Great Basin Spadefoot

Spea intermontanus

(Scaphiopus intermontanus)

Great Basin Spadefoot

Distribution in Wyoming

 

 

 

 

 

 

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The distribution of the Great Basin Spadefoot extends from southern British Columbia into Washington and then south through Oregon, Nevada, Utah, and into the northern reaches of Arizona. In Wyoming it is found in the Great Divide Basin (Wyoming Basin, Red Desert Basin), encompassing all of Sweetwater County with extensions into Lincoln, Carbon, Fremont, and Natrona counties. It inhabits the basins, floodplains, alkali flats, greasewood, and sagebrush communities of the desert and prairie life zones at elevations between 5,000 and 6,500 feet. It prefers the temporary waterholes of cut-bank channels and oxbow pools formed by intermittent streams, the puddles of playas and low lying depressions, and the little kettle holes associated with spring seeps.

Great Basin Spadefoot Great Basin Spadefoot

These spadefoots are stocky anurans (tailless amphibians) with snout-vent lengths (SVL) of about 2 inches. They have pale, moist skin and their dorsal surface is heavily pimpled with small brown or auburn conical glands. Their belly is marshmallow white and free of glands or pigmentation. Key characteristics of the family include the elliptical cat-like pupils of the large bulging eyes and the single cutting tubercle found on each hind foot. This species is distinguished from the Plains Spadefoot (with whom they share a sympatric overlap in Fremont and Natrona counties) by having a glandular rather than bony boss and by having a longer and narrower cutting tubercle.

Great Basin Spadefoot Great Basin Spadefoot

Spadefoots are explosive and opportunistic breeders that take advantage of heavy rains that may fall during early spring and late summer. Adults failing to breed during the first rains may try again later in the summer if suitable conditions exist. Males emerge from their burrows first, scramble to newly formed pools, and begin vocalizing their seductive call: "Wa-wa, Wa-wa." Within a short period of time, a boisterous aggregation will assemble and, with males clasping females, the mating pairs will shed their gametes and then disperse.

Great Basin Spadefoot Great Basin Spadefoot

After the clamor of the breeding frenzy has subsided, the reproductive efforts are abandoned and left behind without parental care; the egg masses rest quietly cradled amongst the submerged vegetation. The fertilized egg, encased within a gelatinous capsule, will divide into a pair of cells, then four, and so on until the multiplying ball of cells (blastula) surround and consume the nourishing yolk. A few hours later the ball will pucker, form a neural groove where the backbone will lie, and then elongate by developing a head and tail.

With the passing of the next two weeks, the waterhole will have shriveled to a puddle and its demise is at hand. The tadpoles, a teaming riotous mob, now stir in a batter that is more flour than water. Those unable to complete metamorphosis are denied even a futile attempt at escape—they dry into chips and are entombed within the mud. The partially transformed begin their exodus. Some take immediate (but alas temporary) refuge in the deeper hoof shaped troughs left by mammals having previously visited the scene. Some seek (sadly still, short-lived) shelter from the drying sun by hiding under blistered and curling plates of mud. Still others drag across the land, leaving a desperate, streaking trail out of the mire, their corpus soon eaten by beetle and ant.