Monkeys are highly social animals that live in groups called troops. They usually include several females with young and either a single male (hamadryas baboons, mandrills) or multiple males (all guenons, most langurs). Monkeys have long limbs that make them suited to life in the trees, where they spend most of their lives, leaping from limb to limb as they travel through the canopy. Some species have prehensile tails, which help them grip branches as they forage for food. Their feet are also flexible, allowing them to traverse narrow branches or swim across rivers. Many monkeys are nocturnal, and some, such as vervet monkeys, emit loud alarm calls that alert other members of their troop to danger.
Like people, monkeys use vocalizations, facial expressions, and body movements to communicate with each other. Baring their teeth, for example, may look like a smile to us but is actually a sign of aggression or fear, Live Science reported. In addition, some monkeys have very long tails that they can wave to signal their moods or warn other monkeys of potential threats.
Some kinds of monkeys, such as colobus monkeys and langurs, have babies that are a different color than their parents. This helps other members of the troop identify and care for the infants.
Some monkeys eat meat, including young antelope and rabbits, while others, such as rhesus macaques, eat leaves. They even have special chambered stomachs to help them digest their leaves. Many species of monkey suffer from parasites, and the prehensile tails of some — such as tamarins and rhesus macaques — come in handy to sweep the worms out of their guts.