Siamang

Siamangs belong to a family of lesser apes called gibbons. Like other apes, they lack a tail and have opposable thumbs on their hands and feet. Their opposable toe is called a greater toe, which allows them to walk and balance along tree branches in the upper canopies. Siamangs are the largest of the gibbon species, weighing around 25 lbs. They stand between 2.5-3 feet tall with an arm span that can reach 2.5 times that of their height.

Siamangs have a thick black coat, with a shallow, hairless face. They are well known for their enlarged throat sac called a gular sac. The gular sac can inflate to be as large as a human head, and allows them to create a loud call that can be heard from miles away.

Siamangs are found in the mountainous regions of Southeast Asia. In particular, they live in the Barisan Mountains of Sumatra and the mountains of the Malay Peninsula. They inhabit rainforests and monsoon forests and stick to the mid-upper canopies.

Siamangs are considered omnivores, but mostly eat fruits, leaves, and berries. Figs are a favorite fruit of the siamangs, likely due to their abundance in Sumatra and Malaysia. On occasion, they will also eat small animals such as birds and small rodents, and opportunistically eggs and insects as well. Siamangs consume more leaves than any other gibbon species, and leaves can constitute just under 50% of their diet. It can take a siamang up to 5 hours a day to eat their fill.

Siamang are diurnal and stick to a fairly strict daily routine. Siamangs mate for life, and every morning in the early hours when they wake up, siamang pairs will perform their “songs”. These songs are calls they compose with each other during courtship. When lost, they can use the songs to communicate and find each other again. No two pairs sing the same songs. The rest of the day for a siamang consists of eating, grooming, and brachiating, a specialized way of swinging from tree branch to tree branch, before settling down in their resting spots to sleep. Because of their rigid lifestyle, they can become upset when anything in their routine changes. Siamangs will chase off any intruders to their territory by bellowing or screaming while running at them with their arms in the air.

Siamangs reach maturity at the age of 6 or 7, at which point they depart their family unity to find a partner. Once a pair has bonded and mated, they stay together for life. If one dies, the widowed gibbon does not take up a new mate and usually dies shortly after. Females give birth to a single offspring every 2-3 years. Their pregnancy lasts 7 months and mothers will continue to nurse their baby for the first 2 years of their lives. Males assist in caring for their young until they are around 3 years old, at which point the juvenile becomes more independent and starts wandering further away from their parents. Their basic family unit usually consists of a mated adult pair and 2 or 3 of their children who have not yet reached maturity. Each child is 2 to 3 years apart from each other.

Oakland Zoo has projects to help end the exotic pet trade and to curb palm oil production, both of which affect siamang in the wild. Here are some ways you can help too:

• Look for sustainable products, especially those that come from the rainforest, like coffee and chocolate. Look into shade grown varieties and companies that use sustainable palm oil or none at all.
• You can help stop the illegal pet trade by getting responsibly bred animals as pets and educating those around you about the plight of wild-caught exotic pets.