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Proboscis Monkey

Last updated date: 28th Feb 2024
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Monkey with Red Nose - Species in Serious Danger

The proboscis monkey (scientific name—Nasalis larvatus), is a massive primate endemic to the island of Borneo. It is named after the long, dangling nose present in males and spends most of its time in the trees near mangrove forests or bush lands. It is also called the long-nosed monkey and domestically as the bekantan. Because of the menace of deforestation in its tropical rainforest habitat, populations of this mammal species are decreasing and it is listed as VULNERABLE on the IUCN Red List.

Proboscis monkeys are not as common as symbols of conservation as other vulnerable species, but they are captivating creatures by themselves and are rapidly disappearing – along with their habitats – at startling rates. They are distinctive primates and there are amazing facts about the species to explore.

Scientific Description



Common Name

Proboscis Monkey

Scientific Name

Nasalis larvatus

Group Name

Harem, band

Animal Type




Male Length

24 to 28 inches

Male Weight

Up to 50 pounds

Biological Description and Natural Environment




Nasalis larvatus





Group Behaviour



Arboreal Primate

Social Structure  

Social, Hierarchical

Conservation Status      


Preferred Habitat


Main Prey Species 

Fruits, Leaves, Shoots, Seeds


Crocodiles, Clouded leopards, Monitor Lizards, Pythons, Birds of Prey

Average Number of Young

1 baby


20 years

Proboscis Monkey Physical Characteristics




Tan, Brown, Red, White, Orange, Grey

Skin Type


Top Speed

15 mph

Age of Sexual Maturity

4 - 5 years

Let’s see what the monkey with a long nose looks like. 

Refer to the Proboscis Monkey Diagram Below:-

[Image will be Uploaded Soon]

Incredible Proboscis Monkey Facts

  • Proboscis Monkey size is relative to a 6-feet tall man

  • Also referred to as Long-Nosed Monkey and Bekantan in Indonesia

  • There are 2 Species

  • Inhabited and found on the island of Borneo!

  • Estimated Population Size is 7,000

  • Population is decreasing

  • Threatened for body part for use in traditional medicinal remedies

  • Males have larger nose than female Proboscis

  • Biggest Threat to monkey with red nose is Habitat loss

  • Most Distinctive Feature Fleshy, long nose and swollen stomach

  • Gestation Period is of 166 days

  • Lives mostly in Coastal mangroves and riverine forests

  • Predators include human, crocodile, clouded leopard

  • Average Litter Size is 1

  • Follows a Diurnal Lifestyle (meaning active during the day)

  • Scientist theorize that male bulbous noses formed an echo chamber which elevates their calls to bewitch females and domineer over other males

The Probiotic Proboscis Monkey

Proboscis monkeys have complicated, chambered stomachs that are largely dependent on a host of bacteria to help fragment some of the hardy plant substance present in their diet. This is same as the process observed in domestic cows which, like proboscis monkeys, will ‘chew their cud’ ahead of enabling bacteria nurture in their gut to allow further in the breakdown of their food.

Particularly, it is the cell walls of plant substance which has cellulose, a substance that needs specialized bacteria to break it down. Moreover, to the additional mechanical breakdown of plant substance that materializes when the monkeys chew their cud, they also count on sustaining these bacteria in their guts to collapse their food further for them. Together, this enables them to maximize the amount of nutritional content acquired from their low nutrient diet.

The Swimming Monkey

Amazingly, Proboscis monkeys remain their entire lives near a water source such as the jungle streams, serene waters of coastal mangroves, and still swampy areas. They have naturally developed a spellbinding affinity for the water, frequently hopping from trees and comically belly flopping into it. However, these water bodies contain crocodiles, one of the most profuse and powerful predators of proboscis monkeys. To amplify their chances of trespassing these threats, proboscis monkeys have formed webbed arms and feet that enable swimming faster than they would be able to. They can even swim for up to 66 feet underwater and have been known to cross vaast rivers and streams.

Proboscis Monkeys Swimming Abilities

They are the primate world’s most bountiful swimmers, often leaping from tree limbs and striking the water with a comical belly flop. They’ve grown webbed hands and feet to aid them outpace the crocodiles which are some of their primary predators.

Proboscis Monkeys Habitat and Behavior

Proboscis monkeys are native to the jungles of Borneo, never going astray far from the coastal mangroves, island’s rivers, and swamps. They are an extremely arboreal species and will set out onto land only sometimes to search for food. They live in organized harem groups with an ascendant male and two to seven females and their offspring. Different groups often gather close to water at night to sleep.

Proboscis Monkeys Threats to Survival

Alas, Borneo’s greatly threatened landscapes are hospice to these extremely specialized primates. The rampant clearing of the region’s rain forests for timber, oil palm plantations and settlement has exhausted vast tracts of their habitat. The disintegration of the proboscis’s range implies they are being forced to descend from the trees more often and frequently must travel treacherously long distances to look for food. Their land predators include jaguars and some local peoples who contemplate proboscis monkeys as a delicacy.

Over the past 40 years, proboscis’s populations have plunged. They are presently protected from hunting or capturing in Borneo.

Proboscis Monkeys Diet and Predators

Proboscis monkeys are omnivores, surviving mostly on leaves, shoots and seeds. They may also occasionally forage from the ground or unripe fruits plucked from the trees in which they subsist. Sometimes, they will eat insects as well.

Predators of the species include big and exotic animals such as jaguars, crocodiles, and pythons. Moreover, humans have historically hunted proboscis, with some local people of the area considering it a delicacy or a product of medicinal remedy

Proboscis Monkeys Reproduction

Males will augment their calls using their long, hanging nose, attracting females. Sexes will use pouting faces and other affectionate displays when soliciting a mate. Subsequent to a short, one-minute copulation and a gestation period of about 160-200 days, females will give birth at night in the protection of a large band. Generally, only one young is born, which nurses from the mother for up to 7 months. At about 6 weeks, the infant will also start to eat some solid foods, augmenting their newborn diet. Females become sexually mature at around 5 years of age while individual monkeys survive for about 20 years.

Proboscis Monkeys Conservation Status

Say to say, but the Proboscis monkey is endemic to one of the most threatened regions in the world. Uncontrolled deforestation of rainforests worldwide – including in Borneo – is ousting and menacing millions of species such as the proboscis monkey. Attempts to Conservation in this innovative and productive area are especially difficult because of it being an island shared between three countries: Brunei, Malaysia and Indonesia.

The habitat of proboscis monkeys has become highly splintered, inducing behavioral changes that need it to take more risk in search of food. This additionally raises their mortality by preying or exposure. Presently, populations are declining and the species is categorized as Endangered by the IUCN.

Proboscis Monkey Talk

In order to sustain their complex social structures primates like the proboscis monkey necessitate a means of communication. With respect to the proboscis monkey, they are known to initiate different calls. Some of these have even been defined as honks. These calls may be incorporated for the purpose of warning other members of their group or band while some are meant to be threatening calls. What is especially unique about the species is, however, that its huge, fleshy nose may support it to make these calls. The nose is thought to augment their calls, enabling it to reach further across the forest and be received by more monkeys than would be possible. This may further help in intimidating other males or to seek attention from females. But, not all communication is verbal. They also take part in non-vocal displays such as shaking branches and baring its teeth at others in a frightening manner.

FAQs on Proboscis Monkey

Q1. How to Identify a Male and Female Proboscis Monkey?

Answer: Let’s find out how to identify a male and female proboscis monkey with their physical description. Male proboscis monkeys can reach up to 22.5 kg (50 lb) while females are just almost half their size. They wear a coat of light brown fur with lots of red near the head and shoulders (that’s also probably one of the reasons they are called monkeys with a red nose). Additionally, they have some tints of grey on their arms and legs.  

The head-body length of males measures about 26-30 inches while females grow to about 20-24 inches in length. Males also have long, bulbous, and commonly hanging noses from which the species also acquired its namesake. Proboscis Monkeys fleshy noses can grow to as long as 4 inches, commonly hanging lower than their mouths. These are missing out in female monkeys which have smaller, triangular noses. All proboscis monkeys are present with webbed toes and fingers that enable swimming.

Q2. What are the Threats to Proboscis Monkeys?

Answer: The proboscis monkey is an announced endangered species, chiefly threatened by habitat loss. Borneo’s landscape is advancing, as huge tracts of rainforest are stripped of for clearing to make way for infrastructure, logging industries and oil palm plantations. This customarily arboreal species is strained to migrate between exploded habitats in search of food on the ground, leaving it susceptible to predators like eagles, crocodiles, clouded leopards, monitor lizards, pythons and poachers. Proboscis monkeys are poached by localities who account for their meat as a delicacy. They are also assassinated for their bezoar stones that fetch a price in the black market for incorporation in traditional Chinese medicine. Numbers have declined by more than 50% over the past 40 years, as the extensive depletion of forests continues. The proboscis monkey has attained PROTECTED status in Borneo.

Q3. What Do Proboscis Monkeys Eat?

Answer: Proboscis monkeys survive chiefly on a diet of leaves, shoots, seeds, and unripe fruits but will sometimes feed upon insects as well. They have complex, chambered stomachs that are dependent on a host of symbiotic bacteria for digestion.