Keith, S. A., Waller, M. S., and Geissmann, T. (2009). Vocal diversity of Klossís gibbons (Hylobates klossii) in the Mentawai Islands, Indonesia. In Lappan, S. M., and Whittacker, D. (eds.) The gibbons: New perspectives on small ape socioecology and population biology, Springer, New York, pp. 51-71.

Vocal diversity of Klossís gibbons (Hylobates klossii) in the Mentawai Islands, Indonesia

Sally A. Keith¹, Melissa S. Waller², and Thomas Geissmann^3
1 School of Conservation Sciences, Bournemouth University, Talbot Campus, Poole
BH12 5BB, UK, E-mail: salkeith@yahoo.co.uk
² Department of Anthropology, Oxford-Brookes University, UK
³ Anthropological Institute, University Zürich-Irchel, Winterthurerstr. 190, CH-8057 Zürich, Switzerland, E-mail: thomas.geissmann@aim.uzh.ch

Abstract: The Mentawai Islands ó off the west coast of central Sumatra ó are known to support four endemic primates, one each of the genera Hylobates, Macaca, Presbytis and Simias. Two distinct taxa have been described for each of these endemic Mentawai primates, except for Klossís gibbon (Hylobates klossii) of which no subspecies are known. In each case, one taxon is endemic to the northernmost island of Siberut, and the second taxon is distributed across the three remaining islands Sipora, North Pagai and South Pagai. We studied the vocal diversity of wild Klossís gibbons at four localities (two on Siberut and one each on Sipora and South Pagai) in order to assess whether vocal differences among populations indicated the occurrence of a distinct subspecies on Siberut, and whether this corresponded to geographical distance or other recognizable patterns. Both female and male calls differ among localities and can be correctly identified using discriminant analysis. Vocal differences among localities exhibit no relationship to geographical distance. In addition, differences between two localities on Siberut are at least as pronounced as those between Siberut and localities on other islands. Affinities among the island populations are of comparable degrees and recognition of a distinct Siberut subspecies is not warranted. We propose that gibbons spread across the Mentawai islands at a considerably later date than the other non-human primates. This and a longer generation span in gibbons may explain why only Klossís gibbons do not exhibit distinct taxa on Siberut and the more southern islands of Mentawai.