The social calls of Kuhl's pipistrelles Pipistrellus kuhlii (Kuhl, 1819): structure and variation (Chiroptera : Vespertilionidae)

The aim of this study was to describe the structure of social calls produce d by Kuhl's pipistrelles Pipistrellus kuhlii. Bats foraging around street l amps in the Campania region, Southern Italy, were recorded. Calls were prod uced by bats during chases and, similarly to those of Pipistrellus pipistre llus, were probably used to repel conspecifics from hunting sites. Calls of ten had three components, lasted on average 34 ms and contained most energy at about 17 kHz. A positive correlation was found between the frequencies of maximum amplitude of echolocation and social calls. Social calls from tw o adjacent populations differed in their peak frequencies, and possible hyp otheses for this variation are given. The structure of P. kuhlii social cal ls was compared with those of the 45 and 55 kHz P. pipistrellus phonic type s. Kuhl's pipistrelle calls lasted longer and showed lower values of minimu m and peak frequencies. These differences can help to discriminate between field recordings of P. kuhlii and P. pipistrellus where the two species occ ur sympatrically.