Hoolock gibbon  (Bunopithecus hoolock)

Gibbons exhibit a blend of characteristics that make them unique among primates. They are territorial, perform elaborate songs and display ‘suspensory behaviour'. They are also monogamous, and have a mainly frugivorous diet (2). Their most spectacular behaviour is probably their ability to travel easily through the canopy, 200 feet above the ground and at speeds of up to 35 mph (7). Gibbons do most of their travelling by swinging alternately from branch to branch and use their hands like hooks, often making long swings, in which neither arm supports them (brachiation) (4). Gibbons rarely descend to the ground, though when they do, they walk upright with the arms held high for balance (4).

The hoolock gibbon, like other gibbons, is active during the day, when it feeds on fruit, leaves, shoots, insects and birds' eggs (5). This species lives in small monogamous family groups of 2 - 5 individuals, which consist of a mated pair and their offspring (5). Territories extend for around 22 hectares and are defended fiercely by the adults, who chase intruders, display acrobatically and break branches to intimidate them (2) (5). The loud calls, often performed in duets, are also thought to contribute to the defence and establishment of territories, as well as being an essential communication tool in the dense forests (7).

Little is known about the reproductive behaviour of gibbons, though it is thought that hoolock gibbons bear offspring between November and March (4). Usually females give birth to single offspring, although twins have been recorded. There is an interbirth period of 2-3 years during which the mother cares for her young (4).