Siamang

Presentation

The siamang (Symphalangus syndactylus) is a large gibbon native to the tropical forests of Sumatra and the Malay Peninsula. It is distinguished by its throat sac, an expandable pouch of skin beneath the throat that amplifies its calls. An arboreal species, it moves by brachiation, swinging from branch to branch using its long arms. Siamangs live in monogamous pairs with their offspring, forming stable family units. It is the largest member of the gibbon family, noticeably bulkier than its cousins in the genus Hylobates. Its powerful and complex dawn calls serve to mark territory and strengthen the pair bond.

The siamang has dense black fur and a slender build adapted to arboreal life. Its arms are proportionally longer than those of other gibbons, giving it an impressive wingspan. The throat sac, which is particularly well developed, can inflate to the size of its head during vocalizations. The second and third toes of its feet are partially fused, a trait that inspired its scientific name 'syndactylus'.

Characteristics

Indicative values: they vary by subspecies, sex and region.

Habitat and distribution

The siamang inhabits primary and secondary tropical rainforests, from lowland areas to medium-altitude mountainous zones. It favors dense and continuous canopies that allow it to move without descending to the ground. The availability of foliage and fruits influences the size of its territory.

Behaviour

The siamang is diurnal and strictly arboreal, rarely coming to the ground. It lives in small territorial family groups, defended by loud vocalizations audible over several kilometers. Pairs sing in duet at dawn, a practice that strengthens the pair bond and signals territory occupation to neighboring groups. The male actively participates in parental care, sometimes carrying the young on his back during the second year of life.

Reproduction

The female gives birth to a single infant after a gestation of approximately seven to eight months. The young remains dependent on its mother for the first two years, after which the father takes on part of its transportation and rearing. Sexual maturity is reached around six to eight years of age. The interval between successive births is typically two to three years, which limits the reproductive rate of the species.

Peculiarities

The siamang's throat sac is a unique anatomical feature among gibbons, allowing it to produce deep and resonant calls. It is the only gibbon to possess a partial fusion of two toes, a trait reflected in its scientific name. Its size and weight make it the largest member of the Hylobatidae family.

Threats and conservation

Deforestation linked to the expansion of oil palm plantations and logging represents the primary threat to the species. Poaching for the illegal pet trade also affects wild populations. Habitat fragmentation isolates family groups and reduces genetic diversity.

References

Profile updated 02 September 2026 · Reviewed by the TunisieVet editorial team.