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Previous studies of hamadryas baboons have described a “star-shaped” sociogram, whereby the strongest social bonds within hamadryas one-male units are those between a leader male and his females and bonds among females are weak by comparison. This type of social organization has also been called “cross bonding” to distinguish it from the “female bonding” found in most papionin monkeys. Models of female primate socioecology have suggested that hamadryas baboons lack female bonding due to their reliance on scarce, widely-dispersed food resources. Here I report observational data from a wild population of hamadryas baboons in Ethiopia indicating that, while females varied widely in their frequency of social interaction with other females, most females spent about as much social time with other females as they did with their leader male and some females even crossed unit boundaries to interact with one another. The size of a unit was positively correlated with the tendency of its females to interact with other females and negatively correlated with the tendency of its females to interact with their leader male. Females were equally likely to spend social time with other females whether or not their leader male was available for social interaction at the time. Overall, this study suggests that a star-shaped sociogram does not necessarily characterize all hamadryas baboons and that female hamadryas may be, to some extent, female-bonded as well as cross-bonded. The lack of more pronounced female bonding in hamadryas is probably due to the behavior of males rather than to ecological factors.


This work was originally published in International Journal of Primatology, available at



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