Monkey Species · Borneo (coastal & riverine forest)
Proboscis Monkey
Big-nosed, pot-bellied and pop-eyed — Borneo's iconic riverine monkey.
By the WARN Research & Conservation TeamChecked against IUCN Red List & CITES sourcesLast updated
In brief
The Proboscis Monkey is Borneo's iconic riverine primate — males carry a huge pendulous nose and pot belly adapted to leaf-eating in mangrove and swamp forest. Its defining trait is aquatic agility combined with Endangered status driven by oil palm expansion and CITES Appendix I protection.
Proboscis Monkey: At a Glance
| Origin | Borneo (coastal & riverine forest) |
|---|---|
| Size | Large (males ~16–24 kg; females ~7–12 kg) |
| Typical weight | 7–24 kg (15–53 lb); males dramatically larger with enlarged nose and belly |
| Lifespan | Around 13–20 years (wild) |
| Coat & markings | Reddish-brown fur on back and shoulders with grey limbs, pale belly and pinkish face on adults. Infants are slate blue. Webbed fingers and toes support swimming between riverbank trees — among the most aquatic of all primates. |
| Temperament | Swamp-forest specialist, strong swimmer |
| Conservation note | Proboscis monkeys cannot be kept as pets — they are Endangered, CITES Appendix I listed and survive only in Borneo's riverine and mangrove forest. Captive breeding has had limited success; wild habitat protection in Indonesia, Malaysia and Brunei is the priority. Support WARN partner programmes and sustainable palm oil advocacy rather than any attempt to acquire these specialised forest monkeys. |
History & Origins
Proboscis monkeys — Nasalis larvatus — live exclusively on Borneo, from coastal mangroves to peat-swamp forest along rivers. Males' oversized noses amplify vocalisations and signal maturity to females. Multi-chambered stomachs ferment tough leaves similarly to ruminants. Oil palm plantations, logging and river pollution destroyed lowland habitat throughout the late 20th century. IUCN estimates populations fell more than 50% over three generations, with fewer than 7,000 mature individuals in fragmented river corridors. Ecotourism along the Kinabatangan and Sekonyer rivers funds local guards, but palm expansion remains the dominant threat.
Proboscis Monkey Fun Facts
- Proboscis monkeys are among the best primate swimmers — they can dive and cross rivers underwater.
- Male noses can exceed 10 cm in length and grow throughout adulthood.
- Proboscis monkeys are endemic to Borneo and found nowhere else in the wild.
- Their pot bellies house bacteria that ferment leaves other monkeys cannot digest.
Proboscis Monkey Common Health Issues
Conditions seen more often in this breed, and how owners and vets help manage them. This is general guidance, not veterinary advice — always speak to your vet.
Habitat loss (wild)
Drainage of peat swamp and mangrove for agriculture removes sleeping trees and food plants along rivers proboscis monkeys never leave.
Care: Protect riparian buffer zones and restore degraded mangrove where troops still persist in Sabah, Sarawak and Kalimantan.
Oil palm expansion
Large-scale conversion of lowland forest to monoculture palm isolates troops and increases human disturbance along river edges.
Care: Support certified sustainable palm oil policies and land-use planning that excludes primate corridors from new concessions.
River pollution
Agricultural runoff, mining sediment and untreated sewage degrade water quality where proboscis monkeys swim and forage.
Care: Fund watershed protection and community monitoring on rivers such as the Kinabatangan and Sekonyer.
Monkeys belong in the wild
Monkeys are intelligent, social primates — not pets. The illegal pet trade and habitat loss threaten species from marmosets to macaques. WARN funds anti-trafficking and habitat work for primates in our partner countries.
