Description of the male advertisement call of Pelobates fuscus insubricus (Anura, Pelobatidae), with general notes on its acoustic repertoire

The advertisement call of Pelobates fuscus insubricus, an endangered subspecies endemic from Po plain in Italy, is described in terms of temporal properties and frequency parameters. Previous papers on acoustics repertoire in the genus Pelobates provide only qualitative information and the only study that analyses acoustic temporal parameters of the Italian spadefoot toad is based on a small sample of recordings made under captivity conditions. This study was carried out on 10 sets of advertisement calls from a sample of 17 males of a population near Ivrea (NW Italy); the vocalizations were recorded in underwater environment during the breeding season. 18 characteristics of the advertisement call were examined. The call, with a mean duration of 0.506 s, usually consists of three (rarely four) two-pulsed notes; the mean duration of the notes varies between notes: on average the first note last 0.0219 s, the second one last 0.0268 s, and the third one last 0.0266 s; the interval between notes ranges from 0.180 s to 0.273 s. The dominant frequency has a mean value of 979.28 Hz in the first pulse, 1033.83 Hz in the second pulse. The second pitch of intensity has a mean value of 2441.03 Hz in the first pulse, 2167.18 Hz in the second pulse. Concerning the effect of water temperature on the call parameters, we found statistically significant negative relationship only with the call duration an the duration of the intervals between the notes. Finally we discuss the results in lights of the social behaviour of P. fuscus and we provide a bibliographic review of its acoustic repertoire.