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NATURAL HISTORY

AMARGOSA TOAD } Bufo nelsoni
FAMILY: Bufonidae

DESCRIPTION: The Amargosa toad has a warty back with a light, mid-dorsal stripe and black speckling on a background ranging widely in color from buff to olive. Its underside is whitish with scattered blotches that merge above the legs, making the toad look as though it’s wearing pants. Males usually reach lengths of three to four inches, while females may reach 3.5 to five inches.

HABITAT: This species occupies the riparian areas of the northern Mojave Desert, where wetlands are rare, geographically isolated, and rich in endemic species. Breeding habitat is found on pond edges, pools and streams, flooded marshes and meadows, ephemeral pools, springs, and artificial water impoundments. Summer ranges include a variety of wet and dry habitats, and winter hibernacula may be in rodent burrows.

RANGE: The historic and current range of the Amargosa toad is believed to be limited to a 10-mile reach of Nevada’s Amargosa River and its associated riparian corridor, adjacent springs and outflow wetland systems, and isolated springs in the surrounding hills.

MIGRATION: Amargosa toads have home ranges of about 800 to 16,000 square meters at Torrance and the Amargosa River Narrows. Toads appear to move more in summer than in winter.

BREEDING: Breeding begins in mid-February, when congregations of toads meet at breeding sites to mate. Female toads lay egg clutches in two long strands along shallow water with little or no flow. Breeding activity usually ends in July.

LIFE CYCLE: Eggs usually become tadpoles within two weeks of hatching, and tadpoles transform into immature toads in about four to eight weeks, or faster in warm waters. Sexual maturity is reached at two to three years and adults may live nine to 12 years.

FEEDING: These toads are nocturnal foragers, feeding on invertebrates such as spiders, insects, snails, and even scorpions.

THREATS: The Amargosa toad is primarily imperiled by habitat destruction, degradation, and fragmentation due to urban, residential, and recreational development. Other threats include the introduction of nonnative predators, ground disturbance or vegetation removal, water extractions and diversions, flood-control activities, off-road vehicle use, road kills, and collecting. The toad is especially at risk because of its greatly reduced populations.

POPULATION TREND: Long-term population trends are not known for this species, but by 1993 the population appeared to have declined dramatically. In 2006, the Nevada Division of Wildlife estimated that the total population included about 2,000 individuals.

Photo © Gary Nafis