Monkeys are a diverse group of mammals known for their fast reactions and smart thinking. These are adaptations for their lives in the treetops, where they form social bonds and work together to problem-solve. Monkeys are found on every continent except Antarctica, with most species living in warm and wet rainforest habitats. Some monkeys are nocturnal, while others such as the mandrill (Mandrillus leucophaeus) can be active at any time of day. Monkeys have long, flexible hands and feet to grasp branches, which also help them travel through the canopy of the forest.
Most monkeys live in troops, which include several females and their offspring along with one or more males. The troops are led by adult females, and the males either stay in the troop where they were born or move to other troops. Some monkeys such as the gray titi monkeys of Bolivia live in monogamous families, while other species such as hamadryas baboons and savanna baboons maintain multi-male families.
Like humans, monkeys can communicate with gestures and vocalizations. They can use their hands and feet to grasp branches, eat seeds and fruits, and hunt insects and small vertebrates. Some monkeys such as pygmy marmosets (Cebuella pygmaea) gnaw holes in gum trees to release sticky secretions that they then lap up.
Many monkeys can swim; they may use their webbed toes to paddle through rivers or streams or simply swim across to avoid predators or get to a new food source. Monkeys can also communicate with scent and a series of grunts. Body language reveals much about the emotions of monkeys, including signs of aggression and fear. For example, when monkeys “grin,” pulling their lips back to show their teeth, they are not making a human smile but showing aggression. Other body movements such as head bobbing and yawning can also indicate aggressive intent.