| Summary: | <p>Entering physical proximity to a conspecific is a resource; it can give an individual opportunities for social learning or affiliative interactions and could provide safety from threats through association. How individuals access this space and the interactions that follow are important aspects of primate signalling and social behaviour. Within the primate signalling literature, there has been much discussion of how species-level signalling repertoires and their complexity may be affected by social complexity and risk (e.g., despotic versus egalitarian species). However, research on how signalling in individual interactions may be affected by similar factors, for example the interpersonal risk posed by an interaction to a signaller, remains limited. This thesis re-examines approach behaviour in baboons, first taking a species-level approach investigating male-male stereotyped greetings in chacma baboons (<em>Papio ursinus griseipes</em>) in the larger context of <em>Papio</em>, then examining the content, outcome, and structure of baboon approach interactions more generally across sex combinations in olive baboons (<em>Papio anubis</em>) and chacma baboons.</p>
<p>The first chapter provides an introduction to the signalling and risk literature and provides a theoretical background for the remainder of the thesis. Chapter 2 discusses the relevance of baboons as a study genus and reviews the existing approach literature in baboons, in particular the male-male greeting and infant approach grunting literatures. An overview of the overall thesis methods, materials, and the two field sites (Gorongosa National Park, Mozambique and Gombe National Park, Tanzania) is provided in Chapter 3. The following three chapters are the empirical chapters, addressing different aspects of baboon approach behaviour. Chapter 4 compares male-male greeting behaviour of chacma baboons in Gorongosa National Park, to that observed in other <em>Papio</em> species. Chacma baboons are often referred to as exhibiting no stereotyped male-male greeting behaviour, unlike the other <em>Papio</em> species, and it has been suggested that this is related to their lack of coalition formation. We provide evidence that similar male-male greetings are seen in chacma baboons, contrary to expectation. Chapter 5 uses a network-analysis approach to study how individual signals are combined during approach interactions in chacma and olive baboons. We compare these across sex combinations and between interactions where infants of the recipient are present or absent. The relevance of how signalling between sex combinations may differ due to philopatry or rank is discussed. The results of the network-analysis are then used to develop hypotheses regarding how identified signal combinations are associated with changes in the outcomes of those interactions. We identified several clusters of signals used together and discuss their relevance to whether contact is made with the recipient or recipient’s infant where applicable. The focus of Chapter 6 is how signalling complexity relates to the level of interpersonal risk faced by the approacher. We use two proxies of risk - first, the sex of the recipient (approaches towards males being higher risk than towards females) and second, where the approacher is a female, whether she has a natal coat infant with her or not. Complexity is assessed using entropy and event size, with a third set of models investigating whether the likelihood of physical contact differs by these proxies for risk. We found weak evidence for differences in event size and physical contact by sex combination and infant presence. Contrary to expectation, differences in entropy ratio were found by approacher sex, but not recipient sex. Chapter 7 provides a final discussion of the thesis findings, key implications, limitations, and future directions.</p>
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