GREAT APES AND HUMANS: Hominidae

PHYSICAL CHARACTERISTICS

Gorillas, chimpanzees, and bonobos are dark-colored, while orangutans are reddish brown. All have arms that are longer than their legs. Gorilla and orangutan males are twice as big as females. Great apes have forward-facing eyes for three-dimensional (height, width, and depth) viewing. They have powerful fingers and toes for gripping branches. They have no tails.

GEOGRAPHIC RANGE

Orangutans are the only great apes residing in Asia, in the countries of Indonesia and Malaysia. Gorillas and chimpanzees live in most countries of Africa, while bonobos are found only in the Democratic Republic of the Congo.

HABITAT

Great apes generally occupy fully developed forest canopies and dense shorter vegetation. They inhabit grasslands, bamboo forests, swamp forests, and mountain forests.

DIET

The diet of great apes includes fruits, leaves, flowers, seeds, barks, insects, and meat.

BEHAVIOR AND REPRODUCTION

African apes are mostly ground-dwellers, walking on their knuckles and feet. The lighter species climb trees, swinging by their arms from branch to branch in a mode of traveling called brachiation (brake-ee-AY-shun). Orangutans are arboreal (tree-dwelling). On the rare occasions that they descend to the ground, they walk on their clenched fists. All great apes are diurnal, foraging during the day and sleeping in nests at night. Some take long breaks for grooming sessions.

Great apes are not seasonal breeders. Females have single births, caring for the young for a lengthy period with no help from the fathers. Male gorillas and chimpanzees engage in rivalries and takeovers that result in infanticide (killing of the young). Bonobo females are constantly receptive to mating. Orangutan males may commit forceful mating.

GREAT APES AND PEOPLE

Great apes are hunted by humans for meat and trophies. Some people believe apes' body parts have medicinal or magical powers. When infants are collected for the pet trade, the mothers are often killed.

A CHOREOGRAPHED DISPLAY

A silverback puts on an impressive threat display to protect his family from an intruder. First he hoots, and then throws vegetation around. Standing erect, he beats his chest with cupped hands. He kicks with one leg and shows his sharp canine teeth. Running on all fours, he rips off more vegetation. Standing up again, he slaps the ground with his hands. Finally, he rushes the intruder, stopping just a few feet away to allow the intruder to leave.

CONSERVATION STATUS

The IUCN lists the Sumatran orangutan as Critically Endangered, facing an extremely high risk of extinction in the wild, due to hunting, as well as habitat loss and degradation from agriculture and logging. The remaining five great ape species are Endangered, facing a very high risk of extinction, for the same reasons.

BORNEAN ORANGUTAN (Pongo pygmaeus): SPECIES ACCOUNTS

Physical characteristics: Bornean orangutans have long, shaggy, reddish brown hair. Facial skin color ranges from pink to red to black. Arms, which are longer than the orangutan is tall, are useful for reaching fruits and brachiating. Scooplike hands and feet have powerful grips for grasping branches. Cheek pads in adult males make the face look larger. A throat pouch is inflated to produce loud, long calls to advertise their whereabouts. Males may reach 200 pounds (90.7 kilograms), with a standing height of about 5 feet (1.5 meters). Females are about 100 pounds (45.4 kilograms), standing 3 feet (1 meter) tall.

Geographic range: Bornean orangutans are found in Indonesia and Malaysia.

Habitat: Bornean orangutans prefer mature forests with fruiting trees. They also inhabit mangroves, swamps, mountain forests, and deciduous forests.

Diet: Orangutans feed mainly on fruits, supplemented with leaves, flowers, buds, barks, honey, insects, and bird eggs. They use tools, such as sticks, to get honey out of beehives.

Behavior and reproduction: Orangutans are mostly arboreal, although heavy adult males travel on the ground, walking on their clenched fists and feet. They ascend trees to feed. Females and juveniles build sleeping nests in trees, while adult males sleep on ground nests. Orangutans use big leaves as umbrellas for protection from the hot sun and rain.

Orangutans do not form social groups. Adult males avoid one another, using long calls to warn neighbors to stay away. When encounters are unavoidable, fights may end fatally. Females with offspring congregate briefly at abundant feeding sites. Females ready to breed pursue males, who leave soon after mating. Both sexes may have several partners. Some males force themselves on unwilling females. Females have single births every four to eight years, the longest interval between births of any mammal. Orangutan young also have the longest childhood of all animals. After nursing for about four years, they stay close to their mothers for another three (males) to five (females) years.

Bornean orangutans and people: Orangutans are hunted for meat and infants are sold as pets.

Conservation status: The IUCN lists the Bornean orangutan as Endangered due to hunting for food and capture of young for the pet trade. Habitat is lost to agriculture, logging, and human settlements. ∎

WESTERN GORILLA (Gorilla gorilla): SPECIES ACCOUNTS

Physical characteristics: The western gorilla has short black hair with red or brown coloration on the top of the head. The face is black. The head is elongated, and a brow ridge sits over the eyes. A protruding belly houses a large intestine for processing a plant diet. The arms are very long, and the thick-skinned knuckles are used for walking. Big toes help grasp tree branches. At ages eleven to thirteen, males acquire silver-gray hair on their back, earning the name silverbacks. Males are bigger than females, averaging 352 pounds (160 kilograms) with a standing height of 5 to 6 feet (1.5 to 1.8 meters). Females weigh 150 to 251 pounds (68 to 114 kilograms), standing 5 feet (1.5 meters) tall.

Geographic range: Western gorillas are found in Angola, Cameroon, the Central African Republic, Congo, the Democratic Republic of the Congo, Equatorial Guinea, Gabon, and Nigeria.

Habitat: Western gorillas occupy open canopies and dense understories and forests that have been cultivated or logged. They inhabit swampy clearings, forests along rivers, and full-canopied primary forests.

Diet: Western gorillas prefer fruits but also feed on plants. In swamp forests, they eat water plants. Juveniles also eat termites and ants.

Behavior and reproduction: The gorilla family typically consists of a dominant male (silverback), a younger male, several adult females, and their offspring. The silverback protects the group, settles conflicts, and determines daily activities. The group forages on the ground, climbing trees only for special fruits or leaves. Members communicate using facial expressions, body language, and vocalizations. Females groom the silverback and mothers and infants groom each other, but other adults do not engage in mutual grooming. Gorillas build sleeping nests in trees, although heavier males nest on the ground.

The silverback mates with all receptive females, but adults of both sexes may have several partners. Females have single births every four years, nursing the young for three years. A young female leaves home to join a lone male or another group. She may change groups several times. A young male may inherit his father's position or leave home. When ready to reproduce, he will try to take over a group. If he succeeds, he kills the infants so that the mothers will be receptive to breeding. Scientists have found that males who stay in the neighborhood after leaving home have nonaggressive encounters, because they may be siblings or half-brothers and, therefore, have a familiar relationship.

Western gorillas and people: Western gorillas are popular in zoo exhibits. They are hunted for meat.

Conservation status: The IUCN lists the western gorilla as Endangered due to hunting, as well as habitat loss and degradation from agriculture, logging, and human developments. ∎

CHIMPANZEE (Pan troglodytes): SPECIES ACCOUNTS

Physical characteristics: Chimpanzees have black hair, which may turn gray with age, accompanied by partial balding. The naked face varies from pink to black and has a short, white beard. They have a brow ridge, protruding snout, and large ears. The thumbs function like those of humans for handling objects. The large toes are used for a firm grip when climbing trees. Males weigh 80 to 130 pounds
(36.3 to 59 kilograms), and females about 70 to 100 pounds
(31.8 to 45.4 kilograms). They stand about 3.8 to 5.5 feet (1 to 1.7 meters) tall.

Geographic range: Chimpanzees are found in many African countries, including Senegal, Guinea, Sierra Leone, Ivory Coast, Ghana,

Nigeria, Cameroon, the Central African Republic, the Democratic Republic of the Congo, Rwanda, Tanzania, Uganda, and Sudan.

Habitat: Chimpanzees occupy mountain forests, open woodlands, and grasslands.

Diet: Chimpanzees are omnivorous, eating both plants and animals. They feed on fruits, nuts, flowers, seeds, and bird eggs. Their favorite prey is the red colobus monkey. They also eat termites, small antelopes, and bush pigs.

Behavior and reproduction: Chimpanzees live in communities of as many as eighty individuals, but may form subgroups of just males, mothers and young, or both sexes of different ages. A dominant male rules a group but may be replaced at any time. Adult males dominate all females. Males defend their territory from outside groups, sometimes killing all the members of the outside group. Chimpanzees sleep in tree nests. They are expert tool users, using rocks to open nuts and sticks to get termites. They communicate through facial expressions and a variety of sounds. Group members groom each other to strengthen social bonds.

Adults have several partners. Females have single births every four or five years. The young nurse for about four years, staying close to their mothers for another four years. Adolescent females may join another group.

Chimpanzees and people: Chimpanzees are popular exhibit animals in zoos and have been used in movies and television shows. They are hunted for food. They are used in medical research and were used in the space program.

Conservation status: The IUCN lists the chimpanzee as Endangered due to hunting for food, as well as habitat loss and degradation for agriculture, logging, and human settlements. ∎

HUMAN (Homo sapiens): SPECIES ACCOUNTS

Physical characteristics: Humans differ in skin color, depending on the amount of the pigment melanin in their skin. The body is hairless, except for the head, armpits, and genital areas. Scientists suggest that early humans had shed their fur to prevent over-heating when chasing their prey, and developed sweat glands on the skin surface to cool the body by perspiring. The subcutaneous fat, or the fatty layer under the skin, preserves body heat when the environment gets cold and serves as an energy source when food is scarce.

Humans possess a distinct trait, bipedalism (bye-PED-ul-ih-zem), or a mode of locomotion on two legs. Strong, muscular legs are adapted for upright walking. The S-shaped curve of the spine keeps an erect human from toppling by distributing the body weight to the lower back and hips. However, the flexible spine, adapted by early humans for running and catching prey, has caused problems to modern humans, especially the weak lower backbone that is not adapted for supporting the heavy head and trunk.

Geographic range: Humans inhabit almost all of Earth's land surfaces. While humans may not be able to live in the very cold regions of Antarctica or in the central Sahara Desert, they are capable of visiting those areas. Modern technology has allowed humans to travel over water, underwater, and through the air. Humans are also able to

live in space, such as in the International Space Station, and have landed on the moon.

Habitat: Humans live in all land habitats.

Diet: Humans are omnivorous, feeding on both plant and animal matter.

Behavior and reproduction: Humans differ from other primates by their use of language, a distinct type of communication that can be manipulated to produce an unlimited number of expressions. Humans use symbols and communicate through symbols, such as art. Another human-specific behavior is their reliance on tools and technology. However, humans' most striking characteristic is their mental ability to create ideas.

Although a monogamous (muh-NAH-guh-mus) family, with a mated male and female, typically represents the human social unit, many cultures practice polygyny (puh-LIH-juh-nee; one male with several mates), polyandry (PAH-lee-an-dree; one female with several mates), and polygamy (puh-LIH-guh-mee; both sexes have several mates). Humans are unique in that they do not generally sever ties with relatives when they move. However, humans are capable of aggressive and violent relationships.

Humans have no breeding seasons. While single births are most common, multiple births occasionally occur. Human young develop slowly, needing care and protection from adults. The young learn social behaviors through imitation. While average life spans can vary around the world, men and women generally live into their sixties and seventies. While males can parent children in old age, females stop reproducing with menopause (generally starting at age fifty), after which they may live many more years.

According to scientists, the human baby, given the big size of its brain, needs about twenty-one months to develop fully in the mother's womb. But, since the female birth canal, through which a baby passes, has evolved to a narrower size to allow for upright locomotion, babies have to be born "prematurely" (after nine months). The brain develops further outside the womb.

FOR MORE INFORMATION

Books:

Arsuaga, Juan Luis. The Neanderthal's Necklace: In Search of the First Thinkers. New York: Four Walls Eight Windows, 2001.

Bright, Michael. Gorillas: The Greatest Apes. New York: DK Publishing, Inc., 2001.

Dunbar, Robin, and Louise Barrett. Cousins: Our Primate Relatives. New York: DK Publishing, Inc., 2001.

Estes, Richard D. The Behavior Guide to African Mammals: Including Hoofed Mammals, Carnivores, Primates. Berkeley, CA: The University of California Press, 1991.

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

Grace, Eric S. Apes. San Francisco, CA: Sierra Club Books for Children, 1995.

Kaplan, Gisela, and Lesley J. Rogers. The Orangutans: Their Evolution, Behavior, and Future. Cambridge, MA: Perseus Publishing, 2000.

Lindsey, Jennifer The Great Apes. New York: MetroBooks, 1999.

Lynch, John, and Louise Barrett. Walking with Cavemen. New York: DK Publishing, Inc., 2003.

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

Povey, Karen. The Chimpanzee. San Diego, CA: Lucent Books, 2002.

Russon, Anne E. Orangutans: Wizards of the Rain Forest. New York: Firefly Books, 2000.

Tattersall, Ian. Becoming Human: Evolution and Human Uniqueness. New York: Harcourt Brace & Company, 1998.

Periodicals:

Bradley, Brenda J., et al. "Dispersed Male Networks in Western Gorilla." Current Biology (March 23, 2004): 510–513.

Jones, Clyde, et al. "Pan troglodytes." Mammalian Species 529 (May 17, 1996): 1–9.

Stanford, Craig B. "Close Encounters: Mountain Gorillas and Chimpanzees Share the Wealth of Uganda's 'Impenetrable Forest,' Perhaps Offering a Window onto the Early History of Hominids." Natural History (June 2003): 46–51.

Web sites:

Friend, Tim. "Chimp Culture." International Wildlife (September/October 2000). Online at http:www.nwf.org/internationalwildlife/2000/chimpso.html (accessed on July 7, 2004).

"Great Apes & Other Primates: Gorillas." Smithsonian National Zoological Park. http://natzoo.si.edu/Animals/Primates/Facts/FactSheets/Gorillas/default.cfm (accessed on July 7, 2004).

Gunung Palung Orangutan Project.http://www.fas.harvard.edu/gporang/index.html (accessed on July 7, 2004).

"Orangutans: Just Hangin' On." Public Broadcasting Service (PBS) Nature. http://pbs.org/wnet/nature/orangutans/index.html (accessed on July 7, 2004).

Sea World Education Department. "Gorillas." Sea World/Busch Gardens ANIMALS. http://www.seaworld.org/animal-info/info-books/gorilla/index.htm (accessed on July 7, 2004).

Stanford, Craig B. "Chimpanzee Hunting Behavior and Human Evolution." American Scientist Online http://www.americanscientist.org/template/AssetDetail/assetid/24543?fulltext=true&print=yes (accessed on July 7, 2004).