BEHAVIORAL-PATTERNS IN BABOON GROUP ENCOUNTERS - THE ROLE OF RESOURCE COMPETITION AND MALE REPRODUCTIVE STRATEGIES

Female Between Group Contest BGC competition for limited and monopolizable ecological resources such as food and water is the conventional explanation for behaviour during primate intergroup encounters. It is further advocated as an explanation for the evolution of social groups. This paper tests this explanation (H1) against two competing hypotheses. These are that patterns of intergroup interaction represent (H2) BGC mediated through males or (H3) male reproductive strategies. Four predictions are generated from these hypotheses and tested with data from two sources: (1) a cross-population Papio baboon literature survey and (2) a population-specific chacma baboon Papio cynocephalus ursinus case study. This population consisted of five groups (four habituated) in the semi-desert Pro-Namib region of Namibia. The predictions were: (P1) female OR male aggression dominates encounters, (P2) the number of females OR males determines the outcome of encounters, (P3) there is frequent aggression OR tolerance at resources during encounters, and (P4) males chase females away from their group OR into their group through herding during group encounters. Tests of these predictions using both databases failed to support H1 or H2, but did provide evidence in favour of H3; namely female aggression was absent, male aggression was infrequent and directed towards either infants of other groups or females of their own group in herding episodes, and encounters with displacements tended to occur only rarely and mostly where resources were either non-monopolizable or absent. These results imply that BGC is not currently a selective force maintaining baboon social groups in either the study population or other populations across Africa. In order to further investigate the complex behavioural patterns observed in baboon intergroup encounters, data describing the demography and relatedness of groups and individuals are required.