Sexual differences in responses to cross-species call interference in the green treefrog (Hyla cinerea)

Abstract

Many species gather in choruses to advertise and search for mates, creating noisy social environments that may impair effective communication. These challenges may be further compounded in mixed-species aggregations, where signals from different species overlap and mate-searching females may perceive heterospecific signals in more attractive relative timing positions. I conducted playback experiments with green treefrogs (Hyla cinerea) to test the effects of cross-species call interference on sexual communication and found that the sexes responded differently to conspecific and heterospecific calls. Females differentiated between call types and preferentially approached the conspecific call, indicating that they were not negatively affected by cross-species call interference. By contrast, males did not differentiate between conspecific and heterospecific calls irrespective of the presented call type and males avoided call overlap and called shortly after the offset of any interfering call. I suggest that the observed sex difference is a function of the time frames that the individual has to evaluate the call before initiating a behavioral response. Slower behavioral responses, like phonotaxis that allows for a repeated sampling of a call during approach, may facilitate finer discrimination. Fast behavioral responses, like timing one’s call relative to the call of a rival, may limit processing and result in higher permissiveness. As a result, similar call timing behavior in response to conspecific and heterospecific signals may be an artifact of strong selection for fast and precise call timing in the conspecific context and may essentially trap males into wasting time and energy interacting with heterospecifics.