Agile gibbon

Scientific name: Hylobates agilis

Country: Indonesia, Malaysia and Thailand

Continent: Asia

Diet: Mostly fruit but also leaves and insects

Food & feeding: Omnivore

Habitats: Tropical rainforests, dry tropical forest.

Conservation status: Endangered

Relatives: Gorilla, orang-utan, chimpanzee, humans.

Description: Agile gibbons are light and mobile arboreal (tree-dwelling) apes, with slender bodies, long arms and no tail. They weigh 4 – 8 kg (about twice the weight of a laptop computer) with a body length of 40 – 60 cm. Their fur varies from very dark brown to a light buff, with white hands, feet and brows. Male agile gibbons can be distinguished from the females by their striking white cheeks. Their specialised thumbs are not attached to their palms, like our hands, but join at the wrist, allowing for more flexible movement.

Lifestyle: Agile gibbons are diurnal (active during the day) and predominantly arboreal (tree dwelling). They move around the canopy using their long arms and form a ‘hook’ with their hands to swing (without gripping) from branch to branch. This way of moving is called brachiation. Agile gibbons can swing up to 3 m and leap more than 9 m. This rapid and direct form of locomotion enables them to exploit dispersed food sources and to defend a large territory. Their home territory usually covers about 25 ha (about 30 football pitches). It is defended from neighbouring families, usually by displays and songs that can carry over several kilometres. Gibbons rarely come down to the ground, but will walk upright on two legs when they do, holding their long arms above their heads for balance.

Family & friends: They are monogamous and mate for life, living in small, stable family groups of three or four.

Keeping in touch: Both male and female gibbons sing. Pairs sing a long and distinctive duet, initiated by the mated females to defend their territory from neighbouring groups and solitary females. The male will also sing a less complex song to keep any potential male rival at bay. Grooming takes place between members of the family group which helps to improve the physical and social development of the young gibbons.

Growing up: Female agile gibbons are monogamous and usually give birth every two to three years. Seven months after successful mating, a single baby is born which initially cling on to the mother. The juvenile is weaned after about two years and will play with their siblings and parents by chasing, jumping, mock biting and brachiation. This acrobatic social play should improve their locomotive ability and coordination and may help to develop social relationships. Once sexually mature at six to eight years, the sub-adults leave the family group, usually pushed out by the same-sexed parent, to establish their own territory.

Conservation news: Habitat fragmentation and deforestation from mining, logging and farming have caused severe decreases in gibbon populations. Agile gibbons are also popular in the pet trade in Asia. They are registered as an endangered animal under the IUCN Red List of Threatened Species. Bristol Zoo currently has a pair of agile gibbons that are part of the European Endangered Species Programme, which aims to maintain the genetic diversity of captive bred animals.