Monkeys are a large and varied group of mammals of the primate order. They live in trees, grasslands, forests, mountains and plains. They are seriously threatened by habitat loss.

The term monkey includes all primates that do not belong to the categories human, ape, or prosimian; however, monkeys do have certain common features. All are excellent climbers, and most are primarily arboreal. Nearly all live in tropical or sub-tropical climates. Unlike most of the prosimians, or lower primates, they are almost all day-active animals. Their faces are usually flat and rather human in appearance, their eyes point forward, and they have stereoscopic color vision. Their hands and feet are highly developed for grasping; the big toes and, where present, the thumbs are opposable. Nearly all have flat nails. Monkeys habitually sit in an erect posture.

Monkeys are most easily distinguished from apes by their tails. Apes have no tails. Apes swing arm-to-arm in trees, but most monkeys don’t. Instead, they run across branches. Their skeletal structure is similar to that of other four-footed animals.

Monkeys live in troops of up to several hundred individuals and travel about in search of food, having no permanent shelter. As in apes and humans, the female has a monthly reproductive cycle, and mating may occur at any time, but in some species mating is seasonal. Usually only one infant is born at a time; it is cared for by the mother for a long period.

Monkeys have their own complex language, using different sounds to identify different types of predators. They have been witnessed banging stones together to warn each other of nearby predators. They also use facial expressions and body movements to communicate with each other. Grinning, yawning, head bobbing, jerking the head and shoulders forward or pulling the lip is usually a sign of aggression. Affection is expressed by grooming.

Some monkeys are monogamous, mating for life. They become distressed when separated. They express affection by holding hands, nuzzling, cuddling, grooming each other, intertwining their tails and lip smacking.

The pygmy marmoset is the smallest monkey in the world measuring less than six inches and weighing only three to five ounces. The male mandrill is the world's largest monkey at just over 3 feet long and weighing over 70 pounds.

Most monkeys eat both plants and animals. Some also eat dirt. Monkeys peel their bananas like humans and do not eat the skins.

Monkeys can grasp with both their fingers and toes. Many monkeys are skilled tool users. They use branches to capture food, use leaves as gloves, smash nuts with rocks, remove spines and hairs from caterpillars by rubbing them against branches and use large branches to club snakes.

There are two large groups, or superfamilies, of monkeys: Old World monkeys (Cercopithecoidea) and New World monkeys (Ceboidea).


The Old World monkeys are found in South Asia, with a few species as far North as Japan and North China, and in all of Africa except the deserts. Most are arboreal, but a few, such as baboons and some macaque species, are ground dwellers. Some Old World monkeys lack tails; when a tail is present it may be long or short but is never prehensile (grasping). The nostrils are close together and tend to point downward. Many species have cheek pouches for holding food, and many have thick pads (called ischial callosities), on the buttocks. Their gestation period is five to nine months. Adult Old World monkeys have 32 teeth. The Old World monkeys, sometimes called true monkeys, are more closely related to the apes and humans than they are to the New World monkeys; the two monkey groups probably evolved separately from ancestral primates.

The Old World monkeys include the many species of macaque, widely distributed throughout Africa and Asia. The rhesus monkey is an Asian macaque. Related to the macaques are the baboons of Africa and South West Asia, as well as the mandrill and mangabey of Africa. The guerezas, or colobus monkeys (genus Colobus), are very large, long-tailed, leaf-eating African monkeys. Their Asian relatives, the langurs and leaf monkeys, include the sacred monkeys of India. The snub-nosed monkey of China and the proboscis monkey of Borneo are langurlike monkeys with peculiar snouts. The guenons (Cercopithecus) are a large group of long-legged, long-tailed, omnivorous monkeys found throughout sub-Saharan Africa. One very widespread guenon species is the green monkey, or vervet, with olive-brown fur.


The New World monkeys are found from South Mexico to central South America, except in the high mountains, and are classified into two families (Callatrichids and Cebids). The Callatrichids are very small, while the Cebids are similar in size to the Old World monkeys. They are all thoroughly arboreal and most have long, prehensile tails with which they can manipulate objects and hang from branches. In most the thumb is lacking. They have widely separated nostrils that tend to point outward; they lack cheek pouches and ischial callosities (a thickened piece of skin found on the buttocks). Their gestation period is four to five months. Adults of most New World species have 36 teeth. The New World monkeys include the marmosets and tamarins, small monkeys with claws that are classified in a family of their own, the Callithricidae. The rest of the New World monkeys are classified in the family Cebidae. They include the capuchin (genus Cebus), commonly seen in captivity, which has a partially prehensile tail. Prehensile tails are found in the spider monkey and woolly monkey as well as in the howler monkey, the largest member of the family, which has a voice that carries several miles. Smaller forms with nonprehensile tails are the squirrel monkey and titi, the nocturnal douroucouli, or owl monkey, the saki, and the ouakari.


Thousands of primates are peddled as "pets" each year, including monkeys, apes and lemurs. Highly intelligent and social animals, they suffer terribly in the inhumane pet trade.

These wild animals are bred in captivity and taken from their mothers within hours or days of birth, or stolen from their mother in the wild who is often killed in the process. Sold like toys by unethical businesses and backyard breeders, profit is put above the welfare of the animals. Unprepared guardians purchase the animals, often with little knowledge on primate care. Adorable baby monkeys quickly grow into aggressive and territorial adults. Guardians often resort to drastic measures to control the animals, such as inhumane tooth removal. Eventually they are abandoned, given to roadside zoos or sold to another unprepared family where the cycle begins again. They end up living their lives in tiny cages, isolated, lonely, deprived of their wild nature and social interaction with their own kind.

The complex physical, psychological and social needs of primates can never be met when they are kept as pets. Living in constant frustration, these wild animals can inflict serious and catastrophic injuries. They can also spread diseases that are deadly to humans, including viral, bacterial, fungal and parasitic infections. It is common for monkeys to carry tuberculosis, hepatitis and simian herpes B.

Even the smallest of monkeys are incredibly strong and become unpredictable when they reach sexual maturity. Hundreds of people have been injured by attacks from primates, sometimes causing permanent disability and disfigurement.


Every year thousands of monkeys are imprisoned in laboratories, where they are abused, neglected and killed in invasive and painful experiments. They are either bred in government or commercial facilities or laboratories, or captured from the wild. Those born in laboratories are torn from their mothers usually within three days of birth. Those from the wild are often taken from their mothers, who are sometimes killed. They are crammed into tiny crates with little to no food or water and taken to filthy holding centers, followed by long and terrifying trips in the cargo holds of passenger airlines. Following the traumatic separation from their families and/or homes, monkeys in laboratories are usually confined to small, barren cages. They barely have enough room to sit, stand, lie down or turn around.

90 percent of primates in laboratories exhibit abnormal behaviors caused by the physical abuse, psychological stress, social isolation and barren confinement that they are forced to endure. Many go insane, rocking back and forth, pacing endlessly in the cages, and engaging in repetitive motions and acts of self-mutilation.

Their fundamental needs and desires are disregarded and they are subjected to painful and traumatic procedures. Most animal experiments are not relevant to human health and do not contribute meaningfully to medical advances. Human clinical and epidemiological studies, human tissue and cell-based research methods, cadavers, sophisticated high-fidelity human patient simulators and computational models are more reliable, more precise, less expensive and more humane than animal experiments.


The use of monkeys as “entertainers” removes animals from their natural habitat; depriving them of the ability to freely engage in instinctual behaviors. Both children and adults are desensitized to animal mistreatment by the animal entertainment industry. Whether they're at a zoo, on a film set, or under a circus tent, monkeys used as entertainment are forced to perform unnatural and painful tasks through abusive training methods.

Animals used in film, television, advertising or as sports mascots are ripped away from their mothers as infants. They are forced to spend most of their lives in small cages. They often live alone, resulting in severe psychological anxiety. “Performing” is stressful, confusing and often torturous. Training methods may involve beating the animals, causing them to be constantly anxious and fearful. When the animals become too large to handle, they are often dumped at shoddy roadside zoos and other substandard facilities, where they spend the rest of their lives in small, barren cages—many in solitary confinement. “Retirement” from entertainment is a long life of misery for these highly intelligent and sensitive animals. The American Humane Association’s (AHA) “No Animals Were Harmed” seal of approval is extremely misleading. AHA does not monitor living conditions of animals off set, during pre-production training, or during the premature separation of infants from their mothers.

Circus animals are forced to travel in box cars or trucks for months at a time with no regard for temperature, exercise or normal interaction with their own kind. These animals do not willingly stand on their heads, jump through rings of fire, or ride bicycles. They don’t perform these tricks because they want to and they don’t do any of these meaningless acts in their natural habitat. They do not perform because they are positively reinforced. Instead, they are trained with varying levels of punishment, neglect and deprivation.

Even under the best of circumstances, captivity is cruel for wild animals. Confined to tiny areas and gawked at by crowds, animals in exhibits and acts endure constant stress. They may suffer from temperature extremes and irregular feeding and watering. Without exercise, they become listless, their immune systems are weakened, and they become prone to sickness; many resort to self-mutilation in reaction to stress or boredom. Mental illness is rampant among confined animals. Torn from their families and deprived of all dignity, every part of their lives is controlled by their captors.

While zoos may appear to be educational and conservation-oriented, most are designed with the needs and desires of the visitors in mind, not the needs of the animals. Many animals in zoos exhibit abnormal behavior as a result of being deprived of their natural environments and social structures. When the facility breeds too many animals they become "surplus" and often are sold to laboratories, traveling shows, shooting ranches, or to private individuals who may be unqualified to care for them.