The Siamang, also called Siamang Gibbon, is a gibbon native to the forests of Malaysia, southern Thailand and Indonesia (Sumatra). It is nearly double the height of other gibbons, reaching around a metre from head to toe without taking account of their extremely long arms. The scientific name "syndactylus" relates to them having two toes palmated (partly webbed) on each foot.
Adult male Siamangs (top and above left) are significantly larger than females (above centre). Both have a large, inflatable pouch at their neck to enhance their "singing".
They form permanent pair bonds and, unusually for primates, the father helps to raise the babies.
Like all Gibbons, they are apes rather than monkeys and so closely related to humans.
Destruction of forest for palm oil plantations has significantly reduced their population (together with that of other forest animals).