What are the leading causes of frog declines and deformities?

There does not appear to be one 'smoking gun'; numerous environmental factors are probably responsible for the declines and deformities. Limited research findings and anecdotal information suggest several possible causes, including habitat loss, introduction of non-native predators such as fishes and bullfrogs, disease, and possibly airborne contaminants. Scientists who have studied amphibian declines and deformities agree that the deformities are unlikely to have caused the extensive, well-documented declines of many amphibian species worldwide. Deformities in different localities probably have different causes. Recent USGS research indicates that some malformations may have both site-specific and time-dependent causes.

Learn more: USGS National Wildlife Health Center: Amphibian Malformations and Declines