Lifestyle and Lifespan
They all have a pronounced and complete white face ring around hairless face, white hands and feet. Color is variable, not related to sex- very dark brown, black, red or light buff. Fur is extremely dense, providing protection from rain. One square centimeter of skin has over 2,000 individual hairs (13,125 per sq. in.) compared to 900 hairs per sq. cm. for Old World monkeys. Arms are very long, fingers are long and hook-like, and thumbs are thin and somewhat reduced. No tail. Ischial callosities are present.
There are 4 subspecies of white handed gibbons, H. l. carpenteri, H. l. entelloides, H. l. lar, and H. l. vestitus. If a specific lar gibbon's place or origin is unknown, it is difficult to assign it subspecifically based on morphology, since the physical differences are not distinct.
Gibbons are apes that are highly adapted to arboreal life. They are called the lesser apes, because they differ from great apes (chimpanzees, gorillas, and orangutans) by being smaller, having longer arms and dense hair, and not making nests. One unique feature of gibbon physiology is that their wrist is a ball and socket joint instead of a saddle joint, like the wrist of humans, which makes the gibbon wrist more flexible and able to rotate. The gibbon's ball-joint wrist greatly reduces both the amount of energy needed in the upper arm and torso and the stress on the shoulder joint. Brachiation in gibbons is further aided by their long hands and feet, with a deep cleft between the first and second digits of their hands.
Middle and upper stories of deciduous monsoon and evergreen rain forest .
Average home range is 0.15 mi. About 76% of that home range is their territory, which they defend from other groups. The home ranges of different groups often overlap, sometimes extensively. They live in small family groups consisting of the mated pair and immature offspring.
Fruit specialists (diet 75% ripe fruit) - figs a favorite. May visit 16 or more widely spaced food trees in a day's foraging. Rest of diet consists of leaves, young plant shoots, flowers, birds' eggs, birds, insects, and spiders. They drink by licking their own fur after a storm, or dipping an arm into a tree hole or rubbing it on wet foliage.
Lives in the middle and upper stories of deciduous monsoon and evergreen rain forest. They are omnivores who mostly eat fruit. Additionally they eat plants, birds, bird eggs, and bugs. Predators to lar gibbons include leopards, tigers, pythons, and eagles. They may mob and chase off potential predators. They live among other primates and apes, including the orangutan, siamangs, macaques, langurs, and slow lorises. Food competition may exist between lar gibbons and macaques as the two species have been seen foraging near one another and sometimes interacting. Lar gibbons competition with siamangs can cause conflicts and reduce feeding success of lar gibbons.
They are active for an average of 8.7 hours a day, leaving their sleeping trees right around sunrise and entering a few hours before sunset. Their days are spent feeding (32.6%), resting (26.2%), traveling (24.2%), in social activities (11.3%), vocalizing (4.0%) and in inter-group encounters (1.9%), although these proportions change over the seasons (when fruit availability decreases, feeding increases while social activity decreases).
These are the most active of all gibbons. They move faster, more quietly, and farther each day than any other forest apes or monkeys. Brachiation comprises 90% of locomotor activity. They can easily span a gap of 30 feet between one tree and another. Because they can not swim, they avoid crossing open water. Adaptations include precision of movement, incredible eye-hand coordination and dexterity. This remarkable agility makes a healthy adult gibbon virtually invulnerable to predation. They sleep sitting on their ischial callosities, hands resting upon flexed knees and head buried between knees and chest. Gibbons can make various vocalizations for different reasons. These include normal duets (vocalizations by the mated pair during the mid-morning or afternoon), calls emitted when disturbed (e.g. from predators, times of alarm, territorial disputes), adult male solos (often given early in the day, around dawn), and contact calls
Gibbons live in small family groups consisting of the mated pair and up to 4 immature offspring. Males are not dominant over females, either socially or physically. The vigorously territorial male can spend over half an hour each morning calling and displaying. The calling can also be for reinforcing the pair bond. Male and females can "sing" a duet. Group gibbons start their day together at sunrise, hanging from a branch to urinate and defecate. Usually, the group will then move to a feeding tree and spend their day feeding and moving to a new tree.
Gibbons are the only pair-bonded higher primate. There is no particular breeding season, as they mate all year, but the most conceptions occur during the dry season (March) with a peak in births during the late rainy season, in October. Estrous cycle is 30 days.Young are born singly at intervals of two to four years after a gestation period of about 210 days. Infants are hairless except for a cap of fur on the crown and must be sheltered between mother's thighs and abdomen to keep warm. Young leave the group at sexual maturity, between ages of six and eight years, driven out by the same-sex parent.
At birth, lar gibbons weigh on average 14 oz and are nearly naked. They are able to vocalize soon after birth. In the wild, infants are carried by clinging to their mother's belly. The ability to brachiate comes after around 9 months. They are weaned after 2 years. Infant mortality is low, under 10% (6.3%) in the first year of life.
Gibbons are absolutely dependent upon old growth tropical forests. Lar gibbons retain only 10% of their original habitat in protected reserves. In 1987, the IUCN estimated that there were 79,000 lar gibbons but to protect the more endangered species, all are listed as endangered by the USDI (1980) and are on appendix 1 of the CITES, prohibiting commercial trade in gibbons. Listed as Endangered by IUCN because of evidence of a decline of more than 50% in the last three generations (45 years) due to rampant deforestation and loss of mature individuals due to hunting.
Population densities for this species range from 2.4 groups/km2 in the Malayan peninsula to 6.5 groups/km2 in Thailand (though in northern Thailand they are very rare). In China, during the 1960s, there were estimated to be 200 individuals on the Nangunhe River but by 1992,they did not find direct evidence for the species' persistence. No population estimates are currently available for Indonesia, Malaysia, and Myanmar.
Oakland Zoo does not directly partner with gibbon conservation efforts. In most of the gibbon's range they are confined to protected conservation areas (ex. in Thailand, no large populations survive outside of protected areas). Unfortunately, these areas are not well patrolled. Poaching and illegal use of forest products is common in these areas. There is an urgent need for improved protection, ideally involving local communities that can benefit from their efforts. Inadequate management and protection, rather than forest destruction, are the main long-term threats and conservation efforts must create new management priorities. Further survey work is also needed to determine current population numbers within protected areas.
Gibbons are the most active of all gibbons. They move faster (up to 35 miles an hour), more quietly, and farther each day than any other forest apes or monkeys.
Gibbons can easily span a gap of 30 feet between one tree and another.
The vigorously territorial male can spend over half an hour each morning calling and displaying.
When gibbons walk bipedally (on two feet), they will raise their arms for balance.
Gron KJ. 2010 November 17. Primate Factsheets: Lar gibbon (Hylobates lar) Taxonomy, Morphology, & Ecology . . Accessed 2017 April 22.
Nowak, Ronald. 1991. Walker's Mammals of the World. 5th ed. Vol. 1. John Hopkins University Press, Baltimore, MD.
Hylobates lar. . Accessed 2017 April 22.