Factors determining greeting behavior in a captive group of yellow baboons

Greetings are non-aggressive behavioral exchanges, common in several primate species yet their structure and function remain poorly understood, particularly outside male-male dyads. We investigated the determinants of greeting behavior in a captive group of yellow baboons (Papio cynocephalus; 12 females, 9 males), focusing on the effects of rank, sex configuration, and context on greeting frequency, complexity, and reciprocity. As grooming constitutes a fundamental social interaction among primates, we also analyzed factors influencing grooming frequency and its relation with both frequency and mean complexity of greetings. We found that male-male dyads engaged in greetings more frequently, with greater complexity, and showed higher reciprocity compared to female-female dyads. Furthermore, in general, individuals who initiated more grooming in the dyads greeted the recipient less often. However, this effect of grooming was found to be significantly influenced by the sex configuration of the dyad. Greetings occurred predominantly in socially neutral contexts, and contextual variables did not significantly predict greeting complexity. Contrary to expectations, rank did not influence greeting behavior, suggesting that greetings do not primarily function as signals of dominance in this group. Interestingly, dyads that groomed each other more frequently exchanged less complex greetings, indicating that strong social bonds may reduce the need for elaborate signaling. In contrast, individuals with weaker affiliative relationships engaged in more complex greetings, potentially to assess or reinforce social ties. Our findings complement the existing literature and may provide a useful basis for comparison in future studies conducted in both wild and captive settings. We show a comprehensive perspective of greeting behaviour in male and female interactions within a captive group of yellow baboons, examining the full repertoire while preserving its multimodal (visual, tactile, and vocal) and multi-component nature. This integrative approach enables a more nuanced assessment of the potential adaptive functions and contributes to a broader understanding of the structural complexity and diversity of greetings. Although female-female greetings were less frequent than male-male greetings, their occurrence was sufficient to warrant consideration. We found no effect of rank on the frequency or complexity of greetings, and which occurred predominantly in socially neutral contexts, suggesting that, in this captive group, greetings primarily serve to reinforce social bonds rather than signaling dominance, as proposed in previous studies of wild yellow baboons.