Male calling activity in syntopic populations of Rana latastei and Rana dalmatina

Rana latastei and Rana dalmatina are two explosive breeders amphibians whose mating seasons last less than one month. The two species keep very different repertoires of vocalizations, as Rana dalmatina uses only one advertisement call while Rana latastei uses two different vocalizations with opposite structural features. In this paper we continually recorded the calling activity of the two species during a whole breeding season in a pond where they breed in syntopy in order to assess the possible functions of their vocalizations. Males of both species increased their activity in coincidence with the peak of activity of females, but Rana latastei males reached the peak 2-3 days before the deposition peak. By contrast, males of Rana dalmatina reached the peak at the same time of the deposition peak, and called at high intensity much after deposition peak. These different acoustic patterns lead us to infer different prevailing functions of vocalizations of these species. Male vocalizations of Rana latastei are addressed only to males in order to gain and confirm their position within male hierarchy. By contrast, Rana dalmatina males might vocalize also in order to attract females other than to deter rival males. Thus vocalization in this second species might also play an intersexual function. The two call types of Rana latastei were used since the beginning of the breeding seasons. No difference was found also in daily activity, and both vocalizations were used preferentially during night time.