Great Plains Toad

Anaxyrus cognatus (Bufo cognatus)

Great Plains Toad

Distribution in Wyoming

 

 

 

 

 

 

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The Great Plains Toad ranges from Canada south through the central plains into Texas and Mexico. In Wyoming it is found in the northeastern counties where it inhabits the shortgrass communities of the prairie life zone below 6,000 feet. It is a highly terrestrial species and is generally found in the water only when breeding. Its distribution overlaps with that of Woodhouse’s Toad (and hybridization is known to occur), but this toad is more often associated with temporary ponds and potholes in slightly higher prairie regions, rather than permanent water bodies in lower floodplains.

Great Plains Toad Great Plains Toad

It is a relatively large toad with a SVL reaching 5 inches, though the average is 3-4 inches. Like most other toads and frogs (anurans), the female is larger than the male of the same age class. Its skin is dry and the dorsal surface is covered with many small, rounded warts, the largest of which is the oval shaped parotoid gland found just behind the eye. Patterns on the dorsal surface are quite distinct and consist of elongated and irregularly shaped dark olive-green blotches resting on a much lighter grayish background; a combination of banding—almost forming short broad stripes—that drifts downward along the sides as they recede to the rear. The ventral skin has a grainy texture and is white or cream in color.

Great Plains Toad Great Plains Toad

It is the cranial crest that greatly aides the observer in distinguishing this species from others found in Wyoming. It begins where the crest is fused into a ridge between the nostrils, and then diverges laterally as the ridges retreat to just behind the orbit of each eye—forming a V shape; the structure then continues with each ridge making a 90 degree, L-shaped bend and forming something of a half-box rim flanking the eye (postorbital ridges).

Great Plains Toad Great Plains Toad

Breeding begins in early summer after heavy rains have filled temporary ponds with clean water; peak activity occurs within the first or second night. Males appear just after sunset and form large congresses which produce an almost deafening ruckus. The vocal pouch is inflated into a sausage shaped extension of the throat and projected upwards in front of the face—issuing a harsh and explosive call that is similar to the clatter of a jackhammer or a motor rattling with all tolerances and adjustments askew. The frequency and volume of the vocalizations are so disruptive to the ear that it can be quite disorientating.

A breeding pair may remain in amplexus into the following day while the eggs are released from the female and fertilized by the male. The resulting gelatinous string is strewn amongst the submerged vegetation and will contain 5,000 to 10,000 eggs. The string is scalloped like beads on a string; each egg is individually encased within its own jelly capsule which then lies pinched or partitioned within the outer secondary membrane of the string itself. The eggs hatch in 2-3 days and the tadpoles undergo metamorphosis 3-6 weeks later. Sexual maturity generally occurs during the 2nd or 3rd year.