1999 Frog and Toad Survey at Isle Royale National Park, Michigan

Isle Royale National Park; Peterson, Trevor; Egan, Alexander; Oelfke, Jack

The populations of anurans (frogs and toads) have been in apparent decline worldwide in recent years, and this has become a cause for concern. Frog and toad populations may serve as indicators of general environmental quality, so if a decline is taking place, it should indeed raise concerns, not only about the populations themselves but also about the environments in which they live. Isle Royale National Park (lSRO), Michigan, established a survey of frogs and toads in 1996 to monitor anuran populations on the island and to integrate these findings with those of the Frog and Toad Survey Program conducted by the Michigan Department of Natural Resources (DNR). Originally, two transects were established along park trails, then a third was added in 1997, and in 1999, a fourth was added. In 1999, frog and toad surveys at ISRO were conducted in the early spring, late spring and summer on all four transects. Each transect has ten survey points, yielding a total of 40 points surveyed per run. The survey is based upon the calls given by the male frog and toads during their various mating seasons. Call indexes of 1,2 or 3 were used to indicate the relative abundance of frogs and toads calling. These indexes were averaged and compared to those recorded in previous years. The intent of conducting three different runs throughout the spring and summer was to include the breeding seasons of all species surveyed. A total of five out of the six anuran species usually found on Isle Royale were recorded on the four transects, but all six were heard at some point during the summer by park staff. The data collected is summarized and compared to that of the previous three years. Recommendations are made for improving the survey in 2000.