Western Hoolock Gibbon
Hoolock hoolock
Overview
The Western Hoolock Gibbon is India's sole representative of the ape family (Hylobatidae) and one of the most endangered primates in South Asia. With an estimated population of fewer than 12,000 individuals in India, concentrated primarily in the fragmented forests of Assam, Meghalaya, Mizoram, and Manipur, every encounter with these remarkable creatures is a privilege.
Gibbons are distinguished from other primates by their mode of locomotion: brachiation, a form of swinging through the trees using their elongated arms. This adaptation allows hoolock gibbons to move through the canopy at speeds approaching 55 km/h, covering distances of up to 10 meters in a single swing. Watching a gibbon family move through the forest canopy at dawn is one of the most extraordinary wildlife experiences available in Northeast India.
The Western Hoolock Gibbon (Hoolock hoolock) is India’s only ape and the westernmost representative of the gibbons, the “small apes” of tropical Asia. Found in the evergreen and semi-evergreen forests of Northeast India, Bangladesh, and western Myanmar, this acrobatic primate is one of the most charismatic and elusive inhabitants of the region’s forest canopy.
Weighing just 6-9 kilograms, hoolock gibbons are built for life in the treetops. Their extraordinarily long arms, which span up to 180 cm, allow them to brachiate through the forest canopy with breathtaking speed and agility, swinging from branch to branch in arcs of up to 10 meters. They rarely descend to the ground, and their entire life cycle, from birth to death, plays out in the upper stories of the forest.
The morning song of the hoolock gibbon is one of the defining sounds of the Northeast Indian forest. Mated pairs perform elaborate vocal duets at dawn, with the male’s deep hooting and the female’s rising whoop-whoop-whoop carrying for over a kilometer through the canopy. These duets serve to reinforce pair bonds and declare territorial boundaries, and locating a gibbon family often begins with simply listening at first light.
Identification Tips
Sexual dimorphism is striking. Adult males are entirely black with prominent white eyebrows that give them a distinguished appearance. Females are golden-brown to buff colored, also with white eyebrows but with a darker face. Both sexes have no tail, a characteristic distinguishing all apes from monkeys. Infants are born whitish and darken as they mature, with males becoming fully black by 6-8 years.
In the field, the most reliable identification method is their distinctive vocalizations. The male produces a series of deep, resonant hoots that accelerate into a rising crescendo. The female's call is a higher-pitched, rapid sequence of whooping notes. The duet, performed primarily at dawn, is unmistakable once heard.
Where to Find
Hoollongapar Gibbon Sanctuary (Assam, near Jorhat): India's only gibbon-dedicated sanctuary, with a habituated population that offers the most reliable sighting opportunities. Gibbon Wildlife Sanctuary (Assam): Another excellent location with good canopy trails. Balpakram National Park (Meghalaya, Garo Hills): Remote but rewarding, with gibbons in pristine forest habitat alongside elephants and red pandas. Nongkhyllem Wildlife Sanctuary (Meghalaya): Accessible from Shillong, with mixed forest habitat supporting a gibbon population.
Ethical Guidelines
Gibbons are sensitive to disturbance. Maintain a minimum distance of 15 meters (even with habituated groups). Move slowly and quietly through the forest. Do not attempt to follow gibbons at speed; instead, let them come to you or move parallel at a respectful distance. Never use playback recordings, which cause acute stress. Keep group sizes small (maximum 4-5 people) and avoid making loud noises or sudden movements.
