Long-term repeatability in social behaviours suggests stable social phenotypes in wild chimpanzees

Abstract

31Animals living in social groups navigate challenges when competing and cooperating with other group 32 members. Changes in demographics, dominance hierarchies or ecological factors, such as food 33 availability or disease prevalence, are expected to influence decision-making processes regarding social 34interactions. Therefore, it could be expected individuals show flexibility in social behaviour over time to 35 maximise the fitness benefits of social living. To date, research across species has shown that stable 36inter-individual differences in social behaviour exist, but mostly over relatively short data collection time 37periods. Using data spanning over 20 years, we demonstrate that multiple social behaviours are 38 repeatable over the long-term in wild chimpanzees, a long-lived species occupying a complex fission-39 fusion society. We controlled for temporal, ecological and demographic changes, limiting pseudo-40repeatability. We conclude that chimpanzees living in natural ecological settings have relatively stable 41 long-term social phenotypes over years that may be independent of life history stage or strategies. Our 42 results add to the growing body of literature suggesting consistent individual differences in social 43 tendencies are more likely the rule rather than the exception in group-living animals. 44 45