Great Plains Toad (Anaxyrus cognatus)
Calling Great Plains Toad, Photo by Young Cage.
Editor’s Note: The scientific name is now Anaxyrus cognatus
To hear the call of this species, follow this link: http://amphibiaweb.org/cgi-bin/amphib_query?special=call&genus=Anaxyrus&species=cognatus
Bufo cognatus is a member of the true toad family and perhaps its most ubiquitous. Adult females can reach over 11.4 cm (4.5 in.) in length, while the male of the species tend to be slightly smaller and possess a large characteristic sausage-shaped vocal sac. Dorsal coloration can be light brown to gray, usually with an olive green hue. A prominent and distinctive “V” shaped boss is formed between the eyes where the cranial crests diverge. Commonly has two to three paired, irregular oval blotches on the dorsum that are separated by a faint mid-dorsal stripe. Hind foot has a large and dark metatarsal tubercle.
In Arizona, this species occurs statewide and is absent from only the Mogollon Rim and most of the White Mts. Found in all of Arizona’s warm and temperate grassland communities. It also enters sagebrush plains, mesquite woodlands, creosote flats, and has occasionally been found in high montane forest. Has adapted well to over-grazed grassland and areas overcome by agriculture.
One of the most prolific breeders in Arizona. Reproductive activity generally takes place during the summer monsoon season, however some toads may breed before the rains come in May and June at sites with permanent water. The breeding call is a loud metallic trill that averages 25 seconds in its duration. This species is most active on wet summer nights, when it’s possible to observe hundreds on roadways that transect suitable habitat.
This toad is often misidentified as Bufo woodhousei (Woodhouse toad). The two may be distinguished by B. cognatus’ “V” shaped boss and its (usually) paired blotches present on the dorsum.
Recent observations indicate that this toad may be out competing, thereby replacing other anuran species within its range. Abusive grazing and agriculture may be at least partly responsible.
Author: Erik F. Enderson
Originally published in the Sonoran Herpetologist 2002 (12 (15)).
For additional information on this species, please see the following volumes and pages in the Sonoran Herpetologist: 2003 Jan:9; 2004 Dec:118.