Sex and Friendship in Baboons
Friends were responsible for nearly all aid that females and their offspring received from males during agonistic interactions with other troop members. This aid benefits the females and juveniles (1) by reducing disruption of their activities and other forms of harassment (when the aggressors are other females and juveniles) and (2) by reducing rates of infliction of wounds (when the aggressors are subadult or adult males). However, friendship sometimes results in costs to females as well as benefits. These costs include increased vulnerability to aggression by males who use the female as a means of manipulating or challenging her male Friend and to mock attacks and use as an agonistic buffer by Friends themselves. Analysis of the complex relationships between males, between females and Non-Friend males, and between females and Friends, suggests that forming a friendship with one or two particular males may be the best response a female can make to the ever-present danger of aggression from other troop members.
Males that have recently transferred into a group have been observed killing infant baboons, and protection from infanticidal attacks may be another important benefit that females derive from friendships with males. This protection is most likely to come from male Friends of the mother, who were much more likely than other males to develop affiliative relationships with infants. Special relationships between males and infants were manifested routinely by proximity between the male and infant and by friendly interactions (e.g., greeting, holding, carrying, and grooming of the infant by the male). When away from their mothers, older infants tended to associate with one or, less often, two particular males, and these males were nearly always Friends of the infant's mother while she was pregnant and during the infant's first few months of life. Friendships with males may benefit infants in several ways, including protection from harassment by other troop members, protection of infants from predators and from other baboons, increased foraging efficiency, and the potential for alternative care-giving when the mother neglects the infant or dies. In some instances, these relationships—and presumably some of the benefits they provide—persist at least until the offspring's third or fourth year of life. The fact that females spent relatively more time near male Friends after giving birth supports the hypothesis that the development of male-infant relationships is one of the most important benefits that females derive from friendship with males.
These results suggest that when a female establishes a friendship with a male, she and her immature offspring acquire a long-term ally in the troop—an ally who, because of his larger size and superior fighting ability, may make a significant contribution to the survival and reproduction of the female and her offspring.