Siamangs are often mistaken for monkeys, but they actually belong to a family of smaller apes called gibbons that are native to Southeast Asia. One way to distinguish monkeys from apes is to look for a tail. Monkeys almost always have tails while apes do not. Siamangs swing through the rainforest canopy using their extremely long arms in a form of locomotion called brachiation. They can travel up to 10 feet in a single swing at speeds approaching 35 mph. They can leap up to 30 feet.
Siamangs are famous for their booming calls that can be heard more than two miles away. Siamang concerts start in the morning and can last 30 minutes. Songs start slow and increase in intensity. These are often duets between a paired male and female, although offspring may join in. Males often accompany their vocalizing with acrobatics. The calls are used to claim territory and put neighboring siamangs on notice. Siamangs have large air sacs in their throats that inflate with each call, acting as resonators.
Siamangs live in family groups of 4 to 6 individuals with a mother, father, and their offspring. Females may give birth every 2 to 3 years. After a 7.5-month pregnancy, a single infant is born. For the first few months, the baby clings to its mother’s stomach as she forages. By the age of one year, the father takes over parental care, grooming, playing with, and carrying the baby. Offspring live with their parents for 5 to 7 years before leaving to start their own families. Siamangs spend most of their time in trees 80 to 100 feet up in the canopy. They are active 8 to 10 hours a day foraging for food, resting, and grooming. Siamang populations have decreased by 50 percent over the past 50 years. An estimated 80 percent of their habitat has been cleared for coffee, oil palm, and rubber tree plantations, as well as logging, and mining. Forests have also been lost due to wildfires. In addition, siamangs are captured for the illegal pet trade.
Siamangs are listed as Endangered by the International Union for Conservation of Nature (IUCN). This is mainly due to capture for the illegal pet trade as well as deforestation, which is largely a result of the palm oil industry.
Siamangs inhabit the tropical forests in Malaysia, Thailand, and Sumatra.
A typical siamang diet consists of fruit and leaves, with some insects, small vertebrates, and bird eggs. Siamangs play an important role in their ecosystem as seed dispersers, which helps forests to regenerate.
The average adult siamang is 2.5 to 3 feet long and weighs 17 to 28 pounds. Lifespan is estimated at 30–40 years.