White-handed Gibbon (Hylobates lar)

MORPHOLOGY: This species has relatively long forearms which assist it in suspensory behavior. This species has throat sac located beneath the chin to help enhance the calls. The white-handed gibbon lacks a tail, caudal vertebrae. The average body mass for an adult male white-handed gibbon is around 5.7 kilograms, and for the female it is around 5.3 kilograms. Pelage color for this species ranges from dark brown to beige. RANGE: The white-handed gibbon is found in the countries of Burma, China, Indonesia, Malaysia, and Thailand. This species is found in semideciduous monsoon forests and tropical evergreen forests, and these are either of primary or secondary forest types.

ECOLOGY:
The white-handed gibbon is a frugivorous species, but will also consume immature leaves and insects. The white-handed gibbon prefers to consume fruits high in sugar such as the fig (Ficus). This an arboreal and a diurnal species. This species sleeps and rests in the emergent trees (Leighton, 1987).

LOCOMOTION:
The white-handed gibbon is a true brachiator which means it moves by suspensory behavior (Fleagle, 1988). The brachiation is of a type where the white-handed gibbon throws itself from tree to tree over gaps of 10 meters or more using there arms (Fleagle, 1988). This species also climbs when moving slowly and feeding (Fleagle, 1988). This species is also able to move for short distances by bipedalism (Fleagle, 1988).

SOCIAL BEHAVIOR:
The white-handed gibbon has a monogamous mating and social system. The basic group structure is the breeding pair and their offspring. Both males and females emigrate from their natal group around adolescence. This is a territorial species. Adolescent and subadult males participate in the defending of the territory against conspecific males with their fathers (Ellefson, 1974). Although females rarely take part in aggressive encounters, newly paired females and females with partners that are weakened will chase away conspecifics of both sexes (Chivers and Raemaekers, 1980). This species has codominance where both the male and the female are dominant (Gittins and Raemaekers, 1980). Although this species is monogamous where it is sympatric with Hylobates pileatus some groups will have females of both species.

VOCAL COMMUNICATION:
duetting: These are vocalizations which occur between the breeding male and female, and is dominated by the female. This vocalization is important because it helps to maintain the pair bond between the breeding pair and also it helps to establish and maintain the territory.

OLFACTORY COMMUNICATION:

VISUAL COMMUNICATION:

TACTILE COMMUNICATION:
social grooming: This is when one individual grooms another and is used to reinforce the bonds between individuals.

REPRODUCTION:
The white-handed gibbon gives birth to a single offspring.

REFERENCES:
Burton, Frances. 1995. The Multimedia Guide to the Non-human Primates. Prentice-Hall Canada Inc.

Chivers, D.J. and Raemaekers, J.J. 1980. Long-term Changes in Behaviour. In Malayan Forest Primates: Ten Years’ Study in Tropical Rainforest. ed. D.J. Chivers. Plenum Press.

Ellefson, J.O. 1974. A Natural History of White-handed Gibbons in Malayan Peninsula. In Gibbon and Siamang, Vol. 3. Ed. D.M. Rumbaugh. Basel: S. Karger.

Fleagle, John G. 1988. Primate Adaptation and Evolution. Academic Press.

Gittins, S.P. and Raemaekers, J.J. 1980. Siamang, Lar, and Agile Gibbons. In Malayan Forest Primates: Ten Years’ Study in Tropical Rainforest. ed. D.J. Chivers. Plenum Press.

Leighton, D.R. 1987. Gibbons: Territoriality and Monogamy. In Primate Societies. eds. B.B. Smuts, D.L. Cheney, R.M. Seyfarth, R.W. Wrangham, and T.T. Struhsaker. University of Chicago Press.

Last Updated: October 8, 2003.
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