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|  Prosimians | Old World Monkeys | New World Monkeys | Lesser Apes | Great Apes Lesser Apes Restricted to the deciduous monsoon and evergreen rainforests of Southeast Asia, lesser apes -- also known as gibbons -- form the family Hylobatidae, which includes four genera, twelve species and sixteen subspecies. Similar to the great apes, the gibbons lack a tail and have the same dental formula but differ in their smaller size, more slender form, longer arms, longer canine teeth, and the presence of buttock pads. In most species males and females remain the same size but are often colored differently. Unique to the family, the basal part of the thumb is freed from the palm allowing for superior locomotion through the trees. Almost wholly arboreal these "dwellers in the trees", are morphologically designed to move agilely by brachiation, a process in which the long arms are suspended above the head to propel the body from branch to branch. Making long swinging leaps, they use their hands like hooks to rapidly cover great distances; Gibbons can leap 9 meters or more in a single bound. When having to transverse short distances on the ground the lesser apes walk bipedely with their arms held upright. Until recently all gibbons were thought to be monogamous, however new research has shown otherwise for some species. A family group will usually consist of an adult pair and two immature offspring. Typically, a bonded pair is strongly territorial and occupies a small home range which is defended by calls and aggressive displays. Considerable study has been done on gibbon vocalizations which are distinct and vary between species. A duet is often preformed by the male and female, lasting for approximately fifteen minutes once a day. The female emits the longest call. Scientists believe that gibbon singing is related to fruiting, breeding, identification of individuals, social change, and territoriality.Increasing human populations and consequently rapid loss of habitat for logging and agriculture in Southeast Asia are having a devastating impact on gibbon populations. Eight of the twelve species are presently listed as threatened by the World Conservation Unions (IUCN) Primate Specialist Group. Estimates for the surviving number of silvery Javan gibbons (Hylobates moloch) are as low as 250 mature individuals, occupying a mere two percent of their original habitat. Priority must be given to establishing protected areas in suitable habitat for remaining populations of all lesser apes. Breeding centers and conservation education campaigns, as well as stricter land management policies are needed to curb impending extinction for these unique creatures. Below is information on gibbons and siamangs (a species of gibbons, until recently thought to be a separate genus of lesser ape). Gibbons Genus: Hylobates, Bunopithecus and Nomascus Taxonomy: 11 Species, 15 subspecies Distribution: Assam, Bangladesh, Burma, China, Indonesia, Malaysia, Thailand, Laos, Brunei, Cambodia and Vietnam Size: Head-body length: 45-65cm, Weight: 121-147lb Appearance: Color of coat distinguishes species, sex and sometimes age Habitat: Deciduous monsoon and evergreen forests Diet: 70 percent fruit, but also eat flowers, leaves, buds, and insects Locomotion: Primarily arboreal, brachiate from branch to branch, skilled leapers, walk bipedely Behavior: Most are monogamous (pair bonded), small family groups, extremely territorial, use a variety of calls, diurnalSiamang Genus: Symphalangus Taxonomy: 1 Species, 1 subspecies Distribution: Indonesia and Malaysia Size: Head-body length: 75-90cm, Weight: 23lb, largest species of lesser ape Appearance: Black coat, large pink or gray throat sac found under the chin that inflates during vocalizations, second and third toes are webbed Habitat: Deciduous monsoon and evergreen forests Diet: Fruit, leaves, flowers and insects Locomotion: Primarily arboreal, brachiate from branch to branch, skilled leapers, walk bipedaly Behavior: monogamous (pair bonded), small family groups, extremely territorial, use a variety of calls including high-pitched barks, diurnalBack to Primate Groupings | ||||||||||||||
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