Interview: Unraveling the Mystery of the Bizarre Deformed Frogs

For the last two decades, strange things have been happening to frogs. Some frog populations have high rates of limb deformities, while others have high incidences of “intersex” — traits associated with both males and females, such as male frogs whose testes contain eggs. David K. Skelly, professor of ecology at Yale University’s School of Forestry & Environmental Studies, set out to discover what was causing these deformities, which some researchers were attributing to an agricultural pesticide. His work has implicated human activity, but not in the way many researchers had thought. In an interview with Yale Environment 360, Skelly describes what chemicals may be causing these abnormalities and explains why this phenomenon may have troubling implications not only for amphibians, but for other vertebrates, including humans. Skelly says one thing is clear: The deformities showing up in frogs are almost certainly not caused by a single chemical, but rather by a whole suite of substances — including medicines excreted by humans into the environment — that act in concert to mimic hormones like estrogen or cause other ill effects.

Read the interview