Proboscis Monkey
A monkey with a nose so large it hangs over its own mouth — and it's a built-in speaker system
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The wacky thing
Adult male proboscis monkeys grow a nose up to 10cm long that droops down past their chin, so large it sometimes has to be pushed out of the way to eat. The oversized nose acts as a resonating chamber, amplifying the male's honking alarm and territorial calls — the bigger the nose, the louder and lower the call, which females appear to find more attractive and rival males find more intimidating.
Overview
Proboscis monkeys are found only on the island of Borneo, living in mangrove forests, swamps, and riverside forest. They're strong swimmers with partially webbed hind feet — an unusual trait among primates — and will readily leap into rivers to escape predators or cross waterways, sometimes swimming through crocodile-infested water. They're also one of the few primates with a multi-chambered stomach, similar to a cow's, that lets them digest large volumes of leaves through bacterial fermentation.
Found in
Mangrove forests, peat swamps, and riverside forests on the island of Borneo.
Things worth knowing
- 1
The multi-chambered, fermenting stomach that lets proboscis monkeys digest tough mangrove leaves also produces gas as a byproduct — giving them a permanently bloated-looking belly.
- 2
Because their leaf-heavy diet is difficult to digest alongside sugar, proboscis monkeys generally avoid sweet, ripe fruit that would upset their specialized stomach bacteria.
- 3
They are excellent swimmers and divers, capable of crossing rivers underwater, and have been recorded leaping from tree branches directly into water from significant heights.
- 4
Male noses keep growing throughout their lives, so the oldest, most dominant males typically have the largest noses and loudest calls in a group.
- 5
Local Malay name for the species, 'monyet belanda' ('Dutch monkey'), reportedly referenced colonial-era Dutch settlers, whom locals thought the monkeys' large noses and round bellies resembled.