All profits made at WildlifeoPedia are donated to charities protecting wildlife. You can help nature by checking out what you can do, here! 🐨🦤🌿🏞️

Proboscis Monkey Profile

Photo Credit: Kjersti Joergensen (Source: One Earth.org)

Source: Dimensions.com

"My nose may raise a smile, but my life depends on the mangroves."

Estimated Population: ~ 7.000 (2025)

✦ A.I-Generated Summary ▼

The proboscis monkey (Nasalis larvatus) is a striking primate native to Borneo, instantly recognized for the large nose of adult males. With reddish-brown coats, long tails, and partially webbed hands and feet, they are perfectly adapted to mangrove forests, riverbanks, and swampy habitats, where they are excellent swimmers and agile climbers.

Key Points:

Diet & Lifestyle: Proboscis monkeys are primarily folivores, feeding on young leaves, unripe fruits, seeds, and flowers. Their multi-chambered stomachs ferment tough plant material, but they are sensitive to dietary changes and human-provided foods.
Reproduction: Gestation lasts about 166 days, usually producing one infant. Young are weaned around 1 year, though they may remain close to mothers longer, with females maturing at ~5 years and males at 6–7 years.
Behavior & Social Structure: Living in harems led by a dominant male or in bachelor groups, they communicate using honks, growls, and other vocalizations amplified by the males’ large noses. Their leaping and swimming abilities make them well-adapted to both trees and rivers.
Threats & Conservation: Endangered due to habitat loss from palm oil plantations, logging, and human settlement, as well as hunting and population fragmentation. Conservation focuses on protecting mangrove forests, ecotourism, and awareness campaigns to maintain genetic diversity and habitat integrity. Help Protect The Proboscis Monkey.

Final Note:
Proboscis monkeys are one of the most unique primates on Earth, with their huge noses, swimming skills, and arboreal agility making them iconic inhabitants of Borneo’s wetlands. Protecting their mangrove and swamp habitats ensures these extraordinary monkeys continue to thrive and maintain the delicate balance of their ecosystem.

PROBOSCIS MONKEY VITAL SIGNS BAR,

For a quick overview of the proboscis monkey...

Learn How To Help At Rain Forest Rescue ➤

Return To Center of The WildlifeoProfiles

24. Proboscis Monkey Profile

Common Name: Proboscis Monkey
Scientific Name: Nasalis larvatus
Genus: Nasalis
Family: Cercopithecidae
Order: Primates
Class: Mammalia
Phylum: Chordata
Conservation Status: Endangered (IUCN)

Physical Description

The proboscis monkey is one of the most distinctive primates in the world, instantly recognized by the large, pendulous nose of adult males. While the exact purpose of this feature is debated, it is believed to play a role in attracting mates and amplifying vocalizations. Their reddish-brown coats fade to gray on the limbs and tail, with lighter underparts. Males are much larger than females and possess longer noses.

Length: 60 – 76 cm (body)
Tail: 55 – 75 cm
Weight: Males 16 – 22 kg; Females 7 – 12 kg

They are semi-aquatic and excellent swimmers, often found near mangrove forests, riverbanks, and swamps in Borneo.

Diet

Proboscis monkeys are primarily folivores but have a varied diet depending on the season.

Leaves: Their main food source, especially young leaves.
Fruits: Particularly unripe fruits, which are easier for their complex stomachs to digest.
Seeds & Flowers: Supplements to their leafy diet.

Their multi-chambered stomachs, similar to those of cows, help them ferment tough plant material. However, they are sensitive to changes in diet and cannot digest sugary or human-provided foods without risk.

Speed & Agility

Despite their bulky appearance, proboscis monkeys are agile in trees and skilled swimmers.

Swimming: Strong, natural swimmers, often crossing rivers. They use a dog-paddle style and can even swim underwater.
Leaping Distance: Up to 9 m (30 ft) in a single leap between trees.
Agility: They move nimbly in mangrove forests and swampy habitats, adapting to both arboreal and aquatic environments.

Social Structure

Proboscis monkeys live in groups called harems, usually consisting of one dominant male, several females, and their offspring. Bachelor groups of males are also common. They communicate with loud honks, honks, and growls, with the large nose of males amplifying these sounds.

Fun Fact: The male’s “honking” calls not only deter rivals but also reassure the group while traveling.

Reproduction

Like many primates, proboscis monkeys reproduce slowly compared to smaller monkeys.

Gestation Period: ~166 days (about 5.5 months)
Offspring: Usually one infant
Weaning: Around 1 year, though young may stay close to mothers for longer
Maturity: Females ~5 years, Males ~6–7 years

Infants are born with dark fur and blue faces, which gradually lighten as they grow.

Did You Know?

Natural Swimmers: They have partially webbed feet and hands, helping them swim efficiently.
“Dutch Monkeys”: Locals once nicknamed them this, mocking Dutch colonists whose long noses and reddish hair resembled the monkeys.
Nose Purpose: Bigger noses may help resonate calls through the dense forest, signaling strength to females and deterring rivals. This is also exactly why only the males have the ''really'' big noses.
Protected Range: They are endemic to Borneo—found nowhere else on Earth.

Role in the Ecosystem

Proboscis monkeys are important seed dispersers, aiding in the regeneration of mangrove and swamp forests. By feeding on unripe fruits and seeds, they maintain plant diversity and support the health of fragile wetland ecosystems.

Why They’re At Risk

Endangered (IUCN Red List)
Their population has declined drastically due to:

Habitat Loss: Large-scale destruction of mangroves and peat swamp forests for palm oil, logging, and human settlement.
Hunting: Once hunted for meat and traditional medicine.
Fragmentation: Small, isolated groups of individuals face extreme difficulties maintaining genetic diversity.

Conservation efforts focus on habitat protection, ecotourism initiatives, and awareness campaigns to prevent further decline of this uniquely charismatic primate.

How You Can Help: Support sustainable palm oil, back organizations protecting Borneo’s forests, and spread awareness about the fragile future of this species - even within the neighbourhood.