Monkey, one of a large group of furred animals whose feet are used much like hands. Nearly all monkeys have tails. Monkeys are mammals, and zoologists classify them in the same suborder and order as humans and the great apes. They are native to tropical and subtropical regions of Central and South America, Asia, and Africa. Most monkeys live in the warm lowlands, but some kinds are found on the cool slopes of mountains. They usually live in trees, but some kinds are ground dwellers.

MonkeysMonkeys are furred animals whose feet are used much like hands.

The different kinds of monkeys vary a great deal in appearance. A monkey's fur is seldom all one color, but usually has markings in two or more colors. Fur colors include white, gray, black, red, gold, brown, and olive green. A monkey's face may be covered with short fur, or may be naked, with black, pink, gray, or brown skin. The face may be surrounded by a ruff of long fur, or there may be a beard. Often hands, feet, top of head, and tip of tail contrast in color with the rest of the body.

Monkeys vary also in size. The smallest monkeys are the pygmy marmosets of South America, whose bodies are only about six inches (15 cm) long, exclusive of a seven-inch (18-cm) tail. Largest are the baboons in Africa. A large male baboon may have a body more than two feet (60 cm) long, exclusive of tail, and may weigh up to 165 pounds (75 kg).

In their wild state, baboons and many other monkeys are aggressive and dangerous to humans. However, most monkeys can be tamed, if captured young. A few kinds, such as the capuchin, or sapajou, of Central and South America, and the rhesus of Africa, are highly intelligent, and make amusing, affectionate pets.

Monkeys are often used in scientific research because of their similarity to humans in anatomy and physiological processes. The blood plasma of the rhesus is used to determine the presence of the Rh factor in human blood. (The name of the substance was formed from the first letters of rhesus.)