Indonesian Primates pp 121-156
Behavioural Ecology of Gibbons (Hylobates albibarbis) in a Degraded Peat-Swamp Forest
Gibbons are small arboreal apes inhabiting the rainforests of South-East Asia, Northwest India and Bangladesh (Carpenter 1940; Chivers 1977). The taxonomy of gibbons is under dispute, as the status of several taxa as species or subspecies is uncertain. Within the family Hylobatideae, there are four genera of gibbons: Bunopithecus (hoolock gibbon), Hylobates, Nomascus (crested gibbons) and Symphalangus (siamangs), and at least 12 species (Brandon-Jones et al. 2004). Apart from the sympatric Hylobates agilis/Hylobates lar and siamangs in Sumatra and peninsular Malaysia, gibbons are allopatric (Leighton 1987; Reichard and Sommer 1997). Some hybrids have been found within the genus Hylobates, including populations in Borneo (Hylobates albibarbis and Hylobates muelleri: Mather 1992), in Thailand (H. lar and Hylobates pileatus: Brockelman and Gittins 1984) and in peninsular Malaysia (H. lar and H. agilis: Brockelman and Gittins 1984). The Bornean agile or southern gibbon (H. albibarbis) occurs in southern Borneo, between the Kapuas and Barito rivers (Brandon-Jones et al. 2004). Its taxonomic status is unclear, but recent molecular evidence identifies it as a separate species, rather than a sub-species of H. agilis (Brandon-Jones et al. 2004; Geissmann 2007; Groves 2001).