Monkeys are highly intelligent animals that often live in groups called troops. The members of a monkey troop usually mate and give birth together, with females typically taking care of their young while the males go out and gather food. Many monkey species breed seasonally, and some (such as the guanana) have a gestation period of 160 to 170 days. Some, such as the guianan squirrel monkey (Saimiri sciureus), only breed in September and November.
Monkeys use vocalizations to communicate with one another, as well as body movements and facial expressions. They may look down or away to avoid threatening other monkeys and thus prevent fights. Monkeys that make loud noises such as barks, screams, grunts, and hoots are likely to be communicating territorial claims or alerting others of a danger. They also use their tails to move from branch to branch, and some types of monkeys have bare areas of skin on their faces and buttocks that are brightly colored.
Most monkeys are omnivorous, eating both plant and animal materials. The diet of the patas monkey, for example, varies with the seasons. During the rainy season when fruit is abundant, it will eat more fruits and berries. But during the dry season, it will focus more on plants such as grass, leaves, and stems (Nakagawa 1989; Gartlan 1965).
Some monkeys are experts at climbing, including mandrills and baboons that can scale trees up to 50 feet or more. Other monkeys spend more time on the ground, like the geladas and golden monkeys that live in mountainous regions of Africa. And some, such as the Japanese macaques, are known to bathe in hot springs during the winter—not just to stay warm, but to lower their stress levels.