Siamangs are the largest species in the gibbon family. They weigh 18-29 pounds and reach approximately 2½ to 3 feet tall. They have an arm spread of as much as 5 feet, allowing them to be spectacular brachiators (arm-over-arm swinging used for locomotion).
Siamangs are arboreal (tree-dwelling) primates that consume leaves fruits, flowers and insects from the upper canopy of mountainous forest regions. They live in monogamous family groups where the adult males and females are bonded for life. Normally a single offspring is born to each family, and it is initially cared for by the mother. Adult males take over raising the young by two years of age, teaching them the necessary socialization and locomotive skills.
One feature that distinguishes siamangs from other primates is the duet song that marks their territory with sound. It consists of loud booms and barks, amplified by resonating sounds across their inflated throat sacs. This vocalization can be heard several miles away.