The siamang (Symphalangus syndactylus) is an arboreal, black-furred gibbon native to the forests of Indonesia, Malaysia, and Thailand. The largest of the gibbons, the siamang can be twice the size of other gibbons, reaching 1 m (3.3 ft) in height, and weighing up to 14 kg (31 lb). It is the only species in the genus Symphalangus. Two features distinguish the siamang from other gibbons. First, two digits on each foot the second and third toes are partially joined by a membrane, hence the specific name syndactylus, from the Ancient Greek, sun-, "with", daktulos, "finger". Second, a large gular sac (throat pouch), found in both males and females of the species, can be inflated to the size of the siamang's head, allowing it to make loud, resonating calls or songs. Two subspecies of the siamang may exist. If so, they are the nominate Sumatran siamang (S. s. syndactylus) and the Malaysian siamang (S. s. continentis, in Malay peninsula). Otherwise, the Malaysian individuals are only a population. The siamang 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 to around 40 years in captivity. While the illegal pet trade takes a toll on wild populations, the principal threat to the siamang is habitat loss in both Indonesia and Malaysia. The palm oil production industry is clearing large swaths of forest, reducing the habitat of the siamang, along with those of other species, such as the Sumatran tiger. The siamang has long, dense, shaggy hair, which is the darkest shade of all gibbons. The ape's long, gangling arms are longer than its legs. The average length of a siamang is 90 cm; the largest they have ever grown is 150 cm. The face of this large gibbon is mostly hairless, apart from a thin mustache. The siamang inhabits the forest remnants of Sumatra Island and the Malay Peninsula, and is widely distributed from lowland forest to mountain forest even rainforest and can be found at altitudes up to 3800 m. It lives in groups of up to six individuals (four individuals on average) with an average home range of 23 hectares. Their day ranges are substantially smaller than those of sympatric Hylobates species, often less than 1 km. The siamang's melodious singing breaks the forest's silence in the early morning after the agile gibbons' or lar gibbons' calls.