Anaxyrus baxteri
Wyoming Toad
family: Bufonidae

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


View distribution map using BerkeleyMapper.


From the IUCN Red List Species Account:


Range Description

This species is restricted to the Laramie Basin, Wyoming, USA. The historical range extent was approximately 2,330kmĀ² (USFWS data). As of 2002, it was extant only at Mortenson Lake National Wildlife Refuge, which encompasses four impoundments: Mortenson, Garber, Gibbs, and Soda lakes; the refuge is closed to the public (USFWS 2002e). The extant occurrence probably would be extirpated without recent annual releases of captive-reared toadlets. Populations at former re-introduction sites (Lake George on the Hutton Lake National Wildlife Refuge, and Rush Lake) have been lost due to drought (USFWS 2002e).

Habitat and Ecology

Historically, it is associated with floodplain ponds along the Big and Little Laramie Rivers; use of lakes might have been limited due to saline conditions; irrigation might have flushed out the lakes and made them more suitable for toads (G. Baxter pers. comm.). Currently, it occurs in the vicinity of lakes and adjacent meadows. It uses rodent burrows for shelter. Eggs and larvae develop in shallow water.


This species was common in the 1950s, but underwent a large decline in the 1960s and 1970s; it was thought to be extinct in the wild in the mid-1980s, but was found again at Mortenson Lake in 1987 and captive propagation began in the mid-1990s using toads from Mortenson Lake (USFWS 2002e). At Mortenson Lake, there has been no natural reproduction by wild toads since 1991; the population is maintained through release of captive-reared young (Parker, Anderson and Lindzey 2000). In June 2002, a survey at Mortenson Lake NWR yielded 124 yearlings and 4 adults (USFWS 2002e). Limited natural reproduction and recruitment of a few metamorphosed juveniles occurred in 2002 (USFWS 2002e). Despite releases of captive-reared individuals, the population at Mortenson Lake NWR appears to be declining (USFWS 2002e).

Population Trend


Major Threats

Mortenson Lake, site of the only known extant population, is infected with the amphibian chytrid fungus (USFWS 2002e). This fungus has been implicated in declines and extinctions of amphibian species worldwide. Retrospective analysis shows that the fungus has been present at Mortenson Lake since at least 1989. In addition, chytridiomycosis is the most commonly seen disease in the captive population. Predation, pesticide use, irrigation practices, and lack of genetic diversity might also limit the abundance of Wyoming Toads in the Laramie Basin. The cause of the original decline remains unknown but might be associated with the invasion of chytrid into the area (USFWS 2002e). Mortenson Lake recently has become more saline (and less suitable for toads) as a result of drought-related increases in evaporation (USFWS 2002e). Salt-cedar was found (and removed) at Hutton Lake NWR in 2002. This plant has the potential to reduce habitat suitability (USFWS 2002e). For the past several years, beginning in late summer, adults with bacterial and fungal infections have been found moribund or dead (Taylor et al. 1999). Predators, probably mustelids, killed several radio-tagged individuals in 1998 (Parker, Anderson and Lindzey 2000).

Conservation Actions

It occurs in Mortenson Lake National Wildlife Refuge, where a recovery programme, using captive-bred animals and re-introductions, is being implemented. TNC recently acquired a 1,800-acre tract at Mortensen Lake and has arranged a conservation easement with an adjacent landowner. Lake George also is a toad refuge. The success of the recovery programme probably depends on finding some way to combat chytridiomycosis in the wild.


Geoffrey Hammerson 2004. Anaxyrus baxteri. In: IUCN 2014


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