Social bonds in female baboons: the interaction between personality, kinship and rank

Previous analyses indicate that female baboons that form strong and stable social bonds reproduce more successfully than others, and that some elements of femalesʹ personalities are associated with the tendency to form close social bonds. Here we use a new method to confirm that femalesʹ personalities were stable over time, although not fixed, and that matrilineal kin had personalities that were no more alike than those of other individuals. Our results indicate that personality similarities enhance the strength of social bonds among some pairs of females but not others. Strong bonds between matrilineal sisters were correlated with similarity in their personalities and ages, but mothers and daughters formed uniformly strong bonds regardless of the similarities in their personalities or ages. Among nonkin, strong bonds were correlated with similarity in age and dominance rank, but not personality. Females adjusted the behaviours that contributed to their personality scores in response to unpredictable demographic events, like the death of a close relative. Results suggest that the personality traits of female baboons do not exist in isolation but are embedded in a network of rank and kin relations. Although a female baboon has little control over her dominance rank or the presence of kin, by varying the tenor of her social interactions she can take advantage of the opportunities, or overcome the constraints, imposed by demographic circumstances. For this reason, selection may have favoured particular personality traits that are relatively independent of rank and the presence of kin.