Northern White-Cheeked Gibbon, Nomascus leucogenys
NORTHERN WHITE-CHEEKED GIBBON
Nomascus leucogenys
Geographic Distribution and Habitat
The northern white-cheeked gibbon is found only in the forests of northwestern Vietnam and northern Laos in regions that are relatively inaccessible to humans. The populations in Vietnam are small and isolated, while Laos has larger populations of these gibbons as a result of taboos against killing them. Just why are these adorable gibbons being killed? More on that later. A small population had also been recorded in southern China as recently as the 1980s, but more recent surveys have failed to find any trace of them in the area; they are therefore now considered extinct in China.
The northern white-cheeked gibbon inhabits subtropical, evergreen, and montane (mountainous) forests at altitudes ranging from 656 to 5,250 feet (200–1,650 m) in elevation.
Size, Weight, and Lifespan
Adult male and female northern white-cheeked gibbons are similar in both size and weight, but males tend to be a bit larger and heavier than females. Head-body length ranges between 18 and 25 inches (47–64 cm), and adults weigh between 15 and 20 pounds (6–9 kg). Both genders have long canine teeth, with the males’ canines being slightly longer on average (0.5 inches; 12.3 mm) than the females’ (0.42 inches; 10.7 mm). These differences in size, weight, and canine length are all examples of sexual dimorphism, or noticeable physical differences between genders. There’s a more obvious example of sexual dimorphism, which will be touched upon in the next section!
The average lifespan of these gibbons is 28 years in the wild.
Appearance
Along with their size, weight, and canine teeth, the most striking example of sexual dimorphism between genders is the coloration! Adult males are almost entirely black, with stripes of white hair along their cheeks. Males also sport a noticeable crest on top of their heads. Females, on the other hand, are a pale golden color with a dark brown patch on top of their heads, although there can be variation in their coloring. Interestingly, all infants of this species are born a golden color and then turn black with white cheek patches during their first year of life, even the females! When they reach sexual maturity, the females then turn golden again while the males remain black! Both genders have dark faces, which are sometimes framed by white in females.
Gibbons are similar in appearance to monkeys, but they are actually apes! As is true of other apes, such as chimpanzees, gorillas, bonobos, and orangutans, they don’t have tails. Compared to the large apes, gibbons are amazingly small. Their size is a necessary characteristic since they spend their entire lives in the treetops. The only other apes who spend a significant amount of time in trees are orangutans. Northern white-cheeked gibbons have extremely long arms in comparison to their body length, longer even than those of many other species of gibbon! Their arms are 1.2 to 1.4 times as long as their legs! These arms are looooong due to the way in which they move about in their tree-based habitat. More on that further down the article.
Diet
The northern white-cheeked gibbon is primarily a frugivore (fruit-eating) and a folivore (leaf-eating), with their diet primarily consisting of ripe fruit and leaves. To a lesser extent, they also consume buds, flowers, and insects.
The northern white-cheeked gibbon moves and feeds primarily in the upper and middle levels of the canopy, and families often feed together in the trees.
Behavior and Lifestyle
In case it wasn’t already obvious, the northern white-cheeked gibbon is arboreal, spending most of the day in the trees and rarely descending to the forest floor. They are also diurnal, or most active during daylight hours, and get around by brachiating from tree to tree. What is brachiating? Brachiation is acrobatically swinging from tree to tree! Such a way of traveling is fast and efficient, and makes traveling between patches of food sources less time-consuming.
The northern white-cheeked gibbon’s day is spent moving around the home range foraging for food, up to one mile (1.6 km) per day. Upon finding some succulent fruit in one of many trees within the territory, they stop to eat. During the rainy season, fruit is widely available, so they do not need to travel very far to find food. During the dry season, however, they travel greater distances and spend more time foraging, while increasing their dependence on leaves.
With regard to sleeping, they do not construct sleeping nests. Rather, they gather amongst high branches of the trees, often hugging one another tightly while sleeping in an upright position. Calloused pads, called ischial callosities, on their rear ends, provide both comfort and balance while they sleep seated on hard branches.
In all, northern white-cheeked gibbons spend 35% of their time traveling, 32% feeding, 30% resting, and 2% on social activity, mostly singing!
Thanks to their maneuverability and the security provided by the trees, northern white-cheeked gibbons have no natural predators other than humans.
Handedness – not just for humans: Adult northern white-cheeked gibbons have been shown to demonstrate a hand preference when swinging through the trees, with individuals being equally likely to be right or left-handed.
“Hey! That’s me!”: All gibbons are intelligent, and the northern white-cheeked gibbon is no exception. Captive individuals recognize themselves in mirrors.
Northern white-cheeked gibbons live in small family groups ranging between three to five members, consisting of an adult breeding pair and their sub-adult offspring. They have home ranges between 75-100 acres (30.6-40.5 ha), which they fiercely defend from other gibbon groups. Territorial defense takes the form of calls from the center of the territory or the boundaries, confrontations and chasing across the boundaries, and, rarely, physical contact between the adult males.
Upon reaching maturity at seven or eight years of age, the offspring of the breeding pair will leave to form groups of their own.
Gibbons are well known for one particular method of communication: singing! These songs are used for a variety of purposes, especially in establishing and defending territorial boundaries, and to attract mates. Several times a day, females will sing songs to defend their territory. If strangers are spotted, the male will scream alongside the female in an attempt to scare them away. If that doesn’t work, the male will shake branches, becoming more aggressive until he finally chases the intruders away in a large, noisy racket.
The calls of northern white-cheeked gibbons are among the most complex of those produced by gibbons and are significantly different between the genders. The most distinctive calls are those made as part of male-female duets. These begin with the female making a series of 15 to 30 notes with an increasing pitch, followed by the male complex call with rapid changes of frequency modulation. The cycle, which lasts less than 20 seconds, then repeats with increasing intensity for five to 17 minutes. The songs are accompanied by body movements and often end with the male swinging between branches and shaking them rigorously.
Facial expressions, gestures, and olfactory (scent-based) cues also play a role in gibbon communication, although much less is currently known about these than is known about the gibbons’ famous songs, thanks to their shyness around humans, and the resulting difficulty in observing them HIGH in the trees.
Northern white-cheeked gibbons are monogamous; that is, breeding pairs are bonded for life.
When ready to breed, females entice males with quick, jerking upper-body movements known as bobbing. After a gestation (pregnancy) period that lasts for approximately 200 days, females give birth to a single infant. The interbirth interval, or time between subsequent pregnancies, is two to three years. The newborn infant clings to Mom’s belly before traveling independently by around two years of age, upon which they are weaned from Mom’s milk and considered juveniles. This period lasts from two to four years. From four to six years of age, juveniles have graduated to adolescence. Upon reaching seven to eight years of age, sexual maturity has been achieved, and members of both genders disperse to find new territories and establish family groups of their own.
As fruit-eaters, northern white-cheeked gibbons aid in the regeneration of their forest habitats by dispersing seeds through their feces as they move around the habitat. In addition, they can also be considered pest controllers, as a result of their diet consisting of insects.
The International Union for Conservation of Nature lists the northern white-cheeked gibbon as Critically Endangered (IUCN, 2015), appearing on the IUCN Red List of Threatened Species.
Northern white-cheeked gibbons have suffered greatly from deforestation through agricultural encroachment into lowland and mountainous areas of their habitat. In addition, timber and fuel-wood extraction within remaining forest habitats has played a major role in the species’ decline. Across their range, the northern white-cheeked gibbon is also hunted for food, traditional “medicines”, as well as the live capture of young individuals for the illegal pet trade.
The northern white-cheeked gibbon is listed in Appendix I of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
The northern white-cheeked gibbon is legally protected in Vietnam and Laos, and even in China, where it is considered extinct, as a Class I Protected Animal under the Chinese Wildlife Conservation Law. However, despite these legal protections, there has been little effective enforcement in any country to protect the species against forest encroachment and poaching.
Conservation actions include hunting control, and within existing protected areas, ensuring habitat protection and improved zoning/planning to take key areas for gibbons into account. Also required is environmental education for local communities and government authorities, and further monitoring of the northern white-cheeked gibbon’s population trends as well as research on the population size/distribution/trends, threats, and actions towards the conservation of this swinging species of ape!
- https://www.alltheworldsprimates.org/Members/Home/MasterPrimate.aspx?tid=622
- https://www.bioexplorer.net/animals/mammals/apes/northern-white-cheeked-gibbon/
- https://www.brookfieldzoo.org/whitecheekedgibbon
- https://en.wikipedia.org/wiki/Northern_white-cheeked_gibbon
- https://www.iucnredlist.org/species/39895/180816530
- https://nationalzoo.si.edu/animals/white-cheeked-gibbon
- https://primate.wisc.edu/primate-info-net/pin-factsheets/pin-factsheet-white-cheeked-gibbon/
Written by Sienna Weinstein, Jun 2025