Bradley Shaffer, professor of evolution and ecology at the University of California, Davis, is an expert on declining California frog populations. Scientists have noticed a steep drop in frog and toad numbers in recent years. Deformed frogs have been found in some places. Several reasons for these changes have been suggested, including pesticide pollution, climate change, increased ultraviolet light, and the introduction of predators such as rainbow trout. Carlos Davidson, a former graduate student in Shaffer's laboratory, used frog surveys, environmental data and detailed mapping to test these theories. Preliminary results suggest that agricultural pesticides are important in the decline of the red-legged frog. The study will be published in April 2001. These findings complement a study reported Thursday by USGS scientists, to be published in June 2001, which found that frogs are absorbing agricultural pesticides. Davidson is now a faculty member at California State University, Sacramento.