Siamang

Siamang — The Siamang (Symphalangus syndactylus) is a tailless, arboreal, black furred gibbon native to the forests of Malaysia, Thailand, and Sumatra. The largest of the lesser apes, the siamang can be twice the size of other gibbons, reaching 1 m in height, and weighing up to 23 kg. The Siamang is the only species in the genus Symphalangus.

The Siamang is distinctive for two reasons. The first is that two fingers on each hand are fused together (hence the name “syndactylus”). The second is the large “gular sac” (found in both male and female of the species), which is a throat pouch that can be inflated to the size of its head, allowing the Siamang to make loud resonating calls or songs.

There may be two subspecies of the Siamang. If so, they are the nominate Sumatran Siamang (S. s. syndactylus) and the Malaysian Siamang (S. s. continentis, in peninsular Malaysia). Otherwise, the Malaysian individuals are only a population. The Siamang is the only gibbon which occurs sympatrically with other gibbons; its two ranges are entirely within the combined ranges of the Agile Gibbon and the Lar Gibbon.

The Siamang can live up to 30+ years in captivity.

While the illegal pet trade takes a toll on wild populations, the principal threat to Siamang is habitat loss in both Malaysia and Sumatra. Palm oil production is clearing large swathes of forest, reducing Siamang habitat, along with other species such as the Sumatran Tiger.

The Siamang inhabits the forest remnants of Sumatra Island and the Malay Peninsula, and are widely distributed from lowland forest to montane forest. The Siamang lives in groups of up to 6 individuals (4 individuals on average) with a home range 23 hectares on average. The Siamang’s melodious choir singing breaks the forest’s silence in the early morning after the Agile Gibbon or Lar Gibbon’s calls. The Siamang in Sumatra and the Malay Peninsula are similar in appearance, but there are some differences between Siamang in Sumatra and the Malay Peninsula in their behaviour.

The Siamang tends to rest for more than 50% of its waking period (from dawn to dusk), followed by feeding, moving, foraging and social activities. It takes more rest during midday, taking time to groom each other or play. During resting time it usually uses a branch of a large tree lying on their back or on their stomach. Feeding behaviors, foraging, and moving are most often in the morning and after resting time.

In the dry season the length of the Siamang’s daily range is longer than in the rainy season. The Siamang in southern Sumatra undertakes less foraging than the Siamang in other places because it eats more fruit and therefore consumes more nutrition, which results in less time needed for looking for food. Sometimes the Siamang will spend all of the day in one big fruiting tree, just moving out when it wants to rest and then coming back again to fruiting trees.