Juvenile primates in the context of their social group: a case study of chacma baboons (Papio ursinus) in an afro-montane environment

Abstract

The prolonged juvenile period between infancy and reproductive maturity is the life history trait that best separates primates from other mammals. Juvenile primates are also the most neglected subjects of primatological research. The principal aim of my study was to examine the behaviour of juveniles and how they compare to older individuals, and in doing so, site this behaviour within the context of a social group of chacma baboons (Papio ursinus).

I collected data on a group of baboons in the Soutpansberg Mountains of South Africa over a 19-month period. I took a multi-faceted approach, using data collected though scan samples, focal animal samples, and GPS data to examine age and sex differences in behaviour. I analysed these data using several methods, including methods novel to primatological studies.

My results indicate that activity budgets and use of vertical space differ by age and sex. As a consequence of this variation in the time spent engaged in activities, I found that chacma groups exhibit low levels of behavioural synchrony as measured by the Kappa coefficient of agreement. My results also indicate that, despite being part of cohesive group, individuals also differ in their movements through the landscape. Individuals that received more agonism from other group members were found to be more constrained in their movements, travelling shorter, but more tortuous routes. My findings also show that young juveniles position themselves spatially in order to have more neighbours in proximity than older individuals, while social interactions amongst group members exhibit phenotypic assortativity, particularly amongst individuals of similar ages.

The behavioural differences found in juveniles relative to older conspecifics arise as a consequence of juveniles’ priorities in not only surviving to adulthood, but also in ensuring future success as adults, with obligate group-living an important factor in the emergence of such differences.