Weird and Wonderful Monkey Facts

Evolution has produced some genuinely improbable primates. This collection focuses on the odd end of the spectrum: strange noses, missing thumbs, chemical shortcuts and bodies that break the rules. For the broader greatest hits, see 50 Amazing Monkey Facts.

Faces That Look Invented

• The male proboscis monkey grows a pendulous nose that amplifies his calls and advertises status to females.
• The bald uakari has a bare, brilliant red face. Pale colouring can indicate poor health, so the flush works as a fitness advert.
• Mandrill faces carry blue ridges and a red stripe that intensify with rank and hormone levels.
• Emperor tamarins grow a drooping white moustache far longer than seems useful.
• Snub-nosed monkeys have almost no external nose, which may reduce frostbite risk in freezing mountain habitats.
• De Brazza’s monkey wears a white beard and an orange brow band, giving it a distinctly professorial look.

Bodies That Break the Pattern

• Colobus monkeys and spider monkeys have lost or hugely reduced the thumb, turning the hand into an efficient hook for swinging.
• Howler monkeys have an inflated hollow hyoid bone that turns the throat into a resonating chamber, producing calls audible for kilometres.
• Geladas have a bare patch of skin on the chest that flushes bright red, which earned them the nickname bleeding-heart monkey.
• Langurs and colobus ferment leaves in a multi-chambered stomach, so a leaf-eating monkey can look bloated and be perfectly healthy.
• Proboscis monkeys have partially webbed feet and will swim across rivers rather than detour, as covered in Can Monkeys Swim?
• Only certain New World monkeys have a prehensile tail with a bare, ridged gripping pad, described in Why Monkeys Have Tails.

Strange Biology

• Marmoset twins exchange cells in the womb, so a single individual can carry two genetic lineages, a condition called chimerism.
• Marmosets have chisel-like lower incisors for gouging bark and feeding on the gum that oozes out.
• Owl monkeys are the only monkeys active at night, and they have traded colour vision for light sensitivity.
• In many New World species, colour vision varies between individuals, so two members of the same troop can literally see fruit differently.
• Geladas have the most specialised diet of any primate, feeding mainly on grass blades and rhizomes.
• Northern muriquis are unusually peaceful, with males rarely fighting over mates, an outlier among the systems described in Monkey Reproduction.

Odd Habits

• Capuchins and squirrel monkeys practise urine washing, rubbing urine on their hands and feet as a scent signal.
• Vervet monkeys on some Caribbean islands raid resorts for cocktails and show individual differences in how much they drink.
• Long-tailed macaques in Thailand have local stone-tool traditions that differ between neighbouring islands.
• Some macaque troops floss their teeth with human hair, and mothers exaggerate the movements when infants are watching.
• Titi monkey pairs sleep with tails braided together.
• Japanese macaques make snowballs with no apparent purpose beyond play.

Records and Extremes

• Mandrills are the heaviest monkeys, while pygmy marmosets are so light that several would fit in one hand. Compare Largest Monkeys on Earth with Smallest Monkey Species.
• Patas monkeys are the fastest runners among monkeys, as detailed in The Fastest Monkey Species.
• Japanese macaques live further north than any non-human primate.
• Barbary macaques are the only monkeys living wild in Europe, and the only macaque in Africa.
• Some monkeys have fingerprints so similar to ours that they have been mistaken for human prints.

Related Reading

• 25 Funny Monkey Behaviors Explained
• Monkey Adaptations
• Monkey Evolution
• Top Monkey Questions Answered
• Incredible Monkey Photos and Stories

Continue at Universal Primates

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Further reading: for independent reference material, Smithsonian’s National Zoo publishes detailed species profiles, and the IUCN Red List records population trends for wild primates.