Baboons
Baboons
Baboons are ground-living monkeys in the primate family Cercopithecidae and are found in Africa and the Arabian Peninsula. Some taxonomists classify baboons in two genera, while others classify them in three or four. All baboons have a strong torso, a snoutlike face, the same dentition with long, sharp canine teeth, powerful jaws, a ground-walking habit, coarse body hair, a naked rump, and a similar social organization.
Baboons, who at the turn of the century were thought to outnumber people in Africa, are still the most populous monkeys on the continent. In contrast to most other primates, which are arboreal forest dwellers, baboons have successfully adapted to living on the ground—like humans. Baboons live in savanna woodland, rocky plains, hill regions, and rainforests, and are mainly terrestrial. They are active during the day and eat both plant and animal materials. Baboons form large groups, called troops, which travel together foraging for food. At night, they will sleep in groups.
Physical characteristics
Male baboons are nearly twice the size of the females. The common savanna baboon (Papio cynocephalus ) inhabits savanna woodlands and forest edges in Ethiopia, Angola, and South Africa. Savanna baboons eat grass, fruit, seeds, insects, and small mammals. These baboons have a gray coat with long hair covering their shoulders, and a patch of shiny black bare skin on their hips. Their tails are hook-shaped,
a result of the fusion of several vertebrae. In East and Central Africa P. cynocephalus is yellow; in the highlands of East Africa this species is olive-colored.
The hamadryas baboon (Papio hamadryas ) is found in the rocky and subdesert regions of Ethiopia, Somalia, Saudi Arabia, and South Yemen, with grass and thorn bush vegetation. These baboons feed on grass seeds, roots, and bulbs. Females and young hamadryas baboons have a brown coat, while adult males have a silver-gray mane over their shoulders and brilliant red bare skin on their face and around their genitals. This baboon was sacred to the ancient Egyptians. It is depicted in Egyptian art as an attendant or representative of the god Thoth, the god of letters and scribe of the gods. This species has been exterminated in Egypt and its numbers are reduced elsewhere in its range.
The Guinea baboon (P. papio ) also feeds on grass, fruit, seeds, insects, and small animals and is found in the savanna woodlands of Senegal and Sierra Leone. These baboons have a brown coat, bare red skin around their rump, and a reddish brown face.
The drill (Mandrillus leucophaeus ) lives in the rainforests of southeast Nigeria, western Cameroon, and Gabon, and feeds on fruit, seeds, fungi, roots, insects, and small animals. Drills have a brown-black coat and a naked rump ranging from blue to purple. A fringe of white hair surrounds a black face and the long muzzle has ridges along its sides. This species is considered endangered by the World Conservation Union (IUCN), largely due to the loss of its mature forest habitat in Cameroon.
The mandrill (Mandrillus sphinx ) is the largest monkey. It lives in southern Cameroon, Gabon, and Congo in rainforests. Its diet includes fruit, seeds, fungi, roots, insects, and small animals. Mandrill males have a blue-purple bare rump, and a bright red stripe running down the middle of their muzzle with blue ridges on the sides and a yellow beard. Female and the young mandrills are similarly colored, but less brilliantly. The mandrill population has declined in recent years due to habitat destruction, and this species is considered vulnerable by the IUCN.
Gelada baboons (Theropithecus gelada ) are found in the grasslands of Ethiopia, where they eat grass, roots, bulbs, seeds, fruit, and insects. Geladas have a long brown coat, hair that is cream colored at the tips and a long mantle of hair covering their shoulders and giving them the appearance of wearing a cape. The bare rump of both sexes is red and somewhat fat. Both sexes also have an area of bare red skin around their necks and the females have small white blisterlike lumps in this area of their bodies that swell during menstruation.
Social behavior
Baboon social behavior is matrilineal, in which a network of social relationships are sustained over three generations by the female members of the species. A troop of baboons can range in number from 30 to over 200 members, depending upon the availability of food. The baboon troop consists of related bands composed of several clans, where each clan may have a number of smaller harem families made up of mothers, their children, and a male. Female baboons remain with the group into which they are born for their whole lives, while the males leave to join other troops as they become mature.
Ranking within the group of females begins with the mother, with female offspring ranking below their mothers. Adult females are either nursing or pregnant for most of their lives, and they spend a great deal of time with other female friends, avoiding the males. During a daytime rest period, the females gather around the oldest female in the troop and lie close together. The way baboons huddle together while they are resting and the other movements in their troops are defense measures against outsiders and predators. The dominant males travel in the center of the troop to keep order among the females and the juveniles, while the younger males travel around the outer fringes of the group.
During their rest periods, baboons spend considerable time grooming one another, which helps to reinforce their social bonds. Females have male baboons that assist them in caring for their infants and protecting them from danger. These males may not be the fathers, but they may later mate with the female.
Baboon friendships
When a young male baboon matures, he leaves the family group to join a new troop. His first gestures are toward an adult female who may make friends with him. His gestures of friendship include lip-smacking, grunting, and grooming. It will take several months of this kind of friendly behavior before a more permanent bond is established between them. A female may have friendships with more than one male, and when she is ready to mate she may do so with all of her male friends. Social grooming between females and males is always between friends. A female benefits from this relationship by gaining protection and help in caring for her offspring. A male benefits by having a female with which to mate. These friendships do not insure the male paternity of infants, but the social benefits seem to outweigh paternity rights in baboon societies.
There are often fights among males for the right to mate with females in estrus. Males do not have the strong ranking order that the females have among their family relatives, and males must compete for mating rights. Among some species of baboon, the older males mate more than younger dominant males because the older males have more friendships with females, and these bonds are of a longer duration.
Baboons, like people, will often trick their peers into getting something they want. Researchers once witnessed a young male baboon tricking an adult female into relinquishing the roots she was digging by signaling that he was being attacked. When his mother came to the rescue and saw only the other female, she chased the other baboon into the woods. As soon as the root digger was chased away, the young male took the tubers for himself. In another example, a female baboon groomed an adult male until he became so relaxed he fell asleep and forgot his antelope meat. Once he was asleep, she took the meat for herself.
Food and foraging habits
Baboons have the same number of teeth and dental pattern as human beings. Baboons, like other members of the subfamily Cercopithecinae, have cheek pouches that can hold a stomach’s worth of food. This enables them to literally eat on the run, and is helpful to them when they have to compete for food or avoid danger. Baboons can quickly fill up their pouches, then retreat to safety to eat at their leisure.
Baboons walk on all four limbs and their rear feet are plantigrade, meaning they walk on the whole foot, not just on their toes. The walking surface of their hands is the complete surface of their four fingers. When feeding, baboons tend to stand on three of their limbs and pluck food while eating with one hand. When baboons are walking, their shoulders are higher than their hips and they are able to easily see what is going on around them as they forage for food.
Baboons are basically fruit-eaters, but they also eat seeds, flowers, buds, leaves, bark, roots, bulbs, rhizomes, insects, snails, crabs, fish, lizards, birds, and small mammals. Young baboons learn what to eat and what not to eat through trial and error. Adults monitor their choices and intervene to prevent younger baboons from eating unusual food. When water is not available, baboons dig up roots and tubers to find liquid and often dig holes in dry river beds to find water.
It has been observed that baboons adapt their food choices to what is available in their habitats. In some regions they have developed group hunting techniques.
Communication
Baboons have a complex system of communication that includes vocalizations, facial expressions, posturing, and gesturing. These vocalizations, which baboons use to express emotions, include grunts, lip-smacking, screams, and alarm calls. The intensity of the emotion is conveyed by repetition of the sounds in association with other forms of communication.
Baboons communicate with each other primarily through body gestures and facial expressions. The most noticeable facial expression is an open-mouth threat where the baboon bares the canine teeth. Preceding this may be an eyelid signal—raising the eyebrows and showing the whites of the eyes—that is used to show displeasure. If a baboon really becomes aggressive, the hair may also stand on end, threatening sounds will be made, and the ground will be slapped.
In response to aggressive facial expressions and body gestures, other baboons usually exhibit submissive gestures. A fear-face—a response to aggression— involves pulling the mouth back in what looks like a wide grin.
Presenting among baboons takes place in both sexual and nonsexual contexts. A female will approach a male and turn her rump for him to show that she is receptive. This type of presentation can lead to mating or to a special relationship between the pair. A female may present in the same way to an infant to let the infant know it may come close to her. She may use this body gesture as a simple greeting to a male, indicating that she respects his position. A female will also present to another female when she want to fondle the other female’s infant. Males present to other males as a greeting signal. Their tails, however, are not raised as high as those of females when they present.
Presentation is also used as an invitation or request for grooming, and for protection. Baboons freely engage in embracing to show affection to infants
KEY TERMS
Estrus— A condition marking ovulation and sexual receptiveness in female mammals.
Foraging— The act of hunting for food.
Matrilineal— Social relationships built around the mother and her children.
Plantigrade— Walking on the whole foot, not just the toes as cats and dogs do.
Presenting— Body gestures that signal intentions or emotions among baboons.
and juveniles. The frontal embrace has also been seen as a gesture of reassurance between baboons when they are upset. Infants have their own forms of communication that involves a looping kind of walk, wrestling, and a play-face. The play-face is an open mouth gesture they use to try to bite one another.
Baboon models
Baboons were studied for a long time as models of primate behavior and used to help construct the evolution of human behavior. More recently, chimpanzees have been used as a model because of their genetically close relationship to humans, and because they exhibit toolmaking, some languagelike ability, and some mathematical cognition. Until recently, baboon troops were thought to be male-dominated. Studies have now demonstrated the cohesive nature of the matrilineal structure of baboon society.
What continues to interest researchers about baboons is how adaptable they are, even when their habitats are threatened. Baboons have become skillful crop raiders in areas where their territories have been taken over by humans for agriculture. In spite of this adaptability, some species are threatened or endangered. For example, the drill is highly endangered due to habitat destruction and commercial hunting. In 1984, in a unique study designed to save three baboon troops from human encroachment, baboon biologist Shirley C. Strum translocated these 132 animals 125 mi (200 km) away from their original home to a harsh outpost of 15, 000 acres (6,075 hectares) near the Ndorobo Reserve on the Laikipia Plateau north of Mt. Kenya. Every baboon of the three different groups was captured to ensure social integrity.
After release, Strum found that the translocated groups watched and followed local troops of baboons to find food and water. Within six weeks, indigenous males joined the translocated troops, providing a good source of intelligence about the area. Strum found that the translocated animals learned by trial and error. The topography of the area meant that some portions of the range had good food in the wet seasons and other portions had good food in the dry seasons. To feed efficiently, the baboons had to learn this difference and to switch their ranging seasonally. Today, there are still a few differences between indigenous and translocated baboons in behavior and diet, but on the whole, it is difficult to tell that the groups had different origins.
Resources
BOOKS
Loy, James, and Calvin B. Peters. Understanding Behavior: What Primate Studies Tell Us about Human Behavior. New York: Oxford University Press, 1991.
MacDonald, David, and Sasha Norris, eds. Encyclopedia of Mammals. New York: Facts on File, 2001.
Mason, William A., and Sally P. Mendoza. Primate Social Conflict. Albany: State University of New York Press, 1993.
Sapolsky, Robert M. A Primate’s Memoir: A Neuroscientist’s Unconventional Life Among the Baboons. New York: Scribner, 2001.
Strum, Shirley C. Almost Human: A Journey into the World of Baboons. New York: Random House, 1987.
PERIODICALS
“Abnormal, Abusive, And Stress-Related Behaviors In Baboon Mothers.” Biological Psychiatry 52, no. 11 (2002): 1047–1056.
Maestripieri, Dario. “Evolutionary Theory and Primate Behavior.” International Journal of Primatology 23, no. 4 (2002): 703–705.
Silk, Joan B., Susan C. Alberts, and Jeanne Altmann. “Social Bonds of Female Baboons Enhance Infant Survival.” Science 302 (November 14, 2003): 1231–1234.
Strum, Shirley C. “Moving The Pumphouse Gang.” International Wildlife (May/June 1998).
OTHER
Amboseli Baboon Research Project. <http://www.princeton.edu/~baboon/index.html> (accessed October 5, 2006).
Vita Richman