(Symphalangus syndactylus)




Facts about this animal

With a head-body length of 75 to 90 cm, an arm span of 1.5 to 1.8 m, and a body mass of 8 to 16 kg, the siamang is the largest of all species of gibbons. Females are slightly smaller, and not as heavy, as the males.


Apart from the eyebrows, which sometimes may be reddish brown, the siamang is uniformly black coloured. The hair is long, soft and shiny. Males have a prominent preputial tuft of about 15 cm long hairs.


The head is small and round. The face is essentially bare with a flat broad nose with big nostrils. The eyes are dark brown. The ears are hidden in the fur. There is a fairly large laryngeal sac, which enhances the siamang’s call, helping make it the loudest of the gibbons. The sac is hairless and puffs up when sounds are emitted.


Like in other gibbons, the siamang's arms are longer than their legs. Palms and fingers, except for the short, opposable thumb, are elongated. Webbing of the second and third finger is a constant feature and may extend to the terminal joint. Their feet have five toes. The big toe is opposable too. Siamangs can grasp and carry things with both their hands and their feet.


Siamangs are very territorial and live in family groups. Siamang pairs usually stay together for life. A siamang family group consists of one adult male and one adult female, along with two or three immature offspring that are only two or three years apart in age.


After a gestation period of 7-8 months usually one single young is born, which weighs about 410-600 g and is hairless except for a small tuft on top of the head. Infants can hold onto their mothers’ fur and cling to her belly soon after they’re born. The youngster is weaned early in its second year when it has reached a body-weight of 2.5 to 3 kg. The father does his share of raising the baby and takes over the daily care of the youngster when it is about one year old. The offspring stay with their families for approximately five to seven years. Then they venture out on their own to start their own family group.


About half of the siamang’s diet in the wild consists of leaves, and most of the rest is fruit, flowers and buds. In addition, insects and small vertebrates are eaten as well.

Did you know?
That siamangs can share territory with other gibbons? This is because they are largely leaf eaters and do not compete for much of the forest fruit other gibbon species depend upon.


Suborder SIMIAE
Name (Scientific) Symphalangus syndactylus
Name (English) Siamang
Name (French) Siamang
Name (German) Siamang
Name (Spanish) Siamang
CITES Status Appendix I
CMS Status Not listed



Photo Copyright by
Su Neko



Range Indonesia (Sumatra), Malaysia (Peninsular Malaysia)
Habitat Rain and monsoon forests
Wild population Unknown, but numbers are decreasing
Zoo population 308 reported to ISIS (2007)

In the Zoo



How this animal should be transported

For air transport, Container Note 33 of the IATA Live Animals Regulations should be followed.


Find this animal on ZooLex


Photo Copyright by
Gordon Gartrell

Why do zoos keep this animal

Without rain forest there are no siamangs. Being very vocal, acrobatic and agile and displaying brachiation, their main way of travelling through the rain forest for many hours a day, the siamang is a perfect ambassador species for the threatened rainforests of south-east Asia.