These small-bodied apes are arboreal, spending most of their time relaxing in the trees or swinging between branches. Siamangs (the largest species of gibbon) are also diurnal; while they are active in the mornings and evenings, they tend to rest in the middle of the day in addition to sleeping at night.

Siamangs are easily distinguishable by the large air sac on their throat. This throat sac can inflate to a size comparable to the siamang’s entire head. They use these sacs to produce their loud, booming calls in order to establish or defend their territory from other siamangs nearby. They generally produce these calls in the morning, but once afternoon rolls around they quiet down to rest. A typical siamang group will have around four members, including an alpha male and female. These apes generally mate for life, and exhibit close pair bonding.


Siamangs are listed as Endangered by the International Union for Conservation of Nature (IUCN). This is mainly due to capture for the illegal pet trade as well as deforestation, which is largely a result of the palm oil industry.


Siamangs inhabit the tropical forests in Malaysia, Thailand, and Sumatra.


A typical siamang diet consists of leaves, fruit, some insects, and small vertebrates. About half of their diet is purely leaves, making them much more folivorous than other gibbons. Since they are also frugivorous, siamangs will disperse seeds through their feces, which helps support forest regeneration. On average, siamangs will spend 80 percent of their waking hours feeding.


The average adult siamang is 2.5 to 3 feet long and weighs 20 to 28 pounds. Both males and females are covered in black hair except for their throat sacs which are hairless. They have long arms which they use to carry them swiftly through the trees, as brachiation is their primary mode of locomotion.