Konrad, R. & Geissmann, T. 2004: Vocal diversity and taxonomy of crested gibbons (Nomascus spp.) in Cambodia. Folia Primatologica 75, Supplement 1: 288-289 (Abstract only).

The Vocal diversity and taxonomy of crested gibbons (genus Nomascus) in Cambodia

Roger Konrad & Thomas Geissmann

Anthropological Institute, University Zurich-Irchel, Zurich, Switzerland
Email: rogerkonrad@access.unizh.ch

Key Words: gibbons, vocal diversity, singing behaviour, communication, phylogeny, Nomascus

In gibbons, species-specific call patterns are largely inherited. Vocal characteristics have been found particularly useful for assessing systematic relationships among hylobatids and to reconstruct their phylogeny. The taxonomy of the crested gibbons (genus Nomascus) is currently under debate. For instance, Geissmann et al. (2000) discovered a large area between the respective distribution ranges of N. leucogenys siki and N. gabriellae in central Vietnam, southern Laos, and possibly northeastern Cambodia, where calls appear to differ from the typical calls of either species. Both fur colouration and vocal data from this area suggest either a large hybridization zone with one species gradually replacing the other, or the existence of a previously unrecognized taxon. Nomascus gabriellae is usually thought to be the only Nomascus species occurring in Cambodia.

We studied the vocal diversity among different Nomascus populations in Cambodia in order to untangle their taxonomic relationships. We tape-recorded song vocalizations of gibbons in their natural habitat east of Mekong River. Tape-recordings were carried out in southern Mondulkiri Privince, in central Ratanakiri Province and in two different districts of Virachey National Park in northern Ratanakiri. In addition, typical N. leucogenys siki songs were tape-recorded near the type-locality of that taxon in the Bach Ma National Park in central Vietnam. A total of 40 song bouts (36 duet songs and 6 male solos) from different gibbon groups were included in this study. We determined time, frequency and qualitative variables and used them for cladistic and a discriminant analyses.

Preliminary data suggest that a considerable vocal diversity occurs among different populations of crested gibbons in Cambodia. We use our results to assess the systematic relationships of populations currently referred to N. leucogenys siki and N. gabriellae.