Size: This is the largest of all the gibbons. Length; 71-90 cm. Weight; 10-12 kg.

Habitat and Distribution: The Siamang is found in the lowland and hill forests of the Barisan Mountains of Sumatra (an island off Indonesia) and in the mountains of the Malay Peninsula, south of the Perak River.

Age: 25-30 years.

Groups and Breeding: They live in small groups of a mating pair and their offspring. Siamangs are extremely faithful; they are monogamous, take a great deal of time to select their mate and if their mate dies, will rarely choose another.

Females breed at around 6 years old. They will produce 1 young every 2-3 years after a gestation of around 230 days. The youngster will cling to the mother’s stomach for several months and will continue to be fed for the first 2 years of life.

Diet: Mainly leaves (around 45-50% of its diet) and fruit, but also insects, eggs and small vertebrates.

• Siamangs' arms can be up to 2.6 times their own body length. These enable them to swing distances of 8 to 10 metres.
• They have an extremely loud call which can be heard up to 3 miles away. They produce this using their throat sacs which can beinflated to a size as big as a human head!
• Males assist in the parental care by helping to defend young, defend the territory, and sometimes by grooming, playing with, or carrying the young.
• This species is extremely territorial. They mark their territory by singing a duet often whilst the male swings through the trees.
• It usually takes a Siamang around 5 hours to eat enough, and they are only usually away from their sleeping tree and active for 8 to10 hours a day.
• Locals often kill mother Siamangs so that they can have the baby as a pet.
• Because they eat large proportions of fruit, this species is extremely important in seed dispersal and forest regeneration.
• The Latin name of the Siamang is Hylobates syndactylus; this comes from the fact that two fingers of each hand are fused together by webbing.