Male calling activity in syntopic populations of Rana latastei and Rana dalmatina (Amphibia: Anura)

Abstract

Rana latastei and Rana dalmatina are two explosive breeder amphibians whose mating seasons last less than 1 month. The two species have very different repertoires of vocalisations, as Rana dalmatina uses only one advertisement call while Rana latastei uses two different vocalisations with opposite structural features. In our research, 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 vocalisations. 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 as the deposition peak, and called at high intensity long after the deposition peak. These different acoustic patterns led us to infer different prevailing functions for the vocalisations of these species. Male vocalisations 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 vocalise also in order to attract females, rather than to deter rival males. Thus, vocalisation 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 season. No difference was found also in daily activity, and both vocalisations were used preferentially during night time.