Ultimate Guide to Monkeys: Species, Behaviour, Diet, Habitat and Conservation

Monkeys are the most diverse group of primates on Earth — roughly 260 to 270 recognised species spread across the rainforests, savannahs, mangroves, mountains and even the city streets of Africa, Asia and the Americas. This guide is the hub of everything we publish about them: what a monkey actually is, how the major families differ, how monkeys behave, what they eat, where they live, and how you can see and help them responsibly.

Key takeaways

• A monkey is a primate in the infraorder Simiiformes that is not an ape — most have tails, narrower chests and a quadrupedal walk.
• Monkeys split into two great groups: Old World monkeys (Africa and Asia) and New World monkeys (Central and South America).
• Body sizes run from the 100-gram pygmy marmoset to the 35-kilogram mandrill — a 350-fold difference.
• Almost every monkey is social, and social life is built on grooming, vocal signals, facial expression and rank.
• Habitat loss, hunting and the illegal pet trade are the three biggest threats; around half of all primate species are now threatened.

What is a monkey?

Monkeys belong to the primate order, alongside lemurs, lorises, tarsiers and apes. Within primates they sit in the group called simians, which is then split into the catarrhines (Old World monkeys and apes) and the platyrrhines (New World monkeys). Because apes evolved from within the catarrhine branch, “monkey” is a useful everyday word rather than a strict evolutionary unit — which is exactly why the ape-versus-monkey question comes up so often.

Practical field markers of a monkey include a tail (present in nearly all species), a relatively narrow chest, forward-facing eyes with excellent depth perception, grasping hands, and a habit of moving along branches on all fours rather than swinging arm-over-arm. Start with What Is a Monkey? for the full definition, then compare it against Monkeys vs Apes and Monkey Adaptations.

How many monkey species are there?

Current primate taxonomies list roughly 160 Old World monkey species and around 110 New World monkey species, though the number moves every year as genetic studies split or merge populations. Our breakdown lives in How Many Monkey Species Exist?, with the wider tour in Monkey Species Around the World and Types of Monkeys.

Old World versus New World at a glance

Feature	Old World monkeys	New World monkeys
Region	Africa and Asia	Central and South America
Nostrils	Narrow, downward-facing	Wide, side-facing
Prehensile tail	Never	In several genera (howler, spider, woolly, capuchin)
Sitting pads	Usually present	Absent
Colour vision	Full trichromacy in both sexes	Often variable between individuals
Typical examples	Baboon, macaque, mandrill, langur	Capuchin, howler, spider, marmoset

Full comparison: Old World vs New World Monkeys.

Popular species profiles

If you are here for a specific animal, start with these deep dives: capuchin, spider monkey, howler monkey, squirrel monkey, vervet, mandrill, Japanese macaque, golden snub-nosed monkey, proboscis monkey and tamarins. Superlatives are covered in Largest Monkeys on Earth, Smallest Monkey Species, Fastest Monkey Species and Rare Monkey Species.

Monkey behaviour and social life

Monkeys are intensely social. Groups range from a monogamous titi pair to Ethiopian gelada herds of several hundred animals. Rank determines who eats first and who sleeps in the safest position, and it is maintained far more by grooming and alliance-building than by fighting. Learn how it works in Monkey Social Hierarchy, Why Do Monkeys Live in Groups? and Why Monkeys Groom Each Other.

Other behaviour reading: communication, facial expressions, play, throwing behaviour, movement through trees, sleep, swimming, defence and tool use.

Diet: what monkeys actually eat

Most monkeys are omnivores with a strong fruit bias. Ripe fruit supplies energy, young leaves and seeds fill the gaps, and insects, eggs, small vertebrates, gum, flowers and fungi supply protein and micronutrients. Leaf specialists such as colobus and langurs run multi-chambered stomachs full of fermenting bacteria, while marmosets gouge tree bark for gum. Start with What Do Monkeys Eat?, then Monkey Diet by Species, Fruits Monkeys Love, Do Monkeys Eat Meat? and Seasonal Diet Changes.

Habitats: from canopy to concrete

Monkeys occupy tropical rainforest, dry forest, savannah woodland, mangrove, montane cloud forest, snow-covered mountains and — increasingly — towns and temples. Explore Where Do Monkeys Live?, Monkey Habitats Explained, Rainforest Monkeys, Mountain Monkeys, Urban Monkeys and the regional guides for Africa, Asia and South America.

Conservation status

Roughly half of the world’s primate species are classed as threatened, and monkeys carry a large share of that burden. The drivers are consistent: forest clearance for agriculture and mining, hunting for meat, capture for the pet trade, roads that fragment ranges, and a warming climate that shifts fruiting seasons out of sync with breeding. Read Threats to Monkey Habitats, Climate Change and Monkeys, Illegal Wildlife Trade, Endangered Monkey Species, How to Protect Monkey Habitats and Success Stories in Monkey Conservation.

Seeing monkeys responsibly

Wild monkey watching is one of the easiest wildlife experiences to get right — and one of the easiest to get wrong. Never feed them, never hold food in the open, keep two metres of distance, and choose operators that do not bait animals. Plan with Best Places to See Monkeys, Monkey Watching Tips, Best Time to See Monkeys, Safety Tips for Travellers and Ethical Wildlife Tourism.

Monkeys and people

Monkeys share 93 percent or more of our DNA depending on the species, which makes them scientifically fascinating and ethically complicated. They are also poor pets — long-lived, strong, and behaviourally impossible to satisfy in a house. See Monkey DNA Compared to Humans, Are Monkeys Good Pets?, Why Wild Monkeys Should Stay Wild and Diseases Shared Between Humans and Monkeys.

Frequently asked questions

Are monkeys and apes the same thing?

No. Apes — gibbons, orangutans, gorillas, chimpanzees, bonobos and humans — have no tail, a broader chest and larger brains relative to body size. Monkeys usually have tails and move on all fours along branches.

How long do monkeys live?

Small species such as marmosets live 10 to 12 years, mid-sized species such as capuchins reach 25 to 45 years in captivity, and large macaques and baboons commonly live 25 to 30 years. See Monkey Lifespan.

What is the smartest monkey?

Capuchins are the usual answer: they use stone tools, plan ahead, and pass laboratory tests that stump much larger-brained animals. Baboons and long-tailed macaques also score highly.

Which monkey is the biggest?

The mandrill, with dominant males reaching 30 to 37 kilograms.

Do all monkeys have prehensile tails?

No — only a handful of New World genera can grip with the tail. No Old World monkey can.

Are monkeys dangerous to humans?

Habituated monkeys around temples and markets bite and scratch often, and those wounds carry a real infection risk. Keep your distance and never offer food.