This species occurs in riparian habitats associated with the Amargosa River, tributary springs of the Amargosa River in Oasis Valley, and isolated spring systems near Beatty, Nye County, Nevada, USA (USFWS, Federal Register, 1 March 1996).
Habitat and Ecology
Usually found near water at desert springs and outflow. Vegetation bordering water consists of cottonwood trees, cattails, and sedges. May congregate at streetlights to feed on attracted insects (Burroughs 1999). Eggs and larvae develop in spring waters (open areas with little vegetation at LaFleur).
The total adult population size is uncertain but is likely to be at least several hundred. Thousands were reported in 1958; estimates of the size of the metamorphosed population at 10 sites in 1993 and 1994 ranged from 30-130, but some sites that were probably occupied have not been surveyed in recent years (USFWS, Federal Register, 1 March 1996). Surveys at 20 sites since 1990 yielded the following results: apparently extirpated from one spring, decreased abundance at four springs, fluctuating but relatively constant populations at 15 sites (USFWS, Federal Register, 1 March 1996; see also unpublished 1993 and 1994 reports by Hoff, prepared for the USFWS, Reno, Nevada). Over the past few decades, the species reportedly has declined greatly from its former range and abundance (Altig and Dodd 1987), but more recent surveys found that distribution and abundance were greater than previously known (USFWS, Federal Register, 1 March 1996).
Factors that may be adversely affecting the toad and its habitat include the effects of variable rainfall on small populations, livestock and feral burro grazing and trampling, off-road vehicle use, grading for flood control, activities related to commercial development, non-native predators (catfish, crayfish, bullfrog (Rana catesbeiana)), water pollution, and water diversion (Froglog, December 1994). Trampling of larvae by cattle may be negatively affecting the LaFleur population, which also may be threatened by road widening (of Route 95). Expansion of non-native salt cedar may degrade habitat (Burroughs 1999).
The majority of available habitat is on private property. BLM has initiated protection (Area of Critical Environmental Concern) for all occupied sites under their jurisdiction. TNC purchased a 60-ha ranch near Beatty for experimental habitat management (Burroughs 1999). Nye County is a co-operator with state and federal agencies in a conservation agreement (Burroughs 1999).
Red List Status
Listed as Endangered because its population size is estimated to number fewer than 2,500 mature individuals, with no sub-population greater than 250 individuals, and it is experiencing a continuing decline.
Geoffrey Hammerson 2004. Anaxyrus nelsoni. The IUCN Red List of Threatened Species 2004: e.T3181A9661222. http://dx.doi.org/10.2305/IUCN.UK.2004.RLTS.T3181A9661222.en