A monkey is a primate of the Haplorrhini suborder and simian infraorder, either Old World or New World (excluding apes and humans). Most species are arboreal but some, such as baboons, spend most of their time on the ground. They have long, prehensile tails, wide-spaced nostrils that usually point outward, and widely separated eyes, which help them to see in low light. Many also have a specialized tongue that can be flicked to show sexual interest.
Monkeys are social creatures and live in groups called troops that can include anywhere from 5 to 30 individuals. They communicate with each other using vocalizations, facial expressions, and body movements, such as staring, to avoid starting fights. They also use signals like bared teeth, yawning, and head bobbing to convey their emotions. For example, a monkey may bare its teeth to express aggression, while yawning can be a sign of fear.
While some monkeys live alone, others spend most of their lives in pairs. When a male and female are ready to mate, they will often display physical changes such as swelling of the genitals or reddening of the face. Then they will make a nest on the ground or in a tree. Monkeys usually give birth to one infant at a time.
Some species of monkeys are in danger of becoming endangered, due to habitat loss and human activities. In the wild, they can be found in tropical forests of Asia, Africa, Central and South America, and the Amazon basin. They can be found at elevations up to 4,300 meters (14,000 ft) and can grow up to 75 cm (30 in). They have a wide variety of food sources, including fruit, leaves, roots, flowers, bark, fungi, insects, and seeds. They are also known for their skills in climbing, leaping, and swinging from branch to branch.