The Proboscis monkey of Borneo

By in Animals
Proboscis Monkey nose

A proboscis monkey showing its giant nose

With their large pendulous nose, giant bellies, and permanent erect penis, the proboscis monkey has one of the most unusual appearances of all primates. Their most distinctive trait is their large protruding nose. Although females already have a very large nose for a primate, the nose of males is so long it often hangs over their mouth, exceeding 10cm in length. Why males have such a large nose is still a matter of dispute but may be a form of sexual selection, with females preferring males with large noses because the nose amplifies vocalisations.

Proboscis monkey in tree

Proboscis monkey chilling in a tree

Another striking characteristic of Proboscis monkeys are their large pot bellies, making them look permanently pregnant. Their bellies are so enourmous because of a very special digestive system which consists of cellulose digesting bacteria, enabling them to eat leaves and unripe fruit. Their stomach is so large, its contents can make up to one quarter of their body weight.

A proboscis monkey shouting

A proboscis monkey shouting to its group mates

Local people referred to these monkeys with their potbellies and red noses as ‘Dutch monkeys’ as they were considered such a caricature of the Dutch colonisers.

Proboscis monkeys can only be found in Borneo and inhabit mangrove, peat swamp, and riverine forests. Although they are mostly arboreal (tree-living), proboscis monkeys are good swimmers and have the most aquatic lifestyle among primates. They usually live in a harem which comprises one adult male and one to eight females and their offspring. The males are much larger, weigh more than twice as much as females, and have an erect penis almost permanently.

Due to ongoing habiat loss by logging and conversion to agriculture, numbers of proboscis monkeys have fallen dramatically in the last 40 years. Huge areas of native rainforest have been cleared for timber and oil-palm plantations. Therefore the proboscis monkey is evaluated as Endangered on the IUCN Red List of Threatened Species, with only some thousands are known to still exist.

Jumping Proboscis Monkey

I was lucky enough to witness a proboscis monkey jump over a river! Photo by me.

I myself encountered proboscis monkeys in the wild on a number of rare occasions while working in Borneo’s tropical rainforest. Visiting Tanjung Puting national park , exploring its many rivers, I had the fortune of seeing a Proboscis monkey actually jumping over a river (see my photos). After shouting nervously for many minutes, the brave monkey eventually jumped and flew more than 15 meters through the air, landing safely in the canopy on the other side.

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  • Jenny Leon

    I believe they called this the “dutch monkey”! How lucky we were to sleep on a boat with them all in the tree above us!

  • Jolle Jolles

    What a great time we had! Do you remember the moment the brave proboscis flew through the air? Wow!

  • Sanne

    Die foto 6-6 van die overvliegende proboscis is echt super mooi!Mooie tekst.

    • Jolle Jolles

      Ha Sanneke! Dat moment dat ie na minuten lang op en neer springend in een boom uiteindelijk de 15 meter over het water sprong was echt heel speciaal! Mooi dat ik ze ook in het wild heb kunnen aanschouwen.

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  • ToddCo

    Great pics! I just got back from Malaysian Borneo and wanted to share with you my 2011 proboscis monkey photography (and video clips): link


    • Jolle Jolles

      Nice photo’s Toddco! Amazing to be around them hey :) I didn’t bring my 100-400 canon lens when I spent 10 weeks in Borneo, but luckily managed to get that shot of one jumping over a 10m wide river!

  • will

    awsome aren’t they work with e’m myself

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    Many thanks for sharing!

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