Monkeys are omnivorous, eating nuts, fruits, leaves, flowers, roots, seeds, vegetables, rodents, birds and invertebrates-pretty much whatever is available in their habitat. They also play an important role in their native habitats as pollinators and seed dispersers. Their flexible feet help them climb and maneuver through the rainforest canopy, and some species can swim.
Monkeys live in small groups that are led by a mature female with her infants or by a single male (hamadryas baboons, mandrills and some guenons). The majority of monkey species live in mixed-gender troops. Some, such as patas monkeys and howler monkeys, have all-male groups.
They are highly social animals that communicate through vocalizations and facial expressions. Some of the sounds they make are alarm calls to warn other monkeys of predators or arousal in their territory. They can also communicate with one another about their moods through posture, eyes and other body movements. For example, when monkeys look away or down, it signals that they are not interested in a confrontation with a stranger.
Some monkeys, such as leaf-eating monkeys and pitheciine monkeys, eat only plants, including fruits and leaves. Their dentition and gut have adapted to support this specialized diet. Others, such as vervet monkeys and colobinae monkeys, eat both insects and plants. They have evolved specialized teeth and stomachs that ferment plant fibers, similar to those of ruminant ungulates.