Monkey (animal)

V

Intelligence and Behavior

Like all primates, monkeys demonstrate great intelligence. Among their mental feats is the apparent ability to create mental maps and calendars, storing information about the locations of different fruit trees and the time of year when the fruits become ripe. Monkeys communicate through body postures, gestures, and vocalizations, all of which require intelligence to be interpreted. Recent fieldwork has documented a rich repertoire of deliberate social deception among monkeys, especially among baboons. Deception requires the ability to think about another’s thoughts. Monkeys even have rudimentary comprehension of basic math concepts. Studies have shown that rhesus monkeys are able to understand the relations that exist among the numbers 1 to 9—that is, they can understand when a number is smaller or larger than another number.

Monkeys are among the most social of all mammals. Some species live in small family groups, but many form much larger troops that may contain more than a hundred animals. The size of these social groups is strongly influenced by what each species eats and the risks it has to take when foraging for food.

Like other primates, monkeys have varied diets. Some species, such as howler monkeys, feed largely on leaves, but most eat a mixture of foods, including leaves, flowers, bird eggs, and small animals. The leaf-eaters often live in small groups, noisily defending their area of forest from their neighbors. Foraging high in the forest canopy, they are safe from most ground-based predators, although they do have to be on their guard against birds of prey. Monkeys that often feed on the ground take greater risks because their food is more scattered. They face a greater chance of being attacked by large predators, such as cheetahs, lions, and hyenas. To survive, they tend to band together into larger troops.

Apart from the fearsome-toothed baboons, few monkeys have good defensive weaponry. Instead, they survive largely by using their intelligence. Ground-feeders, traveling in troops, often take turns acting as sentinel, making specific alarm calls to alert their companions to approaching danger. In trees, monkeys have other ways of outwitting their enemies. Capuchins, for example, sometimes fend off inquisitive predators by urinating on them from high above or by jumping up and down to make dead branches fall on the predators.

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Most monkeys can breed at any time of the year, so their troops often contain young of many different ages. Courtship is typically brief, with few of the complex rituals seen in many other animals (see Animal Courtship and Mating). Female monkeys show that they are receptive to mating by changes in behavior, scents, and visual signals. In Old World monkeys, these signals include color changes in patches of bare skin around the genitals. Unlike many mammals, primates have good color vision, so these changes soon attract the interest of the males.

Monkeys usually give birth to just one or two young, but some, such as marmosets, are known to have triplets. Most monkeys seem to have gestation periods ranging from 4 to 8 months, but the length of gestation of many species is unknown. As with other primates, a long period of growth and development enables the young to learn skills from the adults around them. The young stay with their mothers at least until they are weaned, and in many species the daughters remain with their mother’s family group for life. In many species, males often leave their mother’s family group when they reach adolescence. Depending on the species, adolescent and young adult males may lead solitary lives, live in bachelor groups, or move from group to group.

Compared to other mammals, monkeys are often long-lived. Life spans in the wild are difficult to gauge accurately, but in captivity some monkeys have survived to be more than 50 years old.

VI

Endangered Monkeys

In the tropics, monkeys have traditionally been hunted for food, but today they face a much graver threat through deforestation. Some species are able to survive in areas that have been selectively logged, but very few can survive where the forest is entirely removed.

The most endangered species of monkeys include the South American marmosets, which face the additional hazard of being captured and sold as pets. Many of Africa's forest-dwelling guenons and colobus monkeys are also endangered, partly through deforestation, but also by being hunted for their colorful pelts. In Asia, many of the macaques and langurs are endangered. The lion-tailed macaque, for example, which is found in southwest India and is thought to be the rarest Old World monkey, is in serious danger of extinction.

VII

New Species

New species of monkeys are rarely found, and when they are, their populations are usually so small that they are immediately classified as endangered species or threatened species. The most recent new species to be found, the highland mangabey (scientific classification Lophocebus kipunji), was reported in 2005 in southern Tanzania. Previously, the last new species to be found was in 1984 in Gabon. Scientists estimated that no more than 1,000 members of the highland mangabey exist.

Scientific classification: Monkeys belong to the Primate order. Marmosets make up the family Callitrichidae, Capuchin-like monkeys make up the family Cebidae, and Old World monkeys make up the family Cercopithecidae.

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