Anaxyrus exsul

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. Key studies, e.g., Goebel et al. (2009) and Gordon et al. (2017) indicate that the taxon may be nested within A. boreas sensu lato; the entire group is in need of a comprehensive revision to determine species boundaries (Nicholson 2025).

Small range in Deep Springs Valley, Inyo County, California; habitat is appropriately managed, and population has been relatively stable in recent decades; molecular data suggest that A. exsul may be conspecific with A. canorus--further study is needed.

Range includes several springs feeding Deep Springs Lake (playa), in Deep Springs Valley, Inyo County, California: Buckhorn Spring, Corral Spring and adjacent pond (Schuierer and Anderson 1990), and Bog Mound Springs at an elevation of 1,520 meters (about 5,000 feet). A population at Antelope Springs at about 1,710 meters, about 7 kilometers northwest of Deep Springs Lake, may have been introduced (Schuierer 1962, Murphy et al. 2003, Stebbins 2003). An introduced population occurs in a flowing well near Salt Lake in Saline Valley, Death Valley National Park, Inyo County, California (Murphy et al. 2003). Black toads were introduced at Cottonwood Springs in the Owens Valley in the 1960s (Schuierer 1962), but no there are no subsequent records for that area (Fellers 2005). The species was introduced at Batchelder Spring, Westgard Pass, Inyo County, but apparently it is extirpated there.

Entire range can be regarded as one occurrence; or perhaps subdivided into a half dozen subpopulations.

"Kagarise Sherman (1980) noted tadpole mortality associated with water diversion and a low level of adult mortality presumably caused by cattle trampling. In response, Deep Springs College abandoned irrigation ditch maintenance and related agricultural practices (e.g., raking and burning) that were potentially detrimental to the toads. Cattle exclosures were built around the spring sources in the early 1970s, presumably to protect toad hibernacula from disturbance." (Murphy et al. 2003). Since then, Deep Springs College has abandoned all agricultural practices within black toad habitat, except periodic cattle grazing (Murphy et al. 2003). Cattle exclosures and other areas at Corral Springs have become thickly vegetated; the impact of this on the toads deserves further study (Murphy et al. 2003). Trampling by cattle occurred at Antelope Spring in at least the 1970s.

In addition to habitat concerns, potential threats include chytridiomycosis and introduction of non-native species such as bullfrogs. The small range of the species makes it highly vulnerable to sudden declines that could occur with the introduction of a non-native predator or disease (Fellers 2005).

These toads appear to tolerate periodic droughts and other climate variations (Schuierer 1972) and so may not be highly vulnerable to climate change unless it results in significant reductions in spring outflows.

Excessive collecting by herpetologists may have been a threat in the early 1970s (Schuierer 1972).