Monkey (animal)

I

Introduction

Monkey (animal), any of about 160 species of primates that have grasping hands, forward-facing eyes, and highly developed brains. Most monkeys also have tails, a characteristic that distinguishes them from their larger primate cousins, the apes. Monkeys are highly skilled climbers, and most spend much of their lives in trees. Some have prehensile tails—that is, tails capable of grasping—that they can use as a fifth limb while foraging for food or climbing.

Zoologists classify monkeys into three distinct families: marmosets, Capuchin-like monkeys, and Old World monkeys. Marmosets and Capuchin-like monkeys are found only in Central and South America and are known collectively as New World monkeys. Marmosets are dainty animals with luxurious fur, which is sometimes strikingly colored. One species, the pygmy marmoset, is the world's smallest monkey, measuring just 30 cm (12 in) long, at least half of which is tail, and weighing as little as 113 g (4 oz) when fully grown. The average life span of a pygmy marmoset in the wild is 10 to 12 years. By comparison, the Capuchin-like monkeys, which include capuchin monkeys, douroucoulis, spider monkeys, woolly monkeys, and howler monkeys, are more robust, although they are still lightly built. Howler monkeys, for example, are among the largest species and measure up to 1.8 m (6 ft) from the top of the head to the tip of the tail. Even so, their maximum weight is only about 10 kg (22 lb). Howler monkeys living in the wild have an average life span of around 16 to 20 years. Many New World monkeys have prehensile tails, and all have broad noses with sideways-opening nostrils.

Old World monkeys include guenons, mangabeys, colobus monkeys, macaques, langurs, and baboons. Compared to New World monkeys, their noses are narrower and have downward-opening nostrils. Old World monkeys do not have prehensile tails; instead, most use their tails simply for balance. As a result, these monkeys are less acrobatic than their New World cousins. Most Old World monkeys spend at least part of their time on the ground. While many are careful not to stray too far from the protective cover of trees, baboons are strong and aggressive enough to defend themselves in the open. Armed with fearsome canine teeth and weighing up to 41 kg (90 lb), male baboons are more than a match for many predators. A baboon in the wild can live as long as 30 years.

II

Predators

The predators of Capuchin-like monkeys are humans and birds of prey. The predators of marmosets include small cats, birds of prey, and snakes. The predators of macaques include large cats, such as leopards, tigers, and panthers, and large snakes, such as pythons. The predators of langurs and colobus monkeys include large cats, humans, and some birds of prey. The biggest threat to all monkeys, however, is the loss of habitat.

---

---

III

Range and Habitat

Monkeys are restricted to South and Central America, Africa, and the southern parts of Asia. Most monkeys live in the forests of the tropics and subtropics, where warm temperatures ensure a year-round supply of food. In rain forests, where food is abundant, monkeys often stay in the same area all year, but in drier habitats, they have to range further afield, possibly traveling more than 18 km (10 mi) a day.

Although most monkeys live in warm climates, some do survive in extreme environments. The Japanese macaque manages to survive the winter cold on the Japanese island of Honshū—the only nonhuman primate to survive that far north. A few tropical monkeys survive on high mountains well above the snow line, some at elevations as high as 4,000 m (13,000 ft). These high-altitude species include the Asian snub-nosed langurs, the African vervet, and several species of macaques. Monkeys can also survive in extreme deserts. In southwest Africa, for example, a troop of yellow baboons lives in the Namib Desert, where rainfall averages just a few inches a year.

IV

Physical Characteristics

All monkeys share physical features that are linked to their tree-climbing lifestyle. Foremost among these are forward-facing eyes, which enable monkeys to precisely gauge distances as they move about above the ground. Monkeys' hands and feet are also adapted for climbing. Their fingers and toes are very flexible, and their palms and soles—like those of humans—are usually covered in hairless nonslip skin. Most monkeys have flat nails, but the marmosets have claws, a feature they share with some primitive primates.

Many monkeys have opposable thumbs and opposable big toes, which can be closed against the other fingers or toes to create a tight grip. However, the extent of this feature varies greatly between species. Old World monkeys are often remarkably dexterous and can use their fingers to pick tiny parasites out of each other's fur. By contrast, New World monkeys lack truly opposable thumbs, although most have opposable big toes. Remarkably, one group of Old World monkeys—the colobus monkeys—do not have thumbs at all. Despite this apparent disadvantage, they have no difficulty climbing.

In many monkeys, the sexes differ in size and sometimes also in coloration. The mandrill, a West African baboon, is a striking example. Female mandrills weigh up to 11 kg (25 lb) and have dark faces, but the males can weigh more than 50 kg (110 lb) and their faces are brilliant blue and red. Male mandrills are the world's heaviest monkeys, and unlike the females, they only occasionally climb trees.

	More from Encarta
	•  Presidential Myths Quiz •  Coffee break: Recharge your brain