Geissmann, T., 1991: Sympatry between white-handed gibbons (Hylobates lar) and pileated gibbons (H. pileatus) in southeastern Thailand. Primates 32: 357-363.

Sympatry between white-handed gibbons (Hylobates lar) and pileated gibbons (H. pileatus) in southeastern Thailand

T. Geissmann
Anthropological Institute, University Zürich-Irchel, Switzerland

Key words: Gibbons; white-handed gibbon; pileated gibbon; sympatry; Hylobates lar; Hylobates pileatus.

Abstract: White-handed gibbons (Hylobates lar) are not known to occur to the east or southeast of Bangkok. The reliably documented localities of H. lar nearest to this area are about 120 km northeast of Bangkok. There, in the Kao Yai National Park, is the only known zone of contact between H. lar and the pileated gibbon (H. pileatus), another species of the so-called lar group. Unpublished documents dating from 1925 indicate, however, that sympatry between these two species may also have existed in the region of Sriracha, about 80 km southeast of Bangkok. Therefore, a large zone of overlap in the distribution of the two species may originally have existed. In most parts of this hypothetical zone, gibbon habitat appears to have been destroyed, with the Khao Yai Park possibly representing the last remnant of the once large contact zone.