Proboscis Monkey

Quick Facts 

Name: Proboscis Monkey 

Diet: Leaves, seeds, unripe fruit, and occasionally insects 

Behaviour: Diurnal and primarily social but some individuals may be solitary 

Lifespan: 20 years 

Size: 22kg and 76cm long with a 67cm tail for males. 10kg and 64cm long with a 62cm tail for females 

Habitat/Range: Jungles, swamps, coastal mangroves, and near rivers in Borneo 

Threats: Habitat destruction, poaching, illegal wildlife trade 

Conservation Status: Endangered 

Names & Nicknames: Proboscis monkey, Long-nosed monkey

Size: One of the largest species of monkey in Asia, or at least the males are! This species is sexually dimorphic, meaning that one sex, in this case, the male, is much larger than the other. Males can grow up to 76cm long in addition to a majestic 67cm tail, compared to their female counterparts, who grow to around 62cm long with a (still majestic) 58cm tail. Body size isn't the only thing that male proboscis monkeys do bigger! They also sport their signature appendage, a long fleshy nose over 10cm long; what a snout.

Smell: Despite their impressive male appendage (their nose...), males aren't any better at sniffing out smells than their smaller-nosed female counterparts. Their nose is this great size and bulbous shape for very different reasons; read on to find out!

Communication: Most Proboscis monkeys are social, living in groups of one adult male and several adult females or in groups of all male bachelors, and communication is, therefore, very important. Talking is all vocal – they produce a range of sounds from honks to groans, squalls, roars, and brays. These sounds have different purposes: growls are used by males to calm down agitated group members, honks serve as warning signs, and females may shriek when excited or upset. Adult males have a crucial advantage in their calls thanks to their extraordinary nose that acts like an amplifier, making their calls much louder. When the racket does calm down, Proboscis's monkeys also communicate by grooming, playing, and just sitting close to each other.

Favourite Hangout: Proboscis monkeys are only found on the Island of Borneo, an Island in Southeast Asia shared by Malaysia, Indonesia, and Brunei. They're found in jungles throughout Borneo, and their favourite places to HANG (pardon the pun) are in the trees around rivers, swamps, and coastal mangroves on their island home. They are very arboreal (live in the trees) and rarely come down to the forest floor to search for food.

Favourite Snack: The majority of a Proboscis monkey's diet is made up of leaves, seeds, and unripe fruit. These aren't exactly the easiest things to digest, so these swingers have a complex chambered stomach that relies on a host of symbiotic bacteria to help them digest. This also has the added effect of making them appear a bit... bloated... due to their pot bellies.

Eating Habits: Proboscis monkeys spend a lot of time eating and will feed on at least 90 different species of plant. They will also change their diets based on seasonal availability; when food is scarce, they will eat a wider variety of things, similar to how a fancy gastropub designs their menu through the year!

Toilet Humour: If you were to describe Proboscis monkeys purely from their features, a large bulbous nose, pot belly, and webbed feet, you might think it was some kind of fairy-tale creature. We can all agree that far from being some mythical ogre, they are quite endearing!

Love Language: As you may guess, it all starts with the rather phallic-shaped large nose of the male proboscis monkey. It is not used directly for any monkey business, of course, but instead amplifies the mating calls of males. The louder the male and the bigger his...appendage, the more attractive the male is to females. These monkeys can be pretty frisky, and both male-on-male and female-on-female ‘mounting’ has been observed, as well as between individuals for play.[A sound clip here would be good]

If you see them: These monkeys can be a bit shy, and also spend most of their time up in the trees, where we humans aren't so good at climbing. A good place to see them is from a boat on the river, where they often hang out in the surrounding trees; just watch out that they don't splash you if they decide to jump in and cross the river!

Red Flags: Proboscis monkeys are very fond of their Bornean jungle homes – think winding rivers and mangroves. Unfortunately for them, as much as half of Borneo's forest has been deforested in the last century, and as the trees go down, so do the Proboscis monkeys. As if deforestation wasn't enough, these monkeys are also illegally hunted both to be eaten and so that their bezoar stones (an intestinal secretion) can be used in traditional Chinese medicine, despite there being no evidence these stones actually do anything medicinal.

Epic Journeys: As Proboscis monkey habitats become smaller and more fragmented, groups have to migrate between them. However, this can often put them in danger of predators like clouded leopards and crocodiles and also put them in closer proximity to human settlements and traffic.

Glow-up: As if these monkeys didn't look strange enough as they were, Proboscis monkey babies are born with blue faces! These fade to grey in a couple of months, and then they get their adult crea-coloured faces after around 8 months. A male's all-important schnoz grows steadily until adulthood – around 7 years old – and is then ready to unleash its trumpeting mating call onto the females of the forest.

Facts: Despite their pot-bellied appearance, Proboscis monkeys are the primate world's most prolific swimmers. They have webbed feet and hands to help them even outswim crocodiles, and they will dive into the water from the treetops to cross rivers with an impressive bellyflop.

Who are they in the friendship group: Loud, on the swim team, and struggles to find sunglasses that fit their face...

How threatened are they: Endangered