HOWLER MONKEYS AND SPIDER MONKEYS: Atelidae

PHYSICAL CHARACTERISTICS

The atelids (members of the Atelidae family) are the largest New World primates. They range in color from yellowish beige to dark red to black. Males and females of some howler species differ in color. Many spider monkeys have light-colored masks around their eyes. Howler and woolly monkeys have stocky bodies and shorter limbs, while spider monkeys and muriquis have slimmer bodies and long tails. All tails are prehensile, capable of grasping tree branches, so that the monkeys usually feed while suspended.

GEOGRAPHIC RANGE

Atelids are found in Mexico, all of Central America (Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama), and South America (including Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Peru, and Venezuela).

HABITAT

Howler monkeys and muriquis inhabit secondary forests with open canopies. Spider and woolly monkeys prefer full-canopied primary forests, although spider monkeys are also found in semideciduous and secondary forests.

DIET

Howler monkeys prefer leaves, while other atelids favor ripe fruits. All diets are supplemented with flowers, seeds, and insects.

BEHAVIOR AND REPRODUCTION

All atelids are arboreal (tree-dwelling) but occasionally descend to the ground. They are diurnal (active during the day). Some species have grooming sessions and play time. Atelids do not defend territories. They generally move through the forest on all fours with brachiation (brake-ee-AY-shun; swinging below branches using the arms), usually assisted by the tail.

Adults have several mating partners. Females have single births, which occur at different intervals depending on species. The mother alone tends to the infant. Except for howler monkeys, young males remain with the group, while females leave to join other males. Male howler monkeys form their own group and invade another group, killing the young.

ATELIDS AND PEOPLE

Atelids are valued for their meat. Spider monkeys and muriquis are collected as pets because they are typically good-natured.

A THIRD HAND

All atelids have a prehensile, or grasping, tail. A prehensile tail is muscular and is bare underneath in the last third of the tail. The bare skin has tiny, fingerprint-like ridges that provide a firm grip around branches, just like an extra hand. An animal can wrap its tail around a sturdy branch, freeing up its hands to reach for fruits and new leaves at the end of weaker branches.

CONSERVATION STATUS

The IUCN lists eleven species as threatened because of continued hunting and habitat loss and degradation from human activities. The variegated spider monkey, the northern muriqui, and the yellow-tailed woolly monkey are listed as Critically Endangered, facing an extremely high risk of extinction, dying out, in the wild. The Guatemalan black howler monkey, the white-whiskered spider monkey, and the southern muriqui are listed as Endangered, facing a very high risk of extinction. The Colombian woolly monkey is classified as Vulnerable, facing a high risk of extinction, and two other species are listed as Near Threatened, not currently threatened, but could become so.

VENEZUELAN RED HOWLER MONKEY (Alouatta seniculus): SPECIES ACCOUNTS

Physical characteristics: The Venezuelan red howler monkey has thick, dark red to purplish red fur, with bright orange or gold underparts. The prehensile tail is used as a third hand for picking food. The black face is naked, and the wide jaw is covered with a thick beard. An enlarged hyoid (HYE-oid) bone at the root of the tongue gives the throat a swollen appearance. This bone is responsible for producing the loud howls that gave the monkey its name. Together with the enormous jaw, the swollen throat gives the monkey a grim appearance. It weighs 8 to 25 pounds (3.6 to 11 kilograms) and measures 17.5 to 27 inches (44 to 69 centimeters), with another 21 to 31 inches (54 to 79 centimeters) for the tail.

Geographic range: Venezuelan red howler monkeys are found in Venezuela and Brazil.

Habitat: Red howler monkeys prefer the forest canopy and understory. They inhabit secondary forests where the canopy is less developed but the ground vegetation is dense. They are also found in mountain forests, mangroves, and forests by rivers and streams.

Diet: Leaves make up more than 60 percent of a howler monkey's diet. It prefers the young leaves that are plentiful in the treetops. It also eats fruits, seeds, flowers, and insects.

Behavior and reproduction: Venezuelan red howler monkeys are arboreal and diurnal. Sluggish creatures, these monkeys spend plenty of time resting during the day. At dawn and dusk, they perform deafening howls that can be heard for at least 2 miles (3 kilometers). These calls advertise territory and group size to avoid confrontations with other groups. The monkeys also howl during heavy rainstorms.

Red howlers form groups of three to ten individuals, generally consisting of several unrelated adults. Adults have several mating partners, although the dominant male mates with all the receptive females. Females have single births every eighteen to twenty-four months. Mothers carry infants for about six months, first against the stomach and later on the back. Young howlers leave home by two years of age, although females may stay with the group. Young males leave to form their own all-male groups, which later take over another group, sometimes killing the young.

Venezuelan red howler monkeys and people: Red howler monkeys are hunted for food.

Conservation status: The IUCN does not consider the Venezuelan red howler monkey a threatened species. ∎

GEOFFROY'S SPIDER MONKEY (Ateles geoffroyi): SPECIES ACCOUNTS

Physical characteristics: Geoffroy's spider monkeys have a coarse, shaggy coat that comes in yellow, red, or black, turning lighter on the undersides. The black hands and feet are very long and spidery, giving the monkeys their name. The hands have underdeveloped thumbs. White cheek hair is raised, and the eyes are surrounded by pale skin to form a mask. The prehensile tail, at 25 to 33 inches (63.5 to 84 centimeters), is longer than the head and body length of 12 to 24.8 inches (30.5 to 63 centimeters). The prehensile tail enables the large animal to hang from a sturdy branch to pick fruits at the end of thin branches. The monkey weighs 13 to 20 pounds (6 to 9 kilograms).

Geographic range: Geoffroy's spider monkeys are found in Mexico, Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama.

Habitat: Geoffroy's spider monkeys prefer the top level of the forest canopy, where ripe fruits and young leaves are abundant. They occasionally descend to the middle layers. They inhabit mountain forests and mangroves.

Diet: Spider monkeys eat mainly ripe fruits. They especially prefer those with big seeds. They also feed on young leaves, flowers, buds, insects, insect larvae, and bird eggs.

Behavior and reproduction: Geoffroy's spider monkeys form groups with over forty individuals. When food is scarce, smaller subgroups and lone monkeys split from the main group when feeding. They forage, search for food, mostly in the early morning, resting the remaining part of the day. Spider monkeys are agile climbers, using their tail as an extra limb to move through the trees. They also travel on all fours and brachiate. They can jump down through forest gaps of over 33 feet (10 meters). The monkeys tend to go back to the same sleeping areas at nightfall.

Adults have several partners. Some males and females are dominant over others, but males competing for the same females are seldom aggressive with one another. A female determines which partner she will take. On average, females give birth to a single infant every three years because infants take that long to be independent. This is the longest period of infant dependency known among monkeys. Young females leave home, while young males remain in their birthplace.

Geoffroy's spider monkeys and people: Humans hunt spider monkeys for food.

Conservation status: The IUCN does not list Geoffroy's spider monkey as a threatened species. ∎

COLOMBIAN WOOLLY MONKEY (Lagothrix lugens): SPECIES ACCOUNTS

Physical characteristics: Colombian woolly monkeys range in color from black to blackish brown to lighter gray, with darker undersides, head, limbs, and tail. The fur is short, thick, and soft. The head is large and round, with a flat face and a snub nose. The ears are small. The body is stocky, with a protruding belly and a long, thick, muscular tail. The powerful prehensile tail can hold the large animal while suspended from a branch, as well as function as an additional hand. Woolly monkeys measure 20 to 27 inches (50.8 to 68.6 centimeters), with a tail length of 23.6 to 28.4 inches (60 to 72 centimeters). They weigh about 12 to 24 pounds (5.5 to 10.8 kilograms).

Geographic range: Colombian woolly monkeys are found in Colombia and Venezuela.

Diet: Colombian woolly monkeys feed mainly on fruits, supplemented with leaves, seeds, and occasional insects.

Behavior and reproduction: Colombian woolly monkeys are arboreal, sharing home ranges with other groups of their own species without hostility. They form groups of ten to forty-five individuals. Some males are dominant over other males, and all males are dominant over females, but they have a friendly relationship. They are diurnal, mostly foraging in the early morning and late afternoon, splitting into smaller subgroups when doing so. During midday, they rest, groom each other, and play. They greet each other by kissing on the mouth and embracing. Woolly monkeys travel through the forest on all fours, with some brachiation. They do not jump up but drop down to a branch by as many as 20 feet (6 meters).

Woolly monkeys have several partners, with dominant males mating with all receptive females. Females have single births every two to three years. An infant can cling to its mother's fur right away, first holding on to her stomach and later on to her back or side. Mothers carry the young for six to eight months, but nursing continues for up to twenty months. Young males remain in their birthplace, while females leave home to join other males.

Colombian woolly monkeys and people: Colombian woolly monkeys are hunted for food and trapped for the pet trade.

Conservation status: The IUCN lists the Colombian woolly monkey as Vulnerable due to habitat loss and degradation from logging and human settlement. ∎

FOR MORE INFORMATION

Books:

Emmons, Louise H. Neotropical Rainforest Mammals: A Field Guide. Chicago: The University of Chicago Press, 1997.

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

Kinzey, Warren G., ed. New World Primates: Ecology, Evolution, and Behavior. New York: Aldine de Gruyter, 1997.

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.

Periodicals:

Campbell, Christina J. "Female-Directed Aggression in Free-Ranging Ateles Geoffroyi." International Journal of Primatology (April 2003): 223–237.

Wallace, Robert. "Diurnal Activity Budgets of Black Spider Monkeys, Ateles Chamek in a Southern Amazonian Tropical Forest." Neotropical Primates (December 2001): 101–107.

Web sites:

Broekema, Iris. "Natural History of the Black-Handed Spider Monkey (Ateles geoffroyi)." The Primate Foundation of Panama. http://www. primatesofpanama.org/academicresources/articles/spiderblack.htm (accessed on July 6, 2004).

Broekema, Iris. "Natural History of the Mantled Howler Monkey (Aloutta palliata)." The Primate Foundation of Panama. http://www.primatesofpanama.org/academicresources/articles/howler.htm (accessed on July 6, 2004).

"Spider Monkey." Honolulu Zoo. http://www.honoluluzoo.org/spider_monkey.htm (accessed on July 6, 2004).

"What is a Woolly Monkey?" The Monkey Sanctuary. http://www.ethicalworks.co.uk/monkeysanctuary/woolly.htm (accessed on July 6, 2004).