Proboscis Monkey

Learn more about these big-nosed monkeys. Find out why scientists think these primates have such outsized organs.

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A proboscis monkey photographed at Singapore Zoo

It may seem hard to believe, but male proboscis monkeys use their fleshy, pendulous noses to attract mates. Scientists think these outsize organs create an echo chamber that amplifies the monkey’s call, impressing females and intimidating rival males.

Habitat and Behavior

Proboscis monkeys are endemic to the jungles of Borneo, never straying far from the island’s rivers, coastal mangroves, and swamps. They are a highly arboreal species and will venture onto land only occasionally to search for food. They live in organized harem groups consisting of a dominant male and two to seven females and their offspring. Various groups often congregate near water at night to sleep.

Swimming Abilities

Proboscis monkeys are the primate world’s most prolific swimmers, frequently leaping from tree limbs and hitting the water with a comical belly flop. They’ve evolved webbed feet and hands to help them outpace the crocodiles that are some of their main predators.

Size and Appearance

Among the largest of Asia’s monkeys, male proboscis specimens can reach 50 pounds, although females attain only about half that size. Adults wear a coat of...

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