White-cheeked Gibbon

The northern white-cheeked gibbon is a Critically Endangered gibbon of South East Asia, found today only in northern Vietnam and northern Laos, in primary evergreen subtropical forest. Males are black with white cheek patches and a tuft on the crown, while females are reddish-tan. Both sexes have unusually long arms. It is arboreal and mostly eats fruit, plus leaves, buds and flowers, with up to 10% of the diet being insects and other small animals. Groups of up to six live in territories, sleeping in high branches. Mated pairs form long-lasting bonds and perform complex duet calls.

About the white-cheeked gibbon

The white-cheeked gibbon, more formally the northern white-cheeked gibbon, is a Critically Endangered species of gibbon native to Southeast Asia. It's closely related to the southern white-cheeked gibbon, once considered the same species, and the females of the two are nearly impossible to tell apart. Its genome was sequenced and published in 2011.

The species is strikingly sexually dimorphic. Males are black over their entire bodies except for distinctive white patches on the cheeks, along with a tuft of hair on the crown and a gular sac used for calling. Females, by contrast, are reddish-tan, lack the male's cranial tuft, and instead have a crest of black or dark brown fur running from crown to nape. Reported average weight is 7.5 kg (17 lb), though that figure comes from only a small number of wild individuals, and gibbons in captivity tend to run larger. Like other gibbons in its genus, the white-cheeked gibbon has unusually long arms — 1.2 to 1.4 times the length of its legs — along with heavier thighs and shoulders that suggest greater bodily strength. Individuals show a hand preference while swinging through trees, split evenly between right- and left-handed. It closely resembles the southern white-cheeked gibbon but has slightly longer body hair, subtly different calls, and cheek patches that reach the upper borders of the ears without touching the corners of the mouth — in the southern species, the patches reach only halfway to the ears but fully surround the lips.

Both sexes produce reddish-brown secretions from glands around the upper chest, hips, and ankles, though sweat samples show lower steroid levels than in many other apes, suggesting scent may play a smaller role in their social lives than it does in some relatives.

Behavior and diet

The white-cheeked gibbon is arboreal and primarily herbivorous, feeding mainly on fruit along with some leaves, buds, and flowers; insects and other small animals can make up as much as 10% of the diet. It's a sociable species, living in groups of up to six individuals that don't range far and are believed to hold territories. Gibbons in this species are diurnal, sleeping at night high in the branches, often huddled tightly together. They've also shown the ability to recognize themselves in mirrors in behavioral studies.

Their calls rank among the most complex of any gibbon species and differ markedly between males and females. The signature sound is a male-female duet: the female opens with 15 to 30 rising notes, the male answers with a rapid, frequency-modulated call, and the pair repeats the cycle with rising intensity for five to 17 minutes. In captive studies, pairs that duet most often are also the most likely to mate, suggesting the calls help cement the pair bond. Juveniles sometimes join solo calls to form a full chorus, and males can also produce booming sounds using their gular sacs.

The species is monogamous, forming long-lasting pair bonds. The female ovarian cycle averages 22 days, and gestation lasts 200 to 212 days. Newborns are covered in yellow-buff fur and weigh an average of 480 g (17 oz); around one year old, that fur turns black with pale cheek patches, and the adult, sexually dimorphic coat doesn't appear until four or five years of age. During this stage, juveniles use the female form of the call and spend much of their time in play. Sexual maturity arrives at seven or eight years, and wild individuals have been recorded living at least 28 years.

Range and habitat

Today, the white-cheeked gibbon survives only in northern Vietnam and northern Laos. It once ranged into Yunnan province in southern China, where it was reported near extirpation in 2008 and confirmed extinct by 2013. In Laos, an estimated 57 gibbon groups were counted at the Nam Et-Phou Louey National Protected Area in 2019. In Vietnam, at least 22 groups were confirmed in Pù Mát National Park, near the Laos border, while a monitoring program in the Xuan Lien nature reserve recorded 64 groups and 182 individuals in 2020 — a marked increase from 41 groups and 127 individuals recorded there in 2011. The species lives in primary evergreen subtropical forest between 200 and 1,650 m (660–5,410 ft) in elevation.

Conservation status

The white-cheeked gibbon is Critically Endangered (CR). Its range has already contracted sharply — it disappeared from China entirely by 2013 and now survives only in pockets of northern Vietnam and Laos. Where monitoring programs exist, such as at Xuan Lien nature reserve, group and individual counts have shown recent increases even as the species overall remains at severe risk.