Tyrone's research focuses on the role of steroid hormones in amphibian development, conducting both laboratory and field studies in the U.S. and Africa. His two main areas of interest are metamorphosis and sex differentiation, but he is also interested in growth (larval and adult) and hormonal regulation of aggressive behavior. His work addresses problems on several levels including ecological, organismal, and molecular. In 2002, Nature published research by Hayes and colleagues showing that "developing male frogs exhibited female characteristics after exposure to atrazine ... at exposure levels deemed safe by the US Environmental Protection Agency." More recently, Hayes has been a co-author on work that details atrazine inducing mammary and prostate cancer in laboratory rodents and highlights atrazine as a potential cause of reproductive cancers in humans.