Original Article

Behavioral Ecology and Sociobiology

, Volume 61, Issue 2, pp 183-195

First online:

Social relationships among adult female baboons (papio cynocephalus) I. Variation in the strength of social bonds

  • Joan B. SilkAffiliated withDepartment of Anthropology, University of California Email author 
  • , Jeanne AltmannAffiliated withDepartment of Ecology and Evolutionary Biology, Princeton UniversityDepartment of Conservation Biology, Brookfield ZooNational Museums of Kenya, Institute for Primate Research
  • , Susan C. AlbertsAffiliated withNational Museums of Kenya, Institute for Primate ResearchDepartment of Biology, Duke University

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Sociality has positive effects on female fitness in many mammalian species. Among female baboons, those who are most socially integrated reproduce most successfully. Here we test a number of predictions derived from kin selection theory about the strength of social bonds among adult female baboons. Our analyses are based on systematic observations of grooming and association patterns among 118 females living in seven different social groups in the Amboseli Basin of Kenya over a 16-year period. Females in these groups formed the strongest bonds with close kin, including their mothers, daughters, and maternal and paternal sisters. Females were also strongly attracted toward females who were close to their own age, perhaps because peers were often paternal sisters. Females’ bonds with their maternal sisters were strengthened after their mother’s deaths, whereas their relationships with their maternal aunts were weakened after their mother’s death. In addition, females formed stronger bonds with their paternal sisters when no close maternal kin were available, and they compensated for the absence of any close kin by forming strong bonds with nonrelatives. Taken together, these data suggest that social bonds play a vital role in females’ lives, and the ability to establish and maintain strong social bonds may have important fitness consequences for females.


Social bonds Nepotism Kin selection Friendship Dominance Peer relationships