Behavioural patterns of vocal greeting production in four primate species.

Pawel Fedurek,Stéphanie Mercier,Yaëlle Bouquet,Fredy Quintero,Christof Neumann,Martina Magris,Klaus Zuberbühler

doi:10.1098/rsos.182181

Abstract

Social animals have evolved a range of signals to avoid aggressive and facilitate affiliative interactions. Vocal behaviour is especially important in this respect with many species, including various primates, producing acoustically distinct ‘greeting calls’ when two individuals approach each other. While the ultimate function of greeting calls has been explored in several species, little effort has been made to understand the mechanisms of this behaviour across species. The aim of this study was to explore how differences in individual features (individual dominance rank), dyadic relationships (dominance distance and social bond strength) and audience composition (presence of high-ranking or strongly bonded individuals in proximity), related to vocal greeting production during approaches between two individuals in the philopatric sex of four primate species: female olive baboons (Papio anubis), male chimpanzees (Pan troglodytes), female sooty mangabeys (Cercocebus atys) and female vervet monkeys (Chlorocebus pygerythrus). We found that female vervet monkeys did not produce greeting calls, while in the other three species, low-ranking individuals were more likely to call than high-ranking ones. The effects of dyadic dominance relationships differed in species-specific ways, with calling being positively associated with the rank distance between two individuals in baboons and chimpanzees, but negatively in mangabeys. In none of the tested species did we find strong evidence for an effect of dyadic affiliative relationships or audience on call production. These results likely reflect deeper evolutionary layers of species-specific peculiarities in social style. We conclude that a comparative approach to investigate vocal behaviour has the potential to not only better understand the mechanisms mediating social signal production but also to shed light on their evolutionary trajectories.

Highlights

Why do animals vocalize prior to interacting with each other? One universal function of vocal behaviour is to signal subsequent behaviour [1,2]
We found that female vervet monkeys did not produce greeting calls, while in the other three species, low-ranking individuals were more likely to call than high-ranking ones
We examined the vocal greeting behaviour of these species focusing on three different features known to be associated with the production of greeting calls

Summary

Introduction

Why do animals vocalize prior to interacting with each other? One universal function of vocal behaviour is to signal subsequent behaviour [1,2]. Affiliative or aggressive attitudes, which in turn influences whether social interactions occur and their form [1]. When two individuals approach each other, the prospects of a physical interaction and, aggression increase. Many species produce signals before or during such dyadic ‘encounters’ to reduce the probability of aggression and/or to facilitate friendly interactions [4,5]. If such signals involve vocalizations, they are usually termed ‘greeting calls’—broadly defined as calls produced when approaching, or being approached by, another individual [6,7]. Several more specific functions have been proposed for greeting calls, such as reinforcing social relationships (dominance [4,8]; social bonds [9]), reconciling after a conflict [10,11], facilitating reunions [7] or recruiting social support [12]

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