Nijman, V. & Geissmann, T. 2001: Calling behaviour of male silvery gibbons on Java, Indonesia. In: The XVIIIth congress of the International Primatological Society: Primates in the new millennium. Abstracts and programme, Adelaide, South Australia, p. 128.

Calling behaviour of male silvery gibbons on Java, Indonesia

V. Nijman ¹ & T. Geissmann <sup>2

1</sup> Institute for Biodiversity and Ecosystem Dynamics, Zoological Museum, University of Amsterdam, P.O. Box 94766, Amsterdam 1090 GT, The Netherlands
² Institute of Zoology, Tierärztliche Hochschule Hannover, Bünteweg 17 D - 30559 Hannover Germany

Singing activity of >11 groups were monitored in the easternmost population of silvery gibbons Hylobates moloch. Sex of the singer and starting / ending time of all song bouts were recorded. Groups were identified by individual-specific song characteristics. 86% (n=108) were female solo songs, which started after 05:00 and peaked around 06:00. In contrast to previous studies >10% (n=13) were male solo song bouts. Most male songs (62%) started between 04:20-04:40, when it was still dark. Pre-dawn calling occurred on 4 out of 34 days, averaging >3.75 males. No dueting occurred.