# Siamang — Facts, Threats & Conservation

*Symphalangus syndactylus (Illiger, 1811) — family Hylobatidae*

> The siamang (Symphalangus syndactylus) is the largest gibbon, Endangered across Sumatra and the Malay Peninsula, known for paired morning duets amplified by an inflatable throat sac; oil palm, pulpwood and mining drive forest loss across its range.

**IUCN status:** Endangered — loud duets and throat sacs on forests being cleared for plantations  ·  **WARN range:** Sumatra, Malay Peninsula and southern Thailand

## Quick facts
| Fact | Value |
| --- | --- |
| Weight | Up to ~14 kg |
| Throat sac | Inflates to amplify duets |
| Social unit | Pair plus offspring |
| Movement | Brachiation through canopy |
| IUCN status | Endangered |
| Main threats | Oil palm, pulpwood, mining; pet trade |

## Scientific classification
- **Kingdom:** Animalia
- **Phylum:** Chordata
- **Class:** Mammalia
- **Order:** Primates
- **Family:** Hylobatidae
- **Genus:** Symphalangus
- **Species:** Symphalangus syndactylus

## Conservation status
- **Status:** Endangered
- **Population:** Declining; no precise global count
- **Trend:** Decreasing
- **Assessed:** 2020
- **CITES:** Appendix I
- Hill forest clearance for plantations and infrastructure fragments the continuous canopy required for brachiation and duet territories.

## Key facts: Siamang
- The siamang is the largest gibbon — roughly twice the mass of smaller Hylobates species.
- Pairs perform coordinated morning duets; an inflatable throat sac amplifies calls that carry over a kilometre.
- Siamangs are apes in the family Hylobatidae — tailless, brachiating canopy specialists, not monkeys.
- They are Endangered, with forest loss for oil palm, pulpwood and mining the dominant habitat pressure.
- The pet trade removes infants; plantation roads and logging edges increase hunting and capture.
- Continuous canopy is essential — siamangs are poor on the ground and cannot cross large cleared gaps.

## The gibbon that outsings the rest
All gibbons sing, but siamang duets are the loudest. The throat sac — a loose pouch of skin on the neck — inflates during vocalisation and acts as a resonating chamber, boosting low-frequency notes that travel through dense vegetation. A pair's duet follows a species-specific pattern: male and female phrases interlock, and neighbouring pairs answer, mapping territory acoustically each dawn.

The function is defence without contact. Gibbons eat ripe fruit and young leaves in the canopy; overlapping home ranges would mean competition. Song defines boundaries cheaper than fighting. Where forest is fragmented, duets reveal isolated pairs — still calling, but with no forest bridge to the next group.

## Ape anatomy in the canopy
Siamangs share the gibbon body plan: extraordinarily long arms, hook-shaped hands, reduced thumbs and no tail. Movement is brachiation — hand-over-hand swinging — with occasional bipedal walking along branches. The syndactyly that names the genus Symphalangus refers to partial fusion of toes two and three on each foot, a gibbon trait visible in the siamang's grip.

Family groups are small — typically a pair and one or two offspring. Development is slow; infants depend for years, which makes population recovery slow when adults are removed. Gibbons are among the primates most heavily represented in the illegal pet trade across Southeast Asia, because infants are small and docile before trauma accumulates.

## Oil palm, pulpwood and the Endangered listing
Sumatra has lost a large fraction of its primary forest in two decades, with oil palm and pulpwood plantations the main drivers on lowland and hill land. The Malay Peninsula shows the same pattern at smaller scale but higher fragmentation. Siamangs need hill forest with fruiting trees and connected canopy; plantations provide none of that.

Mining — tin, bauxite and coal depending on region — adds haul roads and clearance patches through remaining forest. Wildlife trade moves captured gibbons through markets for pets and entertainment. The Endangered listing reflects range-wide decline, not a single province. Protected areas help where they exist and are enforced, but gibbon density in oil-palm-dominated landscapes is effectively zero.

## Where siamangs sit among primates
Gibbons are the small apes — Hylobatidae — distinct from great apes and from monkeys. The siamang is their largest member, occupying Sundaland hill forest while smaller gibbons share the same forests or adjacent ranges. WARN's primate type pages group apes, monkeys and lemurs for identification context; siamangs belong in the ape branch as brachiating fruit-eaters whose conservation is inseparable from forest remaining on the ground.

Duets make siamangs audible to anyone near hill forest at dawn. Silence where calls were once routine is often the first sign that a population has been trapped, traded or starved of canopy — not a subtle ecological shift but an absence people can hear.

## What WARN does
WARN publishes free, sourced species education for primates lost to forest conversion and trade. Siamang duets are still heard in remnant hill forest on Sumatra, but oil palm and pulpwood expansion maps directly onto Endangered status — the biology requires canopy the plantation economy removes.

If this guide helps you understand wildlife and the pressures it faces, a gift to WARN supports habitat protection and free public education in our partner countries.

## Frequently asked questions: Siamang
### How big is a siamang?
Up to about 14 kg and roughly a metre tall — the largest gibbon, nearly twice the size of a white-handed gibbon.

### What is the siamang's throat sac for?
It inflates during duets and acts as a resonating chamber, amplifying calls so they carry more than a kilometre through forest.

### Is a siamang a monkey?
No. It is an ape — a gibbon in the family Hylobatidae. Gibbons are tailless and brachiate through the canopy.

### Why are siamangs endangered?
Forest loss for oil palm, pulpwood and mining across Sumatra and the Malay Peninsula, plus capture for the pet trade. They need continuous canopy and reproduce slowly.

### Where do siamangs live?
Hill and montane forest on Sumatra, the Malay Peninsula and southern Thailand. They are absent from pure plantation landscape.

### How do siamang duets work?
Bonded pairs sing coordinated morning duets — alternating male and female phrases — to advertise territory. Neighbouring pairs answer, mapping groups acoustically.

### Are siamangs dangerous?
Siamangs are domesticated animals and are not dangerous to people in the wild-predator sense. The siamang (Symphalangus syndactylus) is the largest gibbon, Endangered across Sumatra and the Malay Peninsula, known for paired morning duets amplified by an inflatable throat sac; oil palm, pulpwood and mining drive forest loss across its range. Usual risks are husbandry and handling, not unprovoked attacks.

### How long do siamangs live?
A precise wild lifespan for siamangs is not firmly established in the sources cited on this guide. The siamang (Symphalangus syndactylus) is the largest gibbon, Endangered across Sumatra and the Malay Peninsula, known for paired morning duets amplified by an inflatable throat sac; oil palm, pulpwood and mining drive forest loss across its range. Where longevity figures appear in the literature they vary by region, sex and whether animals are wild or captive.

### What do siamangs eat?
Gibbons eat ripe fruit and young leaves in the canopy; overlapping home ranges would mean competition. The siamang (Symphalangus syndactylus) is the largest gibbon, Endangered across Sumatra and the Malay Peninsula, known for paired morning duets amplified by an inflatable throat sac; oil palm, pulpwood and mining drive forest loss across its range.

## Sources
- [IUCN Red List — Symphalangus syndactylus](https://www.iucnredlist.org/species/39779/17967894)
- [Gibbon Network — siamang](https://www.gibbonnetwork.org/)
- [CITES Appendices](https://cites.org/eng/app/appendices.php)

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Full guide: https://worldanimalrescuenetwork.org/wildlife-guides/siamang