Konrad, R., and Geissmann, T. (2006). Vocal diversity and taxonomy of Nomascus in Cambodia. International Journal of Primatology 27: 713-745.
Roger Konrad and Thomas Geissmann
Anthropological Institute, Zürich University, Switzerland
Key words: Crested gibbons; diversity; Hylobatidae;
songs; Nomascus; systematics.
Abstract: It is usually thought that Nomascus gabriellae is the only
Nomascus sp. in Cambodia. We studied vocal diversity among different wild
populations of Nomascus in Cambodia to assess their taxonomic relationships
and to examine whether their vocal patterns correspond to forms previously described
for Nomascus leucogenys siki and Nomascus gabriellae. We tape-recorded
crested gibbon songs in southern Mondulkiri Province, in central Rattanakiri Province,
and in 2 different districts of the Virachey National Park in northern Rattanakiri.
We also tape-recorded typical songs of Nomascus leucogenys siki near the type
locality of the taxon in the Bach Ma National Park in central Vietnam. We analyzed
40 song bouts from different gibbon groups, including 151 phrases of 33 females and
235 phrases of 39 males. Discriminant analyses revealed marked separation of the
most southern songs (Mondulkiri) from those of all other localities. Vocal differences
among the 3 gibbon populations in northeast Cambodia (Rattanakiri) are less pronounced;
they do not differ more among each other than each of them differs from the northernmost
sample from Bach Ma (Vietnam). Vocal characteristics of the study populations revealed
no cline, and populations do not differ significantly in vocal variability. We conclude
that Cambodian crested gibbons represent 2 distinct taxa: Those from southern Mondulkiri
are Nomascus gabriellae, those from northeast Cambodia (Rattanakiri) closely
correspond to the sample from Bach Ma (Vietnam) and, together with the latter, represent
a different taxon. We provisionally assign them to Nomascus leucogenys siki
because of the close geographic distance between Bach Ma and the type locality of
the taxon. We postulate that a taxonal boundary exists between southern Mondulkiri
and central Rattanakiri and discuss the possible factors that may have acted as distribution
barriers.
Site by Thomas Geissmann.
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