This species has relatively long forearms which assist it in suspensory behavior. This species has throat sac located beneath the chin to help enhance the calls. The siamang lacks a tail, caudal vertebrae. The average body mass for an adult male siamang is around 10.9 kilograms, and for the female it is around 10.6 kilograms (Fleagle, 1988). The pelage color for both sexes is black. The throat sac has a pinkish or gray color to it.
The siamang is found in the countries of Indonesia and Malaysia. This species is found in semievergreen forests and tropical evergreen forests, and these are either of primary or secondary forest types.
The siamang is a frugivorous species, but will also consume immature leaves and insects. The siamang prefers to consume fruits high in sugar such as the fig (Ficus). This species consumes more leaves than other gibbons. This is an arboreal and a diurnal species. This species sleeps and rests in the emergent trees (Leighton, 1987).
The siamang is a true brachiator which means it moves by suspensory behavior (Fleagle, 1988). The siamang has a brachiation type where it slowly moves through the forest (Fleagle, 1988). This species also climbs when moving slowly and feeding (Fleagle, 1988). This species is also able to move for short distances by bipedalism (Fleagle, 1988).
duetting: These are vocalizations which occur between the breeding male and female, and is dominated by the female. This vocalization is important because it helps to maintain the pair bond between the breeding pair and also it helps to establish and maintain the territory.
social grooming: This is when one individual grooms another and is used to reinforce the bonds between individuals.