|Monkeys, Apes and Humans
Department of Anthropology, University of Missouri-Columbia
FILM: Jane Goodall and the Wild Baboons of Gombe
This film highlights several features of primate societies, especially species with multi-male social systems. Features you should understand include: coalitions, alloparenting, and sexual dimorphism.
Male-male coalitions are readily observable in the film. Male-female "friendships" also occur. We do not know if baboons have the same emotions as we doŚwe should be wary of being anthropomorphic. However, Barbara Smuts, in her book Sex and Friendship in Baboons, argues that long-term relationships between males and females occur. As you'll see in the film, males may take an interest in a female's infant even if he is not the father. This would make a good paper topic. Smuts' book is on reserve at Ellis.
An alloparent takes temporary care of an infant. A female baboon may carry the infant of another female. Their intentions are not clear. Perhaps females are practicing parenting skills. Young males may also carry infants to avoid fights. You'll see this in the film.
Baboons are sexually dimorphic. Males are not only bigger than females but they have more neck hair and longer canines. Why are the sexes so dimorphic in this species?
Goodall studies chimps at the Gombe Park in Tanzania. She has also studied a sympatric species, baboons. Baboons sleep in trees, forage in the forest, and spend most of their day at the beach of a large freshwater lake. Beach Troop, the troop observed in this movie, has about twenty members.
Baboon troops have a dominance hierarchy. Each adult and juvenile has a rank. Each behaves dominantly or submissively toward others. Primatologists can deduce an individual's rank in the troop by several behaviors. Dominant individuals can displace subordinate individuals; they walk near a sitting subordinate individual who relinquishes his place. This causes a chain-reaction in the troop.
Rank is also revealed by threatening and submissive gestures. Examples of displays: Flashing eyelids are a mildly threatening display. The yawn display and the tail-in-face display are extremely threatening. Individuals either ignore or respond to the challenge. Females, who are smaller than adult males, may display threats towards males but do not attack them.
Also, submissive individuals often groom dominant individuals. (Grooming is an important social behavior; it is the social cement of the troop reinforcing and establishing relationships.)
Females take an interest in the infants of other mothers. Mothers may be reluctant to allow females to carry infants. A female carrying a mother's infant may be an alloparent (providing care) or may be kidnapping the infant. Auntie was very interested in carrying Algi whose mother, Apricot, was reluctant to give him up. To get closer to the infant, Auntie groomed the mother.
When a female is in estrus, males are attracted to her. One male, a consort, may accompany the female into the bush, away from the group. He attempts to keep other males away from a female. Rivals display canines and flash eyelids towards the consort who stays close to the female.
In the morning, the baboons forage in the forest. Baboons eat a variety of readily available foods: Fruits, nuts, fish (dropped from fishing nets), edible flowers, insects, and, occasionally, meat. They can store palm nuts in their cheeks. Baboons use stones as tools to scrap sticky fruit sap off their fur.
Feeding and other situations often increase tensions in the troop. Frustrated males may attack subordinates. A single fight may cause a chain reaction of fights (e.g., Fudge and Moses). When tensions are high in the troop, a male may kidnap an infant and carry her until tensions subside. In this way, males use infants as agonistic buffers. They carry infants not to protect them but to protect themselves. Some males, however, appear to take a benevolent interest in infants. For example, Moses protected Mango from Fudge.
Mothers carry their infants. Algi, as a newborn, hangs underneath his mother when she is traveling. At five weeks, Algi begins to ride on top, a significant developmental milestone for baboon young. Infants ride on their mothers for 18 months.
Young adult males leave their native troop and attempt to get into a new one. Stranger waited on the periphery of Beach Troop for a week before attempting to get in. After a week of watching, he moved into the center of the troop and made intimating displays toward dominant males. Males in the troop were agitated by Stranger who had the key ingredients of dominance: strength, size, and bluff. Two baboons formed a coalition against Stranger. Both males cooperated in attacking Stranger but failed to displace him. Stranger was able to break their coalition. After enduring many such encounters, Stranger displayed submissively towards the dominant male of troop. The dominant male, who had remained aloof during the fights, acknowledged the gesture and Stranger became established in the dominance hierarchy.
Why do some primate societies have dominance hierarchies and not others? What costs and benefits do individuals experience in such social systems? Also, why do baboon young spend so much time and energy in play? One hypothesis is that play allows young to practice important skills such as foraging and fighting.
Why did Moses protect Mango? Two possibilities are kin selection and reciprocity. Moses may be the father of Mango; protecting the infant promotes Moses' reproductive success (a kin selection explanation). Or Moses may be doing a favor for Marigold, Mango's mother. In return, Marigold may be more cooperative towards Moses when she becomes sexually receptive (a reciprocity explanation).
Recall that Stranger fought with two male baboons. These two male baboons formed a coalition. Coalitions are common in primate societies. In chimpanzees, males remain in the group while females migrate. In baboons, males move into a troop. Probably as a result, chimpanzee coalitions are more common and stronger than coalitions in baboon troops. Males in a chimpanzee community, usually brothers, frequently form coalitions, patrol the periphery of their home range, and attack solitary chimpanzees from another group.
Department of Anthropology
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revised: fall 2004
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