The Unusual Gibbon – Siamang

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Gibbons belong to the Hylobatidae family of “Lesser Apes”. The term “Lesser” means that they are smaller in size compared to the Great Apes.

Siamang, which can be found in the forest of Malaysia, Indonesia and Thailand, is the unusual one among gibbons. They are not just physically but also behaviorally unique from other gibbons. Let’s get to know them a little better!

Unique Physical Features

Siamang has longer, shaggy black furs than other gibbons. Nevertheless, 2 physical characteristics set the Siamang apart from other gibbons.

First, Siamang has 2 digits on each foot, the second and third toes, which are partially connected by a membrane.

Second, both males and females Siamang have a large gular sac. This grey or pink throat pouch can be inflated to the size of the Siamang’s head, allowing it to make loud, resonating calls.

Unique Behavioural Features

Siamang is the largest gibbon species. Usually, they are almost double the size of other gibbons. It can grow to about 75 to 90 cm tall and weight between 8 to 13 kg.

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Siamang is also the loudest gibbon species thanks to their large gular sac. Their calls can be heard up to 3.2 km away through a forest. They usually start their calling in the early morning and decrease through the day.

Siamang are monogamous creatures. This means they form lifelong pairings and stick together as a family. Their family typically comprises of 4 to 6 individuals, including a father, a mother and their children. They provide excellent maternal care to their newborn, who is normally quite tiny, and weaned when they are about a year old. Their children only leave the family when they reach the age of maturity, which is around 6 to 8 years old.

Siamang celebrates their marriage in their own special way. They sing and call together in a duet to announce their decision to start a family. Usually, it is louder when they are just getting married. After they become more established, the intensity of their duet decreased.

Threat to Siamang

According to IUCN Red List of Threaten Species, Siamang is categorised as endangered species based on the past projection of at least 50% population reduction over 3 generations, which is 45 years. Habitat loss is the major threat to Siamang. Again, congratulations to human! We are once again putting another species on the verge of extinction as a result of our urbanization and agricultural needs.