those populations are isolated from one 
another. This is especially true for species whose populations normally 
function in a metapopulation structure, whereby dispersal or migration 
of individuals to new or formerly occupied areas is necessary. 
Connectivity between these populations is essential to increase the 
number of reproductively active individuals in a population; mitigate 
the genetic, demographic, and environmental effects of small population 
size; and recolonize extirpated areas. Additionally, fewer populations 
by itself increases the risk of extinction.
    The combination of low numbers with the other extant stressors of 
disease, fish persistence, and potential for climate extremes could 
have adverse consequences for the mountain yellow-legged frog complex 
as populations approach the Allee threshold. Small population size is 
currently a significant threat to most populations of mountain yellow-
legged frogs across the range of the species.
Cumulative Impacts of Extant Threats
    Stressors may act additively or synergistically. An additive effect 
would mean that an accumulation of otherwise low threat factors acting 
in combination may collectively result in individual losses that are 
meaningful at the population level. A synergistic effect is one where 
the interaction of one or more stressors together leads to effects 
greater than the sum of those individual factors combined. Further, the 
cumulative effect of multiple added stressors can erode population 
viability over successive generations and act as a chronic strain on 
the viability of a species, resulting in a progressive loss of 
populations over time. Such interactive effects from compounded 
stressors thereby act synergistically to curtail the viability of frog 
metapopulations and increase the risks of extinction.
    It is difficult to predict the precise impact of the cumulative 
threat represented by the relatively novel Bd epidemic across a 
landscape already fragmented by fish stocking. The singular threat of 
the Bd epidemic wave in the uninfected populations of the mountain 
yellow-legged frog complex in the southern Sierra Nevada could 
extirpate those populations as the pathogen spreads. A compounding 
effect of disease-caused extirpation is that recolonization may never 
occur because streams connecting extirpated sites to extant populations 
now contain introduced fishes, which act as barriers to frog movement 
within metapopulations. This situation isolates the remaining 
populations of mountain yellow-legged frogs from one another (Bradford 
1991, p. 176; Bradford et al. 1993, p. 887). It is logical to presume 
that the small, fragmented populations left in the recent wake of Bd 
spread

[[Page 24282]]

through the majority of the range of the Sierra Nevada yellow-legged 
frog may experience further extirpations as surviving adults eventually 
die, and recruitment into the breeding pool from the Bd-positive 
subadult class is significantly reduced. These impacts may be 
exacerbated by the present and growing threat of climate change, 
although this effect may take years to materialize.
    In summary, based on the best available scientific and commercial 
information, we consider other natural and manmade factors to be 
substantial ongoing threats to the Sierra Nevada yellow-legged frog and 
the northern DPS of the mountain yellow-legged frog. These include 
high, prevalent risk associated with climate change and small 
population sizes, and the associated risk from the additive or 
synergistic effects of these two stressors interacting with other 
acknowledged threats, including habitat fragmentation and degradation 
(see Factor A), disease and predation (see Factor C), or other threats 
currently present but with low relative contribution in isolation.

Determination for the Sierra Nevada Yellow-Legged Frog

    We have carefully assessed the best scientific and commercial 
information available regarding the past, present, and future threats 
to the Sierra Nevada yellow-legged frog. The best available information 
for the Sierra Nevada yellow-legged frog shows that the geographic 
extent of the species' range has declined, with local population-level 
changes first noticed in the early 1900s (Grinnell and Storer 1924, p. 
664) although they were still abundant at many sites in the Sierra 
Nevada until the 1960s (Zweifel 1955, pp. 237-238). Population losses 
continued between the 1960s and 1990s (Bradford et al. 1993, p. 883) 
and have continued in recent decades. Now fewer, increasingly isolated 
populations maintain viable recruitment (entry of post-metamorphic 
frogs into the breeding population). Coupled with the observation that 
remnant populations are also numerically smaller (in some cases 
consisting of few individuals), this reduction in occupancy and 
population density across the landscape suggests significant losses in 
metapopulation viability and high attendant risk to the overall 
population of the species. The impacts of the declines on population 
resilience are two-fold: (1) The geographic extent and number of 
populations are reduced across the landscape, resulting in fewer and 
more isolated populations (the species is less able to withstand 
population stressors and unfavorable conditions exist for genetic 
exchange or dispersal to unoccupied areas (habitat fragmentation)); and 
(2) species abundance (in any given population) is reduced, making 
local extirpations much more likely (decreased population viability). 
Knapp et al. (2007b, pp. 1-2) estimated a 10 percent decline per year 
in the number of remaining mountain yellow-legged frog populations and 
argued for the listing of the species as endangered based on this 
observed rate of population loss.
    Threats that face the Sierra Nevada mountain yellow-legged frog, 
discussed above under Factors A, C, D, and E, increase the risk of the 
species' extinction, given the isolation of remaining populations. The 
best available science indicates that the introduction of fishes to the 
frog's habitat to support recreational angling is one of the primary 
causes of the decline of the Sierra Nevada yellow-legged frog and poses 
a current and continuing threat to the species (Factor A). Water bodies 
throughout this range have been intensively stocked with introduced 
fish (principally trout). It is a threat of significant influence, and 
although fewer lakes are stocked currently than were stocked prior to 
2001, it remains prevalent today because fish persist in many high-
elevation habitats even where stocking has ceased. Further, the 
introduction of fish has generally restricted remaining Sierra Nevada 
yellow-legged frog populations to more marginal habitats, thereby 
increasing the likelihood of localized extinctions. Recolonization in 
these situations is difficult for a highly aquatic species with high 
site fidelity and unfavorable dispersal conditions.
    Historical livestock grazing activities may also have modified the 
habitat of the Sierra Nevada yellow-legged frog throughout much of its 
range (Factor A). Grazing pressure has been significantly reduced from 
historical levels, but is expected to have legacy effects on mountain 
yellow-legged frog habitat where prior downcutting and headcutting of 
streams have resulted in reduced water tables and would benefit from 
restoration. Current grazing that complies with forest standards and 
guidelines is not expected to cause habitat-related effects to the 
species in almost all cases, but in limited cases may continue to 
contribute to some localized degradation and loss of suitable habitat. 
The habitat-related effects of recreation, packstock grazing, dams and 
water diversions, roads, timber harvests, and fire management 
activities on the Sierra Nevada yellow-legged frog (Factor A) may have 
contributed to historical losses when protections and use limits that 
are currently afforded by USFS and NPS standards and guidelines did not 
exist. Currently, Federal land management agencies with jurisdiction 
within the current range of the Sierra Nevada yellow-legged frog have 
developed management standards and guidelines that limit habitat damage 
due to these activities, although in localized areas habitat-related 
changes may continue to affect individual populations.
    Competitive exclusion and predation by fish have eliminated or 
reduced mountain yellow-legged frog populations in stocked habitats, 
and left remnant populations isolated, while bullfrogs are expected to 
have negative effects where they occur (Factor C). It is important to 
recognize that, throughout the vast majority of its range, Sierra 
Nevada yellow-legged frogs did not co-evolve with any species of fish, 
as they predominantly occur in water bodies above natural fish 
barriers. Consequently, the species has not evolved defenses against 
fish predation.
    Sierra Nevada yellow-legged frogs are vulnerable to multiple 
pathogens (see Factor C) whose effects range from low levels of 
infection within persistent populations to disease-induced extirpation 
of entire populations. The Bd epidemic has caused extirpations of 
Sierra Nevada yellow-legged frog populations throughout its range and 
caused associated significant declines in numbers of individuals. 
Though Bd was only recently discovered to affect the Sierra Nevada 
yellow-legged frog, it appears to infect populations at much higher 
rates than other pathogens. The imminence of this risk to populations 
in currently uninfected habitats is immediate and the potential effects 
severe. The already-realized effects to the survival of sensitive 
amphibian life stages in Bd-positive areas are well-documented. 
Although some populations survive the initial Bd wave, survival rates 
of metamorphs and population viability are markedly reduced relative to 
historical (pre-Bd) norms.
    These threats described above are likely to be exacerbated by 
widespread changes associated with climate change and by current small 
population sizes in many locations (see Factor E), while instances of 
direct and indirect mortality are expected to have population-level 
effects only in relatively uncommon, localized situations. On a 
rangewide basis, the existing regulatory mechanisms (Factor D) have not 
been effective in protecting populations from declines due to fish 
stocking and continuing presence of fish

[[Page 24283]]

and to disease, although standards and guidelines developed by the USFS 
and the NPS have largely limited threats due to livestock and packstock 
grazing, recreation, and timber use.
    The main and interactive effects of these various risk factors have 
acted to reduce Sierra Nevada yellow-legged frog populations to small 
fractions of their historical habitat and reduce population abundances 
significantly throughout most of its current range. Remaining areas 
that have yet to be impacted by Bd are at immediate and severe risk.
    Given the life history of this species, dispersal, recolonization, 
and genetic exchange are largely precluded by the fragmentation of 
habitat common throughout its current range as a result of fish 
introductions. Frogs that may disperse are susceptible to hostile 
conditions in many circumstances. In essence, Sierra Nevada yellow-
legged frogs have been marginalized by historical fish introductions. 
Populations have recently been decimated by Bd, and the cumulative 
effect of other stressors (such as anticipated reduction of required 
aquatic breeding habitats with climate change and more extreme weather) 
upon a fragmented landscape make adaptation and recovery a highly 
improbable scenario without active intervention. The cumulative risk 
from these stressors to the persistence of the Sierra Nevada yellow-
legged frog throughout its range is significant.
    The Act defines an endangered species as any species that is ``in 
danger of extinction throughout all or a significant portion of its 
range'' and a threatened species as any species ``that is likely to 
become endangered throughout all or a significant portion of its range 
within the foreseeable future.'' We find that the Sierra Nevada yellow-
legged frog is presently in danger of extinction throughout its entire 
range, based on the immediacy, severity, and scope of the threats 
described above. Specifically, these include habitat degradation and 
fragmentation under Factor A, predation and disease under Factor C, and 
climate change and the interaction of these various stressors 
cumulatively impacting small remnant populations under Factor E. There 
has been a rangewide reduction in abundance and geographic extent of 
surviving populations of the Sierra Nevada yellow-legged frog following 
decades of fish stocking, habitat fragmentation, and, most recently, a 
disease epidemic. Surviving populations are smaller and more isolated, 
and recruitment in Bd-positive populations is much reduced relative to 
historical norms. This combination of population stressors makes 
species persistence precarious throughout the current range in the 
Sierra Nevada.
    We have carefully assessed the best scientific and commercial 
information available regarding the past, present, and future threats 
to the species, and have determined that the Sierra Nevada yellow-
legged frog meets the definition of endangered under the Act, rather 
than threatened. This is because significant threats are occurring now 
and will occur in the future, at a high magnitude and across the 
species' entire range, making the species in danger of extinction at 
the present time. The rate of population decline remains high in the 
wake of Bd epidemics, and the remaining Sierra Nevada yellow-legged 
frog populations are at high, imminent risk. Population declines are 
expected to continue as maturing tadpoles succumb to Bd infection, and 
fragmented populations at very low abundances will face significant 
obstacles to recovery. Therefore, on the basis of the best available 
scientific and commercial information, and the threats posed to these 
species under the listing factors above, we are listing the Sierra 
Nevada yellow-legged frog as endangered in accordance with sections 
3(6) and 4(a)(1) of the Act.
    Under the Act and our implementing regulations, a species may 
warrant listing if it is endangered or threatened throughout all or a 
significant portion of its range. The Sierra Nevada yellow-legged frog 
is restricted in its range, and the threats occur throughout the 
remaining occupied habitat. Therefore, we assessed the status of this 
species throughout its entire range. The threats to the survival of the 
species occur throughout the species' range and are not restricted to 
any particular significant portion of that range. Accordingly, our 
assessment and final determination applies to the species throughout 
its entire range.

Final Determination for the Northern DPS of the Mountain Yellow-Legged 
Frog

    We have carefully assessed the best scientific and commercial 
information available regarding the past, present, and future threats 
to the northern DPS of the mountain yellow-legged frog. The best 
available information for the northern DPS of the mountain yellow-
legged frog shows that the geographic extent of the species' range has 
declined, with local population-level changes first noticed in the 
early 1900s (Grinnell and Storer 1924, p. 664), although they were 
still abundant at many sites in the Sierra Nevada until the 1960s 
(Zweifel 1955, pp. 237-238). Population losses continued between the 
1960s and 1990s (Bradford et al. 1993, p. 883) and have continued in 
recent decades. Now fewer, increasingly isolated populations maintain 
viable recruitment (entry of post-metamorphic frogs into the breeding 
population). Coupled with the observation that remnant populations are 
also numerically smaller (in some cases consisting of a few 
individuals), this reduction in occupancy and population density across 
the landscape suggests significant losses in metapopulation viability 
and high attendant risk to the overall population of the species. The 
impacts of the declines on population resilience are two-fold: (1) The 
geographic extent and number of populations are reduced across the 
landscape, resulting in fewer and more isolated populations (the 
species is less able to withstand population stressors and unfavorable 
conditions exist for genetic exchange or dispersal to unoccupied areas 
(habitat fragmentation)); and (2) species abundance (in any given 
population) is reduced, making local extirpations much more likely 
(decreased population viability). Knapp et al. (2007b, pp. 1-2) 
estimated a 10 percent decline per year in the number of remaining 
mountain yellow-legged frog populations and argued for the listing of 
the species as endangered based on this observed rate of population 
loss.
    Threats that face the northern DPS of the mountain yellow-legged 
frog, discussed above under Factors A, C, D, and E, increase the risk 
of the species' extinction, given the isolation of remaining 
populations. The best available science indicates that the introduction 
of fishes to the frog's habitat to support recreational angling is one 
of the primary causes of the decline of the northern DPS of the 
mountain yellow-legged frog and poses a current and continuing threat 
to the species (Factor A). Water bodies throughout this range have been 
intensively stocked with introduced fish (principally trout). It is a 
threat of significant influence, and although fewer lakes are stocked 
currently than were stocked prior to 2001, it remains prevalent today 
because fish persist in many high-elevation habitats even where 
stocking has ceased. Recolonization in these situations is difficult 
for a highly aquatic species with high site fidelity and unfavorable 
dispersal conditions. Climate change is likely to exacerbate these 
other threats and further threaten population resilience.
    Historical livestock grazing activities may also have modified the 
habitat of the northern DPS of the mountain

[[Page 24284]]

yellow-legged frog throughout much of its range (Factor A). Grazing 
pressure has been significantly reduced from historical levels, but is 
expected to have legacy effects to mountain yellow-legged frog habitat 
where prior downcutting and headcutting of streams have resulted in 
reduced water tables that still need restoration to correct. Current 
grazing that complies with forest standards and guidelines is not 
expected to cause habitat-related effects to the species in almost all 
cases, but in limited cases may continue to contribute to some 
localized degradation and loss of suitable habitat. The habitat-related 
effects of recreation, packstock grazing, dams and water diversions, 
roads, timber harvests, and fire management activities on the northern 
DPS of the mountain yellow-legged frog (Factor A) may have contributed 
to historical losses when protections and use limits that are currently 
afforded by USFS and NPS standards and guidelines did not exist. 
Currently, Federal agencies with jurisdiction within the current range 
of the northern DPS of the mountain yellow-legged frog have developed 
management standards and guidelines that limit habitat damage due to 
these activities, although in localized areas habitat-related changes 
may continue to affect individual populations.
    Competitive exclusion and predation by fish have eliminated or 
reduced mountain yellow-legged frog populations in stocked habitats, 
and left remnant populations isolated, while bullfrogs are expected to 
have negative effects where they occur (Factor C). It is important to 
recognize that throughout the vast majority of its range, the northern 
DPS of the mountain yellow-legged frogs did not co-evolve with any 
species of fish, as this species predominantly occurs in water bodies 
above natural fish barriers. Consequently, the species has not evolved 
defenses against fish predation.
    Mountain yellow-legged frogs are vulnerable to multiple pathogens 
(see Factor C) whose effects range from low levels of infection within 
persistent populations to disease-induced extirpation of entire 
populations. The Bd epidemic has caused rangewide extirpations of 
populations of the northern DPS of the mountain yellow-legged frog and 
associated significant declines in numbers of individuals. Though Bd 
was only recently discovered to affect the mountain yellow-legged frog, 
it appears to infect populations at much higher rates than other 
pathogens. The imminence of this risk to currently uninfected habitats 
is immediate, and the potential effects severe. The already-realized 
effects to the survival of sensitive amphibian life stages in Bd-
positive areas are well-documented. Although some populations survive 
the initial Bd wave, survival rates of metamorphs and population 
viability are markedly reduced relative to historical (pre-Bd) norms.
    These threats are likely to be exacerbated by widespread changes 
associated with climate change and by current small population sizes in 
many locations (see Factor E), while instances of direct and indirect 
mortality are expected to have population-level effects only in 
relatively uncommon, localized situations. Rangewide, the existing 
regulatory mechanisms (Factor D) have not been effective in protecting 
populations from declines due to fish stocking and continuing presence 
of fish and to disease, although standards and guidelines developed by 
the USFS and the NPS have largely limited threats due to livestock and 
packstock grazing, recreation, and timber use.
    The main and interactive effects of these various risk factors have 
acted to reduce the northern DPS of the mountain yellow-legged frog to 
a small fraction of its historical range and reduce population 
abundances significantly throughout most of its current range. 
Populations of this species in remaining areas in the southern Sierra 
Nevada that have yet to be impacted by Bd are at immediate and severe 
risk.
    Given the life history of this species, dispersal, recolonization, 
and genetic exchange are largely precluded by the fragmentation of 
habitat common throughout its current range as a result of fish 
introductions. Frogs that may disperse are susceptible to hostile 
conditions in many circumstances. In essence, mountain yellow-legged 
frogs have been marginalized by historical fish introductions. 
Populations have recently been decimated by Bd, and the accumulation of 
other stressors (such as anticipated reduction of required aquatic 
breeding habitats with climate change and more extreme weather) upon a 
fragmented landscape make adaptation and recovery a highly improbable 
scenario without active intervention. The cumulative risk from these 
stressors to the persistence of the mountain yellow-legged frog 
throughout its range is significant.
    The Act defines an endangered species as any species that is ``in 
danger of extinction throughout all or a significant portion of its 
range'' and a threatened species as any species ``that is likely to 
become endangered throughout all or a significant portion of its range 
within the foreseeable future.'' We find that the northern DPS of the 
mountain yellow-legged frog is presently in danger of extinction 
throughout its entire range, based on the immediacy, severity, and 
scope of the threats described above. Specifically, these include 
habitat degradation and fragmentation under Factor A, predation and 
disease under Factor C, and climate change and the interaction of these 
various stressors cumulatively impacting small remnant populations 
under Factor E. There has been a rangewide reduction in abundance and 
geographic extent of surviving populations of the northern DPS of the 
mountain yellow-legged frog following decades of fish stocking, habitat 
fragmentation, and, most recently, a disease epidemic. Surviving 
populations are smaller and more isolated, and recruitment in Bd-
positive populations is much reduced relative to historical norms. This 
combination of population stressors makes species persistence 
precarious throughout the current range in the Sierra Nevada.
    We have carefully assessed the best scientific and commercial 
information available regarding the past, present, and future threats 
to the species, and have determined that the northern DPS of the 
mountain yellow-legged frog, meets the definition of endangered under 
the Act, rather than threatened. This is because significant threats 
are occurring now and will occur in the future, at a high magnitude and 
across the DPS' entire range, making the northern DPS of the mountain 
yellow-legged frog in danger of extinction at the present time. The 
rate of population decline remains high in the wake of Bd epidemics, 
and northern DPS of the mountain yellow-legged frog areas are at high, 
imminent risk. The recent rates of decline for these populations are 
even higher than declines in the populations of the Sierra Nevada 
yellow-legged frog, and as Bd infects remaining core areas, population 
viability will be significantly reduced, and extirpations or 
significant population declines are expected. Population declines are 
expected to continue as maturing tadpoles succumb to Bd infection, and 
fragmented populations at very low abundances will face significant 
obstacles to recovery. Therefore, on the basis of the best available 
scientific and commercial information, and the threats posed to these 
species discussed under the listing factors above, we are listing the 
northern DPS of the mountain yellow-legged frog as endangered in 
accordance with sections 3(6) and 4(a)(1) of the Act.
    Under the Act and our implementing regulations, a species may 
warrant

[[Page 24285]]

listing if it is endangered or threatened throughout all or a 
significant portion of its range. The northern DPS of the mountain 
yellow-legged frog addressed in this final listing rule is restricted 
in its range, and the threats occur throughout the remaining occupied 
habitat. Therefore, we assessed the status of this DPS throughout its 
entire range in the Sierra Nevada of California. The threats to the 
survival of this DPS occur throughout its range in the southern Sierra 
Nevada and are not restricted to any particular significant portion of 
that range. Accordingly, our assessment and final determination applies 
to the DPS throughout its entire range.

Summary of Biological Status and Threats Affecting the Yosemite Toad

Background

Taxonomy and Species Description

    Please refer to the proposed listing rule for the Yosemite toad 
under the Act (16 U.S.C. 1531 et seq.) for additional species 
information, including detailed information on taxonomy. In this 
section of the final rule, it is our intent to discuss only those 
topics directly relevant to the listing of the Yosemite toad (Anaxyrus 
canorus) as threatened.

Habitat and Life History

    Breeding habitat--Yosemite toads are associated with wet meadows 
due to their breeding ecology. Camp (1916, pp. 59-62) found Yosemite 
toads in wet meadow habitats and at lake shores located among lodgepole 
(Pinus contorta) at the lower elevations to whitebark (P. albicaulis) 
pines at the higher elevations. Mullally (1953, pp. 182-183) found 
adult toads common on the margins of high-elevation lakes, streams, and 
pools wherever the meadow vegetation was thicker or more luxuriant than 
usual or where there were patches of low willows (Salix spp.). Liang 
(2010, p. 81) observed Yosemite toads most frequently associated with 
(in order of preference): wet meadows, alpine-dwarf scrub, red fir 
(Abies magnifica), water, lodgepole pine, and subalpine conifer 
habitats.
    Yosemite toads were found as often at large as at small sites 
(Liang 2010, p. 19), suggesting that this species is capable of 
successfully utilizing small habitat patches. Liang also found that 
population persistence was greater at higher elevations, with an 
affinity for relatively flat sites with a southwesterly aspect (Liang 
2010, p. 20; see also Mullally 1953, p. 182). These areas receive 
higher solar radiation and are capable of sustaining hydric (wet), 
seasonally ponded, and mesic (moist) breeding and rearing habitat. The 
Yosemite toad is more common in areas with less variation in mean 
annual temperature, or more temperate sites with less climate variation 
(Liang 2010, pp. 21-22).
    Adults are thought to be long-lived, and this factor allows for 
persistence in variable conditions and more marginal habitats where 
only periodic good years allow high reproductive success (USFS et al. 
2009, p. 27). Females have been documented to reach 15 years of age, 
and males as many as 12 years (Kagarise Sherman and Morton 1993, p. 
195); however, the average longevity of the Yosemite toad in the wild 
is not known. Jennings and Hayes (1994, p. 52) indicated that females 
begin breeding at ages 4 to 6 years, while males begin breeding at ages 
3 to 5 years.
    Adults appear to have high site-fidelity; Liang (2010, pp. 99, 100) 
found that the majority of individuals identified in multiple years 
were located in the same meadow pools, although individuals will move 
between breeding areas (Liang 2010, p. 52; Liang 2013, p. 561). 
Breeding habitat includes shallow, warm-water areas in wet meadows, 
such as shallow ponds and flooded vegetation, ponds, lake edges, and 
slow-flowing streams (Karlstrom 1962, pp. 8-12; Brown 2013, 
unpaginated). Tadpoles have also been observed in shallow areas of 
lakes (Mullally 1953, pp. 182-183).
    Adult Yosemite toads are most often observed near water, but only 
occasionally in water (Mullally and Cunningham 1956b, pp. 57-67). Moist 
upland areas such as seeps and springheads are important summer 
nonbreeding habitats for adult toads (Martin 2002, pp. 1-3). The 
majority of their life is spent in the upland habitats proximate to 
their breeding meadows. They use rodent burrows for overwintering and 
probably for temporary refuge during the summer (Jennings and Hayes 
1994, pp. 50-53), and they spend most of their time in burrows (Liang 
2010, p. 95). They also use spaces under surface objects, including 
logs and rocks, for temporary refuge (Stebbins 1951, pp. 245-248; 
Karlstrom 1962, pp. 9-10). Males and females also likely inhabit 
different areas and habitats when not breeding, and females tend to 
move farther from breeding ponds than males (USFS et al. 2009, p. 28).
    Males exit burrows first, and spend more time in breeding pools 
than females, who do not breed every year (Kagarise Sherman and Morton, 
1993, p. 196). Data suggest that higher lipid storage in females, which 
enhances overwinter survival, also precludes the energetic expense of 
breeding every year (Morton 1981, p. 237). The Yosemite toad is a 
prolific breeder, laying many eggs immediately at snowmelt. This is 
accomplished in a short period of time, coinciding with water levels in 
meadow habitats and ephemeral pools they use for breeding. Female toads 
lay approximately 700-2,000 eggs in two strings (one from each ovary) 
(USFS et al. 2009, p. 21). Females may split their egg clutches within 
the same pool, or even between different pools, and may lay eggs 
communally with other toads (USFS et al. 2009, p. 22).
    Eggs hatch within 3-15 days, depending on ambient water 
temperatures (Kagarise Sherman 1980, pp. 46-47; Jennings and Hayes 
1994, p. 52). Tadpoles typically metamorphose around 40-50 days after 
fertilization, and are not known to overwinter (Jennings and Hayes 
1994. p. 52). Tadpoles are black in color, tend to congregate together 
(Brattstrom 1962, pp. 38-46) in warm shallow waters during the day 
(Cunningham 1963, pp. 60-61), and then retreat to deeper waters at 
night (Mullaly 1953, p. 182). Rearing through metamorphosis takes 
approximately 5-7 weeks after eggs are laid (USFS et al. 2009, p. 25). 
Toads need shallow, warm surface water that persists through the period 
during which they metamorphose; shorter hydroperiods in that habitat 
can reduce reproductive success (Brown 2013, unpaginated).
    Reproductive success is dependent on the persistence of tadpole 
rearing sites and conditions for breeding, egg deposition, hatching, 
and rearing to metamorphosis (USFS et al. 2009, p. 23). Given their 
association with shallow, ephemeral habitats, Yosemite toads are 
susceptible to droughts and weather extremes. Abiotic factors leading 
to mortality (such as freezing or desiccation) appear to be more 
significant during the early life stages of toads, while biotic factors 
(such as predation) are probably more prominent factors during later 
life stages (USFS et al. 2009, p. 30). However, since adult toads lead 
a much more inconspicuous lifestyle, direct observation of adult 
mortality is difficult and it is usually not possible to determine 
causes of adult mortality.
    Yosemite toads can move farther than 1 km (0.63 mi) from their 
breeding meadows (average movement is 275 m (902 ft)), and they utilize 
terrestrial environments extensively (Liang 2010, p. 85). The average 
distance traveled by females is twice as far as males, and home ranges 
for females are 1.5 times greater than those for males (Liang 2010, p. 
94). Movement into the upland

[[Page 24286]]

terrestrial environment following breeding does not follow a 
predictable path, and toads tend to traverse longer distances at night, 
perhaps to minimize evaporative water loss (Liang 2010, p. 98). Martin 
(2008, p. 123) tracked adult toads during the active season and found 
that on average toads traveled a total linear distance of 494 m (1,620 
ft) within the season, with minimum travel distance of 78 m (256 ft) 
and maximum of 1.76 km (1.09 mi).

Historical Range and Distribution

    The known historical range of the Yosemite toad in the Sierra 
Nevada extended from the Blue Lakes region north of Ebbetts Pass 
(Alpine County) to south of the Evolution Lake area (Fresno County) 
(Karlstrom 1962, p. 3; Stebbins 1985, p. 72; see also Knapp 2013, 
unpaginated; Brown 2013, unpaginated). Yosemite toad habitat 
historically spanned elevations from 1,460 to 3,630 m (4,790 to 11,910 
ft) (Stebbins 1985, p. 72; Stephens 2001, p. 12).

Current Range and Distribution

    The current range of the Yosemite toad, at least in terms of 
overall geographic extent, remains largely similar to the historical 
range defined above (USFS et al. 2009, p. 41). However, within that 
range, toad habitats have been degraded and may be decreasing in area 
as a result of conifer encroachment and historical livestock grazing 
(see Factor A below). The vast majority of the Yosemite toad's range is 
within federally managed land. Figure 2, Estimated Range of Yosemite 
Toad, displays a range map for the species.
BILLING CODE 4310-55-P
[GRAPHIC] [TIFF OMITTED] TR29AP14.002


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BILLING CODE 4310-55-C

Population Estimates and Status

    Baseline data on the number and size of historical Yosemite toad 
populations are limited, and historic records are largely based on 
accounts from field notes, or pieced together through museum 
collections, thereby providing limited information on historical 
populations. Systematic survey information across the range of the 
species on National Forest System Lands largely follows the designation 
of the Yosemite toad as a candidate species under the Act. In addition, 
surveys for the Yosemite toad have been conducted within Yosemite, 
Kings Canyon, and Sequoia National Parks (Knapp 2013, unpaginated). 
From these recent inventories, Yosemite toads have been found at 469 
localities collectively on six National Forests (USFS et al. 2009, p. 
40; see also Brown and Olsen 2013, pp. 675-691), at 179 breeding sites 
that were surveyed between 1992 and 2010 in Yosemite National Park 
(Berlow et al. 2013, p. 3), and detected at 18 localities in Kings 
Canyon National Park (NPS 2011, geospatial data). Although we did not 
cite to the information from the National Parks in the proposed rule, 
we had the geospatial occupancy data that is currently included in 
Berlow et al. 2013, and we utilized that data in our analysis for the 
proposed listing (see comments 6 and 7 below, and their respective 
responses). The number of localities identified in these surveys 
reflects more occupied sites than were known before such extensive 
surveys were conducted, and indicates that the species is still 
widespread throughout its range. These inventories were typically 
conducted to determine toad presence or absence (they were not 
censuses), and do not explicitly compare historic sites to recent 
surveys. Moreover, single-visit surveys of toads are unreliable as 
indices of abundance because timing is so critical to the presence of 
detectable life stages and not all potential breeding habitats within 
the range of the species were surveyed (USFS et al. 2009, p. 41; Liang 
2010, p. 10; Brown and Olsen 2013, p. 685). Given these considerations, 
conclusions about population trends, abundance, or extirpation rates 
are not possible from these datasets overall.
    One pair of studies allows us to compare current distribution with 
historic distributions and indicates that large reductions have 
occurred. In 1915 and 1919, Grinnell and Storer (1924, pp. 657-660) 
surveyed for vertebrates at 40 sites along a 143-km (89-mi) west-to-
east transect across the Sierra Nevada, through Yosemite National Park, 
and found Yosemite toads at 13 of those sites. In 1992, Drost and 
Fellers (1996, pp. 414-425) conducted more thorough surveys, 
specifically for amphibians, at 38 of the Grinnell and Storer sites 
plus additional nearby sites. Drost and Fellers (1996, pp. 418) found 
that Yosemite toads were absent from 6 of 13 sites where they had been 
found in the original Grinnell and Storer (1924) survey. Moreover, at 
the sites where they were present, Yosemite toads most often occurred 
in very low numbers relative to general abundance reported in the 
historical record (Grinnell and Storer 1924, pp. 657-660). Therefore, 
by the early 1990s, the species was either undetectable or had declined 
in numbers at 9 of 13 (69 percent) of the Grinnell and Storer sites 
(Drost and Fellers 1996, p. 418).
    Another study comparing historic and current occurrences also found 
a large decline in Yosemite toad distribution. In 1990, David Martin 
surveyed 75 sites throughout the range of the Yosemite toad for which 
there were historical records of the species' presence. This study 
found that 47 percent of historically occupied sites showed no evidence 
of any life stage of the species (Stebbins and Cohen 1995, pp. 213-
215). This result suggests a range-wide decline to about one half of 
historical sites, based on occupancy alone.
    A third study comparing historic and recent surveys indicates 
declines in Yosemite toad distribution. Jennings and Hayes (1994, pp. 
50-53) reviewed the current status of Yosemite toads using museum 
records of historic and recent sightings, published data, and 
unpublished data and field notes from biologists working with the 
species. They estimated a loss of over 50 percent of former Yosemite 
toad locations throughout the range of the species (based on 144 
specific sites).
    The only long-term, site-specific population study for Yosemite 
toads documented a dramatic decline over 2 decades of monitoring. 
Kagarise Sherman and Morton (1993, pp. 186-198) studied Yosemite toads 
at Tioga Pass Meadow (Mono County, California) from 1971 through 1991 
(with the most intensive monitoring through 1982). They documented a 
decline in the average number of males entering the breeding pools from 
258 to 28 during the mid-1970s through 1982. During the same time 
period, the number of females varied between 45 and 100, but there was 
no apparent trend in number observed. During the 1980s, it appeared 
that males continued to decline, females also declined, and breeding 
activity became sporadic. By 1991, they found only one male and two egg 
masses. Sadinski (2004, p. 40) revisited the survey locations annually 
from 1995 and 2001 and found a maximum of two males and two egg masses, 
suggesting the toads in Tioga Meadows had not recovered from their 
decline. In the study of Yosemite toads at nearby Dana Meadows, 
Sadinski (2004, pp. 39-42) documented few adults within the habitats 
surveyed, finding substantial mortality in embryos that he associated 
with effects of ice, water mold, and flatworms. Sadinski (2004, pp. 38-
42) also found high larval mortality when breeding sites dried before 
larvae could reach metamorphosis. Sadinski (2004) stated that the 
proximity of the Kagarise Sherman and Morton (1993) study sites at 
Tioga Meadows and his sites in Dana Meadows practically ensured that 
animals from both sites were part of the same metapopulation. Sadinski 
surmised that perhaps much of that metapopulation experienced events at 
breeding sites similar to those that Kagarise Sherman and Morton (1993) 
observed (Sadinski 2004, pp. 39-40). He further opined that, if each of 
his substantial sites had previously supported hundreds of breeding 
adults in the 1970s, the overall population of Yosemite toads had 
declined dramatically throughout the area since that time.
    Kagarise Sherman and Morton (1993, pp. 186-198) also conducted 
occasional surveys of six other populations in the eastern Sierra 
Nevada. Five of these populations showed long-term declines that were 
evident beginning between 1978 through 1981, while the sixth population 
held relatively steady until the final survey in 1990, at which time it 
dropped. In 1991, E.L. Karlstrom revisited the site where he had 
studied a breeding population of Yosemite toads from 1954 to 1958 (just 
south of Tioga Pass Meadow within Yosemite National Park), and found no 
evidence of toads or signs of breeding (Kagarise Sherman and Morton 
1993, p. 190).
    The most reliable information about Yosemite toad population status 
and trends is the USFS SNAMPH. This study, conducted on National Forest 
System Lands, is designed to provide statistical comparisons across 5-
year monitoring cycles with 134 watersheds (Brown et al. 2011, pp. 3-
4). This approach allows researchers to assess trends for the entire 
range of the toad, rather than at limited survey sites (C. Brown 2012, 
pers. comm., see also Brown and Olsen 2013). The results of this 
assessment indicate the species has declined from historical levels, 
with Yosemite toads occurring in approximately 13 percent of watersheds 
where they existed prior to 1990. This

[[Page 24288]]

study also found that breeding was occurring in approximately 84 
percent of the watersheds that were occupied in the period 1990-2001, 
suggesting that the number of locations where breeding occurs has 
continued to decline. Additionally, the study found that breeding 
currently occurs in an estimated 22 percent of watersheds within the 
current estimated range of the species (Brown et al. 2012, p. 115).
    Moreover, overall abundances in the intensively monitored 
watersheds were very low (fewer than 20 males per meadow per year) 
relative to other historically reported abundances of the species 
(Brown et al. 2011, p. 4). Brown et al. (2011, p. 35) suggest that 
populations are now very small across the range of the species. During 
their monitoring over the past decade, they found only 18 percent of 
occupied survey watersheds range-wide had ``large'' populations (more 
than 1,000 tadpoles or 100 of any other lifestage detected at the time 
of survey). While not all surveys were conducted at the peak of tadpole 
presence and adults are not reliably found outside of the breeding 
season, Brown et al. (2012) surveyed many sites at appropriate times 
and rarely found the large numbers of tadpoles or metamorphs that would 
be expected if population sizes were similar to those reported 
historically. The researchers interpret these data, in combination with 
documented local population declines from other studies (see above), to 
support the hypothesis that population declines have occurred range-
wide (Brown et al. 2012, p. 11).

Summary of Changes From the Proposed Rule for the Yosemite Toad

    Based on peer review and Federal, State, and public comments (see 
comments in the Summary of Comments and Recommendations section, 
below), we clarified information for the Yosemite toad to better 
characterize our knowledge of the species' habitat requirements. 
Specifically, we reorganized and clarified the habitat details (Habitat 
and Life History), southern extent of the species' range (Historic 
Range and Distribution), and species surveys (USFS and NPS). We also 
added information on occupancy in National Parks that was inadvertently 
omitted from the proposed rule (Population Estimates and Status).
    In the Summary of Factors Affecting the Species section, under 
Factor A, we made small changes to the discussion about meadow loss and 
degradation in order to improve clarity. In the Livestock Use (Grazing) 
Effects to Meadow Habitat section, we reorganized the information and 
separated the effects of historic livestock grazing from the effects 
due to current grazing levels, and we added additional references 
received from the USFS. In the Roads and Timber Harvest Effects to 
Meadow Habitat section, we clarified the extent to which these 
activities overlap with the Yosemite toad's range and distinguished the 
effects of past activities from the effects of current activities. We 
added information on road locations and on USFS Forest standards and 
guidelines that currently limit the effects of these activities on 
riparian areas. In this final rule, we found that roads and timber 
harvest activities are not current and ongoing threats to the species. 
However, there may be localized effects where legacy effects of past 
road building or timber harvest continue to modify wet meadows or where 
activities occur in close proximity to extant Yosemite toad 
populations.
    In the Fire Management section, we added information to clarify 
that Yosemite toads primarily occur in higher elevation areas where 
fire suppression activities are rarely conducted. This finding suggests 
that fire suppression has had little effect on forest encroachment into 
meadow habitats in most areas where the species occurs. In the 
Recreation and Packstock Effects to Meadow Habitat section, we added 
additional information on USFS and NPS restoration activities to 
protect meadows, off-highway vehicle effects, packstock use, and agency 
monitoring and protection activities to limit effects due to packstock 
use. We revised our conclusion to clarify that, in general, we do not 
consider habitat-related changes associated with current levels of 
hiking, backpacking, or packstock use to pose a risk to Yosemite toad 
populations. Recreation may have habitat-related effects to toads in 
localized areas where use adjacent to occupied meadows is exceptionally 
heavy, or where heavy or motorized use results in changes to meadow 
hydrology. Accordingly, rangewide, recreation is a threat of low 
prevalence. In the section on Dams and Water Diversions, we added 
information to clarify that almost all reservoirs are located below the 
range of the Yosemite toad. We include small changes in the Climate 
Change section to improve clarity or add information from references 
provided during peer review.
    In Factor B, we added information provided during the comment 
period, which documented the sale of one Yosemite toad from a pet store 
in Southern California (store now closed). We also added information on 
protections provided by agency-required research permits. In Factor C, 
based on peer review comments, we added information on a Bd study on 
Yosemite toads. We removed the discussion of contaminants under Factor 
E, and we refer readers to the proposed rule affirming that the best 
available information indicates that contaminants do not pose a current 
or continuing threat to the Yosemite toad. We also added new 
information in the Other Sources of Direct and Indirect Mortality 
section as a result of information provided during peer review. 
Although we have not changed the determination, we have made a few 
small changes in the wording of the determination for the Yosemite toad 
to reflect the above changes.

Summary of Factors Affecting the Species

    Section 4 of the Act (16 U.S.C. 1533), and its implementing 
regulations at 50 CFR part 424, set forth the procedures for adding 
species to the Federal Lists of Endangered and Threatened Wildlife and 
Plants. Under section 4(a)(1) of the Act, we may list a species based 
on any of the following five factors: (A) The present or threatened 
destruction, modification, or curtailment of its habitat or range; (B) 
overutilization for commercial, recreational, scientific, or 
educational purposes; (C) disease or predation; (D) the inadequacy of 
existing regulatory mechanisms; and (E) other natural or manmade 
factors affecting its continued existence. Listing actions may be 
warranted based on any of the above threat factors, singly or in 
combination. Each of these factors is discussed below, and changes from 
the proposed rule (78 FR 24472, April 25, 2013) are reflected in these 
discussions.

Factor A. The Present or Threatened Destruction, Modification, or 
Curtailment of Its Habitat or Range

    The habitat comprising the current range of the Yosemite toad is 
generally characterized by low levels of physical disturbance (there is 
little to no current development pressure). However, these areas are 
also generally more sensitive to perturbation and take longer to 
recover from disturbances due to reduced growing seasons and harsher 
environmental conditions. Since Yosemite toads rely heavily on shallow, 
ephemeral water, they may be more sensitive to minor changes in their 
habitat. Loss or alteration of suitable breeding habitat can reduce 
reproductive success, which may have a profound impact when population 
numbers are small. Past management and development activity has played 
a

[[Page 24289]]

role in the degradation of meadow habitats within the Sierra Nevada. 
Human activities within these habitats include grazing, timber harvest, 
fuels management, recreation, and water development.
Meadow Habitat Loss and Degradation
    Some of the habitat effects associated with grazing activities that 
were described for the mountain yellow-legged frogs (see the Summary of 
Factors Affecting the Species section for those species, above) also 
apply to Yosemite toads. However, there are differences based on the 
Yosemite toad's reliance on very shallow, ephemeral water in meadow and 
pool habitats versus the deeper lakes and streams frequented by 
mountain yellow-legged frogs. Because Yosemite toads rely on very 
shallow, ephemeral water, they may be sensitive to even minor changes 
in their habitat, particularly to hydrology (Brown 2013, unpaginated). 
Meadow habitat quality in the Western United States, and specifically 
the Sierra Nevada, has been degraded by past activities, such as 
overgrazing, tree encroachment, fire suppression, and road building, 
over the last century (Stillwater Sciences 2008, pp. 1-53; Halpern et 
al. 2010, pp. 717-732; Vale 1987, pp. 1-18; Ratliff 1985, pp. i-48). 
These past activities have contributed to erosion and stream incision 
in areas of the Sierra Nevada, leading to meadow dewatering and 
encroachment by invasive vegetation (Menke et al. 1996, pp. 25-28; 
Lindquist and Wilcox 2000, p. 2).
    Given the reliance of the Yosemite toad on these meadow and pool 
habitats for breeding, rearing, and adult survival, it is logical to 
conclude that the various stressors have had an indirect effect on the 
viability of Yosemite toad populations via degradation of their 
habitat. Loss of connectivity of habitats leads to further isolation 
and population fragmentation. Because of physiological constraints, the 
tendency to move only short distances, and high site fidelity, 
amphibians may be unable to recolonize unoccupied sites following local 
extinctions if the distance between sites is too great, although 
recolonization can occur over time (Blaustein et al. 1994a, p. 8).
    Since the existence of meadows is largely dependent on their 
hydrologic setting, most meadow degradation is due fundamentally to 
hydrologic alterations (Stillwater Sciences 2008, p. 13). There are 
many drivers of hydrologic alterations in meadow ecosystems. In some 
locations, historic water development and ongoing water management 
activities have physically changed the underlying hydrologic system. 
Diversion and irrigation ditches formed a vast network that altered 
local and regional stream hydrology, although these manmade systems are 
generally below the range of the Yosemite toad. Timber harvest and 
associated road construction further altered erosion and sediment 
delivery patterns in rivers and meadow streams. Fire suppression and an 
increase in the frequency of large wildfires due to excessive fuel 
buildup have introduced additional disturbance pressures to the meadows 
of the Sierra Nevada (Stillwater Sciences 2008, p. 13). Many meadows 
now have downcut stream courses, compacted soils, altered plant 
community compositions, and diminished wildlife and aquatic habitats 
(SNEP 1996, pp. 120-121).
    Land uses causing channel erosion are a threat to Sierra Nevada 
meadows. These threats include erosive activities within the watershed 
upslope of the meadow, along with impacts from land use directly in the 
meadows themselves. Compaction of meadow soils by roads or intensive 
trampling (for example, overgrazing) can reduce infiltration, 
accelerate surface run-off, and thereby lead to channel incision (Menke 
et al. 1996, pp. 25-28). Mining, overgrazing, timber harvesting, and 
railroad and road construction and maintenance have contributed to 
watershed degradation, resulting in accelerated erosion, sedimentation 
in streams and reservoirs, meadow dewatering, and degraded terrestrial 
and aquatic habitats (Linquist 2000, p. 2). Deep incision has been 
documented in several meadows in the Sierra Nevada. One example is 
Halstead Meadow in Sequoia National Park, where headcutting exceeds 10 
feet in many areas and is resulting in widening channels, erosion in 
additional meadows, and a lowered water table (Cooper and Wolf 2006, p. 
1).
    The hydrologic effects of stream incision on the groundwater system 
may significantly impact groundwater storage, affecting late summer 
soil moisture and facilitating vegetation change (Bergmann 2004, pp. 
24-31). For example, in the northern Sierra Nevada, logging, 
overgrazing, and road/railroad construction have caused stream 
incision, resulting in dewatering of riparian meadow sediments and a 
succession from native wet meadow vegetation to sagebrush and dryland 
grasses (Loheide and Gorelick 2007, p. 2). A woody shrub (Artemisia 
rothrockii) is invading meadows as channel incision causes shallow-
water-dependent herbs to die back, allowing shrub seedlings to 
establish in disturbed areas during wet years (Darrouzet-Nardi et al. 
2006, p. 31).
    Mountain meadows in the western United States and Sierra Nevada 
have also been progressively colonized by trees (Thompson 2007, p. 3; 
Vale 1987, p. 6), with an apparent pattern of encroachment during two 
distinct periods in the late 1800s and mid-1900s (Halpern et al. 2010, 
p. 717). This trend has been attributed to a number of factors, 
including climate, changes in fire regime, and cessation of sheep 
grazing (Halpern et al. 2010, pp. 717-718; Vale 1987, pp. 10-13), but 
analyses are limited to correlational comparisons and research results 
are mixed, so the fundamental contribution of each potential driver 
remains uncertain. We discuss the contribution of these factors to 
habitat loss and degradation for the Yosemite toad below.
Livestock Use (Grazing) Effects to Meadow Habitat
    The combined effect of legacy conditions from historically 
excessive grazing use and current livestock grazing activities have the 
potential to impact habitat in the range of the Yosemite toad. The 
following subsections discuss the effects of excessive historical 
grazing, current extent of grazing, and current grazing management 
practices.
    Overgrazing has been associated with accelerated erosion and 
gullying of meadows (Kattelmann and Embury 1996, pp. 13, 18), which 
leads to siltation and more rapid succession of meadows. Grazing can 
cause erosion by disturbing the ground, damaging and reducing 
vegetative cover, and destroying peat layers in meadows, which lowers 
the groundwater table and summer flows (Armour et al. 1994, pp. 9-12; 
Martin 2002, pp. 1-3; Kauffman and Krueger 1984, pp. 431-434). Downcut 
channels, no longer connected to the historic, wide floodplains of the 
meadow, instead are confined within narrow, incised channels. 
Downstream, formerly perennial (year-round) streams often become 
intermittent or dry due to loss of water storage capacity in the meadow 
aquifers that formerly sustained them (Lindquist et al. 1997, pp. 7-8).
    Heavy grazing can alter vegetative species composition and 
contribute to lodgepole pine (Pinus contorta) invasion (Ratliff 1985, 
pp. 33-36). Lowering of the water table facilitates encroachment of 
conifers into meadows. Gully formation and lowering of water tables, 
changes in the composition of herbaceous vegetation, increases in the 
density of forested stands, and the expansion of trees into areas that 
formerly were treeless have been documented in California wilderness

[[Page 24290]]

areas and National Parks (Cole and Landres 1996, p. 171). This invasion 
has been attributed to sheep grazing, though the phenomenon has been 
observed on both ungrazed meadows and on meadows grazed continually 
since about 1900 (Ratliff 1985, p. 35), suggesting that other drivers 
may be involved (see ``Effects of Fire Suppression on Meadow Habitats'' 
and ``Climate Effects to Meadow Habitat'' below).

Effects of Historical Livestock Grazing

    Grazing of livestock in Sierra Nevada meadows and riparian areas 
(rivers, streams, and adjacent upland areas that directly affect them) 
began in the mid-1700s with the European settlement of California 
(Menke et al. 1996, p. 7). Following the gold rush of the mid-1800s, 
grazing increased to a level exceeding the carrying capacity of the 
available range, causing significant impacts to meadow and riparian 
ecosystems (Meehan and Platts 1978, p. 275; Menke et al. 1996, p. 7). 
By the turn of the 20th century, high Sierra Nevada meadows were 
converted to summer rangelands for grazing cattle, sheep, horses, 
goats, and pigs, although the alpine areas were mainly grazed by sheep 
(Beesley 1996, pp. 7-8; Menke et al. 1996, p. 14). Stocking rates of 
both cattle and sheep in Sierra meadows in the late 19th and early 20th 
centuries were very heavy (Kosco and Bartolome 1981, pp. 248-250), and 
grazing severely degraded many meadows (Ratliff 1985, pp. 26-31; Menke 
et al. 1996, p. 14). Grazing impacts occurred across the entire range 
of the Yosemite toad, as cattle and sheep were driven virtually 
everywhere in the Sierra Nevada where forage was available (Kinney 
1996, pp. 37-42; Menke et al. 1996, p. 14).
    Grazing within the National Forests has continued into recent 
times, with reduction in activity (motivated by resource concerns, 
conflicts with other uses, and deteriorating range conditions) 
beginning in the 1920s. A brief wartime increase in the 1940s followed, 
before grazing continued to be scaled back beginning in the 1950s 
through the early 1970s. However, despite these reductions, grazing 
still exceeded sustainable capacity in many areas (Menke et al. 1996, 
p. 9; UC 1996a, p. 115). Historical evidence indicates that heavy 
livestock use in the Sierra Nevada has resulted in widespread damage to 
rangelands and riparian systems due to sod destruction in meadows, 
vegetation destruction, and gully erosion (see review in Brown et al. 
2009, pp. 56-58 and in USFS et al. 2009, p. 57). (For additional 
information on historical grazing regimes, refer to the Effects of 
Excessive Historical Grazing section in Factor A analysis for the 
Sierra Nevada and mountain yellow-legged frogs, above).
    Livestock grazing in the Sierra Nevada has been widespread for so 
long that, in most places, no ungrazed areas are available to 
illustrate the natural condition of the habitat (Kattelmann and Embury 
1996, pp. 16-18). Dull (1999, p. 899) conducted stratigraphic pollen 
analysis (identification of pollen in sedimentary layers) in mountain 
meadows of the Kern Plateau, and found significant vegetation changes 
attributable to sheep and cattle grazing by 1900 (though fire regime 
change was also implicated; see below). This degradation is widespread 
across the Sierra Nevada. Cooper and Wolf 2006 (p. 1) reports that 50 
to 80 percent of grazed meadows now dominated by dry meadow plants were 
formerly wet meadows (Cooper and Wolf 2006, p. 1).
    Due to the long history (Menke et al. 1996, Ch. 22, pp. 1-52) of 
livestock and packstock grazing in the Sierra Nevada and the lack of 
historical Yosemite toad population size estimates, it is impossible to 
establish a reliable quantitative estimate for the historical 
significance and contribution of grazing on Yosemite toad populations. 
However, because of the documented negative effects of livestock on 
Yosemite toad habitat, and the documented direct mortality caused by 
livestock, the decline of some populations of Yosemite toad has been 
attributed to the effects of livestock grazing (Jennings and Hayes 
1994, pp. 50-53; Jennings 1996, pp. 921-944). Because Yosemite toad 
breeding habitat is generally in very shallow waters within meadows, 
the breeding habitat is thought to be more vulnerable to changes in 
hydrology caused by grazing because the small shallow pools are more 
easily impacted (Knapp 2002c, p. 1; Martin 2002, pp. 1-3; USFS et al. 
2009, pp. 22, 59-62; Brown 2013, unpaginated). U.S. Geological Survey 
records indicate that Yosemite, Sequoia, and Kings Canyon have no 
meadows within the parks that are documented to have degraded hydrology 
(see NPS 2013, p. 7); conditions in the parks may be related to the 
early elimination of most grazing on national parklands in the Sierra 
Nevada.

Effects of Current Livestock Grazing

    Currently, approximately 33 percent of the estimated range of the 
Yosemite toad is within active USFS grazing allotments (USFS 2008, 
geospatial data). While stocking rates have been reduced or eliminated 
in most areas, legacy effects including eroded channels, soil erosion, 
and stream entrenchment that resulted in lowered water tables, drier 
meadows, and tree encroachment could still be observed in some Sierran 
meadows, especially in National Forests where grazing was more intense 
(Vankat and Major 1978, pp. 386-397). Meadow conditions in the Sierra 
Nevada have improved over time, but local problems could still be found 
as of 1985 (Ratliff 1985, pp. ii-iii) and numerous examples of head-
cutting and stream incision are available within the range of the toad 
(Knapp 2013, unpaginated). (For additional information, see sections 
above pertaining to effects of grazing on the mountain yellow-legged 
frogs.)
    The influence of grazing on toad populations in recent history is 
uncertain, despite more available data on land use and Yosemite toad 
occurrence. In 2005, the USFS, in collaboration with other researchers, 
began a 5-year study with multiple components to assess the effects of 
grazing on Yosemite toads (Allen-Diaz et al. 2010, pp. 1-45; Roche et 
al. 2012a, pp. 56-65; Roche et al. 2012b, pp. 1-11; McIlroy et al.. 
2013, pp. 1-11). Specifically, the goals of the research were to 
assess: (1) Whether livestock grazing under SNFPA Riparian Standards 
and Guidelines has a measurable effect on Yosemite toad populations and 
(2) effects of livestock grazing on key habitat components that affect 
survival and recruitment of Yosemite toad populations. SNFPA standards 
and guidelines limit livestock utilization of grass and grass-like 
plants to a maximum of 40 percent (or a minimum 4-inch stubble height) 
(USDA 2004, p. 56). These companion studies did not detect an effect 
from grazing activity on young-of-year toad density or breeding pool 
occupancy, water quality, or cover (Allen-Diaz et al. 2010, p. 1; Roche 
et al. 2012a, p. 56; Roche et al. 2012b, p. 1-1; McIlroy et al.. 2013, 
p. 1).
    It is important to note that the results of these studies did not 
present a direct measurement of toad survival (for example, mark--
recapture analysis of population trends), and the design was limited in 
numbers of years and treatment replicates. It is plausible that, for 
longer lived species with irregular female breeding activity over the 
time course of this particular study, statistical power was not 
sufficient to discern a treatment effect. Further, a time lag could 
occur between effect and discernible impacts, and significant 
confounding variability in known drivers such as interannual variation 
in climate.
    Additionally, the experimental design in the studies tested the 
hypothesis that forest management guidelines (at 40

[[Page 24291]]

percent use threshold) were impacting toad populations, and this 
limited some analyses and experimental design to sites with lower 
treatment intensities. Researchers reported annual utilization by 
cattle ranging from 10-48 percent, while individual meadow use ranged 
from 0-76 percent (the SNFPA allowable use is capped at 40 percent) 
(Allen-Diaz et al. 2010, p. 5). As a result of the study design, the 
Allen-Diaz study does not provide sufficient information on the impacts 
of grazing on Yosemite toads above the prescribed management 
guidelines. In general, it is not clear to what extent brief episodes 
of intense use (such as in cattle gathering areas) have as negative 
impacts on toads, or over what percentage of the grazed meadow 
landscape such heavier usage may occur.
    The researchers observed significant variation in young-of-year 
occupancy in pools between meadows and years, and within meadows over 
years (Allen-Diaz et al. 2010, p. 7). This variability would likely 
mask treatment effects, unless the grazing variable was a dominant 
factor driving site occupancy, and the magnitude of the effect was 
quite severe. Further, in an addendum to the initial report, Lind et 
al. (2011b, pp. 12-14) report statistically significant negative 
(inverse) relationships for tadpole density and grazing intensity 
(tadpole densities decreased when percent use exceeded between 30 and 
40 percent). This result supports the hypothesis that grazing at 
intensities approaching and above the 40 percent threshold can 
negatively affect Yosemite toad populations.
    Allen-Diaz et al. (2010, p. 2) and Roche et al. (2012b, pp. 6-7) 
found that toad occupancy is strongly driven by meadow wetness 
(hydrology) and suggested attention should focus on contemporary 
factors directly impacting meadow wetness, such as climate, fire regime 
changes, and conifer encroachment (see Factor A above). The researchers 
also stated that meadow use by cattle during the grazing season is 
driven by selection of plant communities found in drier meadows (Allen-
Diaz et al. 2010, p. 2). This suggests that the apparent differences in 
preference could provide for some segregation of toad and livestock use 
in meadow habitats, so that at least direct mortality threats may be 
mitigated by behavioral isolation. Based on the limitations of the 
study as described above, we find the initial results from Allen-Diaz 
et al. (2010, pp. 1-45) to be inconclusive to discern the impacts of 
grazing on Yosemite toad populations where grazing and toads co-occur 
in meadows.
    The available grazing studies focus on breeding habitat (wet 
meadows) and do not consider impacts to upland habitats. The USFS 
grazing guidelines for protection of meadow habitats of the Yosemite 
toad include fencing breeding meadows, but they do not necessarily 
protect upland habitat. Martin (2008) surveyed 11 meadow sites located 
along a stream channel in or near low growing willows both before and 
after cattle grazed the entire meadow, and Martin found that Yosemite 
toads could no longer be located along the stream channel after the 
vegetation was grazed. However, both adults and subadults could be 
found in dense willow thickets or in parts of the meadow that were less 
heavily grazed (Martin 2008, p. 298). Grazing can also degrade or 
destroy moist upland areas used as nonbreeding habitat by Yosemite 
toads (Martin 2008, p. 159), especially when nearby meadow and riparian 
areas have been fenced to exclude livestock. Livestock may also 
collapse rodent burrows used by Yosemite toads as cover and hibernation 
sites (Martin 2008, p. 159) or disturb toads and disrupt their 
behavior. Martin (2008, pp. 305-306) observed that grazing 
significantly reduced vegetation height at grazed meadow foraging 
sites, and since these areas are not protected by current grazing 
guidelines, deduced that cattle grazing is having a negative effect on 
terrestrial life stage survivorship in Yosemite toads. This problem was 
exacerbated as fenced areas effectively shifted grazing activity to 
upland areas actively used by terrestrial life stages of the Yosemite 
toad (Martin 2008, p. 306).
    Although we lack definitive data to assess the link between 
Yosemite toad population dynamics and habitat degradation by livestock 
grazing activity, in light of the documented impacts to meadow habitats 
(including effects on local hydrology) from grazing activity in 
general, we consider this threat prevalent with moderate impacts to the 
Yosemite toad and a potential limiting factor in population recovery 
rangewide. In addition, given the potential for negative impacts from 
heavy use, and the vulnerability of toad habitat should grazing 
management practices change with new management plans, we expect this 
threat to continue into the future.
Roads and Timber Harvest Effects to Meadow Habitat
    Road construction and use, along with timber harvest activity, may 
impact Yosemite toad habitat via fragmentation, ground disturbance, and 
soil compaction or erosion (Helms and Tappeiner 1996, pp. 439-476). 
Roads may alter both the physical environment and the chemical 
environment; roads may present barriers to movement and may alter 
hydrologic and geomorphic processes that shape aquatic systems, while 
vehicle emissions and road-runoff are expected to contain chemicals 
that may be toxic (USFS et al. 2009, pp. 71-73). Timber harvests and 
past development of roads could potentially also lead to increased 
rates of siltation, contributing to the loss of breeding habitats for 
the Yosemite toad.
    Prior to the formation of National Parks and National Forests, 
timber harvest was widespread and unregulated in the Sierra Nevada; 
however, most cutting occurred below the current elevation range of the 
Yosemite toad (University of California at Davis (UCD) UC 1996b, pp. 
17-45; USFS et al. 2009, p. 77). Between 1900 and 1950, most timber 
harvest occurred in old-growth forests on private land (UC 1996b, pp. 
17-45). During this period, forest plans often lacked standards to 
protect riparian areas and associated meadows, leading to harvest 
activities that included cutting to edges of riparian areas and forest 
road construction that often crossed streams, associated aquatic 
habitat, and meadows, and resulted in head-cutting, lowered water 
tables, and loss of riparian habitats; legacies of these past 
activities remain today (USFS et al. 2009, p. 77). Currently on 
National Forests, timber harvest and related vegetation management 
activities overlap with Yosemite toads primarily in the lower elevation 
portions of the species' range; the red fir and lodgepole forests that 
generally surround high-elevation meadows that are Yosemite toad 
habitat do not have commercial value (USFS et al. 2009, pp. 76, 77). 
Forest standards and guidelines currently provide protections for 
riparian areas, such as buffers for timber and vegetation management 
activities.
    The majority of forest roads in National Forests of the Sierra 
Nevada were built between 1950 and 1990, to support major increases in 
timber harvest on National Forests, (USDA 2001a, p. 443), suggesting 
that many forest roads occur at elevations below the current range of 
the Yosemite toad. Relatively few public roads, including trans-Sierran 
State Highways 4 (Ebbetts Pass), 88 (Carson Pass), 108 (Sonora Pass), 
and 120 (Tioga Pass), cross the high elevations of the Sierra Nevada 
within the range of the Yosemite toad (USFS et al. 2009, p. 71), 
although smaller public roads are present in some high-elevation areas. 
One percent of

[[Page 24292]]

Yosemite toad populations occur on private lands where urbanization and 
corresponding construction of new roads may be more likely (USFS et al. 
2009, p. 71); however, we are not aware of any proposals for new road 
construction at this time.
    We expect that the majority of timber harvest, road development, 
and associated management impacts (see ``Effects of Fire Suppression on 
Meadow Habitats'' below) to Yosemite toad habitat took place during the 
expansion period in the latter half of the 20th century. Using a model, 
Liang et al. (2010, p. 16) found that Yosemite toads were more likely 
to occur in areas closer to timber activity, although the high 
correlation between elevation and the distance to harvest activity in 
model results definitive conclusions regarding cause and effect. 
However, they noted that, because timber harvest activities may 
maintain breeding sites by opening the forest canopy and potentially 
preventing encroachment of trees into sites, breeding animals might 
benefit from timber activity (Liang et al. 2010, p. 16). Limited 
information from timber sale areas where low-elevation populations 
occur indicates that such activities may negatively affect upland 
habitat use if burrow sites are crushed (USFS 2013, p. 6). Although 
ground-disturbance due to timber harvest activities has the potential 
to have population-level effects on Yosemite toad habitat, especially 
where habitat is limited, currently the best available information does 
not indicate that the current level of timber harvest occurring within 
watersheds currently inhabited by the Yosemite toad is adversely 
affecting habitat (USFS et al. 2009, p. 77). Therefore the best 
available scientific and commercial information does not indicate that 
ongoing road construction and maintenance or timber harvest are 
significant threats to the Yosemite toad. There may be localized 
effects of these activities in areas where legacy effects continue to 
result in modified wet meadow habitat conditions, or where current 
harvest and road activities occur in close proximity to extant Yosemite 
toad populations.
Effects of Fire Suppression on Meadow Habitats
    Fire management refers to activities over the past century to 
combat forest fires. Historically, both lightning-caused fires and 
fires ignited by American Indians were regularly observed in western 
forests (Parsons and Botti 1996, p. 29), and in the latter 19th 
century, the active use of fire to eliminate tree canopy in favor of 
forage plants continued by sheepherders (Kilgore and Taylor 1979, p. 
139). Beginning in the 20th century, land management in the Sierra 
Nevada shifted to focus on fire suppression as a guiding policy (UC 
2007, p. 10).
    Long-term fire suppression has influenced forest structure and 
altered ecosystem dynamics in the Sierra Nevada. In general, the time 
between fires is now much longer than it was historically, and live and 
dead fuels are more abundant and continuous (USDA 2001a, p. 35). Much 
of the habitat for the Yosemite toad occurs in high-elevation meadows 
within wilderness and backcountry areas where vegetation is sparse and 
fire suppression activities are rarely conducted (USFS et al. 2009, p. 
55), suggesting that fire suppression has played a limited role in such 
locations. At high elevations, encroachment of lodgepole pine at meadow 
edges has been attributed to cessation of sheep grazing or legacy 
effects of high-intensity grazing that reduced water tables, as opposed 
to fire suppression activities (Vankat and Major 1978, pp. 392-395). At 
lower elevations, it is not clear how habitat changes attributed to 
fire suppression have affected Yosemite toad populations. However, 
Liang et al. (2010, p. 16) observed that toads were less likely to 
occur in areas where the fire regime was significantly altered from 
historical conditions, and suggested that the toads are affected by 
some unknown or unmeasured factors related to fire management.
    Evidence indicates that fire plays a significant role in the 
evolution and maintenance of lower elevation forested meadows of the 
Sierra Nevada. Under natural conditions, conifers are excluded from 
meadows by fire and saturated soils. Small fires thin and/or destroy 
encroaching conifers, while large fires are believed to determine the 
meadow--forest boundary (Vankat and Major 1978, p. 394; Parsons and 
DeBenedetti 1979, pp. 29-31). Fire is thought to be important in 
maintaining open aquatic and riparian habitats for amphibians in some 
systems (Russel et al. 1999, pp. 374-384), and fire suppression may 
have thereby contributed to conifer encroachment on meadows (Chang 
1996, pp. 1071-1099; NPS 2002, p. 1). However, fire suppression effects 
are thought to vary with ecosystem fire regime; variable-interval fires 
are characteristic of the upper montane red fir forests (Chang 1996, 
pp. 107, 1072) that are the setting for Yosemite toad habitat at the 
lower elevations of its range, while long-interval fires are 
characteristic of the subalpine lodgepole pine forests (Chang 1996, p. 
1072) that are the setting for Yosemite toad habitats at higher 
elevations. The effects of fire suppression on forest structure is 
thought to be far less important in the longer interval forest types 
(Chang 1996, p. 1072).
    While no studies have confirmed a link between fire suppression and 
rangewide population decline of the Yosemite toad, circumstantial 
evidence to date suggests that historic fire suppression may be a 
factor underlying meadow encroachment at lower elevations. The effect 
of fire suppression, therefore, is thought to be largely restricted to 
lower elevations within the Yosemite toad's range; fire suppression 
activities are rarely conducted where much of the habitat for the 
Yosemite toad occurs (USFS et al. 2009, pp. 51-54). Based on the best 
available information, we find it likely that habitat modification due 
to reduced fire frequency is a moderate threat to Yosemite toad in 
those lower-elevation areas where fire suppression has resulted in 
conifer encroachment into meadows.
Recreation and Packstock Effects to Meadow Habitat
    Recreational activities take place throughout the Sierra Nevada, 
and they can have significant negative impacts on wildlife and their 
habitats (USDA 2001a, pp. 221, 453-500). Recreation can cause 
considerable impact to vegetation and soils in western U.S. Wilderness 
Areas and National Parks even with light use, with recovery occurring 
only after considerable periods of non-use (USFS et al. 2009, p. 66). 
Heavy foot traffic in riparian areas tramples vegetation, compacts 
soils, and can physically damage streambanks. Trails (foot, horse, 
bicycle, or off-highway motor vehicle) can compact the soil, displace 
vegetation, and increase erosion, thereby potentially lowering the 
water table (Kondolph et al. 1996, pp. 1009-1026). However, the 
National Park Service considers current hiking and backpacking 
activities to be a negligible risk factor for the Yosemite toad within 
the Parks. The Parks have also worked to improve impacted meadows by 
reconstructing poorly designed trails that have degraded meadow 
hydrology, also identifying additional Yosemite toad meadows to 
prioritize additional restoration activities (NPS 2013, p. 9). Similar 
activities have been implemented on National Forests; for example, the 
Inyo National Forest has re-routed several trails to avoid the toad's 
breeding habitat (USFS 2013, p. 5).

[[Page 24293]]

    Although much Yosemite toad habitat is located in wilderness or 
other backcountry areas removed from motorized access, the USFS has 
noted locations where proximity of roads or off-highway vehicle routes 
to Yosemite toad breeding habitat has resulted in observed impacts to 
Yosemite breeding habitat. Off-highway vehicles are often the first 
vehicles to pass through roads blocked by winter snows, occasionally 
driving off the road to pass remaining obstacles (USFS et al. 2009, p. 
63). Records of such off-highway vehicle travel in breeding meadows and 
ponds (USFS 2013, pp. 6, 7) suggests that such activities have the 
potential to negatively affect these habitats, although the population-
level effects to Yosemite toads are thought to be limited.
    Packstock use has similar effects to those discussed for livestock 
grazing (for additional information on current packstock use levels and 
management protections, see the Packstock Use section under the 
mountain yellow-legged frogs, above), although this risk factor is 
potentially more problematic as this land use typically takes place in 
more remote and higher-elevation areas occupied by Yosemite toads, and 
packstock tend to graze in many of the same locations that the toads 
prefer (USFS et al. 2009, p. 65). Currently, there are very few studies 
on the effects of packstock grazing on amphibians, especially in the 
Sierra Nevada. However, in Yosemite, Sequoia, and Kings Canyon National 
Parks, packstock use is monitored annually to prevent long-term 
impacts. Additionally, the NPS (2013, p. 9) has indicated that, except 
for a few specific areas, packstock use and Yosemite toads typically do 
not overlap within the Parks. Many areas are closed to packstock use 
entirely or limited to day use due to inadequate trail access or to 
protect sensitive areas. Long-term use data indicate that packstock use 
is declining, with no evidence to suggest that it will increase in the 
future (NPS 2013, pp. 6, 7). Where permitted, current guidelines in the 
National Parks limit trips to 20-25 animals, regulated under 
conditional use permits (Brooks 2012, pers. comm.). Similar standards 
and guidelines limit packstock group size and use within the National 
Forests (USFS 2013, pp. 3-5).
    Habitat-related effects of recreational activities on the Yosemite 
toad may have population-level impacts in localized areas and under 
site-specific conditions, for example, where foot traffic adjacent to 
occupied meadows is exceptionally heavy and results in meadow damage, 
where legacy effects of high recreation use have resulted in continuing 
meadow damage, or where off-highway vehicle use results in changes in 
meadow hydrology. However, in general, we do not consider habitat-
related changes associated with current levels of hiking or backpacking 
to pose a population-level risk to Yosemite toads. Therefore, at this 
time we consider recreational activities to be a low prevalence threat 
across the range of the Yosemite toad.
Dams and Water Diversions Effects to Meadow Habitat
    Past construction of dams, diversion, and irrigation ditches 
resulted in a vast man-made network that altered local and regional 
stream hydrology in the Sierra Nevada (SNEP 1996, p. 120), although, 
with the exception of several dozen small impoundments and diversions, 
almost all of these are located below the range of the Yosemite toad 
(USFS et al. 2009, pp. 76, 77). However, in the past a small number of 
reservoirs were constructed within the historic range of the Yosemite 
toad, most notably Upper and Lower Blue Lakes, Edison, Florence, 
Huntington, Courtright, and Wishon Reservoirs. Construction of several 
high-elevation reservoirs (for example, Edison and Florence) is thought 
to have inundated shallow-water breeding habitat for the toad (USFS et 
al. 2009, pp. 76, 77). Where reservoirs are used for hydroelectric 
power, water-level declines caused by drawdown of reservoirs can lead 
to the mortality of eggs and tadpoles by stranding and desiccation, 
although, with the exception of Blue Lakes, Yosemite toads are 
currently not known from the above reservoirs (USFS et al. 2009, pp. 
78, 79).
    Past construction of these reservoirs likely contributed to the 
decline of the Yosemite toad in the area where they were built. 
Increasing effects from climate change, or new water supply development 
in response to such effects, may exacerbate this risk in the future if 
new reservoirs are constructed within areas occupied by the toad. 
However, we are not aware of any proposals to construct additional 
reservoirs within the Yosemite toads range. We expect that continuing 
reservoir operations may have continued habitat-related effects to toad 
populations in these developed areas, but less so in the current extent 
of the Yosemite toad's (remnant) range. Therefore, we consider this 
threat to be of low prevalence to the Yosemite toad across its range.
Climate Effects to Meadow Habitat
    Different studies indicate that multiple drivers are behind the 
phenomenon of conifer encroachment into meadows. The first factor 
affecting the rate of conifer encroachment into meadow habitats, fire 
suppression, was discussed above. Climate variability is another factor 
affecting the rate of conifer encroachment on meadow habitats. A study 
by Franklin et al. (1971, p. 215) concluded that fire had little 
influence on meadow maintenance in their study area, while another 
study concluded that climate change is a more likely explanation for 
encroachment of trees into the adjacent meadow at their site, rather 
than fire suppression or changes in grazing intensity (Dyer and 
Moffett, 1999, p. 444).
    Climatic variability is strongly correlated with tree encroachment 
into dry subalpine meadows (Jakubos and Romme 1993, p. 382). In the 
Sierra Nevada, most lodgepole pine seedlings become established during 
years of low snowpack when meadow soil moisture is reduced (Wood 1975, 
p. 129). The length of the snow-free period may be the most critical 
variable in tree invasion of subalpine meadows (Franklin et al. 1971, 
p. 222), with the establishment of a good seed crop, followed by an 
early snowmelt, resulting in significant tree establishment. It is 
apparent that periods of low snowpack and early melt may in fact be 
necessary for seedling establishment (Ratliff, 1985, p. 35). Millar et 
al. (2004, p. 181) reported that increased temperature, coupled with 
reduced moisture availability in relation to large-scale temporal 
shifts in climate, facilitated the invasion of 10 subalpine meadows 
studied in the Sierra Nevada.
    Our analyses under the Act include consideration of ongoing and 
projected changes in climate. The terms ``climate'' and ``climate 
change'' are defined by the Intergovernmental Panel on Climate Change 
(IPCC). ``Climate'' refers to the mean and variability of different 
types of weather conditions over time, with 30 years being a typical 
period for such measurements, although shorter or longer periods also 
may be used (IPCC 2007, p. 1450; IPCC 2013a, Annex III). The term 
``climate change'' thus refers to a change in the mean or variability 
of one or more measures of climate (for example, temperature or 
precipitation) that persists for an extended period, typically decades 
or longer, whether the change is due to natural variability, human 
activity, or both (IPCC 2007, p. 1450; IPCC 2013a, Annex III). A recent 
compilation of climate change and its effects is available from reports 
of the Intergovernmental Panel on Climate Change (IPCC) (IPCC 2013b, 
entire). Various types of changes in climate can have direct or 
indirect effects on species. These effects may be positive,

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neutral, or negative, and they may change over time, depending on the 
species and other relevant considerations, such as the effects of 
interactions of climate with other variables (for example, habitat 
fragmentation) (IPCC 2007, pp. 8-14, 18-19). In our analyses, we use 
our expert judgment to weigh relevant information, including 
uncertainty, in our consideration of various aspects of climate change.
    For the Sierra Nevada ecoregion, climate models predict that mean 
annual temperatures will increase by 1.8 to 2.4 [deg]C (3.2 to 
4.3[emsp14][deg]F) by 2070, including warmer winters with earlier 
spring snowmelt and higher summer temperatures (PRBO 2011, p. 18). 
Additionally, mean annual rainfall is projected to decrease from the 
current average by some 9.2-33.9 cm (3.6-13.3 in) by 2070 (PRBO 2011, 
p. 18). However, projections have high uncertainty, and one study 
predicts the opposite effect (PRBO 2011, p. 18). Snowpack is, by all 
projections, going to decrease dramatically (following the temperature 
rise and increase in precipitation falling as rain) (PRBO 2011, p. 19); 
(Kadir et al. 2013, pp. 76-80). Higher winter stream flows, earlier 
runoff, and reduced spring and summer stream flows are projected, with 
increasing severity in the southern Sierra Nevada (PRBO 2011, pp. 20-
22); (Kadir et al. 2013, pp. 71-75).
    Snow-dominated elevations from 2,000-2,800 m (6,560-9,190 ft) will 
be the most sensitive to temperature increases (PRBO 2011, p. 23). 
Meadows fed by snowmelt may dry out or be more ephemeral during the 
non-winter months (PRBO 2011, p. 24). This pattern could influence 
groundwater transport, and springs may be similarly depleted, leading 
to lower water levels in available breeding habitat and decreased area 
and hydroperiod (i.e., duration of water retention) of suitable habitat 
for rearing tadpoles of Yosemite toads. Changes in water transport may 
promote channel incision and result in a shift to non-meadow conditions 
(Viers et al. 2013, p. 31).
    Blaustein et al. (2010, pp. 285-300) provide an exhaustive review 
of potential direct and indirect and habitat-related effects of climate 
change to amphibian species, with documentation of effects in a number 
of species where such effects have been studied. Altitudinal range 
shifts with changes in climate have been reported in some regions. They 
note that temperature can influence the concentration of dissolved 
oxygen in aquatic habitats, with warmer water generally having lower 
concentrations of dissolved oxygen, and that water balance heavily 
influences amphibian physiology and behavior. They predict that 
projected changes in temperature and precipitation are likely to 
increase habitat loss and alteration for those species living in 
sensitive habitats, such as ephemeral ponds and alpine habitats 
(Blaustein et al. 2010, pp. 285-287).
    Because environmental cues such as temperature and precipitation 
are clearly linked to onset of reproduction in many species, climate 
change will likely affect the timing of reproduction in many species, 
potentially with different sexes responding differently to climate 
change. For example, males of two newt species (Triturus spp.) showed a 
greater degree of change in arrival date at breeding ponds (Blaustein 
et al. 2010, p. 288). Lower concentrations of dissolved oxygen in 
aquatic habitats may negatively affect developing embryos and larvae, 
in part because increases in temperature increase the oxygen 
consumption rate in amphibians. Reduced oxygen concentrations have also 
been shown to result in accelerated hatching in ranid frogs, but at a 
smaller size, while larval development and behavior may also be 
affected and may be mediated by larval density and food availability 
(Blaustein et al. 2010, pp. 288-289).
    Increased temperatures can reduce time to metamorphosis, which can 
increase chances of survival where ponds dry, but also result in 
metamorphosis at a smaller size, suggesting a likely trade-off between 
development and growth, which may be exacerbated by climate change and 
have fitness consequences for adults (Blaustein et al. 2010, pp. 289-
290). Changes in terrestrial habitat, such as changed soil moisture and 
vegetation, can also directly affect adult and juvenile amphibians, 
especially those adapted to moist forest floors and cool, highly 
oxygenated water that characterizes montane regions. Climate change may 
also interact with other stressors that may be acting on a particular 
species, such as disease and contaminants (Blaustein et al. 2010, pp. 
290-299).
    A recent paper (Kadir et al. 2013, entire) provides specific 
information on the effects of climate change in the Sierra Nevada. The 
report found that glaciers in the Sierra Nevada have decreased in area 
over the past century, and glacier shrinkage results in earlier peak 
water runoff and drier summer conditions. Another result from the 
report is that the lower edge of the conifer-dominated forests in the 
Sierra Nevada has been retreating upslope over the past 60 years. 
Regarding wildfire, since 1950, annual acreage burned in wildfires 
statewide has been increasing in California, and in the western United 
States, large wildfires have become more frequent, increasing in tandem 
with rising spring and summer temperatures. Finally, the report found 
that today's subalpine forests in the Sierra Nevada are much denser--
that is, comprise more small-diameter trees--than they were over 70 
years ago. During this time period, warmer temperatures, earlier 
snowmelt, and more rain than snow occurred in this region. Many of 
these changes in the Sierra Nevada of California due to climate are 
likely to influence Yosemite toads because they are highly vulnerable 
to climate change because changing hydrology and habitat in the Sierra 
Nevada will likely have impacts on remaining populations (Viers et al. 
2013, pp. 55, 56).
    Historically, drought is thought to have contributed to the decline 
of the Yosemite toad (Kagarise Sherman and Morton 1993, p. 186; 
Jennings and Hayes 1994, pp. 50-53). Extended and more severe droughts 
pose an ongoing, rangewide risk to the species and are expected to 
increase with predicted climate changes (PRBO 2011, p. 18). Such 
changes may reduce both the amount of suitable breeding habitat and the 
length of time that suitable water is available in that habitat (Brown 
2013, unpaginated).
    Davidson et al. (2002, p. 1598) analyzed geographic decline 
patterns for the Yosemite toad. They compared known areas of 
extirpation against a hypothesized model for climate change that would 
predict greater numbers of extirpations at lower altitudes, and in more 
southern latitudes. The researchers did not observe a pattern in the 
available historic data to support the climate change hypothesis as a 
driver of historic population losses, although they acknowledge that 
climate change may be a contributor in more complex or subtle ways. 
Additionally, this study was limited by small sample size, and it is 
possible that climate change effects on the Yosemite toad (a long-lived 
species) may not become evident for many years (USFS et al. 2009, p. 
48). Finally, Davidson et al. (2002, p. 1598) did find an increase in 
occupancy with elevation (greater densities of populations at 
altitude), and this observation is consistent with a pattern that would 
fit a response to climate change (USFS et al. 2009, p. 48). However, 
this observation would also be consistent if the features of these 
particular habitats (such as at higher elevation) were more suited to 
the special ecological requirements of the

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toad, or if other stressors acting on populations at lower elevations 
were responsible for the declines. We, therefore, find these results 
inconclusive.
    Most recently, modeled vulnerability assessments for Sierra Nevada 
montane meadow systems have utilized life history and habitat 
requirements to gauge vulnerability of amphibian species to climate 
change. This assessment indicates that vulnerability to hydro-climatic 
changes will likely be very high for the Yosemite toad, and that 
continued or worsening stream channelization in montane meadows from 
flashy storms may worsen effects by further reductions in the water 
table (Viers et al. 2013, p. 56).
    The breeding ecology and life history of the Yosemite toad are that 
of a habitat specialist, as it utilizes pool and meadow habitats during 
the onset of snowmelt and carefully times its reproduction to fit 
available conditions within ephemeral breeding sites. The most striking 
documented declines in Yosemite toad populations in the historical 
record are correlated with extreme climate episodes (drought) (Kagarise 
Sherman and Morton 1993, pp. 186-198). Given these observations, it is 
likely that climate change (see also discussion in mountain yellow-
legged frog's Summary of Factors Affecting the Species, under Factor E) 
poses a significant risk to the Yosemite toad now and in the future. It 
is quite possible that these impacts are occurring currently, and have 
occurred over the last few decades. However, it is difficult in short 
time intervals to discern the degree of effect from climate change 
within the variability of natural climate cycles.
    In summary, based on the best available scientific and commercial 
information, we consider the threats of destruction, modification, and 
curtailment of the species' habitat and range to be significant ongoing 
threats to the Yosemite toad. The legacy effects of past land uses have 
altered meadow communities through the mechanism of stream incision by 
permanently reducing habitat quantity and quality unless active and 
costly restoration is implemented. Climate change is a current threat 
of high magnitude. Threats considered of moderate magnitude include 
livestock grazing and fire management regime. Threats considered 
currently low magnitude include roads and timber harvest, dams and 
water diversions, and recreational land uses.

Factor B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    We do not have any scientific or commercial information to indicate 
that overutilization for commercial, recreational, or scientific 
purposes poses a threat to the Yosemite toad. There is currently no 
known commercial market for Yosemite toads, although one pet store in 
Los Angeles that is no longer in business had previously sold at least 
one Yosemite toad (USFS et al. 2009, pp. 65-66); and there is also no 
documented recreational or educational use for Yosemite toads.
    Scientific research may cause some stress to Yosemite toads through 
disturbance and disruption of behavior, handling, and injuries 
associated with marking individuals. This activity has resulted in the 
known death of individuals through accidental trampling (Green and 
Kagarise Sherman 2001, pp. 92-103), irradiation from radioactive tags 
(Karlstrom 1957, pp. 187-195), and collection for museum specimens 
(Jennings and Hayes 1994, pp. 50-53). We expect that requirements for 
Federal (USFS and NPS) and State (CDFW) research and special use 
permits, and University ethics requirements provide some protections 
for wildlife-research subjects and limit negative effects to 
individuals. Therefore, we do not currently consider ongoing and future 
scientific research to be a threat to the Yosemite toad. We also 
anticipate that further research into the genetics and life history of 
the Yosemite toad and broader methodological censuses will provide a 
net conservation benefit to this under-studied species.
    Based on the best available scientific and commercial information, 
we do not consider overutilization for commercial, recreational, 
scientific, or educational purposes to be a threat to the Yosemite 
toad.

Factor C. Disease or Predation

Predation
    Prior to the trout stocking of high Sierra Nevada lakes, which 
began over a century ago, fish were entirely absent from most of this 
region (Bradford 1989, pp. 775-778). Observations regarding the effects 
of introduced fishes on the Yosemite toad are mixed. However, re-
surveys of historical Yosemite toad sites have shown that the species 
has disappeared from several lakes where they formerly bred, and these 
areas are now occupied by fish (Stebbins and Cohen 1995, pp. 213-215; 
Martin 2002, p. 1).
    Drost and Fellers (1994, pp. 414-425) suggested that Yosemite toads 
are less vulnerable to fish predation than frogs because they breed 
primarily in ephemeral waters that do not support fish. Further, 
Jennings and Hayes (1994, pp. 50-53) stated that the palatability of 
Yosemite toad tadpoles to fish predators is unknown, but often assumed 
to be low based on the unpalatability of western toads (Drost and 
Fellers 1994, pp. 414-425; Kiesecker et al. 1996, pp. 1237-1245), to 
which Yosemite toads are closely related. Grasso (2005, p. 1) observed 
brook trout swimming near, but the trout ignored Yosemite toad 
tadpoles, suggesting that tadpoles are unpalatable. The study also 
found that subadult Yosemite toads were not consumed by brook trout 
(Grasso 2005, p. 1), although the sublethal effects of trout 
``sampling'' (mouthing and ejecting tadpoles) and the palatability of 
subadults to other trout species are unknown. Martin (2002, p. 1) 
observed brook trout preying on Yosemite toad tadpoles, and also saw 
them ``pick at'' Yosemite toad eggs (which later became infected with 
fungus). In addition, metamorphosed western toads have been observed in 
golden trout stomach contents (Knapp 2002c, p. 1). Nevertheless, Grasso 
et al. (2010, p. 457) concluded that early life stages of the Yosemite 
toad likely possess chemical defenses that provide sufficient 
protection from native trout predation.
    The observed predation of Yosemite toad tadpoles by trout (Martin 
1992, p. 1) indicates that introduced fishes may pose a predation risk 
to the species in some situations, which may be accentuated during 
drought years. At a site where Yosemite toads normally breed in small 
meadow ponds, they have been observed to successfully switch breeding 
activities to stream habitat containing fish during years of low water 
(Strand 2002, p. 1). Thus, drought conditions may increase the toads' 
exposure to predatory fish, and place them in habitats where they 
compete with fish for invertebrate prey. Additionally, although the 
number of lake breeding sites used by Yosemite toads is small relative 
to the number of ephemeral sites, lake sites may be especially 
important because they are more likely to be habitable during years 
with low water (Knapp 2002c, p. 1).
    Overall, the data and available literature suggest that direct 
mortality from fish predation is likely not an important factor driving 
Yosemite toad population dynamics. This does not discount other 
indirect impacts, such as the possibility that fish may be effective 
disease vectors (see below). Yosemite toad use of more ephemeral 
breeding habitats (which are less habitable to fish species as they 
cannot tolerate drying or

[[Page 24296]]

freezing) minimizes the interaction of fish and toad tadpoles. Further, 
where fish and toads co-occur, it is possible that food depletion 
(outcompetition) by fish negatively affects Yosemite toads (USFS et al. 
2009, p. 58).
    Other predators may also have an effect on Yosemite toad 
populations. Kagarise Sherman and Morton (1993, p. 194) reported 
evidence of toad predation by common ravens (Corvus corax) and 
concluded this activity was responsible for the elimination of toads 
from one site. These researchers also confirmed, as reported in other 
studies, predation on Yosemite toad by Clark's nutcrackers (Nucifraga 
columbiana). The significance of avian predation may increase if the 
abundance of common ravens within the current range of the Yosemite 
toad increases as it has in nearby regions (Camp et al. 1993, p. 138; 
Boarman et al. 1995, p. 1; Kelly et al. 2002, p. 202). However, the 
degree to which avian predation may be affecting Yosemite toad 
populations has not been quantified.
Disease
    Although not all vectors have been confirmed in the Sierra Nevada, 
introduced fishes, humans, pets, livestock, packstock, vehicles, and 
wild animals may all act to facilitate disease transmission between 
amphibian populations. Infection of both fish and amphibians by a 
common disease has been documented with viral (Mao et al. 1999, pp. 45-
52) and fungal pathogens in the western United States (Blaustein et al. 
1994b, pp. 251-254). Mass die-offs of amphibians in the western United 
States and around the world have been attributed to Bd fungal 
infections of metamorphs and adults (Carey et al. 1999, pp. 1-14), 
Saprolegnia fungal infections of eggs (Blaustein et al. 1994b, pp. 251-
254), ranavirus infections, and bacterial infections (Carey et al. 
1999, pp. 1-14).
    Various diseases are confirmed to be lethal to Yosemite toads 
(Green and Kagarise Sherman 2001, pp. 92-103), and recent research has 
elucidated the potential role of Bd infection as a threat to Yosemite 
toad populations (Dodge and Vredenburg 2012, p. 1). These various 
diseases and infections, in concert with other factors, have likely 
contributed to the decline of the Yosemite toad (Kagarise Sherman and 
Morton 1993, pp. 193-194) and may continue to pose a risk to the 
species (Dodge and Vredenburg 2012, p. 1).
    Die-offs in Yosemite toad populations have been documented in the 
literature, and an interaction with diseases in these events has been 
confirmed. However, no single cause has been validated by field 
studies. Tissue samples from dead or dying adult Yosemite toads and 
healthy tadpoles were collected during a die-off at Tioga Pass Meadow 
and Saddlebag Lake and analyzed for disease (Green and Kagarise Sherman 
2001, pp. 92-103). Six infections were found in the adults, including 
infection with Bd, bacillary bacterial septicemia (red-leg disease), 
Dermosporidium (a fungus), myxozoa spp. (parasitic cnidarians), 
Rhabdias spp. (parasitic roundworms), and several species of trematode 
(parasitic flatworms). Despite positive detections, no single 
infectious disease was found in more than 25 percent of individuals, 
and some dead toads showed no signs of infection to explain their 
death. Further, no evidence of infection was found in tadpoles. A meta-
analysis of red-leg disease also revealed that the disease is a 
secondary infection that may be associated with a suite of different 
pathogens, and so actual causes of decline in these instances were 
ambiguous (Kagarise Sherman and Morton 1993, p. 194). The authors 
concluded that the die-off was caused by suppression of the immune 
system caused by an undiagnosed viral infection or chemical 
contamination that made the toads susceptible to the variety of 
diagnosed infections.
    Saprolegnia ferax, a species of water mold that commonly infects 
fish in hatcheries, caused a massive lethal infection of eggs of 
western toads at a site in Oregon (Blaustein et al. 1994b, p. 252). It 
is unclear whether this event was caused by the introduction of the 
fungal pathogen via fish stocking, or if the fungus was already present 
and the eggs' ability to resist infection was inhibited by some unknown 
environmental factor (Blaustein et al. 1994b, p. 253). Subsequent 
laboratory experiments have shown that the fungus could be passed from 
hatchery fish to western toads (Kiesecker et al. 2001, pp. 1064-1070). 
Fungal growth on Yosemite toad eggs has been observed in the field, but 
the fungus was not identified and it was unclear whether the fungus was 
the source of the egg mortality (Kagarise Sherman 1980, p. 46). Field 
studies conducted in Yosemite National Park found that an undetermined 
species of water mold infected only the egg masses that contained dead 
embryos of Yosemite toads (Sadinski 2004, pp. 33-34). The researchers 
also observed that the water mold became established on egg masses only 
after embryo death, and subsequently spread, causing the mortality of 
additional embryos of Yosemite toads.
    Sadinski (2004, p. 35) discovered that mortality of Yosemite toad 
embryos may be attributed to an unidentified species of a free-living 
flatworm (Turbellaria spp.). In Yosemite National Park, these worms 
were observed to penetrate Yosemite toad egg masses and feed directly 
on the embryos. In some locations, Turbellaria spp. reached such large 
densities that they consumed all the embryos within a Yosemite toad egg 
mass. Predation also facilitated the colonization and spread of water 
mold on egg masses, leading to further embryo mortality. Further 
studies would be needed to determine which species of Turbellaria feeds 
on Yosemite toad eggs, and the extent of this impact on Yosemite toad 
populations.
    Until recently, the contribution of Bd infection to Yosemite toad 
population declines was relatively unknown. Although the toad is 
hypothetically susceptible due to co-occurrence with the mountain 
yellow-legged frog, the spread and growth of Bd in the warmer pool 
habitats, occupied for a much shorter time relative to the frog, is 
suspected to render individuals less prone to epidemic outbreaks (USFS 
et al. 2009, p. 50). Fellers et al. (2011, p. 391) documented the 
occurrence of Bd infection in Yosemite National Park toads over at 
least a couple of decades, and they note population persistence in 
spite of the continued presence of the pathogen. In a survey of 196 
museum specimens, Dodge and Vredenburg (2012, p. 1) report the first 
presence of Bd infection in Yosemite toads beginning in 1961, with the 
pathogen becoming highly prevalent during the recorded declines of the 
late 1970s, before it peaked in the 1990s at 85 percent positive 
incidence. In live specimen sampling, Dodge and Vredenburg (2012, p. 1) 
collected 1,266 swabs of Yosemite toads between 2006 and 2011, and 
found Bd infection intensities at 17-26 percent (with juvenile toads 
most affected). The studies detected a pattern indicative of the 
historic emergence of Bd, which coincided with the documented decline 
in Yosemite toad (Dodge 2013, p. 1). As such, results from these 
studies support the hypothesis that Bd infection and chytridiomycosis 
have played an important role in Yosemite toad population dynamics over 
the period of their recent recorded decline.
    Carey (1993, pp. 355-361) developed a model to explain the 
disappearance of boreal toads (Bufo boreas boreas) in the Rocky 
Mountains, suggesting immune system suppression from extreme winter 
stress (``winter stress syndrome'') could have contributed to the 
decline in that species. This model may also fit Yosemite toad die-offs 
observed by Kagarise Sherman and Morton (1993,

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pp. 186-198), given the close relationship between the two toads, and 
their occupation of similar habitats. However, an analysis of immune 
system suppression and the potential role of winter stress relative to 
Yosemite toad population trends is not available at this time. Yet, the 
decline pattern observed in the Carey study is mirrored by the pattern 
in the Yosemite toad (heavy mortality exhibited in males first) (Knapp 
2012, pers. comm.). This observation, in concert with the recent 
results from museum swabs (Dodge and Vredenburg 2012, p. 1), provides a 
correlative link to the timing of the recorded Yosemite toad declines 
and Bd infection intensities.
    Although disease as a threat factor to the Yosemite toad is 
relatively less documented, Bd infection causes mass mortalities in the 
closely related boreal toad (Carey et al. 2006, p. 19) and there is 
evidence related to Bd's role in historical die-offs in Yosemite toads. 
Much of the historic research documenting Yosemite toad declines 
predated our awareness of Bd as a major amphibian pathogen. 
Additionally, the life history of the Yosemite toad, as a rapid breeder 
during early snowmelt, limits the opportunities to observe population 
crashes in the context of varied environmental stressors. Currently 
available evidence indicates that Bd was likely a significant factor 
contributing to the recent historical declines observed in Yosemite 
toad populations (Dodge and Vredenburg 2012, p. 1). Although infection 
intensities are currently lower than some peak historic measurements, 
this threat remains a potential factor that may continue to reduce 
survival through metamorphosis, and therefore recruitment to the 
breeding population (Knapp 2012, pers. comm.). Additionally, the 
interaction of disease and other stressors, such as climate extremes, 
is not well understood in the Yosemite toad. Research does suggest that 
the combination of these threats represents a factor in the historical 
decline of the species (Kagarise Sherman and Morton 1993, p. 186).
    In summary, based on the best available scientific and commercial 
information, we do not consider predation to be a threat to the 
species. We consider disease to be a threat to the Yosemite toad that 
has a moderate, ongoing effect on populations of the species rangewide. 
The threat most specifically includes the amphibian pathogen, Bd. 
Although definitive empirical data quantifying the contribution of 
disease to Yosemite toad population declines are not currently 
available, population declines that were concurrent with the prevalence 
and spread of Bd across the Sierra Nevada support the assertion that 
disease has played a role in the observed trend. Further, Bd infection, 
even at lower intensities, may interact with climate extremes and 
continue to depress recruitment of yearling and subadult Yosemite toads 
to breeding Yosemite toad populations. We suspect this threat was 
historically significant, that it is currently having a moderate 
influence on toad populations, and we expect it to be a future concern.

Factor D. The Inadequacy of Existing Regulatory Mechanisms

    In determining whether the inadequacy of regulatory mechanisms 
constitutes a threat to the Yosemite toad, we analyzed the existing 
Federal and State laws and regulations that may address the threats to 
the species or contain relevant protective measures. Regulatory 
mechanisms are typically nondiscretionary and enforceable, and may 
preclude the need for listing if such mechanisms are judged to 
adequately address the threat(s) to the species such that listing is 
not warranted. Conversely, threats on the landscape are not addressed 
by existing regulatory mechanisms where the existing mechanisms are not 
adequate (or not adequately implemented or enforced).
    We discussed the applicable State and Federal laws and regulations, 
including the Wilderness Act, NFMA above (see Factor D discussion for 
mountain yellow-legged frogs). In general, the same administrative 
policies and statutes are in effect for the Yosemite toad. This section 
additionally addresses regulatory mechanisms with a specific emphasis 
on the Yosemite toad.

Taylor Grazing Act of 1934

    In response to overgrazing of available rangelands by livestock 
from the 1800s to the 1930s, Congress passed the Taylor Grazing Act in 
1934 (43 U.S.C. 315 et seq.). This action was an effort to stop the 
damage to the remaining public lands as a result of overgrazing and 
soil depletion, to provide coordination for grazing on public lands, 
and to attempt to stabilize the livestock industry (Meehan and Platts 
1978, p. 275; Public Lands Council et al. v. Babbitt Secretary of the 
Interior et al. (167 F. 3d 1287)). Passage of the Taylor Grazing Act 
resulted in reduced grazing in some areas, including the high Sierra 
Nevada. However, localized use remained high, precluding regeneration 
of many meadow areas (Beesley 1996, p. 14; Menke et al. 1996, p. 14; 
Public Lands Council et al. v. Babbitt Secretary of the Interior et al. 
(167 F. 3d 1287)).
    Existing Federal and State laws and regulatory mechanisms currently 
offer some level of protection for the Yosemite toad. Specifically, 
these include the Wilderness Act, the NFMA, the SNFPA, and the FPA (see 
Factor D discussion for mountain yellow-legged frog complex). Based on 
the best available scientific and commercial information, we do not 
consider the inadequacy of existing regulatory mechanisms to be a 
threat to the Yosemite toad.

Factor E. Other Natural or Manmade Factors Affecting Its Continued 
Existence

    The Yosemite toad is sensitive to environmental change or 
degradation due to its life history, biology, and existence in 
ephemeral habitats characterized by climate extremes and low 
productivity. It is also sensitive to anthropogenically influenced 
factors. For example, contaminants, acid precipitation, ambient 
ultraviolet radiation, and climate change have been implicated as 
contributing to amphibian declines (Corn 1994, pp. 62-63; Alford and 
Richards 1999, pp. 2-7). However, as with the case with the mountain 
yellow-legged frog complex, contaminants, acid precipitation, and 
ambient ultraviolet radiation are not known to pose a threat (current 
or historical) to Yosemite toad and, therefore, are not discussed 
further. Please refer to the proposed listing rule for the Sierra 
Nevada yellow-legged frog, the northern DPS of the mountain yellow-
legged frog, and the Yosemite toad (78 FR 24472, April 25, 2013) for a 
detailed discussion of contaminants, acid precipitation, and ambient 
ultraviolet radiation. The following discussion will focus on potential 
threat factors specifically studied in the Yosemite toad, based on the 
unique life history, population status, demographics, or biological 
factors specific to Yosemite toad populations.
Climate Change Effects on Individuals
    As discussed above in Factor A, climate change can result in 
detrimental impacts to Yosemite toad habitat. Climate variability could 
also negatively impact populations through alteration of the frequency, 
duration, and magnitude of either droughts or severe winters (USFS et 
al. 2009, p. 47). Yosemite toads breed and their tadpoles develop in 
shallow meadow and ephemeral habitats, where mortality from desiccation 
and freezing can be very high, often causing complete loss of an annual 
cohort (USFS et al. 2009, p. 10). Kagarise Sherman and Morton (1993, 
pp. 192-193) documented in a long-

[[Page 24298]]

term population study that Yosemite toad hatching success and survival 
were subject to a balance between the snowpack water contribution to 
breeding pools and the periodicity and character of breeding season 
storms and post-breeding climate (whether it is cold or warm). When it 
is too cold, eggs and tadpoles are lost to freezing. This situation 
poses a risk as earlier snowmelt is expected to cue breeding earlier in 
the year, exposing young tadpoles (or eggs) to killing frosts in more 
variable conditions of early spring (Corn 2005, p. 60). When it is too 
dry, tadpoles are lost to pool desiccation. Alterations in the annual 
and seasonal hydrologic cycles that influence water volume and 
persistence in Yosemite toad breeding areas can thereby impact breeding 
success. The threat of climate change on individuals is significant, 
and is of high prevalence now and into the future.
Other Sources of Direct and Indirect Mortality
    Direct and indirect mortality of Yosemite toads has occurred as a 
result of livestock grazing. Mortality risk from livestock trampling is 
expected to be the greatest for non-larval stages where livestock 
concentrate in Yosemite toad habitat when toad densities are highest; 
early in the season when breeding adults are aggregated and egg masses 
are laid; and at metamorphosis when juveniles are metamorphosing in 
mass along aquatic margins. However, because cattle typically are not 
present during the breeding season, the risk of trampling is expected 
to be greatest for metamorphs (USFS et al. 2009, p. 59). Cattle have 
been observed to trample Yosemite toad metamorphs and subadult toads, 
and these life stages can fall into deep hoofprints and die (Martin 
2008, p. 158). Specifically, Martin (2008, p. 158) witnessed some 60 
subadult and metamorph toad deaths during the movement of 25 cattle 
across a stream channel bordered by willows within a meadow complex. 
Adult Yosemite toads trampled to death by cattle have also been 
observed (Martin 2002, pp. 1-3). This risk factor is likely of sporadic 
significance, and is of greatest concern where active grazing 
allotments coincide with breeding meadows. However, it is difficult to 
determine the degree of this impact without quantitative data.
    Trampling and collapse of rodent burrows by recreationists, pets, 
and vehicles could lead to direct mortality of terrestrial life stages 
of the Yosemite toad. Recreational activity may also disturb toads and 
disrupt their behavior (Karlstrom 1962, pp. 3-34). Recreational anglers 
may be a source of introduced pathogens and parasites, and they have 
been observed using toads and tadpoles as bait (USFS et al. 2009, p. 
66). However, Kagarise Sherman and Morton (1993, p. 196) did not find a 
relationship between the distance from the nearest road and the 
declines in their study populations, suggesting that human activity was 
not the cause of decline in that situation. Recreational activity may 
be of conservation concern, and this threat may increase with greater 
activity in mountain meadows. However, current available information 
does not indicate that recreational activity is a significant stressor 
for Yosemite toads.
    Fire management practices over the last century have created the 
potential for severe fires in the Sierra Nevada. Wildfires do pose a 
potential direct mortality threat to Yosemite toads, although 
amphibians in general are thought to retreat to moist or subterranean 
refuges and thereby suffer low mortality during natural fires (Russel 
et al. 1999, pp. 374-384). In the closely related boreal toad (Bufo 
boreas), Hossak and Corn (2007, p. 1409) documented a positive response 
(increase in occupied breeding sites and population size) following a 
wildfire, with returns to near pre-fire occupancy levels after 4 to 5 
years (Hossack et al. 2012, p. 224), suggesting that habitat-related 
changes associated with wildfires may provide at least short-term 
benefits to Yosemite toad populations. However, data on the direct and 
indirect effects of fire on Yosemite toads are lacking.
    USFS et al. (2009, p. 74) suggested that the negative effects of 
roads that have been documented in other amphibians, in concert with 
the substantial road network across a portion of the Yosemite toad's 
range, indicate this risk factor may be potentially significant to the 
species. Roads may facilitate direct mortality of amphibians through 
vehicle strikes (DeMaynadier and Hunter 2000, pp. 56-65), and timber 
harvest activities (including fuels management and vegetation 
restoration activities) have been documented to result in the direct 
mortality of Yosemite toads (USFS 2013, p. 94). Levels of timber 
harvest and road construction have declined substantially since 
implementation of the California Spotted Owl Sierran Province Interim 
Guidelines in 1993, and some existing roads have been decommissioned or 
are scheduled to be decommissioned (USDA 2001a, p. 445). Therefore, the 
risks posed by new roads and timber harvests have declined, but those 
already existing still may pose risks to the species and its habitat.
    Toads could potentially be trampled or crushed by activities 
implemented to reduce fire danger. USFS et al. (2009, p. 53) report 
that the Forest Service has initiated a fuels reduction program in 
order to reduce the extent and intensity of wildfires. However, most of 
these projects will occur in the Wildland Urban Interface, which is 
below the elevational range of the Yosemite toad and generally near 
human developments. However, in the future some fuels projects may 
occur in limited areas around facilities, such as resorts, pack 
stations, or summer homes, within the lowest portion of the Yosemite 
toad range.
    Collectively, direct mortality from land uses within the Yosemite 
toad range may have impacts to the toad. However, we are aware of no 
studies that have quantified or estimated the prevalence of this 
particular threat to be able to assess its impact to Yosemite toad 
populations. At the current time, direct and indirect mortality from 
roads are not considered to be a significant factor affecting the 
Yosemite toad rangewide.
Small Population Size
    Although it is believed that the range of the Yosemite toad has not 
significantly contracted, the majority of populations across this area 
have been extirpated, and this loss has been significant relative to 
the historical condition (multitudes of populations within many 
watersheds across their geographic range) (see ``Population Estimates 
and Status'' above). Further, growing evidence suggest that the 
populations that remain are small, numbering fewer than 20 males in 
most cases (Kagrise Sherman and Morton 1993, p. 190; Sadinski 2004, p. 
40; Brown et al. 2012, p. 125). This situation renders these remnant 
populations susceptible to risks inherent to small populations (see 
Factor E discussion, ``Small Population Size,'' for mountain yellow-
legged frogs, above) including inbreeding depression and genetic drift, 
along with a higher probability of extirpation from unpredictable 
events such as severe storms or extended droughts.
    Traill et al. (2009, p. 32) argued for a benchmark viable 
population size of 5,000 adult individuals (and 500 to prevent 
inbreeding) for a broad range of taxa, although this type of blanket 
figure has been disputed as an approach to conservation (Flather et al. 
2011, pp. 307-308). Another estimate, specific to amphibians, is that 
populations of at least 100 individuals are less susceptible to 
demographic stochasticity (Schad 2007, p. 10). Amphibian species

[[Page 24299]]

with highly fluctuating population size, high frequencies of local 
extinctions, and living in changeable environments may be especially 
susceptible to curtailment of dispersal and restriction of habitat 
(Green 2003, p. 331). These conditions are all likely applicable to the 
Yosemite toad.
    Therefore, based on the best available commercial and scientific 
information, we conclude that small population size is a prevalent and 
significant threat to the species viability of the Yosemite toad across 
its range, especially in concert with other extant stressors (such as 
climate change).
Cumulative Impacts of Extant Threats
    Interactive effects or cumulative impacts from multiple additive 
stressors acting upon Yosemite toad populations over time are indicated 
by the documented declines in populations and abundance across the 
range of the species. Although no single causative factor linked to 
population declines in Yosemite toads has been confirmed in the 
literature (excepting perhaps extreme climate conditions such as 
droughts) (Kagarise Sherman and Morton 1993, p. 186; Jennings and Hayes 
1994, pp. 50-53), there has been a decline in population abundance and 
numbers of extant populations inhabiting the landscape (Brown et al. 
2012, pp. 115-131; Kagarise Sherman and Morton 1993, pp. 186-198). This 
pattern of decline suggests a factor or combination of factors common 
throughout the range of the toad. The available literature (Kagarise 
Sherman and Morton 1993, pp. 186-198; Jennings and Hayes 1994, pp. 50-
53; USFS et al. 2009, pp. 1-133; Martin 2008, pp. i-393) supports the 
contention that a combination of factors has interacted and is 
responsible for the decline observed in Yosemite toad populations over 
the past few decades.
    Disease has been documented in Yosemite toad populations, and 
recent data documenting historic trends in Bd infection intensity are 
compelling (Dodge and Vredenburg 2012, p. 1), but disease has not been 
definitively tied to the observed rangewide decline. There is 
considerable evidence that various stressors, mediated via impacts to 
meadow hydrology following upslope land management practices over the 
last century, have detrimentally affected the quantity and quality of 
breeding meadows. Many of these stressors, such as grazing, have been 
more significant in the past than under current management standards. 
However, legacy effects remain, and meadows tend not to recover without 
active intervention once excessive stream incision in their watershed 
is set in motion (Vankat and Major 1978, pp. 386-397). Certain 
stressors may be of concern, such as recreational impacts and avian 
predation upon terrestrial life stages of toads, although we do not 
have sufficient data to document the magnitude of these particular 
stressors.
    Given the evidence supporting the role of climate in reducing 
populations and potentially leading to the extirpation of many of the 
populations studied through the 1970s and into the early 1990s 
(Kagarise Sherman and Morton 1993, pp. 186-198), this factor is likely 
either a primary driver, or at least a significant contributing factor 
in the declines that have been observed. Climate models predict 
increasing drought intensity and changes to the hydroperiod based on 
reduced snowpack, along with greater climate variability in the future 
(PRBO 2011, pp. 18-25). These changes will likely exacerbate stress to 
the habitat specialist Yosemite toad through a pronounced impact on its 
ephemeral aquatic habitat, and also through an increase in the 
frequency of freezing and drying events that kill Yosemite toad eggs 
and tadpoles. These changes and the resultant impacts likely will 
effectively reduce breeding success of remnant populations already at 
low abundance and still in decline. If an interaction such as winter 
stress and disease (Carey 1993, pp. 355-362) is the underlying 
mechanism for Yosemite toad declines, then the enhanced influence of 
climate change as a stressor may tip the balance further towards higher 
incidence and increased virulence of disease, which would also lead to 
greater population declines and extirpations.

Determination for Yosemite Toad

    Section 4 of the Act (16 U.S.C. 1533), and its implementing 
regulations at 50 CFR part 424, set forth the procedures for adding 
species to the Federal Lists of Endangered and Threatened Wildlife and 
Plants. Under section 4(a)(1) of the Act, we may list a species based 
on (A) The present or threatened destruction, modification, or 
curtailment of its habitat or range; (B) Overutilization for 
commercial, recreational, scientific, or educational purposes; (C) 
Disease or predation; (D) The inadequacy of existing regulatory 
mechanisms; or (E) Other natural or manmade factors affecting its 
continued existence. Listing actions may be warranted based on any of 
the above threat factors, singly or in combination.
    We have carefully assessed the best scientific and commercial 
information available regarding the past, present, and future threats 
to the Yosemite toad. The Yosemite toad is the most narrowly 
distributed Sierra Nevada endemic, pond-breeding amphibian (Shaffer et 
al. 2000, p. 246). Although it apparently still persists throughout a 
large portion of its historical range, it has been reduced to an 
estimated 13 percent of historical watersheds. (The proposed rule 
indicated that the toad was reduced to an estimated 12 percent of its 
range, peer review corrected this number to 13 percent (Brown 2013, 
unpaginated). In addition, while the best available data do not provide 
information on whether populations are currently stable, or whether 
there is a persistent decline, remnant populations are predominantly 
small.
    Yosemite toad populations are subject to threats from habitat 
degradation associated with land uses that negatively influence meadow 
hydrology, fostering meadow dewatering, and conifer and other invasive 
plant encroachment. These activities include the legacy effects of 
historic grazing activities, the fire management regime of the past 
century, historic timber management activities, and associated road 
construction. The impacts from these threats are cumulatively of 
moderate magnitude, and their legacy impacts on meadow habitats act as 
a constraint upon extant populations now and are expected to hinder 
persistence and recovery into the future. Diseases are threats of 
conservation concern that have likely also had an effect on populations 
leading to historical population decline, and these threats are 
operating currently and will continue to do so into the future, likely 
with impacts of moderate-magnitude effects on Yosemite toad 
populations.
    The individual, interactive, and cumulative effects of these 
various risk factors have acted to reduce the geographic extent and 
abundance of this species throughout its habitat in the Sierra Nevada. 
The combined effect of these stressors acting upon small remnant 
populations of Yosemite toads is of significant conservation concern. 
The Yosemite toad has a life history and ecology that make it sensitive 
to drought and anticipated weather extremes associated with climate 
change. Climate change is expected to become increasingly significant 
to the Yosemite toad and its habitat in the future throughout its 
range. Therefore, climate change represents a threat that has a high 
magnitude of impact as an indirect stressor via habitat loss and 
degradation, and as a direct stressor via enhanced risk of climate 
extremes to all life stages of Yosemite toads.

[[Page 24300]]

    The Act defines an endangered species as any species that is ``in 
danger of extinction throughout all or a significant portion of its 
range'' and a threatened species as any species ``that is likely to 
become endangered throughout all or a significant portion of its range 
within the foreseeable future.'' We find that the Yosemite toad is 
likely to become endangered throughout all or a significant portion of 
its range within the foreseeable future, based on the immediacy, 
severity, and scope of the threats described above. These include 
habitat loss associated with degradation of meadow hydrology following 
stream incision consequent to the cumulative effects of historic land 
management activities, notably livestock grazing, and also the 
anticipated hydrologic effects upon habitat from climate change under 
listing Factor A. Additionally, we find that disease under listing 
Factor C was likely a contributor to the recent historic decline of the 
Yosemite toad, and may remain an important factor limiting recruitment 
in remnant populations. We also find that the Yosemite toad is likely 
to become endangered through the direct effects of climate change 
impacting small remnant populations under Factor E, likely compounded 
with the cumulative effect of other threat factors (such as disease).
    We have carefully assessed the best scientific and commercial 
information available regarding the past, present, and future threats 
to the species, and have determined that the Yosemite toad meets the 
definition of threatened under the Act, rather than endangered. This 
determination is because the impacts from the threats are occurring now 
at high and moderate magnitudes, but are all likely to become of high 
magnitude in the foreseeable future across the species' entire range, 
making the species likely to become in danger of extinction. While 
population decline has been widespread, the rate of decline is not so 
severe to indicate extinction is imminent, but this rate could increase 
as stressors such as climate change impact small remnant populations. 
Further, the geographic extent of the species remains rather widespread 
throughout its historic range, conferring some measure of ecological 
and geographic redundancy. Therefore, on the basis of the best 
available scientific and commercial information, we finalize listing 
the Yosemite toad as threatened in accordance with sections 3(20) and 
4(a)(1) of the Act.
    The term ``threatened species'' means any species (or subspecies 
or, for vertebrates, distinct population segments) that is likely to 
become an endangered species within the foreseeable future throughout 
all or a significant portion of its range. The Act does not define the 
term ``foreseeable future'' but it likely describes the extent to which 
the Service could reasonably rely on predictions about the future in 
making determinations about the future conservation status of the 
species. In considering the foreseeable future as it relates to the 
status of the Yosemite toad, we considered the historical data to 
identify any relevant existing trends that might allow for reliable 
prediction of the future (in the form of extrapolating the trends). We 
also considered how current stressors are affecting the species and 
whether we could reliably predict any future trends in those stressors 
that might affect the species recognizing that our ability to make 
reliable predictions for the future is limited by the quantity and 
quality of available data. Thus the foreseeable future includes the 
species' response to these stressors and any trends.
    Under the Act and our implementing regulations, a species may 
warrant listing if it is endangered or threatened throughout all or a 
significant portion of its range. The Yosemite toad is highly 
restricted in its range, and the threats occur throughout its range. 
Therefore, we assessed the status of the species throughout its entire 
range. The threats to the survival of the species occur throughout the 
species' range and are not restricted to any particular significant 
portion of that range, nor are they concentrated in a specific portion 
of the range. Accordingly, our assessment and final determination 
applies to the species throughout its entire range.

Summary of Comments

    In the proposed rule published on April 25, 2013 (78 FR 24472), we 
requested that all interested parties submit written comments on the 
proposal by June 24, 2013. Given the large number of requests that we 
received to extend the public comment period, we reopened the comment 
period on July 19, 2013 (78 FR 43122), requesting written comments on 
the proposal by November 18, 2013, and again reopened the comment 
period on January 10, 2014 (79 FR 1805), with the close of comment 
period on March 11, 1014. We also contacted appropriate Federal and 
State agencies, scientific experts and organizations, and other 
interested parties and invited them to comment on the proposal. 
Newspaper notices inviting general public comment were published in the 
Sacramento Bee and Bakersfield Californian. We received multiple 
requests for a public hearing. We held two public hearings on January 
30, 2014, in Sacramento, California. We also held two public 
informational meetings, one in Bridgeport, California, on January 8, 
2014, and the other in Fresno, California, on January 13, 2014. We also 
participated in several public forums, one sponsored by Congressman 
McClintock and two sponsored by Congressman LaMalfa. All substantive 
information provided during comment periods has either been 
incorporated directly into this final determination or addressed below.

Peer Reviewer Comments

    In accordance with our peer review policy published on July 1, 1994 
(59 FR 34270), we solicited expert opinion from five knowledgeable 
individuals with scientific expertise that included familiarity with 
the Sierra Nevada yellow-legged frog, the northern DPS of the mountain 
yellow-legged frog, the Yosemite toad, and the habitat and biological 
needs of, and threats to each species. We received responses from four 
of the peer reviewers.
    We reviewed all comments received from the peer reviewers for 
substantive issues and new information regarding the listing of the 
Sierra Nevada yellow-legged frog, the northern DPS of the mountain 
yellow-legged frog, and the Yosemite toad. The peer reviewers generally 
concurred with our methods and conclusions and provided additional 
information, clarifications, and suggestions to improve the final rule. 
However, one of the four peer reviewers suggested the rationale for 
listing Yosemite toad was poorly supported. Peer reviewer comments are 
addressed in the following summary and incorporated into the final 
rule.
    (1) Comment: Two peer reviewers recommended that we refer to Rana 
muscosa as the southern mountain yellow-legged frog in order to reduce 
reader confusion in the final rule.
    Our Response: We have clarified the common names we are using in 
this final rule for each yellow-legged frog species (see Background and 
Taxonomy sections in this final rule). While Crother et al. (2008, p. 
11) accepted the common name of southern mountain yellow-legged frog 
for Rana muscosa, the use of this common name may create additional 
confusion as the reader may interpret the name to imply the yellow-
legged frogs in southern California that are already listed as the 
southern DPS, rather than the R. muscosa in the Sierra Nevada. 
Therefore, we continue to refer to the northern DPS of Rana muscosa as 
the northern DPS of the mountain yellow-legged frog, as we did in the 
proposed

[[Page 24301]]

rule, to minimize confusion for the public.
    (2) Comment: Two peer reviewers suggested that we utilize a 
rangewide analysis for listing Rana muscosa and thereby combine the 
northern and southern DPSs of the mountain yellow-legged frog into one 
listed entity. Clarifying discussions with one peer reviewer suggested 
that we not complete a rangewide analysis, but rather keep the DPSs 
separate (Knapp, pers. comm.).
    Our Response: Given the geographic isolation, different habitat 
requirements, differences in threats, and different management needs 
between Rana muscosa in the Sierra Nevada compared with southern 
California, we have decided to retain the DPS analysis in the proposed 
rule and to maintain the northern and southern DPSs of mountain yellow-
legged frog as separate listed entities. Within the Sierra Nevada, R. 
muscosa is predominantly found within high-elevation lake habitats that 
freeze during the winter months, while in southern California, Rana 
muscosa populations occupy stream habitats that are not typically 
subject to winter freezing. The differences in the habitats utilized by 
the northern and southern DPSs of the mountain yellow-legged frog and 
the differences in the threats to each population segment indicate that 
management actions needed to recover the northern California and 
southern California populations will also be different and are most 
expediently addressed separately by DPS (see Distinct Vertebrate 
Population Segment Analysis in this final rule).
    The factors that are threats to the species also differ between the 
two DPSs. We have identified fish stocking and presence of fish as a 
threat for both the northern and southern DPSs. However, the other 
threats we identified for the northern DPS are primarily habitat 
degradation, disease, and climate change, whereas the main threats for 
the southern DPS consist of recreational activities, roads, and 
wildfire. While there is some overlap in the threats identified for the 
two DPSs, the threats that are important to the species status vary 
substantially between the Sierra Nevada and southern California.
    The differences between the northern and southern DPSs of the 
mountain yellow-legged frog in both habitat use and the factors 
affecting the species results in differences in the actions and 
activities that would be needed to conserve the species in each of the 
two DPSs. Conservation planning, including identifying actions and 
setting priorities for recovery, will be more effective and better 
suited to meet the species' needs if two separate DPSs are retained.
    (3) Comment: One peer reviewer indicated that the frogs within the 
Spanish and Bean Creek areas of Plumas County (low-elevation areas 
within the northern portion of the Sierra Nevada) in which Wengert 
(2008) conducted telemetry studies of frog movement distances, may 
actually be foothill yellow-legged frog (Rana boylii) rather than 
Sierra Nevada yellow-legged frogs (Rana sierrae) (see Habitat and Life 
History section in Background for the mountain yellow-legged frogs of 
this final rule).
    Our Response: We acknowledge and understand some of the challenges 
in correctly identifying the species in areas where the ranges of 
Sierra Nevada and foothill yellow-legged frogs overlap. Recent genetic 
analysis of samples collected from frogs in Spanish and Bean Creeks has 
identified the frogs occurring in Bean Creek as both Sierra Nevada and 
foothill yellow-legged frogs (Lind et al. 2011a, pp. 281-282), while 
Spanish Creek frogs were identified as foothill yellow-legged frog 
(Poorten et al. 2013, p. 4). However, given the small sample size, 
Poorten et al. (2013, p. 4) suggested that followup investigation was 
needed to determine whether Sierra Nevada yellow-legged frogs also 
occur in Spanish Creek.
    While it is not clear whether Wengert (2008) studied Sierra Nevada 
or foothill yellow-legged frogs, given the stream-based ecological 
setting of the study, we expect that the movement distances recorded 
are applicable to the Sierra Nevada yellow-legged frog within a stream-
based system, as the ecology is comparable between the two sister taxa 
in regard to stream systems. Additionally, a study conducted by Fellers 
et al. (2013, p. 159) documented Sierra Nevada yellow-legged frog 
movement distances up to 1,032 m in a 29-day period, suggesting the 
season-long movement distance documented by Wengert (2008, p. 20) is 
applicable.
    (4) Comment: One peer reviewer provided comment that our proposed 
rule did not include more-recent literature on the effects of airborne 
contaminants on the mountain yellow legged frog, including Bradford et 
al. 2011, which measured contaminant concentrations at multiple sites 
in the southern Sierra Nevada and compared their distribution with 
population declines of mountain yellow-legged frogs, finding no 
association between the two. The peer reviewer further recommended that 
we state that frogs are sensitive to contaminants, but measured 
contaminant concentrations in multiple media indicate very low 
exposures to contaminants from upwind sources.
    Our Response: In our proposed rule, we included a discussion of 
environmental factors that affect the mountain yellow-legged frog 
complex, including contaminants. Based on our analysis in the proposed 
rule, we did not identify this environmental factor as a threat to the 
species. Upon our review of additional literature, including a study 
focused specifically on the mountain yellow-legged frog complex, our 
initial discussion remains valid, which indicated that the potential 
threat posed by contaminants is not a factor in the listing of this 
species. We refer to the proposed rule for the discussion of the 
effects of contaminants on the mountain yellow-legged frog.
    (5) Comment: One peer reviewer suggested that recent genetic 
studies (Shaffer et al. 2000, Stevens 2001, and Goebel et al. 2009) do 
not support our conclusion that Yosemite toad is a valid species.
    Our Response: When conducting our review of the Yosemite toad as a 
listable entity under the Act, we incorporated the results of the 
studies mentioned by the peer reviewer. In addition to the previously 
included literature on the genetics of Yosemite toad, we have included 
in this final rule results from Switzer et al. (2009), which provide 
genetic data supporting the Yosemite toad as a valid species. While we 
acknowledge that the evolutionary history of the Yosemite toad is 
complicated and not fully understood, given our conclusions after 
reviewing the taxonomy of the species, and given that the scientific 
community as a whole continues to recognize the Yosemite toad as a 
valid species, we continue to recognize Yosemite toad as a valid 
species (for further discussion, see Taxonomy section above).
    (6) Comment: One peer reviewer provided information regarding the 
number of localities of Yosemite toad within two National Parks, and 
suggested that, had we included these locations, the analysis may have 
had a different outcome.
    Our Response: When we conducted our analysis for the proposed rule 
to determine whether the Yosemite toad warrants listing under the Act, 
we utilized the best available scientific and commercial information. 
Part of that information included the geospatial data for Yosemite toad 
locations within both Yosemite and Sequoia National Parks. These data 
were subsequently used for the proposed critical habitat designation. 
While we did have (and used) the information on Yosemite toad locations 
within the National Parks in

[[Page 24302]]

our analysis, we did not cite to this information into the text of the 
proposed rule. This was updated with the data included in Berlow et al. 
(2013), as well as information received from Sequoia National Park 
staff. Regardless, we utilized the geospatial data in the proposed 
rule, determining that the information suggests that the Yosemite toad 
has disappeared from approximately 47-69 percent of formerly occupied 
sites (Berlow et al. 2013, p. 2). In addition, at many of the remaining 
sites, Yosemite toads exist in very low numbers, indicating that many 
remaining populations are vulnerable to extirpation. Our use of the 
data from both National Forests and National Parks led us to our 
proposed status determination, which is affirmed here.
    (7) Comment: One peer reviewer stated that there is scant evidence 
available to argue that there has been a decline in abundance of the 
Yosemite toad and that the difficulty in accurately quantifying toad 
abundance, coupled with the fact that the proposed rule did not include 
locality data from the National Parks, has weakened the argument for 
our determination.
    Our Response: While we agree that no studies have documented a 
rangewide decline in population abundances in Yosemite toads, and we do 
not have sufficient data to conduct a robust trend analysis or detect 
negative population growth rates, we relied on published literature for 
our determination. At a minimum, the published literature provides 
anecdotally documented declines in numbers of individual Yosemite toads 
at the respective study sites. The best available information shows 
that the Yosemite toad populations have declined, and that the remnant 
populations comprise low numbers of individual adult toads. For our 
analysis, we did utilize the data on toad locations in the National 
Parks (see our response to comment 6) and included it as part of our 
analysis on the estimated loss of historically occupied sites (47-69 
percent of formerly occupied sites (Berlow et al. 2013, p. 2)). We 
mainly focused our analysis on the potential drivers of population 
stability and identified the predominate threats to the species as the 
continuing effects of degradation of meadow hydrology associated with 
historical land management practices and the effects of climate change 
and anthropogenic stressors acting on the small remnant populations. 
(For complete discussion see Summary of Factors Affecting the Species 
section above.)
    (8) Comment: One peer reviewer stated that there are scientific 
uncertainties regarding the long-term population trends and threats to 
Yosemite toad and that these uncertainties should be explicitly 
described.
    Our response: As required by the Act, we based our proposed rule 
and this final rule on the best available scientific and commercial 
data. While there are some uncertainties in the information, we clearly 
articulated these uncertainties when conducting our analysis for the 
rule. (See Population Estimate and Status and Meadow Habitat Loss and 
Degradation sections for examples.)

Federal Agency Comments

    (9) Comment: The Forest Service suggested that the rule does not 
represent the best available scientific and commercial information in 
proposing a determination.
    Our Response: In conducting our analysis, we rely on the best 
available scientific and commercial information, as required by the 
Act. On occasion, we are not aware of certain information that is 
available at the time we issue a proposed rule or new information 
becomes available around the time of publication, which is part of the 
reason we request public comment, as well as peer review. That portion 
of the process helps to inform our final decision by soliciting input 
and seeking additional available information. As a result of this 
process, we have received new scientific and commercial information 
that we have reviewed and incorporated into this final rule.
    (10) Comment: The USFS noted that the proposed rule did not 
identify mining activities as a threat to the mountain yellow-legged 
frog.
    Our Response: We acknowledge that there is some overlap between 
current mining activities and areas occupied by the mountain yellow-
legged frogs, particularly in the northern part of the range; however, 
we do not have information to assess the impact that mining has on the 
species in those areas where mining occurs, and how it acts as either 
an historical or current threat to the species. Within designated 
wilderness, new mining claims have been prohibited since January 1, 
1984. Additionally, while suction dredge mining may have the potential 
to alter microhabitat uses by the species, the current moratorium on 
this practice removes this potential threat. However, we acknowledge 
that this situation may change in the future.
    (11) Comment: The USFS suggested that the uncertainties we 
presented under Factor D as it relates to their Forest Plan revision 
process and protections for mountain yellow-legged frog are not 
applicable and that the protections under the SNFPA will continue as a 
result of consultation with the Service.
    Our Response: We did not identify Factor D as a threat to the 
mountain yellow-legged frog, and we incorporated an analysis of the 
protection that the current Forest Plans offer the species. While there 
is some uncertainty as to whether these protections will remain in the 
revised Forest Plans, the USFS is not required to consult with the 
Service on the Sierra Nevada yellow-legged frog and northern DPS of the 
mountain yellow-legged frog in the absence of the protections afforded 
under the Act. As such, we must evaluate the adequacy of existing 
regulatory mechanisms from the baseline of the species not being 
federally listed under the Act.
    (12) Comment: The USFS suggested the final rule include a 
discussion of the impacts of bullfrog predation on the mountain yellow-
legged frog.
    Our Response: We have limited information on the presence of 
bullfrogs in the Sierra Nevada, but we have included a section on the 
potential threat of American bullfrogs where they are known to occur in 
the Lake Tahoe Basin (see discussion under Factor C for mountain 
yellow-legged frogs).
    (13) Comment: The USFS and several other commenters suggested that 
the information presented as it relates to the impacts of grazing on 
Yosemite toad was inaccurate. Specifically, they suggested that we did 
not include the results of peer-reviewed journal articles in our 
analysis of the impacts posed by livestock grazing.
    Our Response: At the time of the proposed rule, we were aware of 
the peer-reviewed literature related to the impacts of livestock 
grazing on Yosemite toad, and inadvertently omitted the literature from 
the rule. We have reviewed and included the relevant articles in this 
final rule. Additionally, while we did not incorporate all of the 
specifics of the journal articles, we did incorporate the results of a 
5-year study that investigated the impacts of cattle grazing on 
Yosemite toad in our analysis, as they were presented in Allen Diaz et 
al. 2010, and subsequently in the Lind et al. (2011b, addendum).
    (14) Comment: The USFS and several other commenters suggested that 
our reliance on a single non-peer-reviewed study to assess the impacts 
of cattle grazing on Yosemite toads, through direct mortality or the 
modification of their habitat, was inappropriate. Additionally, they 
suggested we discounted the peer-reviewed published

[[Page 24303]]

journal articles related to the impacts of cattle grazing on Yosemite 
toad.
    Our Response: In conducting our analysis, we rely on the best 
available scientific and commercial information, as required by the 
Act. This information does not need to be specifically published in a 
scientific journal. The Martin (2008) study that is being referred to 
by the commenters is a doctoral dissertation that was, in fact, 
reviewed prior to release. We relied on the information presented by 
Martin in assessing the potential for direct mortality of Yosemite toad 
that is attributed to livestock. We also relied on Martin for the 
potential impacts of livestock grazing on overwintering and upland 
areas utilized by Yosemite toad, as the peer-reviewed publications that 
the commenters referred to were based on a study that only assessed 
grazing effects on breeding. As such, the best available scientific and 
commercial information includes Martin (2008). In our proposed rule, we 
evaluated the information that ran contrary to Martin (2008), and we 
have subsequently incorporated the information presented in the peer-
reviewed journal articles in this final rule. Please also see response 
to comment 13.
    (15) Comment: The USFS commented that chytrid fungus, fish 
stocking, and climate change pose the greatest threats to the mountain 
yellow-legged frogs, and that threats from authorized management 
activities are insignificant threats to the species.
    Our Response: We have concluded in this final rule that, in 
general, authorized activities on public lands managed by the USFS and 
the NPS are not significant threats to the mountain yellow-legged 
frogs, but we also recognize that there may be limited site-specific 
conditions where authorized activities could have population-level 
effects, especially where populations are small or habitat areas are 
limited (see Summary of Factors Affecting the Species in this final 
rule).
    (16) Comment: The USFS noted that recent publications indicate that 
livestock grazing that meets current USFS standards and guidelines is 
less of a threat to the Yosemite toad than was described in the 
proposed rule.
    Our Response: We have revised our discussion of grazing in this 
final rule to clarify the conditions under which we consider current 
grazing activities to pose habitat-related threats to the Yosemite toad 
(see Summary of Changes and Factor A discussion for the Yosemite toad).

Comments From States

    (17) Comment: The California Department of Fish and Wildlife (CDFW) 
originally commented that the threats presented in the proposed rule 
suggested that a determination of threatened status would be more 
appropriate than endangered for the Sierra Nevada yellow-legged frog. 
However, CDFW reconsidered this suggestion after discussions with 
Service staff and submitted a followup comment letter that agrees with 
the Service determination and supports listing the Sierra Nevada 
yellow-legged frog as endangered.
    Our Response: We find that an endangered status for the Sierra 
Nevada yellow-legged frog is an appropriate determination and 
appreciate CDFW's reconsideration of their initial comments.
    (18) Comment: CDFW commented that they remain concerned that 
listing the species as endangered could hinder timely implementation of 
the Department's recovery and restoration efforts for the species 
pursuant to its State-listing under CESA. CDFW notes that they have a 
responsibility to continue activities and expand efforts that will 
contribute to the recovery of the Sierra Nevada yellow-legged frog and 
hope that such efforts can be fostered through the 1991 Cooperative 
Agreement between the California Department of Fish and Game and the 
U.S. Fish and Wildlife Service. They also comment that, in his June 13, 
2012, memo to the Service's Regional Directors, the Director of the 
Fish and Wildlife Service acknowledged the Federal-State collaborative 
nature of conservation activities for listed species.
    Our Response: We note that, for research activities that aid in the 
recovery of the species, and that may result in take, a permit issued 
under section 10a(1)A of the Act is the appropriate mechanism. However, 
our regulations at 50 CFR 17.21 state that any qualified employee or 
agent who is designated by CDFW for such purposes, may, when acting in 
the course of his official duties, take endangered wildlife species 
covered by a Cooperative Agreement (developed pursuant to Section 6 of 
the Act) between the Service and the State provided such take is not 
reasonably anticipated to result in: (1) The death or permanent 
disabling of the specimen; (2) the removal of the specimen from the 
State of California; (3) the introduction of the specimen or any of its 
progeny into an area beyond the historical range of the species; or (4) 
the holding of the specimen in captivity for a period of more than 45 
days. Take that does not meet these four conditions would require a 
section 10(a)(1)(A) permit. We acknowledge and appreciate the important 
role that CDFW will play in the recovery of the Sierra Nevada yellow-
legged frog, and look forward to continuing collaborative conservation 
actions with CDFW for this and other listed species in California.
    (19) Comment: CDFW agreed that we should retain the northern DPS 
and the southern DPS designations for the mountain yellow-legged frog 
(Rana muscosa). They provided updates to our discussion of take related 
to State-listing of the mountain yellow-legged frog complex.
    Our Response: We appreciate the support, and we have retained the 
two DPSs in the final determination (see Distinct Vertebrate Population 
Segment Analysis). We have also revised our discussion of CESA to 
provide the updated information on take related to State-listing of the 
mountain yellow-legged frog complex (see Factor D for mountain yellow-
legged frog).
    (20) Comment: CDFW provided comments on our discussion of the 
following threats to the mountain yellow-legged frog complex: 
Recreational activities, past trout stocking versus continued trout 
stocking, and pesticide detection in the Sierra Nevada. They commented 
that the evidence presented in the Recreation section did not support 
the conclusion, urging us to readdress the section and remove claims 
unsupported by appropriate citations, and noted that recreation effects 
to the environment were supported, but no evidence indicates that such 
activities affect the frog populations. In the Recreation section, they 
also noted several errors and inaccuracies in citing other authors. 
CDFW provided extensive comments on our discussion of dams and water 
diversions, commenting that they were of the opinion that dams and 
diversion posed a threat of low significance to the continued existence 
of the mountain yellow-legged frogs and suggesting that the section 
required significant amendments to accurately capture the degree of 
potential impacts. They noted that most dams were constructed below the 
range of extant frog populations, and that some information was 
misapplied from research on lower-elevation amphibian species, such as 
the foothill yellow-legged frog, which resulted in overstatement of the 
potential impact of dams and water diversions on the mountain yellow-
legged frog complex. They provided numerous smaller specific comments 
on text within the section.

[[Page 24304]]

    Our Response: We thank the CDFW for the additional information 
provided to strengthen our analysis. We have addressed these comments 
through changes to the Fish Stocking, Recreation, and Dams and Water 
Diversions sections for the Sierra Nevada and mountain yellow-legged 
frogs in this final rule. We re-checked references and revised the 
sections noted to state more clearly the potential effects of these 
activities, to rely on appropriate citations, and to refine our 
conclusions in agreement with CDFW's comments. Please see Factor A in 
Summary of Factors Affecting the Species for updated information.

Public Comments

    (21) Comment: Several commenters suggested that the Service does 
not have the authority or jurisdiction to designate the Sierra Nevada 
yellow-legged frog and the northern DPS of the mountain yellow-legged 
frog as endangered nor the Yosemite toad as threatened.
    Our Response: The authority for the Service to issue this 
rulemaking comes from the Endangered Species Act of 1973 (16 U.S.C. 
1531 et seq.), as amended, through the 108th Congress. The Service is 
designated as the lead Federal agency for implementing the Act for 
terrestrial and freshwater species. Authority to implement the Act does 
not require Federal jurisdiction or land ownership
    (22) Comment: Multiple commenters indicated that existing Federal 
and State legislation and regulations, such as the Wilderness Act, 
CESA, and CDFW regulations, provide sufficient protection for these 
amphibians, and thereby eliminate the need for listing the species.
    Our Response: We agree that existing Federal and State legislation 
and regulations, such as the Wilderness Act, CESA, and CDFW regulations 
provide some protection for the Sierra Nevada yellow-legged frog, the 
northern DPS of the mountain yellow-legged frog, and the Yosemite toad. 
However, while existing legislation and regulations provide some level 
of protection for the Sierra Nevada yellow-legged frog, the northern 
DPS of the mountain yellow-legged frog, and the Yosemite toad, they do 
not require that Federal agencies ensure that actions that they fund, 
authorize, or carry out will not likely jeopardize the species' 
continued existence (for further information see discussions under 
Factor D). Therefore, we have determined that the Sierra Nevada yellow-
legged frog and the northern DPS of the mountain yellow-legged frog are 
endangered and that the Yosemite toad is threatened under the Act.
    (23) Comment: Several commenters suggest that it is necessary for 
the Service to conduct an analysis of the impacts that listing a 
species may have on local economies prior to issuance of a final rule.
    Our Response: Under the Act, the Service is not required to conduct 
an analysis regarding the economic impact of listing endangered or 
threatened species. However, the Act does require that the Service 
consider the economic impacts of a designation of critical habitat. A 
draft of this analysis is available to the public on http://www.regulations.gov (79 FR 1805).
    (24) Comment: Several commenters suggested that the decline of the 
Sierra Nevada yellow-legged frog, northern DPS of the mountain yellow-
legged frog, and the Yosemite toad is a natural evolutionary process, 
and that the presence of environmental stressors is a normal driver of 
evolution and/or extinction.
    Our Response: Under the Act, we are required to use the best 
available scientific and commercial information to assess the factors 
affecting a species in order to make a status determination. The Act 
requires the Service to consider all threats and impacts that may be 
responsible for declines as potential listing factors. The evidence 
presented suggests that the threats to the species are both natural and 
manmade (see Factor E--Other Natural or Manmade Factors Affecting the 
Species), but that they are primarily the result of anthropogenic 
influences (see Summary of Factors Affecting the Species in this final 
rule). Thus, the threats associated with the declines of these species 
are not part of a natural evolutionary process.
    (25) Comment: Several commenters were concerned about the effects 
of listing on mining and associated activities conducted under the 
General Mining Law of 1872. They suggested that the listing of these 
species will remove 5 million acres from mining and other productive 
uses of the land. One commenter was concerned that there would be no 
assurances that development of a mining claim will result in the 
ability to mine it.
    Our Response: In the proposed rule, we identified unauthorized 
discharge of chemicals or fill material into any water upon which the 
Sierra Nevada yellow-legged frog, the northern DPS of the mountain 
yellow-legged frog, and the Yosemite toad are known to occur as a 
potential threat to these species. On National Forests outside of 
designated wilderness, new mining may occur pursuant to the Mining Law 
of 1872 (30 U.S.C. 21 et seq.), which was enacted to promote 
exploration and development of domestic mineral resources, as well as 
the settlement of the western United States. It permits U.S. citizens 
and businesses to prospect hardrock (locatable) minerals and, if a 
valuable deposit is found, file a claim giving them the right to use 
the land for mining activities and sell the minerals extracted, without 
having to pay the Federal Government any holding fees or royalties (GAO 
1989, p. 2). Gold and other minerals are frequently mined as locatable 
minerals, and, as such, mining is subject to the Mining Law of 1872. 
However, Federal wilderness areas were closed to new mining claims at 
the beginning of 1984 (see Factor D under mountain yellow-legged frogs 
above), thereby precluding the filing of new mining claims in those 
areas designated as Federal wilderness (a large part of the area in 
which the species occur). Authorization of mining under the Mining Law 
of 1872 is a discretionary agency action pursuant to section 7 of the 
Act. Therefore, Federal agencies with jurisdiction over land where 
mining occurs will review mining and other actions that they fund, 
authorize, or carry out to determine if listed species may be affected 
in accordance with section 7 of the Act.
    (26) Comment: Numerous commenters suggested that the listing of the 
Sierra Nevada yellow-legged frog, the northern DPS of the mountain 
yellow-legged frog, and the Yosemite toad are being misused to restrict 
or prohibit access for fishing, hiking, camping, and other recreational 
uses, and implement land use restrictions, management requirements, and 
personal liabilities on the public that are not prudent, clearly 
defined, or necessary.
    Our Response: The listing of the Sierra Nevada yellow-legged frog, 
the northern DPS of the mountain yellow-legged frog, and the Yosemite 
toad does not prevent access to any land, whether private, tribal, 
State, or Federal. The listing of a species does not affect land 
ownership or establish a refuge, wilderness, reserve, or other 
conservation area. A listing does not allow the government or public to 
access private lands without the permission of the landowner. It does 
not require implementation of restoration, recovery, or enhancement 
measures by non-Federal landowners. Federal agencies will review 
actions that they fund, authorize, or carry out to determine if any of 
these three amphibians, and other listed species as appropriate, may be 
affected by the Federal action. The Federal agency will

[[Page 24305]]

consult with the Service, in accordance with Section 7 of the Act (see 
also response to comment 25).
    (27) Comment: Several commenters suggested that listing the Sierra 
Nevada yellow-legged frog and the northern DPS of the mountain yellow-
legged frog under the Act is not necessary given that a majority of the 
range of these species is within wilderness areas afforded protection 
under the Wilderness Act and by the protections afforded under CESA.
    Our Response: We agree that existing Federal and State legislation 
and regulations, such as the Wilderness Act and CESA, provide some 
protection for the Sierra Nevada mountain yellow-legged frog, the 
northern DPS of the mountain yellow-legged frog, and the Yosemite toad. 
However, we identified the main threats to the two frog species as 
habitat degradation and fragmentation, predation and disease, climate 
change, and the interactions of these stressors on small populations. 
Neither the Wilderness Act nor the State's listing status under CESA 
ameliorates these threats to levels that would preclude the need to 
list the species under the Act. (See discussion under Factor D).
    (28) Comment: One commenter suggested that habitat and range of the 
mountain yellow-legged frog is not threatened with destruction or 
modification based on a large portion being located in wilderness, and 
the proposed rule stating ``physical habitat destruction does not 
appear to be the primary factor associated with the decline of the 
mountain yellow-legged frogs.''
    Our Response: While we agree that the loss, destruction, or 
conversion of physical habitat is not a primary factor in the decline 
of the mountain yellow-legged frogs, we discuss both the biological 
modification of habitat due to changes in predator communities, prey 
communities, and in nutrient levels, and due to the habitat 
fragmentation associated with the presence of introduced fish. Although 
the presence of introduced fish does not result in conversion or loss 
of the physical attributes of habitat (for example, removal or filling 
of lakes, ponds, etc.), fish presence does effectively preclude the use 
of the habitat by the mountain yellow-legged frog (see our discussion 
under Factor A). While a large portion of the range of the mountain 
yellow-legged frog is within federally designated wilderness, or on 
National Parks, we identified the main threats to the species as 
habitat degradation and fragmentation, predation and disease, climate 
change, and the interactions of these stressors on small populations. 
Neither the Wilderness Act nor the protections afforded within National 
Parks ameliorates these threats to levels that would preclude the need 
to list the species under the Act (see discussion under Factor D).
    (29) Comment: One commenter stated that we failed to consider the 
effectiveness of restoration activities being conducted by CDFW as part 
of their High Mountain Lakes Project and plans for Yosemite and Sequoia 
and Kings National Parks that are intended to implement restoration 
actions.
    Our Response: We are aware of the activities, including the High 
Mountain Lakes Project (see Factor A discussions above in this final 
rule), being conducted by CDFW, USFS, NPS, and researchers aimed at 
restoring habitat for the mountain yellow-legged frog. While efforts of 
interested parties have resulted in the restoration of habitat for 
these species, the restored habitat represents a small portion of the 
range of the species, and has occurred only in localized areas. As 
such, these activities, while beneficial and important for the recovery 
of the species, do not significantly counter the threats of introduced 
predators, disease, or climate change. Additionally, we are aware of 
planning efforts by Yosemite and Sequoia and Kings National Parks, 
partially implemented, and we are aware that these restoration plans 
have not been finalized.
    (30) Comment: One commenter provided information suggesting 
livestock are responsible for the transportation of Bd in the 
environment.
    Our Response: While livestock may provide a vector for the 
transmission of amphibian disease within the Sierra Nevada, there are 
numerous other mechanisms of transport, including wildlife, as well as 
anthropogenic vectors. Since the importance of differing disease 
vectors related to Bd is poorly understood, we did not include a 
discussion of disease transport associated with livestock grazing in 
this rule (see Factor C for discussion of disease).
    (31) Comment: One commenter provided information to suggest that 
activities associated with illicit cultivation of marijuana on National 
Forest System lands should be identified as a potential threat to the 
mountain yellow-legged frog.
    Our Response: We agree that aspects associated with illegal 
cultivation of marijuana on National Forest System lands may pose a 
risk to the mountain yellow-legged frogs, such as dewatering of 
habitats and contamination from pesticides and fertilizers. There is 
potential overlap with this illegal activity and areas occupied by 
mountain yellow-legged frogs; however, not enough information is 
available at this point to assess the impact that illegal cultivation 
of marijuana has on the species.
    (32) Comment: Several commenters suggest that there is insufficient 
evidence to make a listing determination for the mountain yellow-legged 
frog in accordance with the Act.
    Our Response: As we have presented in both the proposed rule and 
this final rule, a substantial compilation of scientific and commercial 
information is available to support listing both the Sierra Nevada 
yellow-legged frog and the northern DPS of the mountain yellow-legged 
frog under the Act. We have presented evidence that there has been a 
curtailment in range and numbers attributed to habitat degradation and 
fragmentation under Factor A, predation and disease under Factor C, and 
climate change and the interaction of these various stressors 
cumulatively impacting small remnant populations under Factor E (see 
Determination for the Sierra Nevada Yellow-legged Frog and 
Determination for the Northern DPS of the Mountain Yellow-legged Frog 
sections above for a synopsis and see the Summary of Factors Affecting 
the Species for a detailed analysis).
    (33) Comment: Numerous commenters purported that the greatest 
threat to the mountain yellow-legged frog is Bd, and since listing the 
species will not alleviate the threat, the species should not be 
listed. Additionally, it was suggested that these species should be 
reared in captivity until the threat of Bd is resolved.
    Our Response: We agree that Bd is one of the primary contributing 
factors in the current decline of these species; however, it is not the 
only factor responsible for their decline or the only one forming the 
basis of our determination. All Factors are considered when making a 
listing determination (see the Summary of Factors Affecting the Species 
for a detailed discussion). We have also identified habitat 
fragmentation and predation attributed to the introduction of fish and 
climate change as threats to the species. We are required to evaluate 
all the threats affecting a species, including disease under Factor C.
    With respect to the prospect of captive breeding, we acknowledge 
that this activity is one of the suite of tools that can be utilized 
for the conservation of the species. Captive breeding is currently 
being conducted for the southern DPS of the mountain yellow-

[[Page 24306]]

legged frog, and we are currently working with various facilities to 
explore this option. Additionally, when a species is listed as either 
endangered or threatened, the Act provides many tools to advance the 
conservation of listed species; available tools including recovery 
planning under section 4 of the Act, interagency cooperation and 
consultation under section 7 of the Act, and grants to the States under 
section 6 of the Act. All of these mechanisms assist in the 
conservation of the species.
    (34) Comment: Several commenters provided information to suggest 
that livestock grazing is not detrimental to amphibian species and that 
the proposed rule did not adequately capture the neutral or beneficial 
effects of livestock grazing on amphibian species.
    Our Response: We have revised our discussion of grazing in this 
final rule to clarify the conditions under which we consider current 
grazing activities to pose habitat-related threats (see Factor A 
above). In addition, research with a related ranid frog of western 
montane environments, (the Columbia spotted frog, Rana luteiventris) 
has indicated that livestock grazing may reduce vegetation levels in 
riparian and wet meadow habitat, but does not have short-term effects 
on the frog populations, although they caution that the length of the 
study may not capture potential long-term effects (Adams et al. 2009, 
pp. 132, 137). However, George et al. (2011, pp. 216, 232) in a review 
of the effectiveness of management actions on riparian areas, noted 
that continuous grazing often results in heavy grazing use of riparian 
areas, even if an area is lightly stocked, because livestock are 
attracted to the areas from adjacent uplands. They note substantial 
literature that documents that livestock grazing could damage riparian 
areas, and the resulting move, beginning in the 1980s, in Federal and 
State resource agencies to apply conservation practices to protecting 
and improving riparian habitats (George et al. 2011, p. 217). They note 
that studies provide sufficient evidence that riparian grazing 
management that maintains or enhances key vegetation attributes will 
enhance stream channel and riparian soil stability, although variable 
biotic and abiotic conditions can have site-specific effects on results 
(George et al. 2011, pp. 217-227).
    In our proposed rule, we focused on livestock grazing as a 
potential listing factor, and while there are potentially some current, 
localized effects to the Sierra Nevada yellow-legged frog, the northern 
DPS of the mountain yellow-legged frog, and the Yosemite toad, we 
consider the majority of the impacts associated with livestock grazing 
are the legacy effects of historically high grazing intensities.
    (35) Comment: One commenter stated that the discussion of the 
effects of global climate change in the proposed rule for the Sierra 
Nevada yellow-legged frog, northern DPS of the mountain yellow-legged 
frog, and Yosemite toad was not appropriate. The commenter believed 
that the Service ``pushes'' the climate models, both spatially and 
temporally, beyond what the commenter considered to be reliable, and 
ignores their uncertainty. In addition, the commenter claims that no 
credible models can project potential climate change in the Sierra 
Nevada. The commenter stated the Act is not an appropriate mechanism to 
regulate global climate change and greenhouse gases. Finally, the 
commenter suggested if the Service does list the three amphibians, that 
they be designated as threatened species with a section 4(d) rule that 
excludes lawful greenhouse gases from the prohibitions of the Act.
    Our Response: We used the best available scientific and commercial 
information available as it pertains to climate change. In addition to 
the peer-reviewed scientific journal articles and reports that were 
utilized in our analysis and cited in the proposed rule, recently 
published studies have presented data and conclusions that increase the 
level of confidence that global climate change is the result of 
anthropogenic actions (summarized in Blaustein et al. 2010 and 
discussed above). A recent paper (Kadir et al. 2013) provides specific 
information on the effects of climate change in the Sierra Nevada and 
is discussed above. While the Service is concerned about the effects of 
global climate change on listed species, wildlife, and their habitats, 
to date, we have not used the Act to regulate greenhouse gases. We 
evaluated the suggestion that the three amphibians be listed as 
threatened species with a section 4(d) rule excluding prohibitions or 
restrictions on greenhouse gases. However, our determination is that 
the Sierra Nevada yellow-legged frog and the northern DPS of the 
mountain yellow-legged frog meet the definition of endangered, the 
Yosemite toad meets the definition of threatened, and a section 4(d) 
rule for greenhouse gases is not appropriate.
    (36) Comment: One commenter suggested that the discussion of 
genetics for the mountain yellow-legged frog does not support the 
taxonomy of the Sierra Nevada yellow-legged frog and the northern DPS 
of the mountain yellow-legged frog as separate species. The commenter 
further suggested the text of the rule specifying two major genetic 
lineages and four groups does not support listing of the frogs as 
separate genetic groups.
    Our Response: Vredenburg et al. (2007, p. 317) did not rely solely 
on DNA evidence in the recognition of two distinct species of mountain 
yellow-legged frog in the Sierra Nevada, but instead used a combination 
of DNA evidence, morphological information, and acoustic studies. The 
taxonomy of the mountain yellow-legged frogs as two distinct species in 
the Sierras has been widely accepted in the scientific community and by 
species experts. We are not listing a subspecies but rather two 
separate, recognized species, the Sierra Nevada yellow-legged frog and 
the northern DPS of the mountain yellow-legged frog.
    (37) Comment: Several commenters suggested that activities such as 
timber harvest, road construction, recreation, and livestock grazing 
are in decline in the Sierras compared with historical levels and 
should not be included as potential threats to the Sierra Nevada 
yellow-legged frog, the northern DPS of the mountain yellow-legged 
frog, or the Yosemite toad.
    Our Response: In conducting our analysis of the factors affecting 
the species, we did include timber harvest, road construction, 
recreation, and livestock grazing, as potential threats to the species, 
but acknowledge that the major impact on the species was the result of 
the legacy effects of historical practices, and that these activities 
currently pose a lower intensity, localized threat. We have attempted 
to clarify the distinction in this final rule (see Factor A discussions 
above).
    (38) Comment: Numerous commenters stated that listing the mountain 
yellow-legged frogs and the Yosemite toad would prevent fuels-reduction 
activities, leading to fires and loss of habitat.
    Our Response: In this final rule under Factor A for the mountain 
yellow-legged frogs and Yosemite toad, we address potential habitat 
changes that may be related to timber harvest activities, including 
harvests for fuels reduction purposes. We found that most populations 
of the three species occur at high elevations above areas where timber 
harvests are likely. At lower elevations, forest standards and 
guidelines would be expected to limit potential threats to the species 
in most cases, although limited site-specific situations might result 
in habitat effects with population consequences. We also found that 
changed fire regimes have, in some of the same lower elevation areas,

[[Page 24307]]

led to an increased potential for high-intensity fires, which could 
alter habitat and, therefore, pose relatively localized population-
level effects to the species. For the Yosemite toad, we found that 
although ground-disturbance due to timber harvest activities has the 
potential to have population-level effects at lower elevations, 
especially where habitat is limited, currently the best available 
information indicates toads might achieve long-term benefits from 
activities that reduce encroachment of trees into breeding sites. 
Therefore, we expect that fuels-reduction activities in lower elevation 
areas will be generally beneficial to these species.
    (39) Comment: A number of commenters suggested that, given the 
results of more-recent studies that were not included in the proposed 
rule, livestock grazing should be removed as a threat to the Yosemite 
toad (See also comment 13 from the USFS).
    Our Response: In our proposed rule, we addressed the potential 
impacts of grazing on Yosemite toad based on Allen-Diaz et al. (2010). 
The more-recent studies referenced (such as Roche et al. 2012a and 
2012b, and McIlroy et al. 2013) are different publications but are 
based on the results of the companion studies whose initial report, and 
subsequent addendum, we referenced as Allen-Diaz et al. (2010) and Lind 
et al. (2011b). The study conducted determined that livestock grazing 
in accordance with the USFS's standards and guidelines does not affect 
Yosemite toad breeding success. While appropriately managed levels of 
grazing do not impact breeding success, these grazing standards are not 
always met. Additionally, the main impact of grazing on Yosemite toad 
is due to the legacy effects of historical grazing intensities on 
Yosemite toad habitat. Given the limitations of the study (see 
discussion under Factor A) and the documentation that these standards 
are not always met, livestock grazing may continue to pose a localized 
threat to the species.
    (40) Comment: One commenter provided several comments suggesting 
that livestock grazing is not a threat to Yosemite toad in light of the 
results of a current study, the documentation of Yosemite toads 
existing in areas that have been subject to grazing for centuries, and 
because the population declines cited in our proposed rule occurred in 
an area not subject to grazing.
    Our Response: See response to comments 13, 14, and 39. In our 
proposed rule, we identified the impacts of livestock grazing primarily 
from an historical context as a potential contributor to meadow 
degradation. There is a great deal of information, while not specific 
to Yosemite toad, on the negative impacts of high-intensity grazing 
regimes on ecosystem dynamics. Grazing under current Forest Service 
standards does not appear to impact Yosemite toad breeding, however 
when inappropriate levels of grazing do occur, grazing may still 
present a localized impact on Yosemite toads via direct mortality or 
through practices that prevent the hydrologic recovery of historically 
wet meadow systems. While the documented declines of Yosemite toad have 
occurred in areas that are not currently subject to livestock grazing, 
historical grazing occurred throughout the Sierra Nevada. We did not 
implicate livestock grazing in the decline in population sizes, rather 
as a potential historical driver in meadow degradation rangewide. We 
have clarified this distinction in the final rule (see Factor A 
discussion and Summary of Factors Affecting the Species for the 
Yosemite toad).
    (41) Comment: One commenter suggested that livestock grazing 
continues to provide a threat to the Sierra Nevada yellow-legged frog 
and Yosemite toad and provided information documenting habitat 
degradation attributed to current livestock grazing and utilization 
above the standards of the SNFPA.
    Our Response: As we have presented in the proposed and final rules, 
the impact of livestock grazing on these species is primarily one of 
historical significance, with the potential for future localized 
impacts to the species and/or their habitat. Based on the information 
provided regarding habitat conditions and potential impacts to habitat, 
we have maintained our position that current livestock grazing poses a 
localized impact to the mountain yellow-legged frogs and a prevalent 
threat with moderate impacts to the Yosemite toad.
    (42) Comment: One party commented that we have not demonstrated 
that the Sierra Nevada population of the mountain yellow-legged frog is 
a DPS. They indicate that we have not shown that the population is 
significant to the taxon as a whole because we have not shown whether 
other populations of the species could persist in the high-elevation 
Sierra Nevada portion of the species' range or discussed how the Sierra 
Nevada populations are adapted to the area. In addition, they indicate 
that we failed to show that extirpation of the northern population 
would result in a significant gap in the range of the species, and we 
did not show that the populations had markedly different genetics 
characteristics.
    Our Response: The commenters correctly noted that, to recognize a 
population of a species as a DPS, we must establish that the population 
is (1) discrete from the remainder of the populations to which the 
species belongs, and (2) if determined to be discrete, it is also found 
to be significant to the species to which it belongs. However, the 
commenters incorrectly conclude that the population must meet all three 
criteria for significance. We find the northern population of the 
mountain yellow-legged frog to be discrete from the southern population 
because it is separated from the southern frogs by a 225-km (140-mi) 
barrier of unsuitable habitat. The primary basis for our finding that 
the northern population is significant to the species as a whole is 
that loss of the northern population would mean the loss of the species 
from a large portion of its range and reduce the species to small 
isolated occurrences in southern California. The population also meets 
two additional criteria for significance: (1) Evidence of the 
persistence of the discrete population segment in an ecological setting 
unusual or unique for the taxon, and (2) evidence that the discrete 
population segment differs markedly from the remainder of the species 
in its genetic characteristics. We have revised the language in our DPS 
analysis to clarify the basis for the determination (see Distinct 
Vertebrate Population Segment Analysis).
    (43) Comment: Numerous commenters commented that we were required 
to complete a NEPA analysis of the proposed listing.
    Our Response: We have determined that environmental assessments and 
environmental impact statements, as defined under the authority of the 
National Environmental Policy Act (NEPA; 42 U.S.C. 4321 et seq.), need 
not be prepared in connection with listing a species as an endangered 
or threatened species under the Endangered Species Act. We published a 
notice outlining our reasons for this determination in the Federal 
Register on October 25, 1983 (48 FR 49244) (see Required Determinations 
section of this rule).
    (44) Comment: One commenter asked that, if we determine that the 
three amphibian species under consideration are endangered or 
threatened under the Act, then we enter into a cooperative agreement 
with the State of California under section 6 of the Act.
    Our Response: We have been operating under such a cooperative 
agreement with the California

[[Page 24308]]

Department of Fish and Game (now Department of Fish and Wildlife 
(CDFW)) since 1991. http://www.dfg.ca.gov/wildlife/nongame/publications/docs/CDFGCooperativeAgreementWithUSFWS.pdf
    (45) Comment: One commenter stated that if the three amphibians 
considered are listed as threatened or endangered, then research should 
continue into the causes of population decline.
    Our Response: We expect research on these issues to continue into 
the future. Once the three amphibians are listed as threatened or 
endangered species under the Act, additional funding for research and 
other conservation programs for those species will become available 
through grants established under section 6 of the Act. Such grants are 
provided to State agencies with which we have established cooperative 
agreements.
    (46) Comment: One commenter indicated that because of a County 
resolution, we must coordinate with the board of supervisors of that 
County prior to publishing a final rule.
    Our Response: We provide all interested parties an equal 
opportunity to submit comments or information prior to publication of a 
final rule, and we give equal consideration to all such information and 
comments, regardless of source. Our requirements for ``coordination,'' 
however, are established by the Act, by other Federal statutes such as 
the Administrative Procedure Act, and by executive order.
    (47) Comment: Several commenters asked for additional time to 
provide comments. One commenter added that we provided little public 
outreach.
    Our Response: As discussed in the first paragraph of the Summary of 
Comments and Recommendations section (above), we provided two 
additional public comment periods for a total of 240 days 
(approximately 8 months) of public comment. We also hosted two public 
hearings and two public informational meetings at various locations 
within the range of the species under consideration. We also attended 
two additional public meetings hosted by Congressmen representing 
districts within the range of the species. We contacted and sought 
input from appropriate Federal and State agencies, scientific experts 
and organizations, and other interested parties. We also published 
notices in the newspapers with the largest readerships within both the 
northern and southern portions of the ranges of the species. Additional 
public comment periods or outreach were not feasible given limitations 
imposed by available funds and requirements imposed by the Act 
regarding available time in which to publish a final rule.
    (48) Comment: One commenter noted that the Act authorizes the 
Secretary to extend the time available for publication of a final rule 
by up to 6 months if ``there is substantial disagreement regarding the 
sufficiency or accuracy of the available data.'' The commenter stated 
that such substantial disagreement does exist and so requested that the 
available time be extended by 6 months. Specifically, the commenter 
indicated that the available data are not sufficient to support listing 
after taking into account various Federal and State statutes and 
programs currently benefiting the three species. Such statutes and 
programs include the Wilderness Act, the Sierra Nevada Forest Plan, the 
Clean Water Act, the California Endangered Species Act, and the 
discontinuation of fish stocking by CDFW in much of the range of the 
two frogs.
    Our Response: While we agree that these efforts aid in the 
conservation of the three amphibians, we do not consider substantial 
disagreement to exist regarding our conclusion that the Sierra Nevada 
yellow-legged frog and the northern DPS of the mountain yellow-legged 
frog meet the definition of ``endangered species'' under the Act. We 
considered the existing Federal and State statutes and programs in our 
determination. The data documenting population declines and 
extirpations associated with Bd and the presence of introduced fish are 
sufficient for the Service to determine that the two species are ``in 
danger of extinction throughout all or a significant portion of [their] 
range[s].'' Data also show that the Yosemite toad is vulnerable to 
habitat changes and climate change, and thus merits listing as a 
threatened species, which is defined as ``likely to become an 
endangered species within the foreseeable future within all or a 
significant portion of its range.''

Available Conservation Measures

    Conservation measures provided to species listed as endangered or 
threatened under the Act include recognition, recovery actions, 
requirements for Federal protection, and prohibitions against certain 
practices. Recognition through listing results in public awareness, and 
conservation by Federal, State, Tribal, and local agencies, private 
organizations, and individuals. The Act encourages cooperation with the 
States and requires that recovery actions be carried out for all listed 
species. The protection required by Federal agencies and the 
prohibitions against certain activities are discussed, in part, below.
    The primary purpose of the Act is the conservation of endangered 
and threatened species and the ecosystems upon which they depend. The 
ultimate goal of such conservation efforts is the recovery of these 
listed species, so that they no longer need the protective measures of 
the Act. Subsection 4(f) of the Act requires the Service to develop and 
implement recovery plans for the conservation of endangered and 
threatened species. The recovery planning process involves the 
identification of actions that are necessary to halt or reverse the 
species' decline by addressing the threats to its survival and 
recovery. The goal of this process is to restore listed species to a 
point where they are secure, self-sustaining, and functioning 
components of their ecosystems.
    Recovery planning includes the development of a recovery outline 
shortly after a species is listed and preparation of a draft and final 
recovery plan. The recovery outline guides the immediate implementation 
of urgent recovery actions and describes the process to be used to 
develop a recovery plan. Revisions of the plan may be done to address 
continuing or new threats to the species, as new substantive 
information becomes available. The recovery plan identifies site-
specific management actions that set a trigger for review of the five 
factors that control whether a species remains endangered or may be 
downlisted or delisted, and methods for monitoring recovery progress. 
Recovery plans also establish a framework for agencies to coordinate 
their recovery efforts and provide estimates of the cost of 
implementing recovery tasks. Recovery teams (composed of species 
experts, Federal and State agencies, nongovernmental organizations, and 
stakeholders) are often established to develop recovery plans. When 
completed, the recovery outline, draft recovery plan, and the final 
recovery plan will be available on our Web site (http://www.fws.gov/endangered), or from our Sacramento Fish and Wildlife Office (see FOR 
FURTHER INFORMATION CONTACT).
    Implementation of recovery actions generally requires the 
participation of a broad range of partners, including other Federal 
agencies, States, Tribal, nongovernmental organizations, businesses, 
and private landowners. Examples of recovery actions include habitat 
restoration (e.g., restoration of native vegetation), research, captive 
propagation and reintroduction, and outreach and education. The 
recovery of many listed species cannot be

[[Page 24309]]

accomplished solely on Federal lands because their range may occur 
primarily or solely on non-Federal lands. To achieve recovery of these 
species requires cooperative conservation efforts on private, State, 
and Tribal lands.
    Following publication of this final listing rule, funding for 
recovery actions will be available from a variety of sources, including 
Federal budgets, State programs, and cost share grants for non-Federal 
landowners, the academic community, and nongovernmental organizations. 
In addition, pursuant to section 6 of the Act, the States of California 
and Nevada would be eligible for Federal funds to implement management 
actions that promote the protection or recovery of the Sierra Nevada 
mountain yellow-legged frog, Northern Distinct Population Segment of 
the mountain yellow-legged frog, and the Yosemite toad. Information on 
our grant programs that are available to aid species recovery can be 
found at: http://www.fws.gov/grants.
    Please let us know if you are interested in participating in 
recovery efforts for the Sierra Nevada yellow-legged frog, the northern 
DPS of the mountain yellow-legged frog, or the Yosemite toad. 
Additionally, we invite you to submit any new information on these 
species whenever it becomes available and any information you may have 
for recovery planning purposes (see FOR FURTHER INFORMATION CONTACT).
    Section 7(a) of the Act requires Federal agencies to evaluate their 
actions with respect to any species that is listed as an endangered or 
threatened species and with respect to its critical habitat, if any is 
designated. Regulations implementing this interagency cooperation 
provision of the Act are codified at 50 CFR part 402. Section 7(a)(2) 
of the Act requires Federal agencies to ensure that any action 
authorized, funded or carried out by such agency is not likely to 
jeopardize the continued existence of the species or destroy or 
adversely modify its critical habitat. If a Federal action may affect a 
listed species or its critical habitat, the responsible Federal agency 
must enter into consultation with the Service.
    Federal agency actions within the species' habitat that may require 
consultation, as described in the preceding paragraph, include 
management and any other landscape-altering activities on Federal lands 
administered by the USFS, NPS, and other Federal agencies as 
appropriate.
    The Act and its implementing regulations set forth a series of 
general prohibitions and exceptions that apply to all endangered and 
threatened wildlife. The prohibitions of section 9(a)(2) of the Act, 
codified at 50 CFR 17.21 for endangered wildlife, in part, make it 
illegal for any person subject to the jurisdiction of the United States 
to take (includes harass, harm, pursue, hunt, shoot, wound, kill, trap, 
capture, or collect; or to attempt any of these), import, export, ship 
in interstate commerce in the course of commercial activity, or sell or 
offer for sale in interstate or foreign commerce any listed species. 
Under the Lacey Act (18 U.S.C. 42-43; 16 U.S.C. 3371-3378), it is also 
illegal to possess, sell, deliver, carry, transport, or ship any such 
wildlife that has been taken illegally. Certain exceptions apply to 
agents of the Service and State conservation agencies.
    We may issue permits to carry out otherwise prohibited activities 
involving endangered and threatened wildlife species under certain 
circumstances. Regulations governing permits are codified at 50 CFR 
17.22 for endangered species, and at 17.32 for threatened species. With 
regard to endangered wildlife, a permit must be issued for the 
following purposes: for scientific purposes, to enhance the propagation 
or survival of the species, and for incidental take in connection with 
otherwise lawful activities.
    It is our policy, as published in the Federal Register on July 1, 
1994 (59 FR 34272), to identify to the maximum extent practicable at 
the time a species is listed, those activities that would or would not 
constitute a violation of section 9 of the Act. The intent of this 
policy is to increase public awareness of the effect of a listing on 
proposed and ongoing activities within the range of listed species. The 
following activities could potentially result in a violation of section 
9 of the Act; this list is not comprehensive:
    (1) Unauthorized collecting, handling, possessing, selling, 
delivering, carrying, or transporting of the species, including import 
or export across State lines and international boundaries, except for 
properly documented antique specimens of these taxa at least 100 years 
old, as defined by section 10(h)(1) of the Act;
    (2) Introduction of species that compete with or prey upon the 
Sierra Nevada yellow-legged frog, the northern DPS of the mountain 
yellow-legged frog, or the Yosemite toad;
    (3) The unauthorized release of biological control agents that 
attack any life stage of these species;
    (4) Unauthorized modification of the mountain meadow habitats or 
associated upland areas important for the breeding, rearing, and 
survival of these species; and
    (5) Unauthorized discharge of chemicals or fill material into any 
waters in which the Sierra Nevada yellow-legged frog, the northern DPS 
of the mountain yellow-legged frog, or the Yosemite toad are known to 
occur.
    Questions regarding whether specific activities would constitute a 
violation of section 9 of the Act should be directed to the Sacramento 
Fish and Wildlife Office (see FOR FURTHER INFORMATION CONTACT).
    Under section 4(d) of the ESA, the Secretary has discretion to 
issue such regulations as he deems necessary and advisable to provide 
for the conservation of threatened species. Our implementing 
regulations (50 CFR 17.31) for threatened wildlife generally 
incorporate the prohibitions of section 9 of the Act for endangered 
wildlife, except when a ``special rule'' promulgated pursuant to 
section 4(d) of the Act has been issued with respect to a particular 
threatened species. In such a case, the general prohibitions in 50 CFR 
17.31 would not apply to that species, and instead, the special rule 
would define the specific take prohibitions and exceptions that would 
apply for that particular threatened species, which we consider 
necessary and advisable to conserve the species. The Secretary also has 
the discretion to prohibit by regulation with respect to a threatened 
species any act prohibited by section 9(a)(1) of the ESA. Exercising 
this discretion, which has been delegated to the Service by the 
Secretary, the Service has developed general prohibitions that are 
appropriate for most threatened species in 50 CFR 17.31 and exceptions 
to those prohibitions in 50 CFR 17.32. Since we are not promulgating a 
special section 4(d) rule, all of the section 9 prohibitions, including 
the ``take'' prohibitions, will apply to the Yosemite toad.

Required Determinations

National Environmental Policy Act (42 U.S.C. 4321 et seq.)

    We have determined that environmental assessments and environmental 
impact statements, as defined under the authority of the National 
Environmental Policy Act (NEPA; 42 U.S.C. 4321 et seq.), need not be 
prepared in connection with listing a species as an endangered or 
threatened species under the Endangered Species Act. We published a 
notice outlining our reasons for this determination in the Federal 
Register on October 25, 1983 (48 FR 49244).

[[Page 24310]]

Government-to-Government Relationship With Tribes

    In accordance with the President's memorandum of April 29, 1994 
(Government-to-Government Relations with Native American Tribal 
Governments; 59 FR 22951), Executive Order 13175 (Consultation and 
Coordination With Indian Tribal Governments), and the Department of the 
Interior's manual at 512 DM 2, we readily acknowledge our 
responsibility to communicate meaningfully with recognized Federal 
Tribes on a government-to-government basis. In accordance with 
Secretarial Order 3206 of June 5, 1997 (American Indian Tribal Rights, 
Federal-Tribal Trust Responsibilities, and the Endangered Species Act), 
we readily acknowledge our responsibilities to work directly with 
tribes in developing programs for healthy ecosystems, to acknowledge 
that tribal lands are not subject to the same controls as Federal 
public lands, to remain sensitive to Indian culture, and to make 
information available to tribes.

References Cited

    A complete list of references cited in this rulemaking is available 
on the Internet at http://www.regulations.gov and upon request from the 
Sacramento Fish and Wildlife Office (see FOR FURTHER INFORMATION 
CONTACT).

Authors

    The primary authors of this final rule are the staff members of the 
Sacramento Fish and Wildlife Office.

List of Subjects in 50 CFR Part 17

    Endangered and threatened species, Exports, Imports, Reporting and 
recordkeeping requirements, Transportation.

Regulation Promulgation

    Accordingly, we amend part 17, subchapter B of chapter I, title 50 
of the Code of Federal Regulations, as follows:

PART 17--[AMENDED]

0
1. The authority citation for part 17 continues to read as follows:

    Authority: 16 U.S.C. 1361-1407; 1531-1544; 4201-4245; unless 
otherwise noted.

0
2. Amend Sec.  17.11(h), the List of Endangered and Threatened 
Wildlife, by revising the entry for ``Frog, mountain yellow-legged 
(southern California DPS)'' and adding entries for ``Frog, mountain 
yellow-legged (northern California DPS)'', ``Frog, Sierra Nevada 
yellow-legged'', and ``Toad, Yosemite'' to the List of Endangered and 
Threatened Wildlife in alphabetical order under Amphibians to read as 
follows:


Sec.  17.11  Endangered and threatened wildlife.

* * * * *
    (h) * * *

--------------------------------------------------------------------------------------------------------------------------------------------------------
                        Species                                                    Vertebrate
--------------------------------------------------------                        population where                                  Critical     Special
                                                            Historic range       endangered or         Status      When listed    habitat       rules
           Common name                Scientific name                              threatened
--------------------------------------------------------------------------------------------------------------------------------------------------------
 
                                                                      * * * * * * *
            Amphibians
 
                                                                      * * * * * * *
Frog, mountain yellow-legged       Rana muscosa........  U.S.A. (CA)........  U.S.A., northern     E                       834           NA           NA
 (northern California DPS).                                                    California.
 Frog, mountain yellow-legged      Rana muscosa........  U.S.A. (CA)........  U.S.A., southern     E                       728     17.95(d)           NA
 (southern California DPS).                                                    California.
 
                                                                      * * * * * * *
Frog, Sierra Nevada yellow-legged  Rana sierrae........  U.S.A. (CA, NV)....  Entire.............  E                       834           NA           NA
 
                                                                      * * * * * * *
Toad, Yosemite...................  Anaxyrus canorus....  U.S.A. (CA)........  Entire.............  T                       834           NA           NA
 
                                                                      * * * * * * *
--------------------------------------------------------------------------------------------------------------------------------------------------------

* * * * *

    Dated: April 21, 2014.
Daniel M. Ashe,
Director, U.S. Fish and Wildlife Service.
[FR Doc. 2014-09488 Filed 4-25-14; 1:30 pm]
BILLING CODE 4310-55-P