Hormonal Mechanisms of Frog Mating Calling

Injection of Rana pituitaries (pars distalis) or human chorionic gonadotropin will bring Hyla cinerea and H. versicolor males into calling condition. After such treatment they will respond reliably to tape recordings of conspecific mating calls by mating calling. Pituitary injections also increase the frequency of spontaneous mating calling in Rana ipipens. It is specifically the pituitaries, rather than foreign tissue, Ringer's solution, or the stress of handling and injection that is the active factor. Mating calling is abolished in both hylids and Rana by castration. Calling returns in castrated hylids after implantation of testes. The data support the hypothesis that the effect of pituitary injections on mating calling is indirect, through stimulation of testicular hormone production.