SOCIAL CALLS IN CLEAR-WINGED WOOLLY BATSKERIVOULA PELLUCIDAFROM MALAYSIA

Abstract

Kerivoula pellucida is a small (4.5 g) vespertilionid bat, which forages in the understorey of tropical rainforests in Southeast Asia. Most echolocation signals are characteristic for the subfamily (very high-frequency, broadband FM calls (sweeping down from 178 kHz to 58 kHz) of low intensity and short duration (< 3.0 ms)), but this species also produces stereotypical calls of a markedly different structure. The arrangement of signal elements in these calls is unusual, and we present here a detailed analysis of calls from thirteen adult individuals (nine males and four females). These multiharmonic calls are of much lower frequency (fundamental peak frequency of 36 kHz), higher intensity and longer duration (12.0 ms) than the orientation calls, and are composites comprising a long quasi-constant frequency (QCF) syllable followed by an upward frequency modulated sweep (UFM). From considerations of signal design and preliminary field observations, we consider possible functions of these calls.