AmphibiaWeb - Anaxyrus baxteri


(Translations may not be accurate.)

Anaxyrus baxteri (Porter, 1968)
Wyoming Toad
family: Bufonidae
genus: Anaxyrus

© 2009 Endangered Species International (1 of 1)
Conservation Status (definitions)
IUCN Red List Status Account Extinct in the Wild (EW)
NatureServe Use NatureServe Explorer to see status.
National Status Endangerd
Regional Status None
Access Conservation Needs Assessment Report .



View distribution map in BerkeleyMapper.
View Bd and Bsal data (10 records).

The color of Anaxyrus baxteri is dark brown, gray, or greenish with small dark blotches and an indiscernible median line on the dorsal surface. Some have light lateral stripes. The underbelly is spotted and the males tend to have a dark throat. Cranial crest is fused. Adult females grow slightly larger than males. The dorsal-surface of the body has rounded warts smaller than A. cognatus but larger than A. boreas. Cutting tubercles on the hind foot are well developed in adults (Baxter 1980).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: United States

U.S. state distribution from AmphibiaWeb's database: Wyoming


View distribution map in BerkeleyMapper.
View Bd and Bsal data (10 records).
A. baxteri is known only in the Laramie Basin of Albany County in southeast Wyoming, where the habitat of this species includes floodplains, ponds and small lakes (Baxter 1980). Found from around 1,000-7,000 ft. elevation (Stebbins 2003). Temporary congregation at hibernacula is typical of the species before freezing temperatures force them underground for the winter (Parker 2000).

Life History, Abundance, Activity, and Special Behaviors
A. baxteri is a burrowing animal that digs primarily in Mima-type mounds, mounds of firmly compacted gravel and cobblestones. The mounds are probably not used for hibernation, which occurs in old, vegetated sand dunes, from October - February (Stebbins 2003). A. baxteri usually breed from May – July when daytime temperatures reach near 70° F (Baxter 1980). Breeding congregations are usually not more than six males in a pond with a few females. Eggs are laid in a gelatinous string and the larvae usually transform within 1- 1.5 months. The call is a low-pitched buzz lasting 1.3-5 seconds with 80 or more individual trills per second that can be heard approximately 200 meters away (Baxter 1980).

Trends and Threats
A. baxteri was placed on the endangered species list in January 1984, and is now considered to be on the brink of extinction (Baxter 1980; Stebbins 2003).

Local and broad scale population declines are due to depredation, mostly due to introduced predators. Recent investigations involving implanted radio transmitters suggested predator attack primarily from mustelids (Parker 2000). Still, it is not often that naturally occurring predator-prey relationships are the cause of extinction of an entire population.

The original decline may be due to a chytrid fungus, Batrachochytrium dendrobatidis, which has been implicated in amphibian declines worldwide. The current population at Mortenson Lake is infected with the fungus, and has been since 1989 (USFWS 2000).

Translocation results on A. baxteri is discouraging (Seigel 2001).

Possible reasons for amphibian decline

Prolonged drought
Predators (natural or introduced)

Previously considered a subspecies of the Canadian Toad, Anaxyrus hemiophrys.

Hear calls at the Western Sound Archive.


Baxter, G.T. and Stone, M.D. (1980). Amphibians and Reptiles of Wyoming. Wyoming Game and Fish Department, Cheyenne, WY.

Parker, J., Anderson, S., and Lindzey, F. (2000). ''Bufo baxteri (Wyoming Toad). Predation.'' Herpetological Review, 31(3), 167-168.

Seigel, R. A. and Dodd, C.K., Jr. (2001). ''Translocations of amphibians: proven management method or experimental technique?'' Conservation Biology, 16(2), 552-554.

Stebbins, R. C. (2003). Western Reptiles and Amphibians, Third Edition. Houghton Mifflin, Boston.

US Fish and Wildlife Service (USFWS) (2002). Wyoming Field Office Annual Wyoming Toad Report FY 02.

Originally submitted by: Kenny D'Oyen (first posted 2004-02-20)
Edited by: Tate Tunstall, Michelle S. Koo (2012-04-29)

Species Account Citation: AmphibiaWeb 2012 Anaxyrus baxteri: Wyoming Toad <> University of California, Berkeley, CA, USA. Accessed May 20, 2024.

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Citation: AmphibiaWeb. 2024. <> University of California, Berkeley, CA, USA. Accessed 20 May 2024.

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