Animal Spotlight: Siamang Gibbon
Look! Up in the sky! It’s a bird! It’s a plane! It’s a Siamang!
Siamangs don’t fly, but sometimes they seem to. That’s because of the way they move through the treetops where they live. Siamangs (pronounced SEE-uh-mongs or SEE-uh-mahngs) brachiate to get around, and they are very good at it! They hang by their arms and swing from one branch to the next to get where they want to go. It’s like swinging on “monkey bars” on a playground. When a Siamang is moving rapidly through the treetops, it will let go of one branch and “fly” through the air like an acrobat before grasping the next branch. Siamangs can also push off with their legs and jump as far as 30 feet through the air to get from one tree to another. So, Siamangs cannot fly, strictly speaking, but if you’re lucky, you could see one seeming to fly through the air, especially in their planned habitat at the Reid Park Zoo expansion.
Siamangs have long arms and shorter legs. Their bodies are covered by black fur that is relatively long and shaggy. Siamangs have prominent brow ridges, and their faces have forward-facing eyes, flat noses, and relatively little fur. Adults are about two and a half to three feet long from the top of their heads to the end of their bodies, and they weigh about 25–30 pounds. Females and males are usually about the same size. They are primates, the evolutionary branch of mammals that includes humans, apes, monkeys, lemurs, and a few other species. They look a lot like monkeys, but are they monkeys? Nope — no tail. Almost all monkeys have tails, and apes do not; Siamangs don’t have tails. More specifically, these acrobatic apes are a type of gibbon, in fact, the largest type of gibbon.
Siamangs have some physical features that are very useful for brachiating, or swinging around with their l arms above their heads. Like other gibbons, Siamangs’ arms are very strong and extremely long — a Siamang’s arm span is usually about two and a half times the length of its body! (If your arms were that long compared with your body, they would stretch 10 to 15 feet from fingertip to fingertip!) Anyway, Siamangs’ thumbs are unusual, too. They are much shorter than the Siamang’s fingers and they are located higher on the wrist than other primates’ thumbs. Because of this, a Siamang’s hand looks more like a hook than other primates’ hands. And Siamangs have very flexible shoulder joints. The combination of long, strong arms, hook-shaped hands, and very flexible shoulder joints allows a siamang to swing rapidly from handhold to handhold and tree to tree. An adult Siamang can move through the treetops at 35 miles per hour — about as fast as a tiger can sprint!
The amazing Siamangs heading our way are one big reason we are looking forward to the Reid Park Zoo expansion. But be prepared to look UP — they will have elaborate climbing and swinging equipment in their roomy habitat. But they have to come down to ground sometimes, don’t they?
On the occasions when Siamangs come down to the ground, they normally walk on just their hind legs, holding their extremely long arms in the air for balance and to keep them from dragging on the ground. But Siamangs are much slower and more vulnerable to predators on the ground, so they spend most of their time high in the treetops, where they can avoid and elude predators very well.
Question: What does a Siamang have in common with a green tree frog? Siamangs have another unusual physical feature that is unique among species of gibbons: inflatable throat sacs. Both female and male Siamangs have a sac of skin on the front of their throat that sits flat and barely visible at rest, but that the animal can inflate with air until the sac is the size of the animal’s head! The inflated throat sac gives extra resonance and volume to the Siamang’s unmistakable call, a combination of hooting similar to other gibbons and a rapid “barking” that sounds a bit like a dog. Siamangs use their calls to gather together members of their clan and to warn members of other clans not to intrude on their territory.
Siamangs live in family groups and generally mate for life — a given male and female Siamang normally stay together for years. Their offspring stay with them for 5–7 years, until they reach maturity. A Siamang infant clings to its mother and is mainly cared for by its mother for the first 8 months, but is cared for mainly by its father in its second year of life. Wildlife biologists estimate that Siamangs live for somewhere between 25 and 40 years in the wild, and longer than that in zoos, up to 44 years. Reid Park Zoo’s male Lar Gibbon — a species closely related to Siamangs — currently is 49 years old!
Siamangs are diurnal animals — awake during the day and asleep at night. They usually wake after sunrise, spend up to an hour emitting their characteristic call to announce their territory, and then spend several hours foraging for food. Siamangs eat mainly fruit and tender leaves of bamboo and other plants, along with some insects, eggs, and occasional small vertebrates. Foraging for food requires several hours of a Siamang’s day. By eating fruit and later defecating out the seeds, they’re helping to shape their environment by spreading seeds around their habitat. In the afternoons, they usually rest, groom themselves and each other, and travel to that night’s sleeping area. Instead of lying down on a bed of leaves or branches, they sleep sitting upright in trees.
The amazing Siamangs are one more reason we are looking forward to the Reid Park Zoo’s Pathway to Asia expansion!
Siamangs live in tropical forests in Asia. In the past, their range was wider, but now they are found only in the mountains of Malaysia and the nearby Indonesian island of Sumatra. Adult Siamangs really have no natural predators, but even so they are classified as Endangered by the International Union for Conservation of Nature because their number in the wild has been estimated to drop by half in less than 50 years. Threats to Siamangs in the wild come from humans, mainly from an illegal pet trade and destruction of their habitat. Clear-cutting and burning forest land, the Siamang’s natural habitat, in order to grow palm trees for palm oil is an especially common problem. You can help to protect these amazing animals by speaking out against illegal wildlife trading and by choosing products that use sustainable sources of palm oil. Oh, and you’ll be helping their conservation every time you visit them at the Reid Park Zoo. Spread the word!
Originally published at https://reidparkzooexpansion.org on May 18, 2021.