THE STRUCTURE OF SOCIAL RELATIONSHIPS AMONG FEMALE SAVANNA BABOONS IN MOREMI RESERVE, BOTSWANA by JOAN B. SILK 1,2) , ROBERT M. SEYFARTH 3) and DOROTHY L. CHENEY 4,5) ( 1 Department of Anthropology, University of California, Los Angeles, USA; 3 Department of Psychology, University of Pennsylvania, USA; 4 Department of Biology, University of Pennsylvania, USA) (Acc. 7-IV-1999) Summary Here we examine the effects of maternal kinship, reciprocity, and dominance rank on the social relationships of female baboons ( Papio cynocephalus ursinus) in a well-habituated, free-ranging group in the Okavango Delta of Botswana. These data are useful for testing comparative hypotheses about the ecological and demographic factors that shape the evolu- tion of social organization in primates and other animals. In this group, adult females had well-differentiated grooming relationships with one another, and limited their grooming to a relatively small subset of available partners. Although there were 19 adult females in the group, the average female groomed only 8 other females, and devoted at least 5% of her grooming to only four other females. Females groomed maternal kin at signicantly higher rates and for signicantly longer periods than they groomed other females. The bias in favor 2) Corresponding author; e-mail address: jsilk@anthro.ucla.edu 5) We would like to thank the Ofce of the President and the Department of Wildlife and National Parks of the Republic of Botswana for permission to conduct research in the Moremi reserve. We are grateful to R. Boyd, M. Kgosiekdae, J.M. McNutt, M. Mokopi for logistical support in the eld; and to W.J. Hamilton III for making the eld camp and demographic records available to us. We thank Duncan Castles, Peter Henzi, and Carol Saunders for providing unpublished information about the distribution of grooming. We thank Lynn Fairbanks for constructivecomments on the analysis, Michael Pereira for critical comments on a previous draft of the manuscript, and an anonymous reviewer. This research was supported by grants from the National Geographic Foundation, the Research Foundation of the University of Pennsylvania, the Institute for Research in Cognitive Science at the University of Pennsylvania, NIH Grant HD-29433, and National Science Foundation Grant 9213586. c ® Koninklijke Brill NV, Leiden, 1999 Behaviour 136, 679-703