Groups of monkeys, called troops, travel together by day to find food. A troop can number from a few individuals to a thousand or more.
Within huge troops, monkeys form smaller groups, called harems, which include an adult male, several adult females, and their offspring. Unattached adult males, called bachelors, sometimes form their own group. To keep family bonds, monkeys engage in daily mutualgrooming.
One exception to social living is the gray titi monkey, native to the tropical forests of Bolivia. These small monkeys, which only weigh about 2 pounds (0.9 kilograms), live in small, monogamousfamily units made up of the parents and their immature offspring.
Some kinds of monkeys give birth to babies that are a completely different color from the parents. For example, adult colobus have black hair, but a newborn is white; langur babies are orange while their parents are black. This color distinction probably makes it easier for the whole troop to identify and look after the infants. The youngster’s color usually changes within the first six months, when a juvenile becomes an almost perfect copy of the adults.
Infants are helpless at birth, so they get rides by clinging to their mothers. But marmosets and tamarins are different—the fathers have almost all the responsibility! They carry the babies on their back and watch over them, only giving them to Mom for nursing. Another difference—they regularly have twin or triplet, not single, births. Is that because Dad helps out so much?
When the troop is not traveling, monkey babies are very active, spending much of their waking hours playing. These fun activities help young monkeys develop physical and social skills they need for adult life.
Monkeys are very social, so it is important that they communicate well in order to get along in their large groups. They use vocalizations, facial expressions, and body movements to get their messages across. Staring, for instance, is a threat in monkey society. Monkeys look down or away to avoid threatening other monkeys, thus preventing fights. Monkeys with long tails sometimes use them to communicatewithothers and indicate their mood. Loud vocalizations can mean, "stay out—this is my territory.” Using vocalizations instead of fighting is a much safer way to communicate. Monkeys use barks, screams, grunts, squeaks, hoots, wails, and moans to communicate with one another.
Grinning, or pulling the lip up to show the teeth, may seem like a smile to us. But for monkeys, this is a sign ofa*ggressionor anger, because biting is one of the ways monkeys fight and defend themselves. Other signs of aggression include head bobbing, yawning (again, to show the teeth), and jerking the head and shoulders forward. Cotton-topped tamarins raise and lower a crest of fluffy white hair on their head to emphasize their facial expressions.
Monkeys also express affection and make peace with others by grooming each other. Although grooming helps monkeys keep their fur clean of dirt, dead skin, and parasites, it also helps them build and maintain good social relationships. Grooming seems to be a way to make up after fighting or to make friends with other troop members.
