Description: A small to medium-sized toad (head and body: 5 - 7 cm [2 - 3 in.]). The dorsal color is olive to reddish-brown, and harmonizes with the habitat. Lighter colored patches may be present on the head (including the eyelids and portions of the oval parotoid glands), and on the top (sacral humps) of the back. Ventral color is uniformly light with usually no spots in adults and no dusky color on the throat of males. Bony ridges (cranial crests) on the head are absent or small. The skin is rough, but warts are small and are usually not distinctively colored. Other species of toads in southern Nevada have prominent cranial crests (B. woodhousii) or round parotoid glands (B. punctatus). Breeding occurs in streams from March to July. Eggs are laid in 1 - 3 rowed strings of up to 4,000 eggs and deposited on the bottom of shallow, quiet waters among gravel, leaves, sticks, mud, or clean sand. Larvae are dark with variable amounts of gold. Adults are primarily nocturnal, except during breeding season.
Diet: Larvae eat algae, organic debris, and plant tissue. Adults consume a variety of insects and snails, and may cannibalize newly metamorphosed juveniles.
Habitat: Inhabits arroyos, streams, washes and adjacent upland pinyon-juniper habitat. Also found along irrigation ditches, reservoirs, and in flooded fields near streams. It burrows into loose sandy soil. Elevations: up to 1,830 m (6,000 feet), and up to 150 m (500 ft) from water. Most common in tributaries of flowing streams.
Range: This species has been found in scattered locations in southeastern
Nevada, southwestern Utah, northwestern and central Arizona, western New Mexico, and western Mexico. In Clark County, Nevada, it may be found in Meadow Valley Wash, and along the Virgin River and the Colorado River to Hoover Dam.
Comments: The Southwestern toad (B. microscaphus) is now considered to be separate from its geographically disjunct sister species, the Federally Endangered Arroyo toad (B. californicus). It is likely to hybridize with woodhouse toads.