White-handed Gibbon

The lar gibbon, also called the white-handed gibbon, is an ape of the gibbon family found in Indonesia, Laos, Malaysia, Myanmar and Thailand, mainly in lowland and hill rainforest. It has the greatest north-south range of any gibbon. Its fur varies from black and dark brown to sandy, and white hands, white feet and a ring of white hair frame the black face. A true brachiator, it swings beneath branches on extremely long arms and rarely comes to the ground, where it walks on two legs with its arms raised for balance. About half of its diet is fruit, with leaves, insects and flowers making up the rest.

About the white-handed gibbon

The white-handed gibbon, also called the lar gibbon, is a member of the gibbon family, Hylobatidae, and is listed as an endangered primate. It's one of the better-known gibbons and is often kept in captivity. Taxonomists recognize five subspecies: the Malaysian lar gibbon, Carpenter's lar gibbon, the central lar gibbon, the Sumatran lar gibbon, and the Yunnan lar gibbon, which is possibly extinct.

Its fur ranges from black and dark brown to light brown and sandy tones, but the hands and feet are always white, and a ring of white hair surrounds the black face. Males and females look alike in color and are close in size. Like all gibbons, white-handed gibbons are true brachiators — they travel through the forest by swinging under branches with their arms rather than walking along them. That mode of locomotion has shaped their bodies: curved fingers, elongated hands, very long arms, and comparatively short legs. The result is an intermembral index of 129.7, among the highest of any primate. As with other apes, the tailbone has shrunk to the point that gibbons have no functional tail, and they carry tough, bony sitting pads on their buttocks called ischial callosities.

In the wild, the white-handed gibbon has the widest north-south range of any gibbon species, spanning from what was once southwest China down through Thailand and Burma to the whole Malay Peninsula, plus northwestern Sumatra. That range has contracted and fragmented over recent decades, and the species is likely extinct in China; if any animals remain there, they would be confined to the old range in southwest Yunnan. Rivers tend to mark the boundaries of gibbon ranges, so white-handed gibbons live east of the Salween River in Myanmar and west of the Mekong River in northwestern Laos. They share their forests with other primates and apes, including orangutans, siamangs, pileated gibbons, purple-faced langurs, Thomas's langurs, slow lorises, and several macaque species. Thailand is thought to hold between 15,000 and 20,000 white-handed gibbons, while as few as 10 may survive in China, if any do at all.

Behavior and diet

White-handed gibbons are diurnal and arboreal, rarely descending to the ground. They're active for an average of 8.7 hours a day, leaving their sleeping trees around sunrise and returning to them roughly 3.4 hours before sunset. A typical day breaks down as about 32.6 percent feeding, 26.2 percent resting, 24.2 percent traveling, 11.3 percent social activity, 4.0 percent vocalizing, and 1.9 percent intergroup encounters, though these proportions shift across the year. They move through the canopy by brachiating, swinging hand over hand with their hooked hands and building real momentum; the rare times they do touch ground, they walk upright with their arms raised for balance.

The diet is mostly fruit, which makes up about 50 percent of intake, with leaves adding another 29 percent and insects and flowers contributing 13 and 9 percent respectively. Wild gibbons eat figs, small sweet fruits, liana and tree fruit, berries, young leaves, buds, flowers, new shoots, vine shoots, and insects such as mantids and wasps, and they'll even take birds' eggs. When figs and leaves become scarce in summer, insect consumption jumps twentyfold compared with winter levels.

Long thought to be strictly monogamous, family groups turn out to be more flexible than once assumed: long-term study at Khao Yai National Park in Thailand documented extra-pair copulations, partner changes, and polyandrous groupings, possibly tied to cooperative territory use and female defense. Each morning, a family gathers at the edge of its territory for a "great call," a duet sung by the breeding pair that helps ward off other gibbons; each pair has its own variation on the species' typified call. Mating happens year-round, but most conceptions occur in the dry season in March, with births peaking in the late rainy season in October. Females in the wild first reproduce around age 11, notably later than captive females. Gestation runs about six months and usually produces a single infant, which nurses for around two years and reaches full maturity at about eight years old.

Range and habitat

White-handed gibbons live across Indonesia, Laos, Malaysia, Myanmar, and Thailand, with a historic range that once reached from southwest China through Thailand and Burma to the Malay Peninsula and into northwestern Sumatra. That continental range has shrunk and split into fragments in recent decades. The species favors lowland, hill, and upper dipterocarp forest — including primary lowland and submontane rainforest, mixed deciduous bamboo forest, and seasonal evergreen forest — and is rarely found above 1,200 meters (about 3,900 feet) in elevation.

Because gibbon ranges tend to be separated by large rivers, the white-handed gibbon's distribution is patchy along natural boundaries: it occurs in southern and eastern Myanmar only east of the Salween River, and west of the Mekong River in northwestern Laos and northern Sumatra. Within this range, it lives alongside other primates and apes rather than in isolation.

Conservation status

The white-handed gibbon is listed as Endangered on the IUCN Red List, in a 2020 assessment. Threats include hunting for meat and the killing of parent animals so their infants can be captured for the pet trade, but habitat loss is the most pervasive problem. Forests are being cleared for roads, agriculture, ecotourism, domesticated cattle and elephants, and palm oil plantations, and are also being lost to forest fires and both subsistence and illegal logging. New village settlement adds further pressure on remaining habitat. In the wild, potential predators recorded in one study area, the Sikundur Monitoring Post in Sumatra, include Sumatran tigers, Sunda clouded leopards, pythons, and grey-headed fish eagles.