Siamang

Siamangs mostly eat fruits and tender new leaves, eating more leafy greens than other species of gibbons. Sometimes, they also prey on insects, bird eggs, and small animals as part of their diet.

At the Zoo, siamangs are offered a variety of leafy greens, vegetables, fruits, and a specially formulated leaf-eater biscuit.

This species is found in Indonesia, Malaysia, and a small area of southern Thailand.

Siamangs live in mountain rainforests and monsoon forests.

Predators are not well known, but young siamangs may be vulnerable to large birds of prey or snakes.

Siamang populations have decreased by 50% over the last 40 years because of the pet trade and habitat loss. Unsustainable timber practices are a significant threat to siamang survival. When trees are cut down for timber or land is changed for farming, especially for palm oil, it destroys the habitats where siamang live. The illegal pet trade is a large problem in Southeast Asia, and adult siamangs are sometimes killed so poachers can sell their babies.

Siamangs have long, shaggy black fur with gray fur around their chins and mouths. Both males and females have a unique throat sac that can be light gray or pinkish, which they can puff up to the size of a grapefruit. These throat sacs serve as sound boxes, amplifying their loud vocalizations.

With arms that are longer than their legs, siamangs move through the rainforest by swinging hand-over-hand among the branches. This movement, known as "brachiating," is similar to how humans move across a jungle gym. Siamangs do not have a clavicle (collarbone), which allows their arms to move in a complete circle. Their extra-long arms help them cover up to 10 feet in a single swing. They also move by walking along branches with their arms outstretched to help them keep their balance.

Their hands have four long fingers and a smaller opposable thumb. They also have webbed second and third toes and an opposable big toe. This unique anatomy helps siamangs grab and carry things using both their hands and feet.

Siamang pairs usually stay together for life. Their family groups typically include one male, one female, and two to three young ones that are close in age. Female siamangs have a baby every two to three years, after being pregnant for about 230 days. Most of the time, babies are born between December and February. When they are born, siamangs are mostly hairless except for a small tuft of hair on their heads. For the first three to four months, newborns cling to their mothers food and care. Young siamangs are weaned, or transition to solid food, between 18 and 24 months old. During this time, the father takes a more active role in caring for the baby.

After spending five to seven years with their family, the young siamangs leave to start their own families, calling out to find mates as they grow independent. Siamangs usually reach maturity by the ages of six or seven, and females can have up to ten babies in their lifetime.

Vocalization is a key part of how siamangs communicate with each other. They make two main sounds using their throat sac: a deep boom with their mouths closed, and a loud "wow" with their mouths open. The deep boom can be heard over longer distances in the forest compared to the higher-pitched "wow." Siamang calls usually start off slow and then get faster, often with some acrobatic moves. Usually, an adult female initiates a territorial call in the morning, which others in the family join in on. This call can go on for up to 30 minutes and helps communicate territory boundaries to nearby siamang families. Male and female pairs also perform special duets together.

In addition to their vocal sounds, siamangs communicate through touch, like grooming each other, and they also use visual signals such as facial expressions and body movements.

Siamangs sleep during the day by hanging upright on branches with their arms folded and their heads tucked between their knees. This is different from great apes, which build nests or platforms to sleep on. When the sun rises, Siamang families wake up and often go to the bathroom together. Afterward, they enjoy their morning "concert," where they make sounds to communicate. Once they finish their songs, they search for food, which usually takes about 3 to 4 hours. Siamangs spend more than half of their time resting between dusk and dawn. At night, they all climb up to the highest branches of a single tree to sleep safely together.