[Federal Register: December 10, 2002 (Volume 67, Number 237)]
[Proposed Rules]               
[Page 75834-75843]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]

[[Page 75834]]



Fish and Wildlife Service

50 CFR Part 17

Endangered and Threatened Wildlife and Plants; 12-Month Finding 
for a Petition to List the Yosemite Toad

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.


SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
12-month finding for a petition to list the Yosemite toad (Bufo 
canorus) under the Endangered Species Act of 1973, as amended (Act). We 
find that the petitioned action is warranted, but precluded by higher 
priority listing actions. We will develop a proposed rule to list this 
species pursuant to our Listing Priority System (48 FR 43098). Upon 
publication of this notice of 12-month petition finding, this species 
will be added to our candidate species list.

DATES: The finding announced in this document was made on November 27, 
2002. Comments and information may be submitted until further notice.

ADDRESSES: You may send data, information, comments, or questions 
concerning this finding to the Field Supervisor, U.S. Fish and Wildlife 
Service, Sacramento Fish and Wildlife Office, 2800 Cottage Way, Room W-
2605, Sacramento, CA 95825. You may inspect the petition, 
administrative finding, supporting information, and comments received, 
by appointment, during normal business hours at the above address.

FOR FURTHER INFORMATION CONTACT: Susan Moore at the Sacramento Fish and 
Wildlife Office (see ADDRESSES above) (telephone 916/414-6600; 
facsimile 916/414-6712).



    Section 4(b)(3)(B) of the Endangered Species Act of 1973, as 
amended (Act) (16 U.S.C. 1531 et seq.), requires that, for any petition 
to revise the List of Threatened and Endangered Species containing 
substantial scientific and commercial information that listing may be 
warranted, we conduct a status review and make a finding within 12 
months of the date of the receipt of the petition on whether the 
petitioned action is: (a) Not warranted, (b) warranted, or (c) 
warranted but precluded from immediate proposal by other higher 
priority proposals. Section 4(b)(3)(C) of the Act requires that 
petitions for which a requested action is found to be warranted but 
precluded should be treated as though resubmitted on the date of such 
finding, i.e., requiring a subsequent finding to be made within 12 
months. Such 12-month findings are to be published promptly in the 
Federal Register.
    Section 4(b) of the Act states that we may make warranted but 
precluded findings only if we can demonstrate that: (1) An immediate 
proposed rule is precluded by other pending actions, and (2) 
expeditious progress is being made on other listing actions. Due to the 
large amount of litigation over critical habitat, we are working on 
numerous court orders and settlement agreements. Complying with these 
orders and settlement agreements will consume all of our listing budget 
for fiscal year 2003. However, we can continue to place species on the 
candidate species list, as that work activity is funded separately from 
our listing program.


    The Yosemite toad was originally described by Camp (1916), and 
given the common name Yosemite Park toad. Subsequent detections of this 
species indicated that its range extends beyond the boundaries of 
Yosemite National Park, and Grinnel and Storer (1924) referred to this 
species as the Yosemite toad.
    Similarities in appearance of the Yosemite toad and the western 
toad (Bufo boreas) were noted by Camp (1916). Based on general 
appearance, structure and distribution, it appears that these two 
species are closely related (Myers 1942; Stebbins 1951; Mullally 1956; 
Savage 1958). The close relationship between B. boreas and B. canorus 
is also supported by studies of bone structure (Tihen 1962a,b), and by 
the survivorship of hybrid toads produced by artificially crossing the 
two species (Blair 1959, 1963, 1964).
    Camp (1916), using characteristics of the skull, concluded that 
Bufo boreas, B. canorus, and B. nestor (extinct) are more closely 
related to each other than to other North American toads, and that 
these species comprise the most primitive group of Bufo in North 
America. Blair (1972) grouped B. boreas, B. canorus, black toads (B. 
exsul), and Amargosa toads (B. nelsoni), together taxonomically as the 
``boreas group.''
    Feder (1977) found Bufo canorus to be genetically distinctive based 
on samples from a limited geographic range. However, Yosemite toads are 
thought to hybridize with western toads in the northern part of their 
range (Karlstrom 1962; Morton and Sokolski 1978). Shaffer et al. (2000) 
performed genetic analysis of a segment of mitochondrial DNA from 372 
Yosemite toads found in Yosemite and Kings Canyon National Parks. Their 
data showed significant genetic differences in Yosemite toads between 
the two National Parks. They also found significant genetic variability 
within Yosemite National Park between drainages, and within both Parks 
between breeding sites. Their data also indicated that black toads are 
a subgroup within Yosemite toads rather than a separate species. 
Stephens (2001) examined mitochondrial DNA from 8 Yosemite toads 
(selected from the samples examined by Shaffer et al. (2000) to 
represent the range of variability found in that study) and 173 western 
toads. Stephens' data indicate that Bufo in the Sierra Nevada occur in 
northern and southern evolutionary groups, each of which include both 
Yosemite and western toads (i.e., toads of both species are more 
closely related to each other within a group than they are to members 
of their own species in the other group). Further genetic analysis of 
Yosemite toads sampled from throughout their range, and from other toad 
species surrounding their range is needed to fully understand the 
evolutionary history and appropriate taxonomic status of the Yosemite 
toad (Stephens 2001).

Description and Natural History

    Yosemite toads are moderately sized, with a snout-urostyle length 
(measured from the tip of the snout to the posterior edge of the 
urostyle, a bony structure at the posterior end of the spinal column) 
of 30 to 71 millimeters (mm) (1.2 to 2.8 inches (in)) with rounded to 
slightly oval paratoid glands (a pair of glands, one on each side of 
the head, that produce toxins) (Karlstrom 1962). The paratoid glands 
are less than the width of a gland apart (Stebbins 1985). A thin mid-
dorsal (middle of the back) stripe is present in juveniles of both 
sexes. The stripe disappears or is reduced with age, and more quickly 
in males (Jennings and Hayes 1994). The iris of the eye is dark brown 
with gold iridophores (reflective pigment cells) (Jennings and Hayes 
1994). Males are smaller than females, with less conspicuous warts 
(Stebbins 1951). Differences in coloration between males and females 
are more pronounced in the Yosemite toad than in any other North 
American frog or toad (Stebbins 1951). Females have black spots or 
blotches edged with white or cream that are set against a grey, tan or 
brown background color (Jennings and Hayes 1994). Males have a nearly 
uniform dorsal coloration of yellow-green to olive drab to darker 
greenish brown (Jennings and Hayes

[[Page 75835]]

1994). Karlstrom (1962) suggested that differences in coloration 
between the sexes evolved because they provide the Yosemite toad with 
protective coloration. The uniform coloration of the adult male matches 
and blends with the silt and grasses that they frequent during the 
breeding season, whereas the young and females with disruptive 
coloration tend to use a wider range of habitats with broken 
backgrounds; thus coloration may help conceal individual toads from 
    Yosemite toads overwinter in rodent burrows (Jennings and Hayes 
1994). They emerge from hibernation as soon as snowmelt pools form near 
their overwintering sites (Karlstrom 1962; Kagarise Sherman 1980; 
Jennings and Hayes 1994). Observed emergence times range from early May 
to the middle of June (Kagarise Sherman 1980).
    Males form breeding choruses, and breeding begins soon after 
emergence (Jennings and Hayes 1994). Males call during the day and 
early evening (Stebbins 1951). The breeding call is a mellow long 
sustained trill with 10 to more than 20 notes (Stebbins 1951). Males 
have been observed to attack other males to prevent them from calling, 
to amplex (amplexus is a characteristic clasping of the female by the 
male during mating) other toads in trial and error search for females, 
and to attack amplexed pairs and attempt to take over the female 
(Kagarise Sherman 1980). In studies by Kagarise Sherman (1980), males 
that mated successfully were more likely to be larger, have arrived at 
breeding sites earlier, and have stayed at breeding sites longer.
    Eggs are typically deposited in shallow water with silty bottoms 
(Karlstrom 1962). Ideal habitat for egg development is between 2-4 
centimeters (cm) (0.8-1.6 in) deep, and eggs do not survive in water 
deeper than 6 cm (2.4 in) (David Martin, University of California, 
Santa Barbara, pers. comm. 2002). Eggs are deposited in gelatinous 
strings (Stebbins 1951; Karlstrom and Livezey 1955) which are 
intertwined with vegetation and buried in silt (Karlstrom 1962). Eggs 
are relatively large (2.1 mm (0.08 in) average diameter) and brownish 
black to jet black over the upper three quarters, and gray to tannish 
gray over the lower one quarter (Jennings and Hayes 1994). Females are 
estimated to deposit between 1,000 to 1,500 eggs (Kagarise Sherman 
    When not breeding, adults feed in meadow or moist upland habitat 
until they hibernate (Kagarise Sherman 1980; D. Martin, pers. comm. 
2002). Although they are largely diurnal (active during the day) 
(Jennings and Hayes 1994), especially while breeding, recent evidence 
shows that they primarily feed and move at night (D. Martin, pers. 
comm. 2002).
    Eggs generally hatch within 3 to 6 days depending on water 
temperature (Jennings and Hayes 1994), although they may take over 15 
days (Kagarise Sherman 1980). Tadpoles typically transform within 40 to 
50 days after fertilization. Tadpoles are not known to overwinter 
(Jennings and Hayes 1994), although immature tadpoles have been 
observed well into September (Mullally 1956). Tadpoles tend to 
congregate (Brattstrom 1962) and use warm shallow water during the day 
(Cunningham 1963), then retreat to deeper water at night (Mullally 
1953). The tadpoles are uniformly black, the snout is blunt, the 
intestines are scarcely or not at all visible, and the dorsal fin is 
transparent and marked with few relatively large melanophores (dark-
colored pigment cells) (Stebbins 1951). Tadpoles measure 10 to 37 mm 
(0.39 to 1.45 in) in length (Stebbins 1951, 1985).
    Newly metamorphosed juveniles are around 10 mm (0.39 in) in snout-
urostyle length (Jennings and Hayes 1994). Some individuals may 
reproduce at 2 years of age, but growth is slow in both sexes and most 
individuals require more time to reach maturity (Jennings and Hayes 
1994). Males have been observed to first breed at 3 to 5 years and 
females at 4 to 6 years (Kagarise Sherman 1980; Kagarise Sherman and 
Morton 1984). Females probably do not breed every year (Morton 1981). 
Yosemite toads are long lived, with females documented as reaching 15 
years old and males 12 years old (Kagarise Sherman and Morton 1984).
    Kagarise Sherman (1980) observed one female Yosemite toad move 270 
meters (m) (885 feet (ft)) in 65 days and one male move 150 m (492 ft) 
in 9 days. Toads in her study generally moved 150 to 230 m (492 to 755 
ft) each spring from their hibernation sites to their breeding sites. 
In studies in which toads were repeatedly located using radiotelemetry 
equipment (D. Martin, pers. comm. 2002), adult toads were observed to 
moving up to approximately 610 m (2,000 ft) in a single night. During 
the active season (spring-summer), females generally spend less time 
at, and travel further away from, breeding ponds than males (Kagarise 
Sherman 1980). Young of year metamorphs (young toads that have just 
transformed from tadpoles) probably hibernate closer to the ponds in 
which they were born than adult toads (Kagarise Sherman 1980). Stebbins 
(1951) suggested that isolation or semi-isolation of subpopulations of 
Yosemite toads is likely because they are unlikely to cross large, dry, 
forested areas between meadows.
    Adult and juvenile Yosemite toads are lie-and-wait predators. They 
remain motionless until a prey item approaches, then strike and capture 
the prey with their sticky tongues (Kagarise Sherman and Morton 1984). 
The examined stomach contents of Yosemite toads have included beetles, 
ants, centipedes, spiders, dragonfly larvae, mosquitos, and moth and 
butterfly larvae (Grinnel and Storer 1924; Mullally 1953). They will 
also prey on flies, bees, wasps, millipedes (Kagarise Sherman and 
Morton 1984), spider mites, crane flies, springtails, owl flies, and 
damsel flies (Martin 1991).
    Yosemite toad tadpoles graze on detritus and plant material such as 
algae and will also eat other items such as lodgepole pine pollen. 
Yosemite toad tadpoles can also be carnivorous and will eat other 
Yosemite toad tadpoles (see Natural Mortality, below), Pacific chorus 
frog (previously Pacific treefrog) (Pseudacris regilla, previously Hyla 
regilla) tadpoles, diving beetle larvae, and dead mammals (Martin 

Habitat Requirements

    Yosemite toads use meadow habitats surrounded by lodgepole pine 
(Pinus contorta) or whitebark pine (P. albicaula) (Camp 1916). They are 
most likely to be found in areas with thick meadow vegetation or 
patches of low willows (Salix spp.) (Mullally 1953). They are most 
often seen near water, but only occasionally in water (Mullally and 
Cunningham 1956), and use rodent burrows for overwintering and probably 
for temporary refuge during the summer (Jennings and Hayes 1994). They 
also use spaces under surface objects, including logs and rocks, for 
temporary refuge (Stebbins 1951; Karlstrom 1962). Breeding habitat 
includes the edges of wet meadows and slow-flowing streams (Jennings 
and Hayes 1994). Tadpoles have also been observed in shallow ponds and 
shallow areas of lakes (Mullally 1953). Moist upland areas such as 
seeps and springheads are important summer non-breeding habitats for 
adult toads (D. Martin, pers. comm. 2002).

Natural Mortality

    Mountain yellow-legged frogs (Rana muscosa) (Mullally 1953), 
aquatic dragonfly larvae (Jennings and Hayes 1994), diving beetles 
(Dytiscus spp.) (Kagarise Sherman and Morton 1984), and possibly larval 
long-toed salamanders (Ambystoma macrodactylum) (Jennings and Hayes 
1994) prey on the young life stages of Yosemite toads. American robins

[[Page 75836]]

(Turdus migratorius) prey on Yosemite toad tadpoles (Jennings and Hayes 
1994). Garter snakes (Thamnophis spp.) have been observed to eat 
yearling Yosemite toads (D. Martin, pers. comm. 2002), and are probably 
the most significant predator on tadpoles and metamorphs (Karlstrom 
1962; Jennings and Hayes 1994). California gulls (Larus californicus) 
and Clark's nutcrackers (Nucifraga columbiana) have been observed 
killing adult toads (Mulder et al. 1978; Kagarise Sherman 1980; 
Kagarise Sherman and Morton 1993). Cannibalism has been recorded in 
Yosemite toad tadpoles (Martin 1991; Chan 2001). The tadpoles have not 
been observed to kill each other, but they do wound each other in 
feeding frenzies, and have been observed eating dead tadpoles of their 
own species (Martin 1991; Chan 2001; D. Martin, pers. comm. 2002).
    Dessication of breeding habitat before tadpoles metamorphose is a 
major cause of mortality (Zeiner et al. 1988; Kagarise Sherman and 
Morton 1993; Jennings and Hayes 1994). Eggs are sometimes killed by 
freezing (Kagarise Sherman and Morton 1984). Fungal growth has also 
been observed on eggs (Kagarise Sherman 1980), but it is unclear 
whether the fungus causes mortality or grows after the eggs die from 
other causes.
    Toads may die of exposure when crossing snow or ice (Kagarise 
Sherman 1980). Toads that emerge from hibernation early may suffer from 
exposure and inability to feed if there are late-season storms 
(Kagarise Sherman 1980).
    Adult toads of either sex may drown or asphyxiate when multiple 
males attempt to amplex a single female. Kagarise Sherman (1980) 
documented the death of a single female in this manner, and found three 
additional females and two males that may also have died during 
multiple amplexus.

Historic and Current Range and Status

    The historic range of Yosemite toads in the Sierra Nevada occurs 
from the Blue Lakes region north of Ebbetts Pass (Alpine County) to 5 
kilometers (km) (3.1 miles (mi)) south of Kaiser Pass in the Evolution 
Lake/Darwin Canyon area (Fresno County) (Jennings and Hayes 1994). The 
historic elevational range of Yosemite toads is 1,460 to 3,630 m (4,790 
to 11,910 ft) (Stebbins 1985).
    Pre-1990 historic records of Yosemite toad localities are primarily 
from museum records and incidental sightings. Systematic habitat 
surveys looking specifically for Yosemite toad populations have only 
been conducted since the early 1990s. Therefore, it is impossible to 
know how many populations have declined or become extinct, because we 
do not know how many populations originally existed. Sites first 
documented after 1990 are useful to illustrate the current range of the 
species, but are not useful in discussing its decline, due to lack of 
baseline data. Based on the number of historic sites that are no longer 
occupied (see below), it is possible that many populations have 
disappeared without ever having been documented.
    Since 1990, 292 sites throughout Yosemite toads' historic range 
have been surveyed, and 229 sites have been confirmed to be occupied. 
Known Yosemite toad locations by area is based on the most 
comprehensive dataset on Yosemite toad localities available, which was 
collected by the U.S. Forest Service (USFS) for use in their 
conservation assessment of the species (as required by the Sierra 
Nevada Forest Plan Amendment (U.S. Department of Agriculture (USDA) 
2001f)). This data set was compiled by the USFS and came from various 
sources, including University of California and California State 
University researchers, the California Academy of Science, the National 
Park Service (NPS), the U.S. Geological Survey, the California 
Department of Fish and Game (CDFG), and the California Natural 
Diversity Data Base. The following discussion on the number of Yosemite 
toad sites should be considered an approximation, based on best 
available information, because surveys are ongoing and some sites may 
have not yet been reported and added to the database. Also, multiple 
sightings in close proximity to each other have been considered as a 
single site for the purposes of this discussion.
    The historic and current acreage of Yosemite toad habitat (wet 
meadows, shallow breeding waters, and moist uplands) within the 
historic range of Yosemite toads is unknown, although these habitats 
have been degraded and may be decreasing in area as a result of conifer 
encroachment and livestock grazing (see Factor A below). The vast 
majority of land within the range of the Yosemite toad is federally 
managed, with 919,011 hectares (ha) (2,270,918 acre (ac)) (99 percent 
of the range) on USFS, NPS, and Bureau of Land Management lands. Much 
of this land is within designated wilderness. The remaining land within 
the species' range is a mix of State, local government, and private 
    The following known site discussion is based on the California 
Wildlife Habitat Relations range map, obtained as a geographic 
information system data from CDFG for the species, although this map 
includes large areas of unsuitable habitat. However, this map is the 
best available range map for the species, although the species has been 
detected in a few locations outside its boundaries, primarily at the 
southern end of the range. The site specific information is based on 
localized studies that do not represent a comprehensive range-wide 
assessments of the species status.
    (1) Yosemite toads are known from three sites in the southeast 
corner of the El Dorado National Forest where it borders with the 
Toiyabe and Stanislaus National Forests. Two of these three sites have 
been confirmed as occupied since 1990.
    (2) Yosemite toads are known from 25 locations along the west side 
of the Toiyabe National Forest, 15 of which have been confirmed as 
occupied since 1990.
    (3) Yosemite toads are known from 28 sites on the Stanislaus 
National Forest, 22 of which have been confirmed as occupied since 
1990. These sites occur primarily in two groups, one on the northern 
edge of the forest, where it borders with the El Dorado and Toiyabe 
National Forests, and the other in a band extending west across the 
Stanislaus National Forest, from its southeast border with Yosemite 
National Park and the Toiyabe National Forest.
    (4) Yosemite toads are known from 49 sites along the west side of 
Inyo National Forest, 35 of which have been confirmed as occupied since 
    (5) Yosemite toads are known from 91 locations throughout Sierra 
National Forest, of which 84 have been confirmed as occupied since 
    (6) Yosemite toads are known from 78 sites scattered throughout 
Yosemite National Park, 57 of which have been confirmed occupied since 
    (7) Yosemite toads are known from 18 sites throughout the northern 
half of Kings Canyon National Park, 14 of which have been confirmed as 
occupied since 1990.
    It is impossible to fully determine the extent to which Yosemite 
toads have declined, because baseline data on the number and size of 
historic populations are few. The following studies, which reassess the 
current status of historically documented populations, give the most 
insight into the species' decline.
    Jennings and Hayes (1994) 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 mapped 55 historically

[[Page 75837]]

documented general localities throughout the range of the species where 
the toad had been present (based on 144 specific sites), and found that 
Yosemite toads are now absent from 29 of those localities, a decline of 
over 50 percent.
    In 1990, David Martin surveyed 75 sites throughout the range of the 
Yosemite toad for which there are historic records of the species' 
presence, and found that 47 percent of those sites showed no evidence 
of any life stage of the species (Stebbins and Cohen 1997), a decline 
of about 63 percent.
    Grinnell and Storer (1924) surveyed for vertebrates at 40 sites 
along a 143-km (89-mi) west-to-east transect across the Sierra Nevada, 
through Yosemite National Park, in 1915 and 1919. Drost and Fellers 
(1996) conducted more thorough surveys, specifically for amphibians, at 
38 of those sites in 1992. They found that Yosemite toads were absent 
from 6 of 13 sites in which they had been found in the original survey. 
At sites where Drost and Fellers (1996) found Yosemite toads, the toads 
occurred in low numbers (only 15 total adult and juvenile toads at all 
sites), with documented declines in relative abundance in three of the 
Grinnel and Storer (1924) sites, as based on their generalized 
abundance categories such as rare, common, and abundant. Therefore, the 
species has declined or disappeared completely from at least 9 of 13 
(69 percent) of the Grinnel and Storer (1924) sites.
    The only long-term study on the size of a population of Yosemite 
toads indicates that the population has declined dramatically. Kagarise 
Sherman and Morton (1993) studied Yosemite toads at Tioga Pass Meadow 
(Mono County, California) intensively from 1971 to 1982, and made less 
systematic observations from 1983 to 1991. To estimate the adult 
population size, they captured and marked toads entering breeding 
pools. From 1974 to 1978, an average of 258 males entered the breeding 
pools. In 1979, the number of male toads began to decline, and by 1982, 
the number of males had dropped to 28. During the same time period, the 
number of females varied between 45 and 100, but there was no obvious 
trend in number observed. In periodic surveys between 1983 and 1991, it 
appeared that both males and females continued to decline, and breeding 
activity became sporadic. In 1990, the researchers were only able to 
locate one female, two males, and four to six egg masses. In 1991, they 
found only one male and two egg masses. The researchers also surveyed 
non-breeding habitat in the same area and found similar population 
declines. To date, the population at Tioga Pass Meadow has not 
recovered (Roland Knapp, Sierra Nevada Aquatic Research Laboratory, 
pers. comm. 2002).
    Kagarise Sherman and Morton (1993) also conducted occasional 
surveys of six other populations in the eastern Sierra Nevada. Five of 
these populations showed serious, apparently long-term, declines 
between 1978 and 1981, while the sixth population held relatively 
steady until the final survey in 1990, at which time it dropped 
precipitously. In 1991, E.L. Karlstrom revisited the site at which he 
had studied a breeding population of Yosemite toads from 1954 to 1958, 
just south of Tioga Pass Meadow within Yosemite National Park (Tuolumne 
County, California), and found no evidence of toads or signs of 
breeding (Kagarise Sherman and Morton 1993).

Previous Federal Action

    On April 3, 2000, we received a petition to list the Yosemite toad 
as endangered from the Center for Biological Diversity and Pacific 
Rivers Council. On October 12, 2000, we announced a 90-day petition 
finding in the Federal Register (65 FR 60607) concluding that the 
petition presented substantial scientific or commercial information to 
indicate that the listing of the Yosemite toad may be warranted.
    This 12-month finding is made in accordance with a settlement 
agreement which requires us to complete a finding by November 30, 2002 
(Center for Biological Diversity and Pacific Rivers Council v. Norton 
and Jones, No. C-01-2106 (N.D. Calif.)).

Summary of Factors Affecting the Species

    Section 4 of the Act and regulations (50 CFR part 424) promulgated 
to implement the listing provisions of the Act describe the procedures 
for adding species to the Federal lists. A species may be determined to 
be an endangered or threatened species due to one or more of the five 
factors described in section 4(a)(1). In the case of the Yosemite toad, 
the specific relationship between the potential threats under each 
factor and the continued decline of the species remains unclear. These 
factors, and their application to the Yosemite toad, are as follows:
    A. The present or threatened destruction, modification, or 
curtailment of its habitat or range. The following discussion presents 
several threats to the species' habitat or range.


    Livestock grazing began in Sierra Nevada meadow and riparian areas 
with the settlement of California by the Spanish in the mid-1700s, and 
rose to a level that caused significant impacts in the mid-1800s 
following the gold rush (Menke et al. 1996). In general, livestock 
grazing within the range of the Yosemite toad was at a high, but 
undocumented, level until the establishment of National Parks 
(beginning in 1890) and National Forests (beginning in 1905) (Menke et 
al. 1996) in the Sierra Nevada area. Within established National Parks, 
livestock grazing was gradually eliminated, but packstock grazing was 
permitted and has increased over time (Menke et al. 1996).
    Over time within established National Forests, the amount of 
grazing was gradually reduced, better documented, and the type of 
animals grazed shifted from predominantly sheep to cattle and packstock 
(Menke et al. 1996). In general, livestock grazing within the National 
Forests in the Sierra Nevada has continued with gradual reductions 
since the 1920s, except for an increase during World War II (Menke et 
al. 1996). Currently, there are numerous active and inactive livestock 
grazing allotments on the five National Forests that occur within the 
range of the Yosemite toad. Approximately 71 active and 36 inactive 
allotments occur across the Eldorado, Toiyabe, Inyo, Stanislaus, and 
Sierra National Forests (Laura Conway, Stanislaus National Forest, 
pers. comm. 2002; Holly Eddinger, Sierra National Forest, in litt., 
2002; Aimee Smith, Sierra National Forest, in litt., 2002).
    Since 1970, the continuing decrease in grazing permitted on the 
National Forests has been motivated by concern for resource protection 
(Menke et al. 1996). National Forests have conducted projects to 
minimize or rehabilitate areas impacted by grazing, including 
exclosures around some sensitive areas, erosion control structures, and 
replanting of riparian species.
    Packstock grazing is the only grazing currently allowed in National 
Parks, and it is also allowed in National Forests. There has been very 
little monitoring of the impacts of packstock use in the Sierra Nevada, 
which increased after World War II due to increased road access, and 
increases in leisure time and disposable income (Menke et al. 1996). 
The recreational use of packstock and horsebackriding in the Sierra 
Nevada can be expected to increase further as human populations 
increase (State of California 2001; USDA 2001g).
    Mule deer (Odocoileus hemionus) and bighorn sheep (Ovis canadensis) 
have always occurred within the habitats used by the Yosemite toad 
(Ingles 1965).

[[Page 75838]]

However, grazing by dense groups of large herbivores such as cattle and 
horses is not a natural situation in those habitats, and these habitats 
are vulnerable to degradation. Because Yosemite toad breeding habitat 
is shallow, that habitat is very vulnerable to changes in hydrology 
caused by grazing (D. Martin, pers. comm. 2002; R. Knapp, pers. comm. 
    Direct and indirect mortality of Yosemite toads have occurred as a 
result of livestock grazing. Cattle have been observed to trample 
Yosemite toad eggs and disturb eggs such that they fall into hoofprints 
or other deeper water and die. Metamorph Yosemite toads have been 
observed to fall into cattle hoofprints or to be defecated on by 
cattle, become trapped, and die, and adult Yosemite toads have been 
observed trampled to death in cattle hoofprints (D. Martin, pers. comm. 
2002). Preliminary research data indicate that Yosemite toad tadpoles 
in grazed areas take longer to metamorphose and produce smaller 
metamorphs than those in areas being rested from grazing, presumably 
due to high bacteria and nutrient levels, causing low water quality in 
the grazed areas (D. Martin, pers. comm. 2002).
    Grazing removes vegetative cover, and before/after surveys have 
shown reductions in the number of Yosemite toads using an area after 
the herbaceous cover was grazed (D. Martin, pers. comm. 2002). Grazing 
can also cause erosion by disturbing the ground, removing vegetation, 
and destroying peat layers in meadows, which lowers the groundwater 
table and summer flows (Armour et al. 1994; D. Martin, pers. comm. 
2002). Consequently, this may increase the stranding and mortality of 
tadpoles, or make these areas completely unsuitable for Yosemite toads 
(D. Martin, pers. comm. 2002). Grazing can also degrade or destroy 
moist upland areas used as non-breeding habitat by Yosemite toads (D. 
Martin, pers. comm. 2002), 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, or disturb toads and disrupt their behavior.
    The impacts of grazing on habitat can be inferred by observing the 
recovery of vegetation, ground stability, and water flow that occurs 
when riparian areas are fenced to exclude livestock (Kattelmann and 
Embury 1996). An example of this, from a drainage occupied by Yosemite 
toads, is provided by a study of fish habitat on Silver King and Coyote 
Valley Creeks (tributaries of the Carson River, Alpine County, 
California). In this study, stream reaches were fenced to exclude 
cattle and, over time, bank stability increased and stream channels 
became deeper and narrower than the unfenced reaches. This indicated 
that streambank sloughing had been reduced and vegetation was 
stabilizing soils and reducing erosion (Overton et al. 1994; Kattelmann 
and Embury 1996).
    Livestock grazing in the Sierra Nevada has been so 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). Due to the long, and historically unregulated history (Menke et 
al. 1996) of livestock and packstock grazing in the Sierra Nevada, and 
the lack of historic Yosemite toad population size estimates, it is 
difficult to make a quantitative link between grazing and reductions in 
Yosemite toad populations. However, because of the documented negative 
effects of livestock on Yosemite toad habitat, and documented direct 
mortality of the species caused by livestock, the decline of some 
populations of Yosemite toad has been attributed to the effects of 
livestock grazing (Jennings and Hayes 1994; Jennings 1996).

Roads and Timber Harvest

    Any activity that severely alters the terrestrial environment, such 
as road construction and timber harvest, is likely to result in the 
reduction and occasional extirpation of amphibian populations in the 
Sierra Nevada (Jennings 1996). By creating gaps in the natural 
vegetation, roads and harvested areas may act as dispersal barriers and 
contribute to the fragmentation of Yosemite toad habitat and 
populations. Habitat fragmentation has been shown to have a negative 
effect on amphibian species richness (Lehtinen et al. 1999). Timber 
harvest removes vegetation and causes ground disturbance and soil 
compaction, which makes that ground more susceptible to erosion (Helms 
and Tappeiner 1996). Much of the erosion caused by timber harvests is 
from logging roads (Helms and Tappeiner 1996). This erosion could 
damage Yosemite toad breeding habitat by lowering the water table, and 
drying out riparian habitats used by the species.
    Prior to the formation of National Parks and National Forests, 
timber harvest was widespread and unregulated, but primarily took place 
at low elevations on the west slope of the Sierra Nevada, below the 
elevational range of the Yosemite toad (University of California (UC) 
1996). Between 1900 and 1950, the majority of timber harvest took place 
on old growth forests on private land (UC 1996). The majority of roads 
in National Forests of the Sierra Nevada were built between 1950 and 
1990 to allow access to the forests for timber harvest (USDA 2001h). 
Between 1950 and the early 1990s, the USFS allowed major increases in 
timber harvest on National Forests and at higher elevations, and the 
majority of impacts on Yosemite toads probably took place during this 
    Roads may cause the potential for direct mortality of amphibians 
through roadkill (deMaynadier and Hunter 2000), and the possible 
introduction of contaminants such as petroleum products, herbicides, 
and pesticides. The 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, or are scheduled for, decomissioning (USDA 2001h). 
Therefore, the risks posed by new roads and timber harvests have 
declined, but those already existing still pose risks to the species 
and its habitat through erosion, roadkill, and contaminant 

Vegetation and Fire Management Activities

    Vegetation management includes the removal of small trees and brush 
to reduce fuels, and to reduce competition which allows faster growth 
of desired tree species (Helms and Tappeiner 1996). These activities 
may disturb the ground and increase erosion, which could cause damage 
to Yosemite toad habitat through siltation and lowering of groundwater 
levels. Brush removal sometimes includes the use of herbicides, which 
may run off into Yosemite toad habitat, causing lethal or sublethal 
effects on individuals (see Factor D and E below).
    Long-term fire suppression has influenced changes in forest 
structure and dynamics in the Sierra Nevada. In general, the fire 
return interval is now much longer than it was historically, and live 
and dead fuels are more abundant and continuous (USDA 2001c). Fire is 
thought to be important in maintaining open aquatic and riparian 
habitats for amphibians in some systems (Russel et al. 1999).
    Fire suppression, and changes in fire frequency and hydrology, has 
probably contributed to the decline of Yosemite toads through habitat 
loss caused by conifer encroachment on meadows (Chang 1996; NPS 2002). 
Under natural conditions, conifers are excluded from meadows by fire 
and soils too saturated for their survival. But as conifers begin to 
encroach on a meadow, if they are not occasionally set back by fire, 

[[Page 75839]]

transpire water out of the meadow, reducing the saturation of the 
soils, and facilitating further conifer encroachment. Therefore, some 
vegetation treatment may be needed to maintain or restore Yosemite toad 
    Increases in fuel abundance have created the potential for 
catastrophic fires which could cause direct mortality of Yosemite 
toads; however, data on the direct effects of fire on Yosemite toads 
are lacking. Fires and mechanical fire suppression activities (such as 
cutting fire lines) could cause erosion and siltation that could 
negatively impact Yosemite toad habitat. However, amphibians in general 
are thought to retreat to moist or subterranean refuges and thereby 
suffer low mortality during natural fires (Russel et al. 1999).
    Fire retardant chemicals contain nitrogen compounds or surfactants 
(soaps). Laboratory tests of these chemicals have shown that after 
surfactants and ammonia are released when they are added to water, they 
cause mortality in fish and aquatic invertebrates (Hamilton et al. 
1996), and likely have similar effects on amphibians. Therefore, if 
fire retardant chemicals were dropped in or near Yosemite toad habitat, 
they could have negative effects on individual toads. The majority of 
vegetation and fire management activities take place at lower 
elevations, but they do pose a threat to the species when they take 
place within the species' elevational range.


    Recreational activities take place throughout the Sierra Nevada and 
can have significant negative impacts on wildlife and their habitats 
(USDA 2001a). Recreation is the fastest growing use of National Forests 
(USDA 2001f). Heavy foot traffic in riparian areas tramples vegetation, 
compacts soils, and can physically damage streambanks. Trails (foot, 
horse, bicycle, or off-highway motor vehicle) compact soil in riparian 
habitat, which increases erosion, replaces vegetation, and can lower 
the water table (Kondolph et al. 1996). Trampling or the collapsing of 
rodent burrows by recreationists, pets, and vehicles could lead to 
direct mortality of all life stages of the Yosemite toad. Recreational 
activity may also disturb toads and disrupt their behavior (Karlstrom 

Dams and Water Diversion

    Several artificial lakes are located in or above Yosemite toad 
habitat, most notably Edison, Florence, Huntington, Courtright, and 
Wishon Reservoirs. By altering the timing and magnitude of water flows, 
these reservoirs have caused changes in hydrology which may have 
negatively altered Yosemite toad habitat. Changes in water flows have 
caused increased water levels upstream of the reservoirs, which may 
have reduced the suitability of shallow water habitats necessary for 
egg laying, or allowed the invasion of predatory fish into those 
habitats. Water flow changes may have contributed to the mortality of 
eggs and tadpoles either by stranding during low water or innundation 
during high water. The reservoirs themselves probably cover what was 
once Yosemite toad habitat. Most native Sierra Nevada amphibians cannot 
live in or move through reservoirs (Jennings 1996). Therefore, 
reservoirs represent both a loss of habitat and a barrier to dispersal 
and gene flow. These factors have probably contributed to the decline 
of Yosemite toads and continue to pose a risk to the species.
    B. Overutilization for commercial, recreational, scientific, or 
educational purposes. There is no known commercial market for Yosemite 
toads. There is also no documented recreational or educational use for 
Yosemite toads, although it is likely that they have been handled by 
curious members of the public and collected as pets.
    Scientific research may cause some stress to Yosemite toads through 
disturbance and disruption of behavior, handling, and injuries 
associated with marking individuals. Scientific research has resulted 
in the death of a few individuals through accidental trampling (Green 
and Kagarise Sherman 2001), irradiation where Karlstrom (1957) 
collected data on Yosemite toad movements by implanting them with 
radioactive tags, and collection for museum specimens (Jennings and 
Hayes 1994). Given the current reduced size and number of populations 
(Jennings and Hayes 1994), further collection could pose a serious 
threat to Yosemite toad populations.
    C. Disease or predation. Prior to the stocking of high Sierra 
Nevada lakes with salmonid fishes, which began over a century ago, fish 
were entirely absent from most of this region (Bradford 1989). 
Introduced fish, such as rainbow and golden trout (Oncorhynchus mykiss 
ssp.), brown trout (Salmo trutta), and brook trout (Salvelinus 
fontinalis), have been shown to have a negative impact, primarily 
through predation, on native populations of Sierra Nevada amphibians, 
including the mountain yellow-legged frog (Bradford 1989; Knapp and 
Matthews 2000) and Pacific chorus frog (Matthews et al. 2001).
    Data on the effects of introduced fish on Yosemite toads are less 
clear, although re-surveys of historic Yosemite toad sites have shown 
that the species had disappeared from several lakes where they formally 
bred and which are now occupied by fish (Stebbins and Cohen 1997; D. 
Martin, pers. comm. 2002). Drost and Fellers (1994) state that Yosemite 
toads are less vulnerable to fish predation than frogs because they 
breed primarily in ephemeral waters that do not support fish. The 
palatability of Yosemite toad tadpoles to fish predators is unknown 
(Jennings and Hayes 1994), but is often assumed to be low based on the 
unpalatability of western toads (Drost and Fellers 1994; Kiesecker et 
al. 1996), to which Yosemite toads are closely related. Brook trout 
have been observed to prey on Yosemite toad tadpoles and to ``pick at'' 
Yosemite toad eggs, which later became infected with fungus (D. Martin, 
pers. comm. 2002). Brook trout have been observed to swim near, but 
ignore, Yosemite toad tadpoles, which gives evidence towards tadpoles 
being unpalatable, at least in some situations. If Yosemite toad 
tadpoles are unpalatable to trout, some tadpoles may still be taken by 
trout that have not learned to avoid them yet (R. Knapp, pers. comm. 
2002). The palatability of metamorph Yosemite toads to trout is also 
unknown, but metamorph western toads have been observed in golden trout 
stomach contents (R. Knapp, pers. comm. 2002).
    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 
(Phil Strand, Sierra National Forest, pers. comm. 2002). Thus, drought 
conditions can increase the toads' exposure to predatory fish. Also, 
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 useable during 
years with low water (R. Knapp, pers. comm. 2002).
    The effects of introduced fish on Yosemite toads needs further 
study, especially palatability experiments to determine the level of 
predation. Because Yosemite toads primarily breed in ephemeral waters, 
fish are probably less of an impact on them than on amphibians that 
breed primarily in perennial lakes and streams. However, the observed 
predation of Yosemite toad tadpoles by trout (Martin 1992; D. Martin, 
pers. comm. 2002) indicate that introduced fish do pose a risk to the 
species in some situations, which may

[[Page 75840]]

be accentuated during drought years. Therefore, introduced fish have 
probably contributed to the decline of the species. As Yosemite toad 
populations become smaller and more fragmented, the impacts of 
predation may be significant.
    Various diseases have been confirmed in dead Yosemite toads (Green 
and Kagarise Sherman 2001). Those diseases, in concert with other 
factors, are likely to have contributed to the decline of Yosemite 
toads and continue to be a risk to the species. Mass die-offs of 
amphibians have been attributed to: chytrid fungal infections of 
metamorphs and adults (Carey et al. 1999); Saprolegnia fungal 
infections of eggs (Blaustein et al. 1994); iridovirus infection of 
larvae, metamorphs, or adults; and bacterial infections (Carey et al. 
1999). Humans, pets, livestock, packstock, vehicles, and wild animals 
may all act as disease vectors. Although it has not been observed in 
the Sierra Nevada, introduced fish may also serve as disease vectors to 
amphibians. Infection of both fish and amphibians by the same pathogen 
has been documented with viral (Mao et al. 1999) and fungal (Blaustein 
et al. 1994) pathogens.
    Tissue samples from dead or dying adults and from healthy tadpoles 
were collected during a die-off of adult Yosemite toads at Tioga Pass 
Meadow and Saddlebag Lake and analyzed for disease (Green and Kagarise 
Sherman 2001). Several infections were found in the adults, including: 
chytridiomycosis (chytrid fungal infection), bacillary bacterial 
septicemia (red-leg disease), Dermosporidium (a fungal infection), 
myxozoan infection (parasitic cnidarians (relatives of jellyfish)), 
Rhabdias spp. (a parasitic roundworm) infection, and several species of 
trematode (parasitic flatworm) infection. However, no single infectious 
disease was found in more than 25 percent of individuals, and some dead 
toads showed no infection that would explain their death. No evidence 
of infection was found in tadpoles. 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 diagnosed infections. This seems likely 
considering the evidence suggesting environmental contaminants as a 
factor contributing to the decline of Yosemite toads (see Factor E).
    Carey (1993) developed a model to explain the disappearance of 
boreal toads (Bufo boreas boreas) in the Rocky Mountains. In that 
model, she hypothesized that the toads were stressed by some unknown 
environmental factor. This stress caused a physiological response that 
suppressed the immune system, which was further hindered by cold 
temperatures typical of the toads' high-elevation environment. The 
toads then died of infection by pathogens normally found in their 
environment. This model may fit Yosemite toad die-offs, given the close 
relationship between the two toads and their occupation of similar 
    Saprolegnia ferax is a species of water mold that commonly infects 
fish. This mold has been documented to cause massive lethal infection 
of eggs of western toads in Oregon (Blaustein et al. 1994). However, it 
is unclear whether the infection 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. Subsequent laboratory experiments (Kiesecker et 
al. 2001), showed that the fungus could be passed from hatchery fish to 
western toads. Fungal growth on Yosemite toad eggs was observed by 
Kagarise Sherman (1980), but the fungal species was not determined, and 
it was unclear whether the fungus killed the eggs or grew on them after 
they died of some other cause.
    D. The inadequacy of existing regulatory mechanisms. The Yosemite 
toad occurs on Federal, State, and private lands. Existing regulatory 
mechanisms do not fully protect this species or its habitat on these 
lands. Federal, State, and local laws have been insufficient to prevent 
past and ongoing losses of the limited habitat of the Yosemite toad.
    Under section 404 of the Clean Water Act (CWA), the U.S. Army Corps 
of Engineers (Corps) regulates the discharge of fill material into 
waters of the United States, including wetlands. However, 99 percent of 
the Yosemite toad's range is on Federal land, so few projects that 
include fill of wetlands are likely in these areas. Therefore, section 
404 of the CWA is not likely to be relevant to the Yosemite toad in 
most cases.
    Yosemite toads may not be taken or possessed within a National Park 
without a special permit from the NPS. In addition, cattle grazing, 
stocking of invasive fish, and most timber harvest are prohibited 
within National Park boundaries (NPS 2001). However, Yosemite toads 
have continued to decline within the National Parks in which the 
species occurs. This may be, in part, due to the Parks allowing such 
activities as packstock grazing and recreation in Yosemite toad 
habitat, as well as chemical contamination of the species and its 
habitat from sources outside the Parks.
    The Wilderness Act of 1964 calls for designated wilderness land 
``to be protected and managed so as to preserve its natural 
conditions.'' Timber harvest and the use of motor vehicles are 
generally prohibited within wilderness areas, but cattle grazing and 
invasive fish stocking are permitted within National Forest wilderness 
lands and pose a threat to the species and its habitat. The species has 
declined sharply (Jennings and Hayes 1994) regardless of wilderness 
designation in large portions of its range.
    The Yosemite toad is considered a sensitive species by the USFS. 
Each National Forest was required to complete a Land and Resource 
Management Plan (LRMP) by the Forest and Rangeland Renewable Resources 
Planning Act of 1974, as amended by the National Forest Management Act 
of 1976 (NFMA). Those acts require that the LRMPs provide for multiple 
use and sustained yield of the products and services obtained from the 
National Forests, including wildlife. The Sierra Nevada Forest Plan 
Amendment (Amendment) (USDA 2001d) amends the LRMPs of National Forests 
within the Sierra Nevada to address issues pertaining to: old forest 
ecosystems and associated species; aquatic, riparian, and meadow 
ecosystems and associated species; fire and fuels; noxious weeds; and 
lower westside hardwood ecosystems. The Amendment calls for the 
preparation of a conservation assessment, activity-related standards 
and guidelines, and conservation measures by the USFS to protect 
Yosemite toads and their habitat occurring in National Forests within 
the Sierra Nevada.
    Under the Amendment to the LRMPs of National Forests within the 
Sierra Nevada, (USDA 2001f), the USFS is to provide the following 
conservation measures for Yosemite toads under: (A) Exclude livestock 
(including pack and saddle stock) from standing water and saturated 
soils in wet meadows and associated streams and springs occupied by 
Yosemite toads, or identified as ``essential habitat'' in the 
conservation assessment for the Yosemite toad during the breeding and 
rearing season (as determined locally). If physical exclusion of 
livestock, such as fencing, is impractical, then exclude grazing from 
the entire meadow until the meadow has been dry for 2 weeks. Wet 
meadows are defined as relatively open meadows with low to moderate 
amounts of woody vegetation that have standing

[[Page 75841]]

water and saturated soils after the first of June; if these conditions 
do not persist in the meadow for more than 2 weeks, allow grazing only 
in those portions of the meadow where dry conditions exist; (B) Monitor 
a sample of occupied Yosemite toad sites to assess: (1) Habitat 
conditions, and (2) Yosemite toad occupancy and population dynamics. 
Based on the monitoring data, modify or suspend grazing if Yosemite 
toad conservation is not being accomplished. These grazing restrictions 
may be modified through formal adaptive management studies, developed 
in cooperation with the USFS's Pacific Southwest Research Station, 
designed to assess the effects of grazing intensity and frequency on 
Yosemite toad habitat conditions and site occupancy; and (C) Conduct 
surveys of unoccupied suitable habitat for the Yosemite toad within 
this species' historic range to determine presence of Yosemite toads. 
Complete surveys of these areas within 3 years of January 2001. If 
surveys are not completed within the 3-year period, consider unsurveyed 
meadows as occupied habitat and apply restrictions for excluding 
livestock described in (A).
    Conservation measures also include direction to avoid application 
of pesticides within 152 m (500 ft) of known Yosemite toad sites, and 
the removal of invasive fish from some areas of mountain yellow-legged 
frog habitat, which could benefit Yosemite toads if they are also using 
those areas (USDA 2001d). The conservation measures also set limits for 
grazing utilization of grasses and shrubs, livestock use and road 
construction in willow flycatcher (Empidonax trailii) habitat (which 
includes areas that may also be inhabited by Yosemite toads), packstock 
use of Yosemite toad habitat during the breeding and rearing season, 
and disturbance of streambanks and lakeshores. The conservation 
measures also recommend removing livestock gathering and handling 
facilities from riparian and meadow areas and providing off-stream 
watering devices for livestock. The Amendment also includes 
requirements for monitoring to review how well the objectives 
established by the Amendment have been met, and how closely management 
standards and guidelines have been applied (USDA 2001e).
    The USFS has been implementing these conservation measures since 
2001, but they have not yet been fully implemented. The Amendment is 
currently being reviewed, and it remains unknown if these measures will 
be changed, or if any additional protection of the Yosemite toad will 
be included. Therefore, the Amendment has not yet provided sufficient 
protection for the Yosemite toad and its habitat, and it is not known 
if it will in the future. Also, the effect of the LRMPs in place on 
National Forests within the Sierra Nevada is unknown. Yosemite toads 
have continued to decline (Jennings and Hayes 1994).
    The State of California considers the Yosemite toad a species of 
special concern, but it is not State listed as a threatened or 
endangered species under the California Endangered Species Act. 
California Sport Fishing Regulations include the Yosemite toad as a 
protected species that may not be taken or possessed at any time except 
under special permit from the CDFG. This gives the Yosemite toad some 
legal protection from collecting, but does not protect it from other 
causes of mortality or alterations to its habitat.
    The California Environmental Quality Act (CEQA) requires review of 
any project that is undertaken, funded, or permitted by a State or 
local governmental agency. If a project with potential impacts on 
Yosemite toad were reviewed, CDFG personnel could determine that, 
although not listed, the toad is a de facto endangered, threatened, or 
rare species under section 15380 of CEQA. Once significant effects are 
identified, the lead agency has the option of requiring mitigation for 
effects through changes in the project or to decide that overriding 
considerations make mitigation infeasible (CEQA Sec. 21002). In the 
latter case, projects may be approved that cause significant 
environmental damage, such as destruction of listed endangered species 
or their habitat. Protection of listed species through CEQA is, 
therefore, dependent upon the discretion of the agency involved.
    The California Forest Practice rules set guidelines for the design 
of timber harvests on private land to reduce impacts on non-listed 
species. However, these rules have little application to the protection 
of Yosemite toad because approximately 99 percent of the species' range 
is on Federal land.
    The California Department of Pesticide Regulation has authority to 
restrict the use of pesticides. Their Toxic Air Contaminant (TAC) 
Program includes assessment of the risks posed by airborne pesticides 
by collecting air samples near sites of pesticide application and in 
communities near those sites. If air samples indicate that reductions 
in exposure are needed, mitigation measures are developed to bring 
about those reductions (California Department of Pesticide Regulation 
2001). However, the TAC program is intended primarily to protect human 
health, and air samples are not taken at far distant locations from 
application sites, like those inhabited by Yosemite toads.
    E. Other natural or manmade factors affecting its continued 
    Yosemite toads probably are exposed to a variety of pesticides and 
other chemicals throughout their range. Environmental contaminants 
could negatively affect the species by causing direct mortality; 
suppressing the immune system; disrupting breeding behavior, 
fertilization, growth or development of young; and disrupting the 
ability to avoid predation (Carey and Bryant 1995). Hydrocarbon and 
other contamination from oil production and road runoff; the 
application of numerous chemicals for agricultural production; roadside 
maintenance; and rodent and vector control programs may all have 
negative effects on Yosemite toad populations. Also, the airborne 
transport of pesticides as a result of drift from agricultural 
applications, including chlorothalonil, malathion, diazinon, and 
chlorpyrifos, from the Central Valley of California to the Sierra 
Nevadas, has been documented (Aston and Seiber 1997; McConnell et al. 
1998) in samples of air, rain, snow, lake water, and pine needles.
    Cholinesterase is an enzyme that functions in the nervous system 
and is disrupted by organophosphorus pesticides, including malathion, 
chlorpyrifos, and diazinon (Sparling et al. 2001). Reduced 
cholinesterase activity and pesticide residues have been found in 
Pacific chorus frog larvae collected in the Sierra Nevada downwind of 
the Central Valley (Sparling et al. 2001). Cholinesterase activity was 
significantly lower in samples from the Sierra Nevada than from samples 
taken from coastal California, upwind of the Central Valley. No samples 
were taken above approximately 1,500 m (4,900 ft) elevation (Sparling 
et al. 2001), which barely overlaps the 1,460 to 3,630 m (4,790 to 
11,910 ft) elevational range (Stebbins 1985) of Yosemite toads. 
However, significant amounts of pesticide residues have been documented 
as high as 1,920 m (6,300 ft) in Sequoia National Park, south of 
Yosemite and Kings Canyon National Parks (Aston and Seiber 1997; 
McConnell et al. 1998). In addition to interfering with nerve function, 
contaminants may act as estrogen mimics (Jennings 1996), or may 
otherwise disrupt endocrine function (Carey and Bryant 1995), and may 
have a negative effect on amphibian populations.

[[Page 75842]]

    Dichlorodiphenyltrichloroethane (DDT) and its residues were found 
in frogs throughout the Sierra Nevada during the late 1960s (Corey et 
al. 1970), and those residues still appear in Pacific chorus frog 
larvae collected in the late 1990s (Sparling et al. 2001), over 25 
years after DDT was banned for use in the United States.
    Spatial analysis of populations of Yosemite toads shows a trend 
towards greater decline in populations downwind of areas of the Central 
Valley with more agriculture, where there is presumably more pesticide 
use; however this trend is not statistically significant (Carlos 
Davidson, California State University, Sacramento, in litt., 2002).
    Snow core samples from the Sierra Nevada contain a variety of 
contaminants from industrial and automotive sources including: hydrogen 
ions (indicative of acidic precipitation), nitrogen and sulfur 
compounds (NH4, NO3, SO2, and 
SO4), and heavy metals (Pb, Fe, Mn, Cu, and Cd) (Laird et 
al. 1986). The pattern of recent frog extinctions in the southern 
Sierra Nevada corresponds with the pattern of highest concentration of 
air pollutants from automotive exhaust, possibly due to increases in 
nitrification (or other changes), caused by those pollutants (Jennings 
    The effects of contaminants on amphibians needs further research 
(Hall and Henry 1992), and there are few, if any, studies on the direct 
effect of contaminants on Yosemite toads. However, we know of one study 
which shows that there are significant levels of contaminants that have 
been deposited in the Sierra Nevada, and the correlative evidence 
between areas of contamination in the Sierra Nevadas and areas of 
amphibian decline (Jennings 1996; Sparling et al. 2001; C. Davidson, in 
litt., 2002), and the significant evidence of an adverse physiologic 
effect of pesticides on Sierra Nevada amphibians in the field (Sparling 
et al. 2001), indicate that contaminants may be a severe risk to the 
Yosemite toad and may have contributed to the species' decline.
    Rodent control programs probably have an adverse indirect effect on 
Yosemite toad populations. Control of rodents that create burrows, such 
as ground squirrels, could significantly reduce the number of burrows 
available for use by Yosemite toads that require them for hibernation. 
Because the burrow density required to support Yosemite toads in an 
area is not known, the loss of burrows as a result of control programs 
cannot be quantified at this time. Active rodent colonies probably are 
needed to sustain Yosemite toads because inactive burrow systems become 
progressively unsuitable over time. Loredo et al. (1996) found that 
burrow systems collapsed within 18 months following abandonment by, or 
loss of, the ground squirrels. Rodent control programs must be analyzed 
and implemented carefully in Yosemite toad habitat so the persistence 
of the species is not threatened. Much of the species' range is 
occupied by livestock, primarily cattle, and most livestock owners seek 
to eliminate rodent burrows because of the threat of cows breaking 
their legs if they accidentally step into a burrow.
    The last century has included some of the most variable climate 
reversals, at both the annual (extremes and high frequency of El Nino 
and La Nina events) and near decadal scales (periods of 5- to 8-year 
drought and wet periods) that has been documented (USDA 2001b). These 
events may have negative effects on Yosemite toads. Severe winters (El 
Nino) would force longer hibernation times, and could stress the toads 
by reducing the time available for them to feed and breed. Severe 
winters may also depress reproductive effort. Morton (1981) theorized 
that fluctuations in energy storage from year to year may explain why 
many female Yosemite toads do not breed on a yearly basis. Alternately, 
during mild winters (La Nina), precipitation is reduced. This reduction 
in precipitation could lead to stranding and death of Yosemite toad 
eggs and tadpoles, a major documented source of mortality (Zeiner et 
al. 1988; Kagarise Sherman and Morton 1993; Jennings and Hayes 1994), 
or to increased exposure to predatory fish.
    Changes in climate that occur faster than the ability of endangered 
species to adapt could cause local extinctions (U.S. Environmental 
Protection Agency (EPA) 1989). Analysis of the Antarctic Vostok ice 
core has shown that over the past 160,000 years, temperatures have 
varied with the concentrations of greenhouse gasses such as carbon 
dioxide and methane (Harte 1996). Since the pre-industrial era, 
atmospheric concentrations of carbon dioxide have increased nearly 30 
percent, methane concentrations have more than doubled, and nitrous 
oxide (another greenhouse gas) levels have risen approximately 15 
percent (EPA 1997). The burning of fossil fuels is the primary source 
of these increases (EPA 1997). Global mean surface temperatures have 
increased 0.3 to 0.7 Celsius (0.6-1.2 Fahrenheit) since the late 19th 
century (EPA 1997). Climate modeling indicates that the overall effects 
of global warming on California will include higher average 
temperatures in all seasons, higher total annual precipitation, and 
decreased spring and summer runoff due to decreases in snowpacks (EPA 
1989, 1997). Decreases in spring and summer runoff could lead to the 
loss of breeding habitat for Yosemite toads and an increase in 
stranding mortality of eggs and tadpoles.
    Changes in temperature may also affect virulence of pathogens to a 
different degree than the immune systems of amphibians (Carey et al. 
1999), and may make Yosemite toads more susceptible to disease. An 
experimental increase in stream water temperature was shown to decrease 
density and biomass in invertebrates (Hogg and Williams 1996), thus 
global warming might have a negative impact on the Yosemite toad prey 
    Drought has contributed to the decline of Yosemite toads (Jennings 
and Hayes 1994), and the effects of climate change may also have 
contributed to that decline. These effects pose an ongoing, range-wide 
risk to the species.
    Acid precipitation has been hypothesized as a cause of amphibian 
declines in the Sierra Nevada, because waters there are extremely low 
in acid neutralizing capacity, and therefore susceptible to changes in 
water chemistry due to acidic deposition (Bradford et al. 1994). 
Precipitation acidity in the Sierra Nevada has been documented to have 
significantly increased at a collection station at approximately 2,100 
m (6,900 ft) elevation near Lake Tahoe (Byron et al. 1991). In addition 
to raising the acidity of water, acidic deposition may also cause 
increases in dissolved aluminum, because aluminum is more soluble at 
higher acidity. These increases in dissolved aluminum may be toxic to 
amphibians (Bradford et al. 1992). In laboratory experiments (Bradford 
et al. 1992; Bradford and Gordon 1992), high acidity and high aluminum 
concentrations did not have significant effects on survival of Yosemite 
toad embryos or newly hatched tadpoles. However, at pH 5.0 (pH 
represents acidity on a negative scale, with 7 being neutral and lower 
numbers being more acidic) and at high aluminum concentrations, 
Yosemite toad embryos hatched earlier and the tadpoles showed a 
reduction in body size. In a complementary field study of 235 randomly 
selected potential amphibian breeding sites (Bradford et al. 1994), no 
significant difference was found in pH between sites occupied and 
unoccupied by Yosemite toads. These data indicate that acid 
precipitation is an unlikely cause of decline in Yosemite toad

[[Page 75843]]

populations (Bradford et al. 1994). Therefore, acid deposition is 
considered a low risk to the species at this time, but should still be 
considered in conservation efforts because of the possibility of 
sublethal effects (Bradford et al. 1992), of its interaction with other 
factors, and the potential for more severe acidic deposition in the 
    Ambient ultraviolet-b (UV-B) radiation (280 to 320 nanometers (11.0 
to 12.6 microinches)) has increased at north temperate latitudes in the 
past two decades (Adams et al. 2001). Ambient levels of UV-b were 
demonstrated to cause significant decreases in survival of western toad 
eggs in field experiments (Blaustein 1994). In a laboratory experiment 
(Kats et al. 2000), metamorph western toads exposed to levels of uv-b 
below those found in ambient sunlight showed a lower alarm response to 
chemical cues of injured toads than metamorphs that were completely 
shielded from UV-B. This indicates that ambient levels of UV-B may 
cause sublethal effects on toad behavior that may increase their 
vulnerability to predation. In a field experiment (Kiesecker and 
Blaustein 1995), the synergistic effects of exposure to ambient levels 
of UV-B radiation, and exposure to a pathogenic fungus (Saprolegnia), 
were shown to cause significantly higher mortality of western toad 
embryos than either factor alone.
    Sadinsky et al. (1997) observed a high percentage of embryo 
mortality in Yosemite toads at six breeding sites in Yosemite National 
Park, but in a preliminary field experiment this mortality did not 
appear to be related to UV-B. In spatial statistical analysis of extant 
and extinct populations, higher elevation was shown to have a positive 
effect on the likelihood that populations of Yosemite toads were 
extant. This is counter to what would be expected if UV-B were the 
primary cause of decline (C. Davidson, in litt., 2002), as sites at 
higher elevations would be expected to receive more solar radiation due 
to the thinner atmosphere. The increase in UV-B at high elevations in 
the Sierra Nevada has not been more than 5 percent in the past several 
decades (Jennings 1996). These data indicate that UV-B has probably not 
contributed significantly to the decline of Yosemite toads and is 
probably currently a low risk to the species. However, as with acid 
precipitation, UV-B should still be considered as a risk to the species 
because of the potential for sublethal effects, synergistic effects 
with other factors, and the potential for further increases in UV-B 
radiation in the future.


    We have carefully assessed the best scientific and commercial 
information available regarding the past, present, and future threats 
faced by this species. We reviewed the petition, information available 
in our files, and other published and unpublished information submitted 
to us during the public comment period following our 90-day petition 
finding. We also consulted with recognized Yosemite toad experts and 
other Federal and State resource agencies. On the basis of the best 
scientific and commercial information available, we find that proposing 
to list the Yosemite toad is warranted, but is precluded by higher 
priority listing actions.
    In making this finding, we recognize that there have been declines 
in the distribution and abundance of Yosemite toads, primarily 
attributed to habitat degradation, airborne contaminants, and drought.
    We conclude that the overall magnitude of threats to the Yosemite 
toad is moderate, and that the overall immediacy of these threats is 
non-imminent. Pursuant to our Listing Priority System (48 FR 43098), a 
species for which threats are moderate and non-imminent is assigned a 
Listing Priority Number of 11. While we conclude that proposing to list 
the Yosemite toad is warranted, an immediate proposal to list is 
precluded by other higher priority listing actions. During fiscal year 
2003, we must spend all of our Listing Program funding to comply with 
court orders and judicially approved settlement agreements, which are 
now our highest priority actions. The Yosemite toad will be added to 
the list of candidate species upon publication of this notice of 12-
month finding. We will continue to monitor the status of this species 
and other candidate species. Should an emergency situation develop 
concerning this species, we will act to provide immediate protection, 
if warranted.
    We intend that any proposed listing action for the Yosemite toad 
will be as accurate as possible. Therefore, we will continue to accept 
additional information and comments from all concerned governmental 
agencies, the scientific community, industry, or any other interested 
party concerning this finding. We are especially interested in further 
genetic information on the proper taxonomic status of the Yosemite toad 
and further information on the current range and status of the species, 
factors contributing to its decline, and conservation efforts.

References Cited

    A complete list of all references cited is available on request 
from the 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: November 27, 2002.
Steve Williams,
Director, Fish and Wildlife Service.
[FR Doc. 02-30800 Filed 12-9-02; 8:45 am]