Pictures of siamangs (Hylobates syndactylus), native to mainland Malaysia and Sumatra. They live in evergreen tropical rainforests and mountain regions and spend most of their time in trees about 30 feet up.
Mostly they eat leaves and fruit, but occasionally they'll eat flowers, buds, and insects. The species is currently endangered due to humans encroaching on their habitat.
They weigh 22-32 pounds and have an arm span of 4-5 feet. They live 25-35 years. After they get pregnant, they give birth to a single baby in 189-235 days.
Siamangs swing from branches and vines using an arm-over-arm swing--a method of movement called brachiation. Their arms are longer than their legs, and each swing can cover about ten feet. When they walk, they hold their arms in the air for balance.
Siamangs are a type of gibbon, which is a lesser ape. They're monogamous, and each mating pair performs a 20-25 minute unique song--a duet, in fact, alternating between the male and female parts. When they sing, their large throat sac inflates to amplify their calls. The calls, which can be heard over a mile away, establish a siamang family's territory. The male and female sing duets that strengthen the bond between them. Just two animals calling can sound like many more. They use social grooming to maintain the bond between the pair.
Siamangs live in Sumatra and the Malay Peninsula in Southeast Asia.