Woodhouse’s Toad (Anaxyrus woodhousii)
Woodhouse's Toad, Yuma Co., AZ. Photo by Jim Rorabaugh
Woodhouse’s Toad is a relatively large (<127 mm SVL), chunky toad, the dorsum of which is yellow-brown to gray-brown with scattered dark spots and a light mid-dorsal stripe. The parotoid glands are prominent, large, and elongated. Well-developed cranial crests are present between and in front of the eyes, but they are not united into a boss on the snout. In the 100-Mile Circle, this species is found from Sonoran desertscrub upslope through semi-desert grassland, Plains grassland, and sparingly into oak woodland. It is most abundant along major rivers and in agricultural lands, including ditches and canals. Rosen and Funicelli (2009) found that Woodhouse’s Toad was extirpated from urban Tucson while eleven other anurans, such as the Great Plains Toad, Sonoran Desert Toad, and Couch’s Spadefoot, were still persisting in such areas. Woodhouse’s Toads are doing better in the Phoenix metropolitan area where they probably follow major canals and the Salt River into the city.
In our area, Woodhouse’s Toads breed from March into early summer in more permanent waters such as rivers and canals, and but then also later in temporary pools created by the summer monsoons. The male advertisement call is a loud nasal “waaah!”, 1-3 seconds in duration, which resembles the call of a sheep. Follow this link to hear its call:
As many as 28,000 eggs per clutch are laid in long strings on the bottom of quiet ponds. Larger tadpoles are dark brown to slate gray, often with indistinct mottling, pigment is absent on the lower third of the tail, and they grow to about 30 mm TL prior to metamorphosis.
In Arizona, the smallest calling male was 69 mm SVL, and the smallest reproductive female was 84 mm SVL. Males average a smaller size than females, have smoother skin, and possess a dark throat that is most noticeable during the breeding season. Metamorphs resemble small adults and are 12-15 mm SVL. The diet consists of a variety of invertebrates; tadpoles are primarily herbivorous.
In agricultural lands and along major rivers in southern Arizona, the Woodhouse’s Toad coexists with and breeds in the presence of often a diversity of non-native fishes, frogs, turtles, and crayfish. It is the only toad consistently found along the lower Colorado River in the Yuma area, which is awash in non-native species.
Hybridization with the Red-Spotted Toad, Sonoran Desert Toad, Great Plains Toad, and Arizona Toad has been documented in our area. In central Arizona, primarily out of the 100-Mile Circle, dams on major rivers have created ponded water conditions that favor Woodhouse’s Toads over Arizona Toads, and in these areas the two species often hybridize, threatening Arizona Toad populations. Woodhouse’s Toad is listed as a species of least concern on the IUCN Red List. Most of the literature on this species is under the name Bufo woodhousii.
Brennan, T.C., and A.T. Holycross. 2006. Amphibians and Reptiles in Arizona. Arizona Game and Fish Department, Phoenix, AZ.
Rosen, P.C., and C. Funicelli. 2009. Conservation of urban amphibians in Tucson, Part 1. Sonoran Herpetologist 22(10):106-110.
Sullivan, B.K. 1989. Mating system variation in Woodhouse’s toad (Bufo woodhousii). Ethology 83:60-68.
Sullivan, B.K. 2005. Bufo woodhousii Girard, 1854 Woodhouse’s Toad. Pages 438-440 in: M.J. Lannoo (editor), Amphibian Declines: The Conservation Status of United States Species. University of California Press, Berkeley.
Author: Jim Rorabaugh