Social System of a Hybrid Baboon Group (Papio anubis × P. hamadryas)

Abstract

We describe the social organization, mating system, and social structure of a group of hybrid baboons (Papio anubis×P. hamadryas) in Ethiopia's Awash National Park. The group contained elements of both hamadryas and anubis societies. Overall, the group was a multimale, multifemale group that lacked cohesion and frequently formed subgroups. Subgroup formation was more strongly associated with predation risk than food availability. Although there were several hamadryas-like one-male units OMUs within the group, there was no evidence of a hamadryas multilevel society. Male and female members of OMUs were phenotypically more hamadryas-like than non-OMU individuals. The group contained substantial variation in the strength of inter- and intrasexual bonds: some females primarily groomed males while other females primarily groomed females, and the patterns were consistent with the OMU substructure. Despite some promiscuous mating, mating was biased towards the hamadryas condition for all group members. Additionally, rates of immigration and emigration were very low, and mean pairwise relatedness within the group is rising. For measures of intersexual bonding, all members of the group were intermediate between anubis and hamadryas individuals in less hybridized groups. The group was phenotypically and behaviorally more intermediate than it was in the 1970s (Sugawara, K. (1988). Primates 29: 429–448.) and the changes may indicate a relatively young and dynamic hybrid zone.