A grey tree frog (Hyla versicolor). Amphibian species are declining globally, and pesticides may play a role, but their concentrations are often low in nature. Carbaryl is a common pesticide that can become more lethal for frogs under certain environmental conditions. A recent study has found that predatory stress, a common pressure for most amphibians, can make carbaryl exposure much more deadly to gray tree frogs. This suggests that apparently safe concentrations of pesticides can become more deadly to some amphibian species when combined with predator cues. This photograph originally appeared on the cover of Ecological Applications (13:4) in December of 2003.