The call of the Siamang excels that of other gibbons because of the animal's sound-amplifying throat sac. The female emits a series of barks alternated with booms resonated in the vocal pouch, which she blows up like a balloon. It is quite a display of territory and power and can be heard for a considerable distance. Siamangs eat fruit, leaves, insects, nuts, small animals, birds and bird's eggs. In the zoo they are fed fruit, vegetables and monkey chow.
Siamangs bear one offspring after a seven- month gestation period.
At birth, the young are naked, and for the first few months, the baby clings to the mother's abdomen. She, in turn, keeps her legs partially raised to provide warmth and support. By the age of two, the baby is independent but still very much a part of the family. Sexual maturity is reached at about seven years of age. In the wild they live from 25 to 30 years.