biology for 11 February 2026

The Proboscis Monkey (Nasalis larvatus) is a large arboreal Old World monkey found only on the island of Borneo. It belongs to the genus Nasalis, named after the Latin word nasus meaning nose. The species is well known for the male’s long hanging nose and pot shaped belly. It lives mainly in mangrove, coastal and riverine forests and is one of the best swimming monkeys in Asia.

Proboscis Monkeys Features

Proboscis Monkeys show clear differences between males and females in size and nose shape.

• Large Nose: Male noses can grow over 10 cm long. The large nasal cavity helps produce loud honks and roars for attracting females and showing dominance.
• Colour: Fur is reddish-brown with lighter underparts. Babies are born with blue faces. 
• Adaptation: Partially webbed toes help them swim and cross rivers.
• Diet: They eat leaves, unripe fruits, seeds and flowers from over 55 plant species. 
• Groups: Groups usually have one male and several females, while larger bands can reach 60 individuals.

Also Read: Tropical Evergreen Forests

Proboscis Monkeys Distribution

Proboscis Monkeys are limited to Borneo. The island divided in three countries: 

• Indonesia: Found mainly in Kalimantan, including Tanjung Puting and Kutai National Parks. The largest populations remain here.
• Malaysia: Present in Sabah and Sarawak, especially along the Kinabatangan River and Bako National Park.
• Brunei: Found in small riverine and coastal forest areas with legal protection.

Also Read: Coniferous Forest

Proboscis Monkeys Conservation Status

The Proboscis Monkeys species is facing serious decline. The conservation efforts include:

• IUCN Status: Listed as Endangered.
• Population: More than 50% population decline in about 40 years. 
• CITES: Listed under Appendix I.
• Threats: Main threats include logging, oil palm plantations and hunting.
• Conservation: Found in protected areas across Brunei, Indonesia and Malaysia to support conservation efforts.