Patuxent Wildlife Research Center

NAAMP III Archive - deformed frogs
Home | Archive by Alphabetical Order | Archive by Category

Recent Observations of Deformed Anurans in Wisconsin

Robert D. DuBois

Department of Natural Resources
6250 S. Ranger Rd.
Brule, WI 54820

Since 1992, deformed anurans have been reported to the Department of Natural Resources (WDNR) from 16 sites in 15 counties throughout Wisconsin. Reported sightings of deformed anurans were apparently rare prior to 1992, with only two reports, both during the 1970's, coming from two additional counties. Most of these reports have not been substantiated with either specimen collections or photographs, and in only one case was a follow-up survey conducted.

Deformity observations have included 7 species (Bufo americanus, Hyla versicolor, Rana catesbeiana, R. clamitans, R. pipiens, R. septentrionalis, R. sylvatica) and a variety of manifestations including supernumerary and misplaced limbs, reduced or missing limbs, bony projections, unresorbed/deformed tails, and missing or misplaced eyes. Sites where deformed anurans have been observed have included relatively pristine lakes within heavily forested areas, largely agricultural watersheds, and near-urban settings. Thus, there does not appear to be an obvious common denominator in terms of site characteristics associated with these phenomena. Most sites are in east-central, southeastern, and northwestern parts of the state.

Although anuran deformity observations are not new to science, discussions with present and retired WDNR personnel with long work histories involving anurans suggest that the present, widespread occurrence of deformities is a recent development. It is imperative that a clearing house for reporting anuran deformities be maintained in Wisconsin, that this issue be widely publicized so that people understand where to report observations, and that research be initiated to identify the causes.

Figure 1.

U.S. Department of the Interior
U.S. Geological Survey
Patuxent Wildlife Research Center
Laurel, MD, USA 20708-4038
Contact: Sam Droege, email:
Last Modified: June 2002