Habitat and General Information
about the Gibbon
From left to right: female Hylobate pileatus (pileated), male Hylobate lar (white-handed),
and female Nomascus gabriellae (yellow-cheeked crested) gibbon
Courtesy of Thomas Geissmann; The Gibbon Research Lab
General Information
The Gibbon is a relatively small ape species. Its discovery and documentation dates back as long as there was written history. One philosopher that died in the year 122 B.C. mentioned the gibbon in his Chinese proverbs. They were viewed as symbols of the mysterious and supernatural. Many Chinese dynasties displayed gibbons in paintings and other artwork. Throughout ancient China, Kings kept gibbons as pets. Infant gibbons were caught by shooting their mother with a poisoned dart and then extracting the infant still clinging to the mother's body after they fell to the ground (Geissman B, 2001).
Their most distinguishing characteristics include arms two and a half times the length of their bodies and their lack of a tail. Their long arms and hooked shaped hands are adaptive for swinging efficiently through trees. This process is called brachiation. Eleven species of gibbons have been identified and divided into four main groups. The most distinguishing characteristic between species is their pelage (coat) coloration as demonstrated in the pictures above. Adult pelage ranges from whitish/yellow to silver/gray to brownish/black. Some species show sexual dimorphism In these species females have the lighter pelage (yellow, beige, or gray) while the males show darker colors (dark brown, gray, black). The two common species include the lar gibbon (having white hands) and the hoolock gibbon (possessing a white frame around their eyes and face). Infant pelage changes with maturation. One other large difference among generas include different diploid chromosome numbers. (Genus Bunopithecus has 38; Symphalangus- 50; Nomascus- 52; Hylobates -44) . Gibbons have recently been discovered to have more genetic difference between generas than between that of humans and chimpanzees. Considered "the lesser ape," gibbons only weigh 10-13 lbs and have an average head and body length of 60-90 cm. Males and females are monomorphic in size. Gibbons have a long life span, sometimes reaching 50 years of age (Geissmann, 2001).
Habitat
Gibbon species range across Southeast Asia including China, India, Bangladesh, Burma, and the Malay Peninsula (Fuentes, 2001). Their habitat consists of tropical evergreen forests, wet tropical semi deciduous evergreen forests, sub-tropical monsoon evergreen broadleaf forests, and sub-tropical evergreen broadleaf hills or mountain forests(Geissmann, 2001). Despite a large geographical range, gibbons remain near moist forests (Chivers, 1984). Their range has diminished severely due to deforestation, human encroachment and poaching. Territories are rarely abandoned as a result of the large energy invested within them. This high level of attachment has proven problematic and usually fatal as a result of deforestation. Gibbons are arboreal (tree-dwelling) and prefer the upper canopy of forests (Geissmann, 2001). All gibbon territories possess a special sleeping tree towards their periphery. Sleeping trees are usually liana-free, emergent trees sometimes situated on a hill. This extra height minimizes nocturnal predation (Tenaza, 1975).
Food Distribution
Food preferences also limit gibbons to certain forests. Gibbons are classified as frugivores. They prefer ripe fruit with juicy pulp(Chivers, 1984). Other food sources consumed include young leaves, flowers, and figs. Non fig-fruits are the most heavily consumed followed by young leaves. Monthly flower abundance dictates gibbon intake. High abundance results in species eating more flowers and less fruit. High rainfall indicates a higher intake of (non-fig) fruit (McConkey et al., 2003). Because of their complex environment, there is always some fruit in season (Chivers, 1984). Their poor detoxification ability in comparison to their low-fiber diet could be a factor causing them to seek more diverse and less seasonal fruit. Gibbons must compete with birds and squirrels more than with other primates since they rely on the small, scattered fruit sources. (Chivers, 1984). Another article found flowers to be the predominant food choice. One supporting argument for this stated that their relatively small group size and ability to locate several food sources each day within their home range lowered dependency on fruit. (McConkey et al., 2003).
Gibbons spend all of their time in trees. They very rarely drop to the ground, even when seeking food. Their long arms make swinging from branch to branch a very efficient mode of travel. This locomotion is called brachiation. Adaptations facilitating brachiation include long upper limbs with very flexible shoulders and upper arms, and a higher center of body mass (Grand, 1972). This makes brachiation energetically beneficial (Geissmann, 2001). Gibbons feed in trees by hanging beneath the resource and sometimes find nearby footholds for extended periods. This method allows a larger reach than other arboreal animals that may sit on the branch of feeding (such as the macaque). Also, by hanging from the branch, the body weight pulls the food directly towards the gibbon (Grand, 1972). If the branch is closer to the ground and may pose a threat from ground predators, gibbons will grab sturdy, higher branches and swing until they can grab hold of the lower resource. In this way, should a danger present itself, the gibbon can swing or jump out of reach from the sturdy, taller branch (Ellefson, 1976).
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