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Hoolock Gibbon (Hylobates hoolock)


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 hoolock gibbon lacks a tail, caudal vertebrae. The average body mass for an adult male hoolock gibbon is around 6.9 kilograms, and for the female it is around 6.4 kilograms (Fleagle, 1988). The male has a black pelage color where the female’s pelage color is reddish-brown.

RANGE:
The hoolock gibbon is found in the countries of Bangladesh, Burma, China, and India. This species lives in undisturbed primary forests, evergreen forests, scrub forests, subtropical monsoon forests, and humid mountainous broadleaf evergreen forests.

ECOLOGY:
The hoolock gibbon is a frugivorous species, but will also consume immature leaves, flowers, and invertebrates. This an arboreal and a diurnal species. This species sleeps and rests in the emergent trees (Leighton, 1987).

LOCOMOTION:
The hoolock gibbon is a true brachiator which means it moves by suspensory behavior (Fleagle, 1988). The brachiation is of a type where the hoolock 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 hoolock 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.

VOCAL COMMUNICATION:
duetting: These are vocalizations which occur between the breeding male and female, and is dominated by the female. The male begins the duet with high notes sung in a short series. There are three phases to this call: the introduction, the interlude, and the great-call. There is no difference between the structure of the call done by the male and 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 hoolock gibbon gives birth to a single offspring.

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

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