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Gibbons and Siamangs

Species Of Gibbons And Siamangs

The hoolock gibbon (Hylobates hoolock) occurs in Southeast Asia. Male hoolock gibbons are black, while the females are variable in color, ranging through black, grey, and brown, with a white band across the forehead.

The white-handed or lar gibbon (Hylobates lar), occurs in parts of mainland Southeast Asia, Malaya and Sumatra. The fur of this species has a basal color of black, brown, or yellow, but the upper surfaces of the hands and feet are white-colored, and the face is circled by white.

The dark-handed gibbon (Hylobates agilis) occurs on the Malayan Peninsula and Sumatra. The fur of this species varies from yellowish to dark-brown, and the upper surfaces of the hands and feet are always dark-colored.

The grey gibbon (Hylobates moloch) occurs in Java and Borneo. The fur of this species is light or dark grey, and the face is black.

The black gibbon (Hylobates concolor) occurs in Southeast Asia, particularly Vietnam, Myanmar (Laos), and Thailand. This is a dark-colored animal, with a distinctive, erect crest of long hair on the crown of the head, especially elongate in adult males. The black gibbon has a throat pouch, used to amplify its territorial noises, similar to the siamangs.

The siamang (Symphalangus syndactlyus) occurs in parts of Malaya and the island of Sumatra in Indonesia, while the dwarf siamang (S. klossi) is native to the Mentawei Islands off the west coast of Sumatra. Siamangs are heavier than gibbons, typically weighing 17-29 lbs (8-13 kg), with a body length as great as 36 in (90 cm), and an arm-spread of up to 5 ft (1.5 m). Siamangs have black fur, and a distinctive throat-pouch, which appears to amplify the booming and bellowing territorial noises of these animals. Siamangs are somewhat less agile than the true gibbons. Siamangs occur in montane and sub-montane forests between about 2,000-6,400 ft (600-2,800 m) in elevation. These animals defend their foraging range, and live in social groups consisting of an adult male and an adult female, plus any babies and sub-mature offspring that may be associated with the parents. These family groups defend a territory of about 25 acres (10 hectares) or more in area.

Resources

Books

Else, J.G., and P.C. Lee, eds. Primate Ecology and Conservation. Cambridge: Cambridge University Press, 1987.

Fleagle, J.G. Primate Adaptation and Evolution. San Diego: Academic Press, 1988.

Nowak, R.M., ed. Walker's Mammals of the World. 5th ed. Baltimore: Johns Hopkins University Press,1991.

Smuts, B.B., D.L. Cheney, R.M. Seyfarth, R.W. Wrangham, and T.T. Struhsaker. Primate Societies. Chicago: University of Chicago Press, 1987.

Stephens, M.E., and J.D. Paterson, eds. The Order Primates: An Introduction. New York, 1991.

Wilson, D.E., and D. Reeder. Mammal Species of the World. 2nd ed. Washington, DC: Smithsonian Institution Press, 1993.

Wolfheim, J. H. Primates of the World. Distribution, Abundance, and Conservation. Newark, NJ: Gordon and Breach Science Publications, 1983.


Bill Freedman

KEY TERMS

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Anthropoid apes

—These consist of the gibbons, orangutan, chimpanzee, and gorilla, all of which lack a tail, have an upright posture, and a well-developed brain. Anthropoid apes are the closest living relatives of humans.

Brachiation

—A method of arboreal locomotion involving hand-over-hand travelling, while holding onto branches. This is a characteristic locomotion of gibbons and some types of monkeys.

Monogamous

—A breeding system in which a mature male and a mature female live as a faithful, mated pair.

Montane forests

—Forests that occur relatively high on mountains, but below the open grasslands and tundra. Montane forests at low latitudes, for example in Southeast Asia, have a relatively cool and temperate climatic regime.

Polygynous

—A breeding system in which a single male breeds with more than one mature female.

Additional topics

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