Anaxyrus canorus - (Camp, 1916)
Yosemite Toad
Other English Common Names: Yosemite toad
Synonym(s): Bufo canorus Camp, 1916
Taxonomic Status: Accepted
Related ITIS Name(s): Anaxyrus canorus (Camp, 1916) (TSN 773515)
Unique Identifier: ELEMENT_GLOBAL.2.105396
Element Code: AAABB01040
Informal Taxonomy: Animals, Vertebrates - Amphibians - Frogs and Toads
Kingdom Phylum Class Order Family Genus
Animalia Craniata Amphibia Anura Bufonidae Anaxyrus
Genus Size: D - Medium to large genus (21+ species)
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Concept Reference
Concept Reference: Frost, D. R. 1985. Amphibian species of the world. A taxonomic and geographical reference. Allen Press, Inc., and The Association of Systematics Collections, Lawrence, Kansas. v + 732 pp.
Concept Reference Code: B85FRO01HQUS
Name Used in Concept Reference: Bufo canorus
Taxonomic Comments: The genus Anaxyrus was split from Bufo by Frost et al. (2006). However, taxonomy within the genus Bufo remains controversial and many references still use the long-established Bufo.

"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 (now Anaxyrus) 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)." (USFWS 2002).

Molecular data indicate that Anaxyrus exsul is phylogenetically nested within Anaxyrus canorus; further data are needed to determine whether Anaxyrus exsul should be subsumed with Anaxyrus canorus (Shaffer et al. 2000).

Phylogenetic analyses of mtDNA data from throughout the range of the Anaxyrus boreas species group (including boreas, canorus, exsul, and nelsoni) by Goebel et al. (2009) identified three major haplotype clades. The Northwest clade (NW) includes both subspecies of boreas (boreas and halophilus) and divergent minor clades in the middle Rocky Mountains, coastal, and central regions of the west and Pacific Northwest. The Southwest (SW) clade includes exsul, nelsoni, and minor clades in southern California. Anaxyrus canorus, previously identified as paraphyletic, has populations in both the NW and SW major clades. The Eastern major clade (E) includes three divergent lineages from southern Utah, the southern Rocky Mountains, and north of the Great Basin at the border of Utah and Nevada. Goebel et al. (2009) tentatively suggested that some or many of the clades might warrant recognition as distinct species. However, the authors refrained from delineating new species circumscriptions, noting that additional research might suggest different taxonomic outcomes (e.g., recognizing the traditionally defined Anaxyrus canorus as two distinct species or, conversely, combining it with other minor groups and thus broadening its scope).
Conservation Status

NatureServe Status

Global Status: G2G3
Global Status Last Reviewed: 20Jul2013
Global Status Last Changed: 20Jul2013
Ranking Methodology Used: Ranked by calculator
Rounded Global Status: G2 - Imperiled
Reasons: Still widepsread within small range in the Sierra Nevada, California; has declined in area of occupancy and abundance in recent decades; cause of decline is uncertain but primarily may be related to interacting factors including habitat degradation (e.g., such as caused by livestock grazing), disease, and climate change.
Nation: United States
National Status: N2N3 (20Jul2013)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States California (S2S3)

Other Statuses

U.S. Endangered Species Act (USESA): LT: Listed threatened (29Apr2014)
U.S. Fish & Wildlife Service Lead Region: R8 - California-Nevada
IUCN Red List Category: EN - Endangered

NatureServe Global Conservation Status Factors

Range Extent: 5000-20,000 square km (about 2000-8000 square miles)
Range Extent Comments: This species is endemic to California. It occurs only in the Sierra Nevada, historically from
the Blue Lakes region north of Ebbetts Pass (Alpine County) and the vicinity of Grass Lake (Eldorado County) southward to south of Kaiser Pass and to Evolution Lake in Kongs Canyon National Park (Fresno County), at elevations 1,460-3,630 meters (mostly above 2,740 meters) (Stebbins 2003, Davidson and Fellers 2005, USFWS 2013).

Number of Occurrences: 21 - 300
Number of Occurrences Comments: Recent surveys found this species at 469 localities (USFWS 2013). The number of distinct occurrences has not been determined using standardized criteria but is much fewer than 469.

Population Size: 2500 - 10,000 individuals
Population Size Comments: Total adult population size is unknown but likely is at least a few thousand.

Number of Occurrences with Good Viability/Integrity: Unknown

Overall Threat Impact: High - medium
Overall Threat Impact Comments: USFWS (2013) summarized threats as follows: habitat loss associated with degradation of meadow hydrology following stream incision consequent to the cumulative effects of historical land management activities, notably livestock grazing, and also the anticipated hydrologic effects upon habitat from climate change; direct effects of climate change impacting small remnant populations, likely compounded with the cumulative effect of other threat factors (such as disease).

Relative to habitat loss ad degradation, USFWS (2013) concluded that climate change is a current threat of high magnitude, whereas livestock grazing and fire management regime are threats of moderate magnitude roads, and timber harvest, dams and water diversions, and recreational land uses are low magnitude threats.

USFWS (2013) reviewed available information and concluded that disease has a moderate, ongoing effect on populations of the species rangewide. The threat most specifically includes chytridiomycosis, caused by the amphibian pathogen, Bd. Although definitive empirical data quantifying the contribution of disease to Yosemite toad population declines are not currently available, the concurrence of population declines with the prevalence and spread of Bd across the Sierra Nevada support the assertion that disease has played a role in the observed trend (USFWS 2013). Further, Bd infection, even at lower intensities, may interact with climate extremes and continue to depress recruitment of yearling and subadult Yosemite toads to breeding Yosemite toad populations. USFWS (2013) suspected that this threat was historically significant, that it is currently having a moderate influence on toad populations, and expected it to be a future concern.Cause(s) of the decline are uncertain. Decline in the eastern Sierra Nevada between the early 1970s and early 1990s evidently was caused primarily by drought, disease, or avian predation, varying with location; some of these factors may have had anthropogenic components (Kagarise Sherman and Morton 1993).

USFWS (2013) also concluded that: contaminants do not pose a significant threat; UV-B has likely not contributed significantly to the decline and currently poses a low risk to the species; the threat posed by the effects of climate change on individuals is significant; small population size is a prevalent and significant threat to the species viability of the Yosemite toad across its range, especially in concert with other extant stressors (such as climate change); a combination of factors has interacted and is responsible for the decline observed in Yosemite toad populations over the past few decades.

Short-term Trend: Decline of 10-30%
Short-term Trend Comments: Trend over the past 10 years or three generations is uncertain, but distribution and abundance probably are declining.

Long-term Trend: Decline of 80-90%
Long-term Trend Comments: Relatively stable in extent of occurrence, apparent substantial decline in population size, area of occupancy, and number/condition of occurrences.

USFS SNAMPH survey results (summarized in USFWS 2013) indicate that this species has declined from historical levels, with Yosemite toads occurring in only 12 percent of watersheds where they existed prior to 1990; breeding currently occurs in an estimated 22 percent of watersheds within their current estimated range (breeding was occurring in 81 percent of the watersheds that were occupied from 1990-2001, suggesting that the number of locations where breeding occurs has continued to decline (Brown et al. 2011). Overall abundances in the intensively monitored watersheds were very low (fewer than 20 males per meadow per year) relative to other historically reported abundances of the species (Brown et al. 2011). Brown et al. (2011) suggested that populations are now very small across the range of the species: only 18 percent of occupied survey watersheds rangewide had ''large'' populations over the past decade (more than 1,000 tadpoles or 100 of any other lifestage detected at the time of survey).

Other relevant studies:

Populations may have disappeared from about 50 perent of historically known sites (based on 144 specific sites; Jennings and Hayes 1994).

At Tioga Pass, an average of 258 males entered breeding pools in the 1970s, and the number of females was 45-100; by the 1990s, researchers found only one male and two egg masses (Kagarise Sherman and Morton 1993). Six other populations that were surveyed also declined greatly between the 1970s and 1990s.

Drost and Fellers (1996) found that Yosemite toads were absent from 6 of 13 sites where they had been found in an earlier survey (Grinnell and Storer 1924). At the sites where toads were present, they occurred in very low numbers relative to general abundance reported in the historical record (Grinnell and Storer 1924: 657-660). By the early 1990s, the species was either undetectable or had declined in numbers at 9 of 13 (69 percent) of the Grinnell and Storer (1924) sites.

In 1990, David Martin surveyed 75 sites throughout the range of the Yosemite toad for which there were historical records of the species' presence. This study found that 47 percent of historically occupied sites showed no evidence of any life stage of the species (USFWS 2013).

Intrinsic Vulnerability: Moderately vulnerable

Environmental Specificity: Narrow to moderate.

Other NatureServe Conservation Status Information

Global Range: (5000-20,000 square km (about 2000-8000 square miles)) This species is endemic to California. It occurs only in the Sierra Nevada, historically from
the Blue Lakes region north of Ebbetts Pass (Alpine County) and the vicinity of Grass Lake (Eldorado County) southward to south of Kaiser Pass and to Evolution Lake in Kongs Canyon National Park (Fresno County), at elevations 1,460-3,630 meters (mostly above 2,740 meters) (Stebbins 2003, Davidson and Fellers 2005, USFWS 2013).

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
Endemism: endemic to a single state or province

U.S. & Canada State/Province Distribution
United States CA

Range Map
Note: Range depicted for New World only. The scale of the maps may cause narrow coastal ranges or ranges on small islands not to appear. Not all vagrant or small disjunct occurrences are depicted. For migratory birds, some individuals occur outside of the passage migrant range depicted. For information on how to obtain shapefiles of species ranges see our Species Mapping pages at

Range Map Compilers: IUCN, Conservation International, NatureServe, and collaborators, 2004

U.S. Distribution by County Help
State County Name (FIPS Code)
CA Alpine (06003), Fresno (06019), Inyo (06027), Madera (06039), Mariposa (06043), Mono (06051), Tulare (06107), Tuolumne (06109)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
16 Upper Carson (16050201)+, East Walker (16050301)+, West Walker (16050302)+
18 Upper Kern (18030001)+, South Fork Kern (18030002)+, Upper King (18030010)+, Upper San Joaquin (18040006)+, Upper Merced (18040008)+, Upper Tuolumne (18040009)+, Upper Stanislaus (18040010)+, Upper Mokelumne (18040012)+, Mono Lake (18090101)+, Crowley Lake (18090102)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
Basic Description: A toad.
Reproduction Comments: Breeding occurs May-July, and possibly August, the time depending on the depth of spring snowpack and time of its melt; most females spawn during a 2-3-day peak each year (Kagarise Sherman and Morton 1993). Eggs are laids in strings and clusters, hatch in about 1.5 weeks. Tadpoles metamorphose about 5-7 weeks after egg deposition. Males first breed at 3-5 years, females at 4-6 years. Some individuals may live at least 15 years. Basically a late-maturing, long-lived species (Kagarise Sherman and Morton 1993).
Ecology Comments: Primarily solitary, except during the breeding season.
Habitat Type: Freshwater
Non-Migrant: N
Locally Migrant: Y
Long Distance Migrant: N
Mobility and Migration Comments: Individuals may migrate 1 km or more between breeding and nonbreeding habitats (see USFWS 2013).

Martin (2008, cited by USFWS 2013 radio-tracked adult toads during the active season and found that on average toads traveled a total linear distance of of 494 meters within the season, with minimum travel distance of 78 meters and
maximum of 1.76 km.

Kagarise Sherman (1980) observed one female move 270 m in 65 days and one male move 150 m in 9 days. Toads in her study generally moved 150 to 230 m each spring from their hibernation sites to their breeding sites. Radio-tagged toads have moved approximately 610 m in a single night (D. Martin, pers. comm., 2002, cited by USFWS 2002).

Riverine Habitat(s): CREEK, Low gradient, Pool
Lacustrine Habitat(s): Shallow water
Palustrine Habitat(s): Riparian, TEMPORARY POOL
Terrestrial Habitat(s): Grassland/herbaceous
Special Habitat Factors: Benthic, Burrowing in or using soil, Fallen log/debris
Habitat Comments: Habitat includes moist mountain meadows and borders of forests. Individuals shelter in rodent burrows as well as in dense vegetation. Breeding occurs in shallow edges of snow melt pools and ponds or in shallows or along edges of lakes and slow-moving streams. Some breeding sites dry up before larvae metamorphose.
Adult Food Habits: Invertivore
Immature Food Habits: Herbivore
Food Comments: Diet includes various small invertebrates such as beetles, flies, ants, centipedes, millipedes, etc. Larave probably eat minute plant material, detritus, etc.
Adult Phenology: Diurnal, Hibernates/aestivates
Immature Phenology: Diurnal, Hibernates/aestivates
Phenology Comments: These toads are inactive in cold temperatures and hot, dry weather. They are primarily diurnal and commonly frequent sunny open sites. They emerge from underground retreats soon after snow melt and are most active mainly April-October (Stebbins 1985). At Tioga Pass Meadow, they emerge from hibernation in May or June (Kagarise Sherman and Morton 1993).
Colonial Breeder: Y
Length: 8 centimeters
Economic Attributes Not yet assessed
Management Summary
Stewardship Overview: Conservation needs include clarification of the taxonomic status of this species and its relatives (see taxonomy comments), protection of wet meadow habitat from excessive alteration by cattle and human activities, and regular monitoring for changes in toad populations and threats.

U.S. Forest Service, which manages most of the habitat, now excludes cattle grazing from wet meadows with known populations. USFS management plans also include monitoring of certain populations and avoidance of pesticide applications within 152 meters of known toad sites (Davidson and Fellers 2005).

Restoration Potential: High levels of among-pond genetic variation suggest that management should focus on individual ponds, and that extirpated populations likely will not naturally reestablish--reintroductions may be needed (Shaffer et al. 2000). Stock for such efforts should be from geographically proximate sites, especially in Yosemite (Shaffer et al. 2000).
Management Requirements: Population genetic data that Yosemite and Kings Canyon national parks should be considered separate management units and managed as such (Shaffer et al. 2000).
Population/Occurrence Delineation
Group Name: Bufonid Toads

Use Class: Not applicable
Subtype(s): Breeding Site
Minimum Criteria for an Occurrence: Occurrences are based on evidence of historical presence, or current and likely recurring presence, at a given location. Such evidence minimally includes collection or reliable observation and documentation of one or more individuals (including larvae or eggs) in or near appropriate habitat where the species is presumed to be established and breeding.
Separation Barriers: Busy major highway such that toads rarely if ever cross successfully; roads with nonpermeable barriers to toad movement; urbanized areas dominated by buildings and pavement.
Separation Distance for Unsuitable Habitat: 1 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Opportunistic observations of various toad species in lowland habitats indicate regular movements of up to at least several hundred meters from the closest known breeding site (G. Hammerson, pers. obs.). Sweet (1993) recorded movements of up to 1 km in Bufo californicus. In defining critical habitat for B. californicus, USFWS (2000) included breeding streams and upland areas within a 25-m elevational range of each essential stream reach and no more than 1.5 km away from the stream. In northwestern Utah, Thompson (2004) recorded movements of Bufo boreas of up to 5 km across upland habitat between two springs during the summer-fall season. Another toad moved 1.3 km between May of one year and May of the next year; the following June it was back at the original breeding location (Thompson 2004). Most studies of toad movements have not employed radiotelemetry and were not designed to detect long-range movements or dispersal.

The separation distance for unsuitable habitat reflects the nominal minimum value of 1 km. The separation distance for suitable habitat reflects the good vagility of toads, their ability to utilize ephemeral or newly created breeding sites, and the consequent likely low probability that two occupied locations separated by less than several kilometers of suitable habitat would represent truly independent populations over the long term.

Inferred Minimum Extent of Habitat Use (when actual extent is unknown): .5 km
Date: 27Apr2005
Author: Hammerson, G.
Population/Occurrence Viability
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
NatureServe Conservation Status Factors Edition Date: 20Jul2013
NatureServe Conservation Status Factors Author: Hammerson, G.
Element Ecology & Life History Edition Date: 20Jul2013
Element Ecology & Life History Author(s): Hammerson, G.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

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  • Sherman, C. K. 1980. A comparison of the natural history and mating system of two anurans: Yosemite toads (BUFO CANORUS) and black toads (BUFO EXSUL). Ph.D. dissertation, Univ. Michigan, Ann Arbor. xiv + 394 pp.

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