[Federal Register: October 12, 2000 (Volume 65, Number 198)]
[Proposed Rules]               
[Page 60603-60605]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]

[[Page 60603]]



Fish and Wildlife Service

50 CFR Part 17

Endangered and Threatened Wildlife and Plants: 90-Day Finding on 
a Petition To List the Mountain Yellow-legged Frog as Endangered

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 90-day petition finding.


SUMMARY: The U.S. Fish and Wildlife Service (Service) announces a 90-
day finding on a petition to list the mountain yellow-legged frog (Rana 
muscosa) as endangered, under the Endangered Species Act (Act) of 1973, 
as amended (16 U.S.C. 1531 et seq.). We believe that the petition 
presents substantial information indicating that listing the species 
may be warranted. A status review is initiated.

DATES: The finding announced in this document was made on October 5, 
2000. To be considered in the 12-month finding for this petition, 
comments and information should be submitted to the Service by December 
11, 2000.

ADDRESSES: Data, information, comments, or questions concerning this 
petition should be submitted to the Field Supervisor; Sacramento Fish 
and Wildlife Office; Sacramento Fish and Wildlife Office; 2800 Cottage 
Way, Room W-2605; Sacramento, California 95825. The petition finding, 
supporting data and comments are available for public inspection, by 
appointment, during normal business hours at the above address.

FOR FURTHER INFORMATION CONTACT: Jason Davis or Maria Boroja at the 
Sacramento Fish and Wildlife Office (see ADDRESSES section above), or 
at (916) 414-6600.



    Section 4(b)(3)(A) of the Endangered Species Act (Act) of 1973, as 
amended (16 U.S.C. 1531 et seq.), requires that the Service make a 
finding on whether a petition to list, delist, or reclassify a species 
presents substantial information indicating that the petitioned action 
may be warranted. To the maximum extent practicable, this finding is to 
be made within 90 days of the receipt of the petition, and the finding 
is to be published promptly in the Federal Register. If the finding is 
that substantial information was presented, the Service will commence a 
review of the status of the involved species. This finding is based on 
information contained in the petition, supporting information submitted 
with the petition, and otherwise available to the Service at the time 
the finding was made.
    The processing of this petition conforms with our final listing 
priority guidance published in the Federal Register on October 22, 1999 
(64 FR 57114). The guidance clarifies the order in which we will 
process rulemakings. Highest priority is processing emergency listing 
rules for any species determined to face a significant and imminent 
risk to its well-being (Priority 1). Second priority (Priority 2) is 
processing final determinations on proposed additions to the lists of 
endangered and threatened wildlife and plants. Third priority (Priority 
3) is processing new proposals to add species to the lists. The 
processing of administrative petition findings (petitions filed under 
section 4 of the Act) is the fourth priority. The processing of 
critical habitat determinations (prudency and determinability 
decisions) and proposed or final designations of critical habitat will 
be funded separately from other section 4 listing actions and will no 
longer be subject to prioritization under the listing priority 
guidance. The processing of this petition finding is a Priority 4 
    We have made a 90-day finding on a petition to list the mountain 
yellow-legged frog (Rana muscosa) as an endangered species. On February 
10, 2000, we received a petition, dated February 8, 2000, to list the 
Sierra Nevada Mountain population of the mountain yellow-legged frog as 
an endangered species. The petition was submitted by the Center for 
Biological Diversity and Pacific Rivers Council. The letter clearly 
identified itself as a petition, and contained the names, signatures, 
and addresses of the two parties submitting the petition. The 
petitioners argued that the ``Sierra Nevada population of the mountain 
yellow-legged frog'' qualifies for listing under our Distinct 
Vertebrate Population Segment Policy (61 FR 4722). Included in the 
petition was supporting information relating to the species' taxonomy 
and ecology, adequacy of existing regulatory mechanisms for the 
species, and the historic and present distribution, current status, and 
potential causes of decline. This notice constitutes the 90-day finding 
for the February 10, 2000, petition.
    On July 10, 1995, we were petitioned to list the southern 
California population of the mountain yellow-legged frog a distinct 
population segment (DPS) of the mountain yellow-legged frog. The 
southern California population is isolated from the main part of the 
species' range, in the Sierra Nevada Mountains, by the Tehachapi 
Mountains and a distance of 225 kilometers (km) (140 miles(mi)). On 
December 22, 1999, we published a proposed rule to list the Southern 
California DPS of the mountain yellow-legged frog as an endangered 
species (64 FR 71714). In the proposed rule we recognized the southern 
population according to our policy on distinct vertebrate population 
segments (61 FR 4722). On March 20, 2000, we published a notice in the 
Federal Register to reopen the comment period on the proposal to list 
the southern California DPS of the mountain yellow-legged frog as 
endangered for a 30-day period.
    As the present petition (and this finding) addresses the remainder 
of the species' range, in the Sierra Nevada from Tulare County, 
California, in the south to Plumas County, California, in the north, we 
find no reason to recognize mountain yellow-legged frogs that occur in 
the Sierra Nevada as a DPS. Throughout the rest of this finding we 
refer to the petitioned entity, all mountain yellow-legged frogs that 
occur north of the Tehachapi Mountains in the Sierra Nevada, as the 
mountain yellow-legged frog.
    The petition and accompanying documentation state that the species 
qualifies for listing pursuant to the Act due to potential habitat 
destruction and modification, the presence of disease in combination 
with natural predation, the inadequacy of existing regulatory 
mechanisms, and other natural or human-caused factors affecting its 
continued existence. The petitioners contend that natural and human-
induced changes to mountain yellow-legged frog habitats, including (1) 
non-native fish introductions, (2) contaminant introductions, (3) 
livestock grazing, (4) acidification from atmospheric deposition, (5) 
nitrate deposition, (6) ultraviolet radiation, (7) drought, and (8) 
other factors, separately and in combination are responsible for an 
estimated 70 to 90 percent decline in mountain yellow-legged frog 
populations throughout the historic range of the species in the Sierra 
Nevada Mountains.
    The introduction of nonnative fish, including rainbow trout 
(Oncorhynchus mykiss), is one the best documented causes of decline of 
Sierra Nevada Mountain populations of mountain yellow-legged frogs. 
Careful study of the distributions of introduced trout and mountain 
yellow-legged frogs for several years has shown conclusively that

[[Page 60604]]

introduced trout have had negative impacts on mountain yellow-legged 
frogs over much of the Sierra Nevada Mountains (Bradford 1989; Knapp 
1996). Bradford (1989) and Bradford et al. (1994) concluded that 
introduced trout have eliminated many populations of mountain yellow-
legged frogs. In addition, the presence of trout in intervening streams 
sufficiently isolates other frog populations so recolonization after 
stochastic (random, naturally occurring) local extinctions is 
essentially impossible. This mechanism is sufficient to explain the 
elimination of mountain yellow-legged frogs from the majority of sites 
they once inhabited in the Sierra Nevada Mountains.
    Several studies have shown that significant levels of contaminants 
have been deposited in high Sierran aquatic ecosystems from pesticide 
drift, acid precipitation, and smog drift (Seiber et al. 1998; Aston 
and Seiber 1997; Cahill et al. 1996; Miller 1996; Byron and Goldman 
1991; Nikolaidis 1991; Laird et al. 1986). The petitioners present 
general evidence that the presence of contaminants in water, sediment, 
and aquatic vegetation can harm frog populations through lethal and 
sublethal effects including delayed metamorphosis, reduced breeding and 
feeding activity (Berrill et al. 1993, 1994, 1995, 1998; Boyer and Grue 
1995; Beaties and Tyler-Jones 1992; Corn and Vertucci 1992; Hall and 
Henry 1992). In addition, contaminant introduction may weaken the 
immune systems of frogs rendering them more susceptible to disease such 
as chytrid fungus and red-legged disease (Carey et al. 1993, 1995, 
1999; Jennings 1996; Drost and Fellers 1996; Sherman and Morton 1993). 
The petitioners cite recent work by Carlos Davidson (U.C. Davis, 
unpublished manuscript) that shows a positive relationship between 
amphibian declines in the Sierra Nevada Mountains that occur upwind 
from areas in California's Central Valley that apply large amounts of 
wind-borne agrochemicals. In particular, Davidson found agricultural 
land use to be twice as high downwind of sites where mountain yellow-
legged frogs had disappeared compared to sites where the species is 
still present (Davidson, unpublished manuscript).
    Livestock grazing can directly impact mountain yellow-legged frogs 
through trampling of individuals. Indirectly, livestock can have a 
significant effect on frog populations by: (1) Altering the hydrology 
and morphology of high mountain streams and ponds, (2) trampling of 
cover and vegetation along the periphery of wetland systems that are 
important egg laying and larval rearing areas, and (3) introducing 
nitrates into breeding areas resulting in elevated levels of bacteria 
(Armour et al. 1994; Duff 1977; Bohn and Buckhouse 1985; Kauffman and 
Krueger 1984; Kauffman et al. 1983; Marlow and Pogacnik 1985; Meehan 
and Platts 1978; Stephenson and Street 1978; U.S. Forest Service 2000).
    Acidification, nitrate deposition, and ultraviolet radiation have 
been implicated as other factors that may contribute to the range wide 
decline of mountain yellow-legged frogs. The petitioners state these 
factors may have negative effects on mountain yellow-legged frogs that 
include reduced growth rates, reduced feeding activity, disequilibrium, 
physical abnormalities, paralysis, embryonic failure, and even death 
among tadpoles and young frogs (Blaustein et al. 1994, Bradford and 
Gordon 1993, Carey et al. 1999, Clark and LaZerte 1985, Freda 1990, 
Marco et al. 1999, Marco and Blaustein 1999).
    During periods of prolonged drought, amphibians find refugial 
habitat in deeper, permanent sources of water which are also suited for 
fish. These refugial habitats allow for repopulation of more peripheral 
areas during wetter years (Bradford et al. 1993; Knapp 1996; Drost and 
Fellers 1996). The presence of nonnative fish has eliminated many of 
the permanent sources of refugial habitat from the mountain yellow-
legged frog, thus rendering frog populations more vulnerable to 
drought-related extinction events (Bradford et al. 1993; Knapp 1996; 
Drost and Fellers 1996).
    The petitioners state that disease likely plays a significant role 
in the widespread decline of mountain yellow-legged frogs. Two diseases 
potentially affecting mountain yellow-legged frogs are red-legged 
disease (Aeromonas hydrophila), which is caused by a freshwater 
bacteria, and chytrid fungus. The petitioners cite an article by 
Bradford (1991) reporting the loss of a mountain yellow-legged frog 
population in the Sierra Nevada due to red-legged frog disease and 
predation by Brewer's blackbirds (Euphagus cyanocephalus). In addition, 
they cite studies reporting mortality of adult Yosemite toads (Bufo 
canorus) in the Sierra Nevada and boreal toads (Bufo boreas boreas) in 
the Rocky Mountains due to red-legged disease (Sherman and Morton 1993; 
Carey 1993). Chytrid fungus, an aquatic pathogen discovered after 1993, 
has led to the mortality of many amphibian species in the United States 
and worldwide. The chytrid fungus attacks the mouthparts of tadpoles 
affecting their ability to feed. Chytrids have recently been discovered 
in larval mountain yellow-legged frogs in the Sierra Nevada (Gary 
Fellers, U.S. Geologic Survey, pers. comm. 1999). Roland Knapp (Sierra 
Nevada Aquatic Research Lab, pers. comm. 2000) reported a significant 
decline of mountain yellow-legged frogs at Dry Creek near Mono Lake, a 
site that had thriving population in 1998. He attributed the population 
crash to the chytrid fungus after detecting deformed mouthparts in 
several tadpoles at the site. The petitioners also cite a personal 
communication with Vance Vredenburg (University of California, 
Berkeley, Museum of Vertebrate Zoology, pers. comm. 2000) who reported 
the complete loss of another mountain yellow-legged frog population in 
the Emigrant Wilderness due to the chytrid fungus. There have been 
reports of chytrid fungus attacking other Sierra Nevada amphibians, 
including the Yosemite toad. An investigation of museum specimens of 
Yosemite toads collected by Sherman and Morton at Tioga Pass during a 
1977-1978 die-off found those toads to be infected with chytrid fungus 
(Carey et al. 1999). The petitioners state that there is significant 
information yet to be discovered regarding aquatic pathogens and their 
relationship to the ecology of mountain yellow-legged frogs. Should 
evidence indicate that mountain yellow-legged frogs have evolved with 
aquatic pathogens, then other stressors including contaminant 
introductions and UV-radiation may be reducing the ability of frogs to 
fight off infection from these pathogens (Sherman and Morton 1993; 
Drost and Fellers 1996; Carey et al. 1993, 1995, 1999; Jennings 1996; 
Taylor et al. 1999).
    Up to the 1960s, the mountain yellow-legged frog was widely 
distributed and abundant across the Sierra Nevada (Zwefel 1955; Cory et 
al. 1970, Jennings and Hayes 1994). Since then, however, the overall 
population has declined dramatically. The most pronounced declines have 
occurred within the northernmost 125 km (78 mi) of the range, north of 
Lake Tahoe, and the southernmost 50 km (31 mi) of the range, below 
Sequoia and Kings Canyon National Parks, where only a few populations 
remain (Jennings and Hayes 1994; Fellers 1999). Jennings and Hayes 
(1994) noted a 50 percent decline in the species across the Sierra 
Nevada based on sampling historic mountain yellow-legged frog locations 
conducted before the 1970s. Knapp and Matthews (2000) noted that the 50 
percent decline may be conservative, as the sampling conducted by 
Jennings and Hayes took place in Sequoia and Kings Canyon National 
Parks, where mountain yellow-

[[Page 60605]]

legged frog populations are larger and more abundant compared to 
populations north of the Sierra National Forest.
    However, even in the protected areas of Sequoia and Kings Canyon 
National Parks, mountain yellow-legged frog populations have undergone 
significant declines. Bradford et al. (1994) published results of two 
separate studies which resurveyed historic sites where mountain yellow-
legged frogs were documented between 1959 and 1979 in Sequoia and Kings 
Canyon National Parks. They found mountain yellow-legged frogs at only 
12 of 49 sites surveyed in 1989 and 1990. In addition, mountain yellow-
legged frogs had disappeared from one of these 12 sites by 1991.
    Outside of Sequoia and Kings Canyon National Parks, Bradford et al. 
(1994) reported the absence of mountain yellow-legged frogs at 21 of 24 
historic sites. In another study, Drost and Fellers (1996) resurveyed 
14 sites originally surveyed in 1915 by Grinnell and Storer (1924), and 
found only two now occupied by the mountain yellow-legged frog. These 
surveys all strongly suggest that the mountain yellow-legged frog has 
systematically declined throughout its range.
    We have reviewed the petition and other information available in 
the Service's files. Based upon this review, we believe that 
substantial evidence exists that listing the mountain yellow-legged 
frog as endangered may be warranted. When we make a positive finding, 
we also are required to promptly commence a review of the status of the 
species. Based upon available and any newly obtained information, we 
will issue a 12-month finding as required by section 4(b)(3)(B) of the 
Act. Petitioners also requested that critical habitat be designated for 
the Sierra Nevada population of the mountain yellow-legged frog. The 
12-month finding will address this issue.

Public Information Requested

    The Service hereby announces its formal review of the species' 
status pursuant to this 90-day petition finding. We request any 
additional data, comments, and suggestions from the public, other 
concerned government agencies, the scientific community, industry, and 
any other interested parties concerning the status of the mountain 
yellow-legged frog. Of particular interest is information regarding: 
(1) The existence and status of additional subpopulations, (2) the 
impact of nonnative fish introductions, contaminants, livestock 
grazing, acidification from atmospheric deposition, nitrate deposition, 
ultraviolet radiation, drought, disease, and other factors that may be 
responsible for the range-wide decline of the species, (3) the 
implementation of any actions that are benefitting the species, and (4) 
genetic variability in known subpopulations.
    If you wish to comment, you may submit your comments and materials 
concerning this finding to the Field Supervisor, Sacramento Fish and 
Wildlife Office (see ADDRESSES section). Our practice is to make 
comments, including names and home addresses of respondents, available 
for public review during regular business hours. Respondents may 
request that we withhold their home address, which we will honor to the 
extent allowable by law. There also may be circumstances in which we 
would withhold a respondent's identity, as allowable by law. If you 
wish us to withhold your name and/or address, you must state this 
request prominently at the beginning of your comment. However, we will 
not consider anonymous comments. To the extent consistent with 
applicable law, we will make all submissions from organizations or 
businesses, and from individuals identifying themselves as 
representatives or officials of organizations or businesses, available 
for public inspection in their entirety. Comments and materials 
received will be available for public inspection, by appointment, 
during normal business hours at the above address.

References Cited

    A complete list of all references cited herein is available on 
request from the Sacramento Fish and Wildlife Office, (See ADDRESSES 
    Author: The primary author of this document is Jason Davis, 
Sacramento Fish and Wildlife Office (see ADDRESSES section).


    The authority for this action is the Endangered Species Act of 
1973, as amended (16 U.S.C. 1531 et seq.).

    Dated: October 5, 2000.
Jamie Rappaport Clark,
Director, Fish and Wildlife Service.
[FR Doc. 00-26179 Filed 10-11-00; 8:45 am]