Siamang: Facts You Won’t Believe!

Siamang facts like they are larger than other gibbons are interesting.

The siamang is a black-furred, arboreal gibbon that is native to the forests of Thailand, Malaysia, and Indonesia. The only species in the Symphalangus species, it is the largest of the gibbons and can weigh about twice the size of any other gibbon. They can weigh about 14 kg and reach 1 m in height.

There are two features distinguishing the siamang from any other gibbon. The first one is having two digits on each foot, webbing between their second and third toes, partially connected by a membrane. It is also the reason why it got its specific name ‘syndactylus’ from Ancient Greek. The second feature is a large throat sac or throat pouch that can be found in males as well as females siamangs. This sac can inflate and reach the size of the siamang’s head. This also helps the species make loud and resonating songs or calls.

There are two subspecies of the Symphalangus syndactylus - nominate Sumatra siamang and the Malaysian peninsula. Even though they can occur sympatrically with other species of gibbons, their two ranges have been entirely within the ranges of the lar gibbon and the agile gibbon.

The illegal pet trade of the Symphalangus syndactylus or siamang has taken a toll on the wild population. It is also the principal threat to the species resulting in habitat loss in Malaysia as well as Indonesia. The palm oil production industry has been clearing large swaths of forest which have reduced the habitat of siamang and other species like the Sumatran tiger. Read on for more on the endangered siamangs.

You may also enjoy the fact files on the indri and uakari from Kidadl.

Siamang Facts

Fact File

What do they prey on?

Insects, leaves, and fruits

What do they eat?


Average litter size?


How much do they weigh?

23 lb (10 kg)

How long are they?

24-36 in (60-91 cm)

How tall are they?

29-35 in (74-89 cm)

What do they look like?


Skin Type


What are their main threats?


What is their conservation status?


Where you'll find them

Rain forests


Southeast Asia





Scientific Name

Symphalangus syndactylus





Siamang Interesting Facts

What type of animal is a siamang?

Also known as the siamang Symphalangus syndactylus (scientific name), the siamangs from the class Mammalia, are the arboreal apes from the gibbon family that can be found in the forests of Malaya and Sumatra. Even though these order primates might look like other gibbons, they are more robust than any of them.

In order to distinguish this gibbon species from other gibbons, you need to check the dilatable hairless air sac on their throat or the webbing between their second and third toe. The air sac is used by the gibbons for producing a booming and resonant call. Also, they have completely black, shaggy fur. Just like the gibbon, this species is arboreal, diurnal, and moves through brachiation (swinging from its arms to move from one point to another).

This gibbon species mainly feeds on fruit and lives either alone or in small groups. They have a gestation period of 230 days and their births are usually single. Up until 2005, they were classified in the Hylobates genus as H. syndactylus with other gibbons. Now, they are the only members of the Symphalangus genus.

What class of animal does a siamang belong to?

Siamangs, from the genus Symphalangus, the arboreal inhabitants of the Sumatran monsoon and rain forests and the Malay Peninsula, belong to the Mammalia class. Because of habitat loss and the illegal pet trade, this species of primates, both males and females, are currently endangered.

How many siamangs are there in the world?

There are less than 200,000 siamangs left in the world.

Where does a siamang live?

These great apes mainly live in the mountains of Sumatran monsoon and rainforests and the Malay Peninsula. They have a range of 0.24 sq km or 60 acres, which is relatively small. They travel about half of this range daily which is also the reason why they need to eat a bigger percentage of their common food - leaves.

What is a siamang's habitat?

A Siamang ape habitat is a rainforest that is known to be a warm, wet, and lush habitat. Most of the trees in the rainforest are very tall as they have to compete for sunlight.

Who do siamangs live with?

A siamang gibbon can live alone or choose to be in a family group. The pairs stay together for life which makes them one of the small number of primates that do this. When it comes to family, siamang gibbons stick together. Their family group includes one adult male and female and two to three offspring that are two to three years apart.

They defend their range as a group territory. Since their loud calls lead to the creation of more space between groups and very rare confrontations, determining boundaries for these great apes can be very hard.

How long does a siamang live?

The average lifespan of a siamang gibbon is 40 years.

How do they reproduce?

The gestation period for a siamang from Sumatra and Malay is about seven and a half months. Every two to three years, the female gives birth to a single offspring who clings to the bellies of their mother constantly for the first few months. Once the infant is about two years old, their father might start carrying them during the time of weaning. Siamangs become mature at the age of about seven and the female doesn’t give birth to more than 10 offspring in her lifetime.

What is their conservation status?

Currently, since their population is decreasing at an alarming rate, the siamang is listed as Endangered species.

Siamang Fun Facts

What do siamangs look like?

All the males, females, and infant siamangs have shaggy and long black coats with pale hairs around their chin and mouth. The males also have a longish hair tuft in their genital region. The siamang monkey is known for its pinkish or grayish throat sac that inflates during vocalizations. It can become as big as a grapefruit. Their feet and hands are broader and their arms are longer than the white-cheeked gibbon’s leg. The length of their arms can be two and a half times the size of their body. Another feature that differentiates them from other gibbons is the webbing between the second and third toes. Both males and females have opposable thumbs, long canine teeth, and a great toe deeply separated from other toes. However, just like other primates, they have a highly developed brain.

Siamangs are usually bipedal on the ground which means that they move on their two legs. When they are in the trees, they move by hand-over-hand swinging and acrobatic movement through the branches. This process is known as brachiating. If they move slowly while grabbing one branch and releasing it before they grab the next, they will swing like a pendulum and their body will be projected freely through the air. Flights of 15-32 ft or 8-10 m have already been witnessed.

Siamangs are very territorial.

How cute are they?

Some might consider siamangs cute animals, especially the infants.

How do they communicate?

Communication through vocalization is a main social investment for siamangs. Both male and female siamangs call together. While vocalizing, they can produce two different types of siamang sound using their throat sac - a loud ‘wow’ (when they sing into the sac with their mouth opened) and a deep boom (when they sing into the sac with their mouth closed). The high-pitched wow sound doesn’t carry the sound farther in the forest than the deep boom sound.

Siamangs are also known to make a vocalization that sounds like a bark. They will repeat the set calls one after another by starting off slowly and then increasing in speed. The siamang gibbon call is usually accompanied by behavioral acrobatics.

How big is a siamang?

Compared to other gibbons, siamangs are slightly bigger. They are 29-35 in or 74-89 cm tall.

How fast can a siamang run?

Siamangs don’t run. They use their arms for swinging from one branch to another and can reach a speed of up to 56 kmph.

How much does a siamang weigh?

The average weight of a siamang is 10 kg or 23 lb.

What are their male and female names of the species?

There are no separate names for male and female siamangs.

What would you call a baby siamang?

A baby siamang is called an infant as with other primates.

What do they eat?

The primary food of a siamang diet is new leaves and fruit. In fact, their diet includes a larger leafy matter proportion than any other gibbon. From time to time, they can also eat a small amount of bird eggs, small vertebrates, and insects. Siamangs spend 45% of their eating time on leaves and 44% on eating fruit. During feeding time, they suspend themself with one arm. When they are kept in captivity, their diet might be a mixture of primate chow, cabbage, kale, carrots, green beans, sweet potatoes, oranges, bananas, and apples multiple times a day. How much they eat and what their diet is depends on the ages and makeup of the group.

Are they aggressive?

Even though siamangs can be territorial of their area, they express it in a non-violent fashion. This is different from other apes who are violent or physically aggressive towards intruders. However, siamangs can turn to slapping and biting the intruders entering their territory, but this is very rare.

Would they make a good pet?

No, siamangs are territorial. They do not make a good pet. In fact, the illegal pet trade is what has decreased their wild population.

Did you know...

Siamangs live in a flexible social group. Just like the white-cheeked gibbon, their group mainly comprises an adult pair and an offspring. In most gibbon species, the male exhibits infant care. During the second year of their infant’s life, they are the ones who carry them the majority of the time.

This species is also noted for having more contact and coordination during daily activities, especially concerning their territory. The family becomes a unit to forage for food. They are fiercely territorial and use daily siamang singing rituals for defending their territory. Boundary disputes are very rare and if they do occur, it involves high-speed chase in the forest involving a lot of biting and slapping.

All siamang monkeys have a daily routine or pattern. They get up at sunrise, perform their morning singing ritual, and set out to search for food. In most cases, it takes them about five hours to eat their fill. Once they have completed their activities for 8-10 hours, they find a place to sleep or just rest.

Just like most primates, grooming is among the most important social activities for a siamang. An adult siamang apes grooms themselves for about 15 minutes every day. For them, grooming is a sign of dominance. If they are more dominant, they will receive more grooming than they give. The male siamang apes will groom the female and the infant males. During the breeding season, their focus will be more on the female siamang.

What is the main mode of movement for siamangs?

There are four locomotion patterns used by the siamang living in Southeast Asia - brachiation, leaping, bipedalism, and climbing. Depending on the size of their arboreal supports and major behavioral activity, the pattern of the siamang locomotion can vary. For traveling while protecting their territory, they mainly use brachiation along large boughs. When they are moving while feeding, they climb on small branches. During feeding, the siamang uses seated postures on large supports and suspensory postures among small supports.

What do siamangs sound like?

The Siamang is the biggest of all the gibbon species living in Southeast Asia. Also, they are the only species in the Symphalangus apes species. They are more muscular and significantly heavier than other gibbons. One of the main characteristics that differentiate the Siamang from other gibbons is their large inflatable throat sac. The reason behind the inflation of the sac is amplifying their deep booming calls that can be heard from three kilometers away. Many times, duetting pairs from family groups use deep sounds along with occasional bitonal screams and high-pitch barking notes. Another difference between the siamang and other apes is that the former starts to sing at dawn. They tend to start singing bouts in the morning with their peak call activity between 9-10 am.

Here at Kidadl, we have carefully created lots of interesting family-friendly animal facts for everyone to discover! Learn more about some other mammals including chimpanzees, or emperor tamarins.

You can even occupy yourself at home by drawing one on our Siamang coloring pages.



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