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


Animals living in social groups navigate challenges when competing and cooperating with other group members. Changes in demographics, dominance hierarchies or ecological factors, such as food availability or disease prevalence, are expected to influence decision-making processes regarding social interactions. Therefore, it could be expected individuals show flexibility in social behaviour over time to maximise the fitness benefits of social living. To date, research across species has shown that stable inter-individual differences in social behaviour exist, but mostly over relatively short data collection time periods. Using data spanning over 20 years, we demonstrate that multiple social behaviours are highly repeatable over the long-term in wild chimpanzees, a long-lived species occupying a complex fission-fusion society. We controlled for temporal, ecological and demographic changes, limiting pseudo-repeatability. We conclude that chimpanzees living in natural ecological settings have relatively stable long-term social phenotypes over years. Determining the functional consequences of these stable social phenotypes across the chimpanzee lifespan will benefit our broader understanding of how social tendencies emerge and shape sociality in our closest living relatives. © 2019 The Author(s)

Royal Society Open Science, https://doi.org/10.1098/rsos.200454