Monkey Facts: The Ultimate Guide to Monkeys - Pictures & In-Depth Info (2024)

On this page you'll find monkey facts, pictures and information. Read on for the ultimate guide to monkeys!

Monkey Facts: The Ultimate Guide to Monkeys

Monkeys are among our closest relatives in the animal kingdom. Although we’re not directly descended from today’s monkeys, we share with them the same ancestors and many of the same characteristics.

On this fact-filled page we’ll find out what a monkey is, how monkeys are related to other primates (including us), the different types of monkey, where monkeys live, what they eat, and many other aspects of their lifestyles.

You can read the whole page to become a monkey expert, or use the links below to find the specific information you need:

Page Index

  • What Is A Monkey?
  • Monkey Characteristics
  • Smallest And Largest Monkeys
  • Types Of Monkey
  • Examples of New World Monkeys
  • Examples of Old World Monkeys
  • Monkey Habitat
  • Behavior
  • Monkey Intelligence
  • Communication
  • Family Life
  • What Do Monkeys Eat?
  • Monkey Predators
  • Are Some Monkeys Endangered?
  • Discover More With Active Wild

What Is A Monkey?

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Monkeys are small to mid-sized, social, (mostly) tree-dwelling mammals. There are two main types of monkey: old world monkeys and new world monkeys.

There are around 267 species of monkey, 132 of which are new world monkeys and 135 of which are old world monkeys.

Both types of monkey are part of a larger group of mammals known as primates. This group also includes animals such as apes, lemurs, and gibbons.

(We’ll find out more about the monkey family tree and related animals further down the page).

Monkey Characteristics

Most monkeys live in trees, and even those that don’t are evolved from animals that did. Monkeys are therefore well-adapted for an arboreal (tree-dwelling) lifestyle. Monkeys have long, flexible limbs and highly-dexterous hands and feet for climbing and gripping onto branches.

All but one species of monkey (the Barbary macaque) have tails.

This characteristic is a simple way of separating monkeys from apes: monkeys have tails, apes do not.

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Monkeys have forward-facing eyes; another result of their arboreal existence. Having forward-facing eyes gives an animal good depth perception – useful for judging the distance between branches while jumping through the trees.

Being mammals, monkeys have hair, give birth to live young and feed their young with milk produced by the females’ mammary glands.

  • For other characteristics of mammals, see this page: Mammals: The Ultimate Guide.

Monkeys are intelligent animals with large brains in relation to their body size. They are social animals, usually living in groups and demonstrating complex social behavior.

Most monkeys are omnivores, supplementing a diet of fruit and foliage with a range of small and mid-sized animals.

Smallest And Largest Monkeys

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Monkeys come in many different shapes and sizes. The smallest monkey is the pygmy marmoset (Cebuella pygmaea). This South American monkey weighs only a little over 100 g (3.5 oz.) and has a head-body length of just 11.7 cm (4.6 in).

The mandrill (Mandrillus sphinx), a threatened species from the rainforests of western Africa, is the world’s largest monkey. It weighs around 36 kg (79 lb.) and has a body length of nearly 1 m (3.3 ft.).

  • You can find out more about the mandrill on this page: Mandrill Facts

Types Of Monkey

Old World Monkeys Vs New World Monkeys

As we’ve found, there are two main monkey groups: old world monkeys and new world monkeys. Let’s take a look at the major differences between the two…

New World Monkeys

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The term ‘New World monkey’ refers to species belonging to any of the five families in the parvorder* Platyrrhini.

* A parvorder is a sub-group of an order, which itself is a large group of animals with shared characteristics. You can find out more about what words such as ‘order’ and ‘family’ mean here: Animal Classification

New world monkeys – as their name suggests – are found in the Americas.

A typical New World monkey is small to medium in size and has a flattened face and nose, slender limbs, and a long tail. The nostrils of new world monkeys point out to the side, whereas those of old world monkeys point downwards.

The tails of new world monkeys in the family Atelidae (which includes howler monkeys, spider monkeys and woolly monkeys) are prehensile (i.e. able to grasp objects). This means that the tail can operate as a ‘fifth hand’ when the monkey is climbing.

Unlike those of the old world monkeys, the thumbs of new world monkeys are not opposable.

Examples of New World Monkeys

Monkeys such as marmosets, capuchins, howler monkeys, spider monkeys and tamarins are all new world monkeys.

The five new world monkey families are:

  • Callitrichidae (marmosets, tamarins)
  • Cebidae (capuchins, squirrel monkeys)
  • Aotidae (night monkeys)
  • Pitheciidae (titis, sakis, uakaris)
  • Atelidae (howler monkeys, spider monkeys, woolly spider monkeys, woolly monkeys)

Old World Monkeys

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The term ‘Old World monkey’ refers to species in the parvorder Catarrhini, which contains just one family: Cercopithecidae.

Old world monkeys are found in Africa and Asia (just one species, the Barbary macaque, is found in Europe; this endangered species lives in the British territory of Gibraltar.)

A typical Old World monkey is medium to large in size and has an elongated face, robust hind limbs, and a non-prehensile tail. The nostrils of old world monkeys point downwards and to the front. All Old World monkeys have fully opposable thumbs.

Examples of Old World Monkeys

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Examples of old world monkeys include baboons, the mandrill, black-and-white colobuses, the Barbary macaque, the Japanese macaque and the proboscis monkey.

85 - 55 Million Years Ago

The very first primates appeared in Africa sometime between 85 and 55 million years ago (yes, the very first primates may have lived alongside dinosaurs).

65 Million Years Ago

Around 65 million years ago the primates split into two main groups: the strepsirrhines, which today are represented by the lemurs, galagos, and lorises; and the haplorhines, which today are represented by monkeys, apes and tarsiers.

60 Million Years Ago

Around 60 million years ago the haplorhines themselves split into two groups: the simians (the group that includes monkeys and apes), and the tarsiers.

  • You can find out more about tarsiers on this page: Tarsier Facts

40 Million Years Ago

Around 40 million years ago, the New World monkeys split from the other simians. They had made their way to South America either via a land bridge or after having been carried over the sea on a natural raft.

25 Million Years Ago

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Around 25 million years ago, the apes (the group that includes gibbons, gorillas, chimpanzees, orangutans and humans) split from the other old world simians.

Interestingly, this means that old world monkeys are more closely related to apes (including humans) than they are to new world monkeys.

Although apes are simian primates and are placed in the same parvorder as the Old World monkeys, they are generally not referred to as monkeys.

Monkey Habitat

Monkeys occur in a wide range of habitats, including tropical rainforests, savannas and mountains.

New World monkeys typically live in dense forests, and some (e.g. marmosets and tamarins) never leave the trees.

Several species of Old World monkeys (e.g. the baboons and the gelada), spend most of their time on the ground.

The majority of monkeys live in warm climates, but the Japanese macaque (Macaca fuscata) is a notable exception; this species inhabits areas that are covered in snow for several months of the year. This old world monkey is found further north than any other primate other than man. It is present on three of Japan’s four main islands.

Monkey Facts: Behavior

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Monkeys are generally very social animals. They spend a significant amount of time maintaining their social bonds with behavior such as grooming.

Depending on the species, monkeys may live in troops of up to 250 individuals, or in small family groups consisting of a mated pair and their offspring.

Large troops usually have a strict social hierarchy, with dominant individuals enjoying better access to mates and resources.

The majority of monkey species are diurnal (active during the day). The nocturnal night monkeys (family Aotidae) are the only exception.

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Monkey Intelligence

Compared to other mammals of similar size, monkeys tend to have large brain-to-body ratios.

Spider monkeys have been found to be adept at problem-solving, while Japanese macaques are able to learn new behaviors by observing other individuals.

Tool use (a good indicator of animal intelligence) has been observed in Capuchins, who use rocks to open nuts.


Many monkey species use a large range of vocalizations, facial expressions, and postures as well as touch to communicate with other individuals.

Howler monkeys (subfamily Alouattinae) have the loudest call of any land mammal; a group of howler monkeys can be heard from a distance of 3 mi (4.8 km).

Family Life

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Most monkey species mate throughout the year, but there is often a peak in mating when food is most abundant.

It is common for old world monkeys to be polygamous (i.e. mating with multiple partners). New world monkeys are more likely to be monogamous, with pairs staying together and males playing a larger role in caring for their young

A new world Night monkey for example, forms a close and long-lasting bond with its mate, and the father provides extensive parental care to his offspring.

Tree-dwelling monkey species construct nests the trees in which they give birth, while ground-dwelling monkeys give birth on the ground.

Although most monkeys give birth to a single infant, tamarins and marmosets (family Callitrichidae) regularly give birth to twins.

A newborn monkey is usually helpless and needs to be carried around and fed by its mother.

What Do Monkeys Eat?

Most monkeys are omnivorous. Many species consume fruits when available. Other foliage, including leaves, grasses, nuts and seeds may also be eaten. Depending on the species a plant-based diet may be supplemented with eggs and small animals including insects, lizards and rodents.

Monkey Predators

Monkeys are vulnerable to predation by a number of animals, including large cats, birds of prey and snakes. Many monkey species find safety in numbers and use warning calls to alert others of danger. Juvenile monkeys are at most risk of predation.

Are Some Monkeys Endangered?

Around half of all monkey species are considered vulnerable to extinction. Of these, over 20 species are rated ‘Critically Endangered’ by the IUCN. These include the Roloway monkey (Cercopithecus roloway), the Tonkin snub-nosed monkey (Rhinopithecus avunculus), and the Caquetá Tití monkey (Plecturocebus caquetensis).

Monkeys and other primates suffer greatly from habitat loss caused by human activities such as the expansion of agriculture, logging, mining and urban development.

Hunting and illegal pet trade also contribute to the decline of many monkey species.

Discover More With Active Wild

Now that you’re a monkey expert, why not find out more about other members of the animal kingdom?

Primates: The Ultimate Guide To Our Closest Relatives

Animals: The Ultimate Guide to the Animal Kingdom

Mammals: The Ultimate Guide

Reptiles: The Ultimate Guide

Amphibians: The Ultimate Guide

Animals A to Z

Monkey Facts: The Ultimate Guide to Monkeys - Pictures & In-Depth Info (2024)
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