Symphalangus syndactylus

At the Zoo

The siamangs can be found in the Thelma and Henry Doelger Primate Discovery Center.

Fascinating Facts

Physical Characteristics

Siamangs weigh between 17 and 28 pounds and are superbly adapted for life in the trees. Their arms are longer than their legs, spanning up to five feet in a large adult. They move between the trees by brachiating, using their long, hook-fingered hands. Efficient and graceful in the trees, they are awkward on the ground, and will sometimes walk with their hands held overhead for balance like tightrope walkers.

Their jet black coat is heavy, shaggy fur. The face is naked except for scattered and sparse stubble of moustache and beard.

All of the lesser apes have loud voices, but the siamang also has a large inflatable throat sac to further magnify its calls. The siamang “song”, usually performed at dawn and several times throughout the day, is a combination of deep, resonant hoots and higher-pitched shrieks. These calls act help to maintain territories and communicate with other siamang groups.

Lifespan is 20 – 25 years in the wild and up to 30 in captivity.


Siamangs spend almost all of their time high in the rainforest canopies of Sumatra, mainland Malaysia and southern Thailand. They are often found in areas with a high concentration of figs, their favorite fruit.

Siamangs are omnivores and feed primarily on fruits, buds, foliage and flowers but will also eat insects, spiders, small lizards and bird eggs. At the Zoo, the siamangs are fed a diet of apples, oranges, bananas, lettuce, bread and cooked sweet potatoes.

Social Behavior

Family groups consists of an adult pair and as many as four of their offspring. Within each family, food is generously shared and fighting rarely occurs. Siamangs are territorial and members of the same family will drive off intruders. Grooming is the most important social behavior to reinforce bonds between individuals.

Every two or three years they give birth to single young after a gestation period of 230 days. Siamangs are monogamous and display an unusually high level of parental care. At about one year of age, the adult male takes over most of the daily care of the young. But the prolonged maternal care of infants by the mother may last as long as 20 months. Juvenile siamangs will leave the group to find a mate and establish a family at around six years of age.

Status In The Wild

Siamangs are listed as endangered by the IUCN and on appendix I of CITES. They are most threatened by habitat loss and fragmentation. Deforestation over much of their range is caused by logging, agriculture and road development. Siamangs are also sought after as pets, being one of the most traded gibbon species.

What can you do to help siamangs?

Animals & Exhibits