OLD WORLD MONKEYS: Cercopithecidae

PHYSICAL CHARACTERISTICS

Old World monkeys are divided into the leaf-eating monkeys (including langurs [lang-GURZ] and colobus and proboscis monkeys) and the cheek-pouched monkeys (including macaques [muh-KOCKS] and mandrills). Most have subdued dark colorations with lighter undersides. Some, such as mandrills, have spectacular color combinations. All species have forward-facing eyes and short snouts. The buttocks have two hardened pads for prolonged sitting. Most have long tails. Leaf-eaters have a four-chamber stomach for digesting their main diet of plants. The cheek pouches are used for storing food to be safely eaten in trees.

GEOGRAPHIC RANGE

Leaf monkeys are found in Asia and Southeast Asia, except for the colobus monkeys. Cheek-pouched monkeys are found in Africa, including the Barbary macaque. All other macaques are found in Southeast Asia.

HABITAT

Old World monkeys live in virtually all land habitats, including grasslands, open dry forests, dense evergreen forests, mangroves, swamps, and forests along rivers. Some live near humans.

DIET

Leaf monkeys eat mainly leaves. Cheek-pouched monkeys consume fruits, seeds, insects, and occasionally young leaves.

BEHAVIOR AND REPRODUCTION

Old World monkeys are diurnal (active during the day). Most are arboreal (tree-dwelling), traveling on all fours. They can also leap, using the tail for balance. Some species use some brachiation (brake-ee-AY-shun, a type of locomotion in which an animal swings below branches using its arms. Social groups vary in size. Larger groups may split into subgroups when foraging. They are polygynous (puh-LIH-juh-nus), with males having several partners. Females have single births. Young females leave their birthplace, while young males stay with the group.

OLD WORLD MONKEYS AND PEOPLE

Old World monkeys are hunted for food. Some species are used in medical research.

POT BELLIES

The western red colobus, the proboscis monkey, and the red-shanked douc langur, all considered leaf monkeys, have evolved a four-chamber stomach that brings about a pot-bellied look. The stomach houses bacteria that break down fibrous leaves, the monkeys' main diet. The bacterial action not only releases nutrients from the leaves but also renders harmless the poisons found in some leaves.

CONSERVATION STATUS

The World Conservation Union (IUCN) lists five species as Critically Endangered, facing an extremely high risk of extinction, due to hunting, as well as habitat loss and degradation from agriculture, logging, and other human activities. These are the eastern red colobus, the Tonkin snub-nosed monkey, the Delacour langur, the white-headed langur, and the Mentawai macaque. Twenty-two species are classified as Endangered, facing a very high risk of extinction in the wild; seventeen are Vulnerable, facing a high risk of extinction in the wild; and twenty are Near Threatened, not currently threatened, but could become so.

WESTERN RED COLOBUS (Piliocolobus badius): SPECIES ACCOUNTS

Physical characteristics: The western red colobus monkeys are black or dark gray with bright red undersides. The cheeks and the lower parts of the limbs are also bright red. The Greek word kolobos, meaning "cut short," describes the missing thumbs, which allow for faster brachiation because thumbs do not get caught in the branches. The long tail maintains balance when leaping. Males measure about 23 inches (57 centimeters), with a tail length of 26.5 inches (66.5 centimeters), and weigh 18.4 pounds (8.36 kilograms). Females are slightly smaller.

Geographic range: The monkeys are found in Cameroon, Ivory Coast, the Democratic Republic of the Congo, Gambia, Ghana, Guinea-Bissau, Liberia, Nigeria, Senegal, and Sierra Leone.

Habitat: Red colobus monkeys prefer rainforests that provide young leaves year round. They inhabit primary and secondary forests, forests along rivers and streams, and wooded grasslands.

Diet: Western red colobus monkeys feed mainly on leaves, especially young leaves, but also eat flowers and shoots. They consume only unripe fruits. Ripe fruits contain sugar, which can be broken down by stomach bacteria, causing gas and acid formation that may be fatal.

Behavior and reproduction: Western red colobus monkeys form groups of nineteen to eighty individuals with numerous adult males and females. They do not defend their territory. They are arboreal and diurnal, splitting off into smaller subgroups when foraging. They move through the trees on all fours, with some brachiation. However, they are not agile climbers.

Males have several mating partners. Females give birth to a single infant every two years. The mother alone carries the infant. Young females leave home, transferring from one group to another. Males stay in their birthplace, forming a close association with one another.

Western red colobus monkeys and people: Western red colobus monkeys are hunted for food.

Conservation status: The IUCN lists the western red colobus as Endangered due to hunting for meat, as well as habitat loss and degradation from agriculture, logging, and human settlement. ∎

PROBOSCIS MONKEY (Nasalis larvatus): SPECIES ACCOUNTS

Physical characteristics: The proboscis monkey got its name from its bulbous nose, which in the male is long and drooping. It is thought that females are attracted to the large nose. The naked face is pinkish brown. The head and back are reddish orange, while the shoulders, neck, and cheeks are pale orange. The undersides, legs, and tail are grayish white. The webbed feet are useful for swimming. Males weigh about 45 pounds (20.4 kilograms) and measure about 30 inches (74.5 centimeters), with a tail length of 26.5 inches (66.5 centimeters). Females are about half the male size, weighing 21.6 pounds (9.8 kilograms) and measuring 25 inches (62 centimeters), with a tail length of 23 inches (57.5 centimeters).

Geographic range: Proboscis monkeys are found in Borneo.

Habitat: Proboscis monkeys occupy coastal mangrove forests and forests along rivers.

Diet: Proboscis monkeys feed mainly on leaves, supplemented with flowers and seeds. They eat unripe fruits but not ripe fruits, which, when processed by stomach bacteria, can cause potentially deadly gas and acid formation.

Behavior and reproduction: A proboscis monkey family consists of an adult male and several females and their offspring. Females give birth to a single infant and are assisted by other females with childcare. Young males are usually expelled upon puberty, traveling alone for a while or joining other bachelors. Proboscis monkeys do not defend their territory, but adult males threaten intruders with loud honks using their nose.

They are arboreal and diurnal, foraging in the early morning, then taking a long rest to digest their food. They may eat again before dark. The monkeys move on all fours and brachiate through the trees. They often jump from the trees into the water, from heights of as much as 53 feet (16 meters). They swim well and can stay underwater to escape a predator. They sleep in trees with branches that extend over water, perhaps as a lookout for their main predator, the clouded leopard.

Proboscis monkeys and people: Proboscis monkeys are hunted for meat.

Conservation status: The IUCN lists the proboscis monkey as Endangered due to hunting, as well as habitat loss and degradation from logging. ∎

RED-SHANKED DOUC LANGUR (Pygathrix nemaeus): SPECIES ACCOUNTS

Physical characteristics: The red-shanked douc langur is a colorful monkey. The back and upper arms are a grizzled gray, turning to a lighter gray on the undersides. Black hair covers the top of the head, and long, white whiskers frame the golden face. The eyelids are pale blue. The lower arms, wrists, and tail are white, and the hands and feet are black. The thighs are black, and the lower legs are maroon. Males weigh about 24.4 pounds (11 kilograms), and females weigh about 18.6 pounds (8.45 kilograms). Males measure 23.5 inches (58.5 centimeters), plus a tail length of 27 inches (68 centimeters). Females are 24 inches (60 centimeters) long, with a tail of the same length.

Geographic range: Red-shanked douc langurs are found in Vietnam and Laos.

Habitat: Douc langurs inhabit primary and secondary forests. They also live in evergreen forests, as well as in monsoon deciduous forests, characterized by heavy rainfall and dry periods during which leaves drop. They also occupy lowland and mountain forests.

Diet: Red-shanked douc langurs eat leaves, buds, flowers, fruits, and seeds.

Behavior and reproduction: Red-shanked douc langurs form groups of four to fifteen individuals, typically with more females than males. Both sexes have dominant individuals, but males are always dominant over females. The langurs are arboreal and diurnal, moving through the forest canopy on all fours and by leaping from branch to branch, landing on their hind legs. They socialize by grooming, going through each other's fur to remove dirt and parasites. They are vocal, using growls and squeaks to communicate.

Males have several mating partners. Every two years, females give birth to a single infant who receives plenty of attention and care from other females. Males sometimes tend to the young. Young males and females leave home when they are ready to start their own families.

Red-shanked douc langurs and people: Red-shanked douc langurs are hunted for meat.

Conservation status: The IUCN lists the red-shanked douc langur as Endangered due to habitat loss and degradation from human activities. ∎

RHESUS MACAQUE (Macaca mulatta): SPECIES ACCOUNTS

Physical characteristics: Rhesus macaques have long, brown hair with pale brown undersides. The hair at the top of the head is short. Facial skin is pinkish, while the rump is red. Males are slightly bigger than females, weighing about 17 pounds (7.7 kilograms) and measuring 21 inches (53 centimeters), with a tail length of 10 inches (24.5 centimeters). Females are about 11.8 pounds (5.4 kilograms), measuring 18 inches (45 centimeters), with a tail length of 9 inches (22 centimeters).

Geographic range: Rhesus macaques are found in Afghanistan, Pakistan, India, Nepal, Bhutan, Bangladesh, Myanmar, China, Thailand, Laos, and Vietnam.

Habitat: Rhesus macaques are adaptable, able to thrive in mangrove swamps, cedar-oak forests, woodlands, semi-desert scrub forests, forests along rivers, and even human settlements.

Diet: Rhesus macaques eat fruits, seeds, leaves, flowers, grasses, roots, bark, gum, and insects.

Behavior and reproduction: Rhesus macaques live in groups of eight to 180 individuals, although the average size is about twenty, with two to four times as many females as males. There are dominant males and females within a group, with the offspring inheriting the mother's rank. Macaques are arboreal but descend to the ground to forage and to move among human settlements. They prefer to sleep in the trees at night. They communicate through facial expressions, body language, and vocalizations, including barks, squawks, and growls. Adults have several partners. Females give birth to a single infant annually. Females remain with the group, while males may transfer from one group to another.

Rhesus macaques and people: The Rh factor in humans is named after the rhesus macaque, which was discovered to have this substance in its blood. Rhesus macaques are popular zoo animals. Farmers consider them pests for eating crops.

Conservation status: The IUCN lists the rhesus macaque as Near Threatened, meaning it could become threatened, due to hunting and habitat loss and degradation from human activities. ∎

MANDRILL (Mandrillus sphinx): SPECIES ACCOUNTS

Physical characteristics: Mandrills have a grizzled brown coat and gray-white undersides. Males have the most striking coloration of all mammals. The large, bright red nose is enclosed by blue bony bulges. The whiskers are white and the beard is golden. A tuft of hair on top of the head and a mane over the shoulders can be erected for threat displays. The rump has shades of red, blue, and lilac, and is used as a signal when leading the group through the dense forest. Females have almost similar colorations, but are not as striking. They have black faces. The largest of the Old World monkeys, male mandrills weigh about 69.7 pounds (31.6 kilograms), more than twice as heavy as females, who weigh 28.4 pounds (12.9 kilograms). Males measure 27.5 inches (70 centimeters), with a tail length of 3 inches (8 centimeters). Females measure 22 inches (54.5 centimeter), with a tail length of 3 inches (7.5 centimeters).

Geographic range: Mandrills are found in Cameroon, the Democratic Republic of the Congo, Equatorial Guinea, and Gabon.

Habitat: Mandrills occupy evergreen forests and forests along rivers and coasts.

Diet: Mandrills have a varied diet of fruits, seeds, grains, leaves, bark, mushrooms, tubers, snakes, and insects.

Behavior and reproduction: Although a typical mandrill family consists of a male and several females and their offspring, large groups with as many as 800 members have stayed together year after year, foraging for food, breeding, and fighting. A group having 1,350 individuals had been recorded. However, when not mating, males tend to be loners. Males prefer to forage on the ground, while females and the young climb trees. They may travel as much as 5 miles (8 kilometers) a day while feeding. All sleep in the trees. Mandrills communicate using grunts and crowing sounds. Adults have several partners, and females have single births. Young females stay with the group, but young males leave home, fighting fiercely during mating season, using their large, sharp canines.

Mandrills and people: Mandrills are hunted for meat.

Conservation status: The IUCN lists the mandrill as Vulnerable due to continued hunting, as well as habitat loss and degradation from agriculture, logging, and human settlements. ∎

FOR MORE INFORMATION

Books:

Fleagle, John G. Primate Adaptation and Evolution, 2nd ed. San Diego, CA: Academic Press, 1999.

Kavanagh, Michael. A Complete Guide to Monkeys, Apes and Other Primates. New York: The Viking Press, 1983.

Napier, John R., and Prue H. Napier. The Natural History of the Primates. Cambridge, MA: The MIT Press, 1986.

Nowak, Ronald M. Walker's Primates of the World. Baltimore: The Johns Hopkins University Press, 1999.

Preston-Mafham, Rod, and Ken Preston-Mafham. Primates of the World. New York: Facts on File, Inc., 1992.

Sterry, Paul. Monkeys & Apes: A Portrait of the Animal World. New York: Todtri Productions Limited, 1994.

Periodicals:

Angier, Natalie. "In Mandrill Society, Life Is a Girl Thing." New York Times on the Web.http://www.nytimes.com/library/national/science/052300sci-animal-mandrill.html (accessed on July 6, 2004).

Ferrero, Jean-Paul. "Swingers of Borneo." International Wildlife (November/December 1999): 53–57.

Laman, Tim. "Borneo's Proboscis Monkeys Smell Trouble." National Geographic (August 2002): 100–117.

Web sites:

"Cercopithecids (Cercopithecidae)." Singapore Zoological Garden Docents. http://www.szgdocent.org/pp/p-cercop.htm (accessed on July 6, 2004).