Male Calling Behavior in Response to Playback of Conspecific Advertisement Calls in Two Bufonids

Abstract

ABSTRACr.-Previously it has been hypothesized that male anurans in breeding aggregations vocalize asynchronously to reduce acoustic overlap with neighbors. The prediction was tested that in Bufo woodhousei and B. punctatus a male will lower his call rate in response to playback of conspecific advertisement calls. Male B. woodhousei reduced their call rates in response to playback of both high and low rate recordings, although call rates were lowered to a significantly greater degree during playback of high rate recordings. Contrastingly, male B. punctatus did not reduce their call rates in response to playback of conspecific calls. Male B. woodhousei reduced their rate of calling, apparently to avoid acoustic overlap with playback recordings. Male B. punctatus, however, usually initiated a call during each call broadcast during playback, resulting in extensive acoustic overlap. In B. woodhousei, mean call rate of males in a chorus was negatively correlated with chorus size. None of the current hypotheses concerning the significance of call alternation in anurans explains these results satisfactorily.