Range

Asia is the native home of the siamang. Here they can be found in Indonesia, Malaysia and Thailand. In Indonesia they are found on the island of Sumatra.

Reports exist of this species from Myanmar but scientists believe these are certainly an error.

Habitat

They make their home in semi-deciduous and tropical evergreen forests. Siamangs appear to have a level of tolerance to habitat disturbance and can persist in some secondary forest areas.

Reproduction

Siamang pairs will partner for life, a rare trait among primates. Mating will typically occur from May to July leading to the birth of an infant from December to February.

Their gestation is 7-8 months long. At the conclusion of this a single infant is born at a time which lacks hair across its body except for a small tuft on top of their head. At birth they weigh 170g (6oz).

They start their life by clinging to the fur of the mother who will carry the infant through the forest.

Around 1 year old the male will take over daily care responsibilities for the infant, another unusual behavior for a primate.

Infants are weaned by 2 years old. The infant remains with its parents for a further five to seven years. This extended care period means they are with the parents while they raise multiple siblings and allows them to learn the necessary skills to raise their own young.

At the conclusion of this period they move off to form their own pair. It can take multiple years for them to find a partner.

As many as ten infants may be produced by a female in her life.

Behavior

One of the most recognizable behaviors of the siamang is their call. This loud, throaty vocalization is amplified by the throat sac. Males and females perform their call as a duet and this helps to strengthen family bonds. These calls can travel up to 2km (1mile).

Another way to reinforce their bond is to groom with adults typically grooming one another in the morning.

Each family which is made up of the pair and their offspring maintains a territory which is defended against intruders.

Most of their movement occurs in the trees where they will swing from tree to tree assisted by their long arms. On the ground though they are considered to be the most skilled gibbons at walking upright.

At night the siamang will sleep on a tree branch sitting upright with their arms folded.

Predators and Threats

Their large size and ability to move quickly through the trees mean they have no recorded predators.

Humans have had a large role in the decline of the siamang. They are threatened by habitat loss which is undertaken for logging, conversion of the land to plantations including for palm oil and poaching for the illegal wildlife trade.

Quick facts

The siamang is the largest member of the gibbon family. On average they are twice the size of other gibbons.

Siamangs are one of the few primates that form permanent pairings with their mates.