Population Density and Habitat of Siamang and Agile Gibbon in Bala Forest, Southern Thailand

Main Article Content

Sutthirak Nongkaew
Sara Bumrungsri
Warren Y. Brockelman
Tommaso Savini
Anak Pattanavibool
Siriporn Thong-Ari


Siamang (Symphalangus syndactylus) and agile gibbon (Hylobates agilis) were censused and mapped in Bala Forest, part of the Hala-Bala Wildlife Sanctuary, Narathiwat Province, South Thailand. Nineteen groups of siamangs and 136 groups of agile gibbons were found in this 168- km2 area. This is the northernmost population of the siamang in Asia. Densities of siamangs were positively related to altitude, which reaches a maximum of 953 m in Bala Forest. In comparison with agile gibbons, siamangs occurred at higher altitude, lower-slope terrain, shorter distances from ridge-tops, and on more east-facing terrain. Both species occurred mostly in areas far from villages and the forest edge. Diminished submontane forest in Thailand, as well as competition with agile gibbons, may be limiting the distribution of siamang at the northern end of its range.

Article Details