Trophic Level III: Omnivores and Small Carnivores Olive Baboon Page 49

  Papio cynocephalus anubis

Length: 72.5 cm (29 inches)

Tail: 56-84cm (22-34inches)

Weight: 11-30 kg (24-66 lb.) female, 22-50 kg (48-110 lb.) male

Status: Common; considered a pest in agricultural lands where the species regularly raids farmers’ crops.

Habitat: The olive baboon is the most widespread of all the various races of baboon. It is found in a wide variety of habitats. It prefers areas where there is a grassland-forest mix.

Olive baboons are found in the Serengeti-Mara ecosystem. Not far away in Kenya’s Amboseli National Park, the closely related yellow baboon is found. They are of a slighter build than the olive baboon but otherwise resemble them in behavior and social patterns. Where the two species meet there is interbreeding with the resultant offspring resembling olive baboons.

It appears that of all Africa's baboons, the olive is the most successful at adapting to humans and is therefore expanding its range.

Food: Olive baboons are omnivorous and eat a wide variety of foods depending on the season and their location. They eat grass in open areas and fruits in forests. In dry seasons, they will eat resin and gum. Locusts are eaten when they are abundant. Other foods include tubers, bulbs, roots, leaves, buds, flowers, seeds, shoots, twigs, bark, aquatic plants, mushrooms and lichens. In the dry season, baboons will dig up and eat nutritious corms and rhizomes.

Olive baboons eat locusts and other insects and invertebrates including spiders and scorpions. Along rivers, olive baboons will eat clams but freshwater oysters are sealed too tightly for them to open.

Vertebrate animals that may be eaten include frogs, fish, birds, crocodile eggs, lizards, turtles, small rodents, and hares.

Males will occasionally find and kill young gazelles in the hiding stage that they stumble over while they are foraging. Young vervet monkeys are also caught and eaten. One well studied troop in Kenya has actually evolved hunting strategies for finding young antelope. In this troop, females also participate in the hunt.

Social System: A baboon troop may be active anytime during the daylight hours. Generally, they begin foraging activity well after sun-up and are back to roosts by dark. Roosts are either in trees or on the side of cliffs. Both are used in the Serengeti-Mara.

Home ranges vary in size depending on the richness of the environment. They may be as small as 400 hectares (988 acres) or as large as 4 000 hectares (9,880 acres). Troops may have overlapping ranges but they avoid each other most of the time.

Troop life is complex. Once it was believed that the dominant males were the true leaders of the troop but recent studies have shown the importance of dominance among females.

(Author's note: Baboon research was begun in the late 1950s and was carried out mainly by men. Female researchers, notably Shirley Strum, decided to look at females and discovered a whole new approach to animal behavior studies. Today, both male and female researchers try to avoid bias in their studies.)

Several factors influence the social system of the baboon. Gender, dominance, male-female and male-male alliances all affect the troop.

All baboons in a troop compete for dominance regardless of their gender. Typically, a troop consists of 30 to 40 members, half of which are juveniles. Adult females out-number males two or three to one. Females never leave their natal troop. As with spotted hyenas, juvenile females assume their mother's rank within the troop. Each mother heads her own mini-troop consisting of both her male and female offspring. The youngest in the troop is the most dominant after her. Babies are tolerated and pampered.

Growing Up Baboon

As a juvenile female grows up, her mother (and siblings) reinforce her dominance so that her rank is imposed on others. Once she is 2.5 years old, her rank is firmly established and will not change.

Dominance allows females to displace lesser females and juveniles from the best watering places and food sources. The more dominant a female is, the more she is groomed and the less she grooms others.

Estrus females may mate with any of the dominant males in her troop but she will normally associate with one or two (sometimes three) males more often than with others. She will roost near these "special" males at night and will groom them even when she is not in estrus. When the troop is foraging, she can usually be found within 15 meters (45 feet) of these males. She seldom allows other males within 15 meters of her location. It is not surprising then that when she does enter estrus, one of these males is more likely to mate with her than other males.

By associating with these large males and seeking their favor, the female gains a measure of protection from predators and from other males that may seek to bully her during dominance fights. These males will also protect her offspring and come to their aid whether or not they are the juvenile's father.

Young males remain in their mother's troop until they are four years old. At that age, they go

through a growth spurt and develop the larger body size and long canine teeth of an adult male. They are then big enough to dominate females. It is also at this stage that they become increasingly annoying to the resident males who do not tolerate the adolescent males.

Making Their Way

It will be three to five years before the young male is big enough to compete with dominant males. in order to avoid stress and conflict, the adolescent males leave their troops to seek acceptance elsewhere. Males that migrate must seek the favor and companionship of a female.

A young male baboon takes his time when he sets out to join a new troop. He will spends days following the troop around letting them get used to his presence. Slowly, almost timidly, he will gradually make his way into the troop. He is careful to avoid the dominant males. His goal is to make physical contact with a ranking female.

At first, females avoid him, so he plays with juveniles, always careful not to threaten the youngster. As the females gain confidence in him, they allow him to groom them. Gradually, the male is accepted as a new troop member.

Acceptance

Only after acceptance will he challenge dominant males and begin climbing the social ladder. Males that are threatened by other males will grab juveniles as hostages. By holding onto a black baby, the subordinate male can use the infant to threaten a more dominant male.

Baboons give birth year round. When they are first born, the infant is black. Most births occur at night while the troop is roosting.

At first, the baby baboon will cling to its mother's chest while she walks. When it is 6 to 12 weeks old, it will ride jockey-style on her back. By two months old, the baby is picking up and investigating things on the ground. At three months, they are playing with their peers and baby-sitters. Yearlings are independent but still maintain close bonds with their mother’s kinship group.

When a female enters estrus, her behind swells up noticeably. This is the sign to males that she is ready to mate.

Behavior: Baboon troops are usually a beehive of activity with males chasing other males. The conflict between males can cause serious damage. They are big, well-armed animals. Screaming, chasing and fighting are obvious conflict behaviors but baboons have also developed more subtle gestures of intimidation. Dominance or threat displays include staring at a rival and the raising of eyebrows. The area of skin below the baboon's brow ridge is quite light and by repeatedly raising the eyebrows, the light skin is flashed. This indicates stress and aggression and is a clear sign to other baboons to back off.

Baboons also yawn, displaying their large canine teeth. This, too, is a clear threat display aimed at others in the troop. Some other dominance or threat displays include tooth-grinding, slapping the ground, rearing on hind legs and branch shaking.

Avoiding A Fight

Baboons also have a series of behaviors designed to inhibit aggression. These submissive actions include: avoidance, social grooming, social presenting (a subordinate will present its hind quarters for inspection by a dominant animal), erecting the tail, rapid glancing around and crouching.

Although baboons always seem to be fighting amongst themselves, they act together when a predator is near. Males will often rush to face the danger, barking and slapping the ground. Alone, they are no match for a leopard, but together, they can scare off the cat.

Baboons need effective anti-predator behavior to succeed in living away from the safety of trees. Not only will males confront most predators (lions are an exception), so too will females and adolescents when there is no other choice. Males will stand guard in trees watching over the troop as it forages.

Predators: Leopards are the major predator but not the only one. Lions pose a threat too. Baboons will usually flee from a lion and take to the trees. Even several males are unlikely to deter a determined lion or lioness. There are very few documented cases of lion predation on baboons however.

Chimpanzees (not found in the Serengeti-Mara) will deliberately set out to hunt baboons. The chimps are organized and several males will panic the baboons into flight. Then one is grabbed, killed and eaten. Oddly, chimps and baboons are often seen living peacefully side by side.

Other predators include rock pythons, martial eagles, spotted hyenas and humans.

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Dave Taylor's African Safari - Book 4: Trophic Level III: Omnivores and Small Carnivores (Standard Version)
Copyright © 1999 Dave Taylor & James Cash