Proboscis monkey fact file Find out more about the monkey that sometimes has to move its nose to be able to eat...

31st August 2023

While beauty is in the eye of the beholder, there are some species out there who continue to be overlooked because… well, because of how they look.

A species unlikely to spring to mind when we think of a monkey is the Proboscis – though we believe this endangered creature deserves their own feature! Animal Friends Insurance has teamed up with World Land Trust to create this (fun!) fact file all about the Proboscis monkey.

Brace yourself, it’s about to get ‘ugly’!

What are they?

Mammals (more specifically, primates).

Where are they from?

The proboscis monkey is endemic (belongs to one place) to the island of Borneo, in southwestern Asia.

Greatest populations of proboscis monkeys can be found in Sabah, Malaysian Borneo, and in the Lower Kinabatangan floodplains – a Key Biodiversity Area (KBA).

What’s their average life span?

In the wild, they can live for up to 20 years!

What do they look like?

They have a long coat with bright orange, reddish brown, yellowish brown, or brick red fur on their back, and light grey, yellowish, or light orange underfur.

Infants are born with a blue-coloured face that darkens to grey by the time they’re two-and-a-half months old. By eight months of age, proboscis monkey infants become cream coloured, like their parents.

Female proboscis monkeys have an upturned nose. But male proboscis monkeys have a large, drooping nose that allows them to make loud, bellowing sounds – the bigger their nose, the louder they sound!

Having a large nose is considered attractive to female proboscis monkeys, too.

Their round, pot belly helps the proboscis monkey eat young leaves, unripe fruit, and seeds that other primates can’t eat.

Also, proboscis monkeys have partially webbed feet, which makes them great swimmers capable of deep dives up to 20m under water! They’ll jump into the water while foraging or fleeing from a threat.

How big are they?

Proboscis monkeys can be 53-76cm in length, though their weight is different depending on whether they’re male or female:

  • Male proboscis monkeys weigh up to 22kg.
  • Female proboscis monkeys weigh 7-11kg.

How fast are they?

Unknown. Proboscis monkeys are arboreal, which means they live in trees and try to avoid the ground wherever possible. 

What do they eat?

Seeds, young leaves, and shoots of mangroves. Proboscis monkeys also eat unripe fruit, because ripe fruit contains sugar that will ferment (create bacteria that forms bubbles) in their stomachs, causing fatal bloating.

However, proboscis monkeys are omnivores, so they’ll occasionally eat caterpillars, larvae, and other invertebrates, too!

Are they nocturnal?

Not exactly – Proboscis monkeys are ‘diurnal’, which means they’re most active from late afternoon into the night.

Do they mate for life?

While they don’t mate for life, male and female proboscis monkeys move between social groups throughout their lives.

Males will defend their group by exposing their teeth and making loud, honking signals – females are responsible for foraging and caring for their babies.

Do they live in groups?

Yes, proboscis monkeys are highly social and live in ‘troops’ of 2-30 animals!

Their social groups can be made up of a single male with a ‘harem’ (group) of females, or a bachelor group of males.

A group of proboscis monkeys is called a ‘troop’, ‘band’, or ‘harem’.

Are they intelligent?

Monkeys are generally considered to be intelligent, social creatures.

Why are they important?

Proboscis monkeys have a vital role in forming forests by managing the vegetation in their environment.

What are the risks if they become extinct?

Due to the punishing conditions they endure to study the proboscis monkey (from swarming mosquitoes to the threat of crocodiles), researchers from around the world are still studying the true impact of proboscis monkey populations on ecosystems within their habitats.

However, it is likely the decline of proboscis monkey populations would have a devastating impact on the health of forests and other animals within their ecosystems.

How many are there?

While exact population size isn’t known, the International Union for Conservation of Nature (IUCN) Red List suggests there are less than 1000 monkeys in Sarawak – which shows that numbers of proboscis monkeys are decreasing every day.

What is their rate of decline?

Proboscis monkeys have declined at a rate of approximately 50% in the last 40 years.

Why are they declining?

Habitat destruction is one of the main reasons for the proboscis monkey’s decline, because their homes are being destroyed by logging for palm oil. Many people favour the proboscis monkey’s habitats for farming and settlement, too.

As well as habitat destruction, proboscis monkeys are hunted for food and traditional Chinese medicines. Due to their docile nature, proboscis monkeys are easy prey for hunters who want to use the monkeys’ ‘bezoar stones’, an intestinal secretion, in medicine.

World Land Trust is working with their conservation partner HUTAN to limit forest loss in Sabah, and to protect wildlife in that globally recognised Key Biodiversity Area (KBA). By expanding forests through working with local communities to plant trees, HUTAN’s work allows wildlife corridors to be created. Wildlife corridors allow animals to move freely along the Kinabatangan River, without having to interact with people.

Fun facts from the World Land Trust

  1. As well as being agile in trees, the proboscis monkey has been known to leap into the water from heights of up to 50ft!
  2. A proboscis monkey’s stomach has many ‘chambers’, like a cow’s stomach! Each chamber is filled with healthy bacteria, to help the monkey digest their food.
  3. Some male proboscis monkeys have such a big nose that they have to push it out of the way to be able to eat.

Who is the World Land Trust?

Since 1989, World Land Trust (WLT) has been empowering local partners and their communities to save the critically threatened habitats of wildlife around the world.

WLT also has some famous patrons, including Sir David Attenborough!

For more information, visit the World Land Trust charity page.