A monkey is a primate of the Haplorrhini suborder and the simian infraorder (excluding apes). Most monkey species are predominantly arboreal, leaping from limb to limb as they move through trees. They typically have five digits on their hands and feet, though the thumb and big toe are separate. They use their hands to grab and hold objects.
Monkeys have large brains and are known for their inquisitiveness and intelligence. They can use tools such as stones to crack nuts, and are adept at problem-solving. However, in contrast to the great apes, monkeys seem to lack a capacity for learning from their peers—individuals must discover and develop new behaviours on their own.
Many monkeys live in social groups called troops. They have complex social structures, including hierarchies and different ways of reinforcing their relationships. One common way monkeys bond is through mutual grooming, called allogrooming. This helps them keep their fur clean of dirt, parasites, and dead skin. But it also appears to be a way for monkeys to express affection and make peace in their groups.
Unlike their Old World cousins, New World monkeys are diurnal—active during the day. They have long, prehensile tails that they can hang by from tree branches to eat or rest. They have a wide range of habitats, from the tropical rainforests of Asia and Africa to the savannas of Central and South America. Some, such as geladas and golden monkeys, are mountain dwellers. Others, such as Japanese macaques, are found in areas that snow; when winter comes they seek out hot springs and spend their days sitting in them—kind of like a monkey Jacuzzi!