Wyoming Toad

Anaxyrus baxteri (Bufo baxteri)

Wyoming Toad

Distribution in Wyoming

 

 

 

 

 

 

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The Wyoming Toad is a relict species, left behind and isolated in Wyoming during the retreat of the last glacial episode in the Pleistocene era about 10,000 years ago. Its nearest living relative, the Canadian Toad, Anaxyrus hemiophrys, resides about 500 miles to the north in North Dakota, Minnesota, and the south-central provinces of Canada. Until recently, this species was found only in Wyoming and only in a small area of the shortgrass communities within the Laramie Basin. There it inhabited areas adjacent to the margins of ponds and small lakes, and the floodplains and irrigated fields along the Laramie Rivers. Now, however, its distribution range has become even more isolated: it is restricted to the sedge, rush, and cattail habitats within the Mortenson Lake NWR west of Laramie—and to the sterile habitat of test tubes, Petri dishes, and plastic pools belonging to the dozen or so laboratories, rearing facilities, and zoos dedicated to its survival and propagation.

Wyoming Toad Wyoming Toad

The Wyoming Toad was abundant in the Laramie Basin during the 1950’s and 1960’s but by the mid 1970’s a drastic decline in its population had occurred. In 1984 the toad was federally listed as endangered. Plausible explanations such as fungal infections, pesticide usage, increased predation, and changes in irrigation practices have been investigated but no single causative agent has been demonstrated. Ongoing studies include: monitoring the existing population, captive breeding and husbandry, and the reintroduction of laboratory raised tadpoles and toadlets.

Wyoming Toad Wyoming Toad

The toad was first reported in 1946 as Bufo hemiophrys by Dr. George Baxter in his master’s thesis from the University of Wyoming. Its name was later upgraded to Bufo hemiophrys baxteri when research suggested it was sufficiently different from the northern gene pool to warrant the classification of subspecies. Later its name was changed again to Bufo baxteri when additional research supported even greater genetic differentiation. In 2008 numerous species belonging to the genus Bufo were regrouped, resulting in its current name of Anaxyrus baxteri.

Wyoming Toad Wyoming Toad

The Wyoming Toad is a medium sized toad with an average SVL just over 2 inches. Its dorsal surface has a white midline stripe running across a gray, olive, or brown background. This background is covered by darker blotches which are bordered with a cream or white margin. Each blotch has one or two rounded, rust colored warts protruding from it and the blotching pattern extends down along the sides and onto the legs. Each hind foot has two well developed cutting tubercles used for burrowing. The granular textured belly is white or cream and lightly peppered with black or dark olive colored flecks; the pelvic region is covered by an apron of dull pink or light orange pigmentation. Its cranial crest is composed of two ridges lying between the eyes; these parallel ridges are pinched together and may be fused near their middle, forming an hourglass shape like two opposing parenthesizes “)(”.