Monkeys communicate through body postures, gestures, and vocalizations, all of which require intelligence to be interpreted. A male rhesus monkey threatens members of its group by staring, opening its mouth and showing its teeth, or slapping the ground with its hands. All species of monkeys live together in social groups. New World monkey troops usually consist of no more than 20 members. Old World monkey groups usually have 30 to 100 members.
Family groups consist of an adult male, an adult female, and their young.
Multimale groups consist of a number of adult males, about twice as many adult females, and their young. Most New World monkeys live in such groups, including capuchins , spider monkeys , squirrel monkeys , and marmosets. One-male groups consist of one adult male, several adult females, and their young. Young adult males and females may also belong to the group. Certain species of Old World monkeys live in such groups.