The siamang is an endangered arboreal, black-furred gibbon native to the tropical rainforests of Indonesia, Malaysia, and Thailand. The largest of the gibbons, the siamang can be twice the size of other gibbons, reaching 1 m in height and weighing up to 14 kg, and is the only species in the genus Symphalangus. It has dense black fur, long slender arms, and a highly distinctive feature: a large gular (throat) sac found in both males and females, which can be inflated to the size of the siamang’s head, allowing it to produce powerful resonating calls. Another distinguishing trait is that two digits on each foot — the second and third toes — are partially joined by a membrane, hence the species name syndactylus.
Key facts
Lifestyle
Siamangs mostly eat fruits and tender new leaves, eating more leafy greens than other species of gibbons. Sometimes they also prey on insects, bird eggs, and small animals. They spend most of their time in the mid-to-upper forest canopy. Their primary mode of locomotion is brachiation — swinging hand-over-hand through the branches. Males and females sing together to build their relationship and mark their territory, and their calls can be heard from as far as two miles away through the thick rainforest. Groups occupy small ranges of about 24 hectares, of which around 60% is actively defended as territory.
Conservation status
Siamang numbers have declined by 50% over the last 40 years as a result of their two biggest threats: habitat destruction and the illegal pet trade — infants are captured as pets, which often involves the killing of adults. Only 4% of their habitat is protected.
Distribution
The siamang is found throughout the Barisan Mountains of Sumatra (Indonesia) and in the mountains of the Malay Peninsula, south of the Perak River. It inhabits mountain forests of the Malay Peninsula, and the rainforests, monsoon forests and lowland forests of Sumatra, at altitudes up to 3,800 m.
