Few primates are as noisy as the siamang gibbon, with members of a pair calling repeatedly to each other as they move through the rainforest. The siamang is the largest of the gibbons, occupying the midupper layers in the forest, the siamang has entirely black fur. It is also distinguished by the web that unites the second and third toes of each foot.

All species of gibbon live in trees, and are among the most agile animals in the world. When moving slowly through the trees, they grab a branch with one hand before releasing the other, but when travelling at a quicker pace, they use their momentum to carry them through the air. The distance across the outstretched arms of a siamang can be up to 1.7 m (5.6 ft) - far greater than its standing height. At night, they sleep on high, strong branches. Fruit, especially figs, is a staple food, and they also eat flowers, leaves and shoots, some insects and even birds' eggs.

Siamangs use their long arms to swing, or brachiate, through the trees, and can move 3 m (10 ft) in a single swing. They are very territorial by nature, with the male seeking to drive out any intruders, which can include people. Siamangs do not tolerate other gibbons in their territories, and use loud calls which can be heard from several kilometres away to warn away intruders. Both male and female siamangs possess naked throat sacks that inflate with breath and resonate their calls. Sometimes male and female siamangs sing together in duets, the male making booms and loud screams and the female barking and booming at the same time.

Females usually give birth to a single offspring, which they nurse for several months. Males take an active part in caring for the young, carrying the infants around with them. Adult siamang pairs live together in a territory with their offspring of different ages, but unmated adults live alone. The newborn baby is almost hairless and clings to its mother for safety and warmth.

To help grasp wide branches, gibbons have long thumbs, which attach at the wrist rather the palm - like those of great apes and humans.

Distribution: Restricted to areas of the rainforest in Southeast Asia, ranging from the Malay Peninsula southwards to the island of Sumatra.

Habitat: Rainforests up to 1,800 m (6,000 ft) altitude.

Weight: 10 - 12 kg (22 - 26 lb).

Length: 100 cm (39 in).

Maturity: 7 - 9 years for both sexes.

Gestation Period: About 235 days; the youngster may be carried by its mother for 3 - 4 months.

Breeding: 1, occasionally twins; weaning occurs at 18 - 24 months.

Diet: Mainly fruit, especially wild figs; also eats young leaves, seeds and flowers.

Lifespan: Up to 30 years.

Status: Threatened.

Facial hair

The area around the eyes and nose, reaching the lower chin, is free from hair.


These are twice as long as the body, allowing the siamang to swing along below branches.

Throat sac

This allows amplification of the duetting calls of these gibbons.


Two of the fingers on foot are fused together, aiding their grip.


These gibbons must walk with their hands help up, because their length means they would otherwise drag along the ground.

Young siamang gibbons have to cling on to the underside of their mother’s body as she moves through the forest.