A small toad of the family Pelobatidae, the genus is characteristically short-legged and squat, having vertical "cat-eye" pupils, and a black, keratinized spade (used for burrowing) on the underside of each hind foot.Their skin is relatively smooth compared to the rough, warty epidermis of truetoads (genus Bufo). Females are slighty larger than males. Distinguishing features include a slightly upturned, "pug-nose", a raised callus, or boss, between the eyes, and a dark brown or orange spot on each upper eyelid. Dorsal coloration is similar to that of other Spea and Scaphiopus species: Usually a brown, gray, or olive background, mottled with darker spots posessing light-colored centers. The ground color is variable and often matches the substrate. The venter is light gray, white, or creamy.
Tadpoles have large, globular or ovoid bodies, reaching 70 mm in total length. Their dorsal coloration is black, brown, or dark gray and flecked with metallic golds and rusts, while the abdomen displays an overall golden irridescence. The spiracle is located low on the abdomen, and to the left side.
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Canada, United States
U.S. state distribution from AmphibiaWeb's database: Arizona, California, Colorado, Idaho, Nevada, Oregon, Utah, Washington, Wyoming
Canadian province distribution from AmphibiaWeb's database: British Columbia
This species lives in western North America, in the United States and Canada. In Calfornia, they occur east of the Sierra Nevada, and north of San Bernardino Co. They occur throughout Nevada and Utah east of the Colorado River, push just south into northwest Arizona, and north into northwest Colorado and southwest Wyoming. In Canada, Washington and Oregon, they are sandwiched between the Cascade and Rocky Mtn. ranges, but occur throughout lower Idaho. They are found in arid regions, often associated with high desert scrub and sagebrush, but also reach past the pinion-juniper woodland, and into the spruce-fir belt at about 2800 m (9200 ft).
Little is known about abundance due, in part, to its explosive breeding habits, but it is often heard in temporary pools and flooded ditches immediately after winter and spring rains.
Activity varies with local conditions, but it is most active during and after winter, spring, and sometimes summer rains, when it may emerge to breed or forage on wet nights.
Life History, Abundance, Activity, and Special Behaviors
An explosive, opportunistic breeder, Spea intermontana is well adapted to the unpredictable and usually harsh seasons typical of the high desert areas it inhabits. Males have loud calls which attract females and probably other males to temporary or vernal pools where breeding takes place. Males are non-territorial, clumping and calling to females from partially submerged positions near the shore of pools. They appear to engage in a mad scramble for mates as they arrive. After breeding, adults disappear underground by using the spades on their hindfeet to burrow backward into the soil, thereby avoiding evaporative water loss to the dry desert air.
Eggs are laid underwater in groups of 10-40, and depending on the type of vegetation and substrate available, are arranged in either flat sheets, short strings, or golfball sized clusters.
Tadpoles may be either herbivorous or carnivorous, depending on local environmental conditions. The carnivorous morph has an enormous head, large jaw adductor muscles, and a sharp keratinous beak for tearing and cutting flesh. Tadpoles develop quickly to avoid dessication in their rapidly drying temporary pools.
Trends and Threats
Officially unthreatened, but recent studies have detected possible declines (Orchard 1992) and a repeat survey of historic collecting sites in the Sierra Nevada (Drost and Fellers 1996) found no specimens of Spea intermontana.
Drost, C. A., and Fellers, G. M. (1996). "Collapse of a regional frog fauna in the Yosemite area of the California Sierra Nevada, USA." Conservation Biology, 10(2), 414-425.
Orchard, S.A. (1992). ''Amphibian population declines in British Columbia.'' Declines in Canadian amphibian populations: designing a national monitoring strategy. C. A. Bishop nd K.E. Petit, eds., Canadian Wildlife Service, 10-13.
Written by Josh Whorley (crotalus75 AT hotmail.com), University of California, Berkeley
First submitted 1999-02-17
Edited by Vance Vredenburg (19 Sept 2000) (2001-06-04)
Species Account Citation: AmphibiaWeb 2001 Spea intermontana: Great Basin Spadefoot <http://amphibiaweb.org/species/5280> University of California, Berkeley, CA, USA. Accessed Oct 26, 2020.
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Citation: AmphibiaWeb. 2020. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 26 Oct 2020.
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