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Monkey | Definition, Characteristics, Types, Classification, & Facts | Britannica Ask the Chatbot Games & Quizzes History & Society Science & Tech Biographies Animals & Nature Geography & Travel Arts & Culture ProCon Money Videos monkey Introduction Old World monkeys versus New World monkeys Classification References & Edit History Related Topics Images & Videos At a Glance monkey summary Quizzes Ultimate Animals Quiz Animal Group Names Deadliest Animals Quiz Wild Words from the Animal Kingdom Vocabulary Quiz Match the Baby Animal to Its Mama Quiz Related Questions What is the main characteristics that define vertebrates? How are vertebrates classified in terms of their morphology? How do amphibians differ from reptiles in terms of reproduction? How are mammals distinct from other animals? 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External Websites PNAS - Monkey visual behavior falls into the uncanny valley National Center for Biotechnology Information - PubMed Central - MonkeyÂ’s Social Roles Predict Their Affective Reactivity Palomar College - Monkeys San Diego Zoo Animals - Mammals - Monkey Live Science - Monkeys: Facts about the largest group of primates A-Z Animals - Monkey Britannica Websites Articles from Britannica Encyclopedias for elementary and high school students. monkey - Children's Encyclopedia (Ages 8-11) monkey - Student Encyclopedia (Ages 11 and up) Old World and New World monkeys (more) monkey primate Ask Anything Quick Summary Homework Help Written by Colin Peter Groves Professor of Biological Anthropology, Australian National University, Canberra. Author of A Theory of Human and Primate Evolution and others. Colin Peter Groves Fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Last updated Apr. 18, 2026 • History Britannica AI Ask Anything Quick Summary Table of Contents Table of Contents Quick Summary Ask Anything Top Questions What is a monkey? How are monkeys different from apes? Where do most monkeys live in the world? What do monkeys eat in their natural habitats? How do monkeys communicate with each other? What are some ways monkeys help their environments or ecosystems? Show more Show less monkey , in general, any of nearly 200 species of tailed primate , with the exception of lemurs , tarsiers , and lorises . The presence of a tail (even if only a tiny nub), along with their narrow-chested bodies and other features of the skeleton, distinguishes monkeys from apes . Most monkeys have a short, relatively flat face without great prominence of the muzzle, although baboons and mandrills are notable exceptions. The vast majority of species live in tropical forests , where they move on all four limbs. All but the durukuli of tropical Central and South America are active during the day, moving frequently in bands as they search for vegetation, birds’ eggs, smaller animals, and insects to eat. Monkeys are capable of sitting upright, and, consequently, their hands are freed for many manipulative tasks. Except for a few Old World forms, monkeys are predominantly arboreal, leaping from limb to limb in their travels among the trees. Their hands and feet are both used for grasping and typically have five digits, the thumb and big toe being divergent from the others. Commonly, the digits have flattened nails , but the marmosets have claws on all digits except the big toe, which bears a nail. On the ground, monkeys walk with the entire sole of the foot touching the ground but with the palm of the hand raised. They almost never walk on two legs (bipedally) and can stand erect for only short periods, if at all. common squirrel monkey Common squirrel monkeys have olive or grayish crowns and are found only in South America. (more) Monkeys have large brains and are known for their inquisitiveness and intelligence. Brain development, combined with the freeing of the hands and well-developed vision, allows them a great latitude of activity. Most are good at solving complex problems and learning from experience, but they do not quite reach the cognitive levels of great apes. Some, especially the capuchins (genus Cebus ), spontaneously use objects as tools (e.g., stones to crack nuts). Others, such as baboons, readily learn to use sticks to obtain food. However, in strong contrast to the great apes (gorillas, chimpanzees, and orangutans), most monkeys do not appear to be very good at learning from each others’ experience—individuals more or less have to learn new behaviours for themselves. A significant exception is the Japanese macaque ( Macaca fuscata ). In field experiments, these monkeys were introduced to new foods such as sweet potatoes and candies wrapped in paper. Once a few individuals had solved the problems of getting at the new foods, their innovations gradually spread throughout entire troops. These experiments have had implications in redefining cultural behaviour. mandrill Mandrill ( Mandrillus sphinx ). (more) Monkeys are highly social animals, and almost all live in troops consisting of several females with young and either a single male (as in hamadryas baboons, mandrills, most guenons , and most langurs ) or several males (as in savannah baboons and macaques). Usually, but not universally, the females stay in the troop in which they were born and are thus closely related to each other. Males join new troops on maturity, and so they are unrelated to each other and somewhat antagonistic. Like humans and apes, female monkeys nurse their young and have a menstrual cycle , albeit less copious . In some species, sexual activity is strictly confined to the period around ovulation ( estrus ); in others, there appears to be little or no restriction. Some species breed all year round; others have a period several months long during which they experience no sexual cycles (anestrus). Britannica Quiz Ultimate Animals Quiz Old World monkeys versus New World monkeys saki; macaque From left, head of a saki ( Pithecia ) and a macaque ( Macaca ). (more) Monkeys are arranged into two main groups: Old World and New World. Old World monkeys all belong to one family, Cercopithecidae , which is related to apes and humans, and together they are classified as catarrhines (meaning “downward-nosed” in Latin). The New World monkeys are the platyrrhines (“flat-nosed”), a group comprising five families. As their taxonomic names suggest, New World (platyrrhine) and Old World (catarrhine) monkeys are distinguished by the form of the nose. New World monkeys have broad noses with a wide septum separating outwardly directed nostrils, whereas Old World monkeys have narrow noses with a thin septum and downward-facing nostrils, as do apes and humans. Old World monkeys have hard, bare “sitting pads” ( ischial callosities) on the buttocks; New World monkeys lack these. Many Old World monkeys have thumbs that can be opposed to the other fingers and so can handle small objects precisely. None of the New World monkeys has such manual dexterity . Indeed, in the hands of many species, the main divergence is between the index and middle fingers; in a few species, the thumb is reduced or even absent. Some New World monkey species have prehensile tails capable of supporting the entire body weight or of grasping, for example, a proffered peanut. No Old World monkeys have this ability, and macaques are nearly tailless. cotton-top tamarin Cotton-top tamarin ( Saguinus oedipus ) used in an experiment to determine whether music containing calls from others of the same species affected behaviour. (more) New World monkeys live primarily in tropical South America , especially the Amazon rainforests; the range of a few species extends northward as far as southern Mexico or southward into northern Argentina. Among the smaller New World forms that have endeared themselves to humans with their antics and their tamability are the alert marmosets , often tufted and colourfully arrayed , and the inquisitive squirrel , woolly , and capuchin monkeys—all of which exhibit in marked degree the curiosity and cleverness ascribed to monkeys generally. Larger New World species include the acrobatic spider monkeys and the noisy howlers . Other New World monkeys include uakaris , sakis , and titis . moustached monkey ( Cercopithecus cephus ) The moustached monkey ( Cercopithecus cephus ) is a species of guenon. (more) Old World monkeys live throughout Africa, on the Red Sea coast of Arabia, and in Asia from Afghanistan to Japan and southeast to the islands of the Philippines, Celebes, Bacan, and Timor. Some Old World monkeys have been successfully naturalized in Gibraltar, France, Mauritius, Belau, and a few islands of the West Indies . Old World monkeys include many that are often seen in zoos , especially the beautifully coloured African guenons (e.g., mona , diana , white-nosed, green, vervet, and grivet monkeys), colobus , mangabeys , and the chiefly Asiatic macaques . The macaques include the Barbary “ape