Meerkat close calling patterns are linked to sex, social category, season and wind, but not fecal glucocorticoid metabolite concentrations.

Ines Braga Goncalves,André Ganswindt,Jelena Mausbach,Michael Heistermann,Marta B Manser

doi:10.1371/journal.pone.0175371

Abstract

It is well established that animal vocalizations can encode information regarding a sender’s identity, sex, age, body size, social rank and group membership. However, the association between physiological parameters, particularly stress hormone levels, and vocal behavior is still not well understood. The cooperatively breeding African meerkats (Suricata suricatta) live in family groups with despotic social hierarchies. During foraging, individuals emit close calls that help maintain group cohesion. These contact calls are acoustically distinctive and variable in rate across individuals, yet, information on which factors influence close calling behavior is missing. The aim of this study was to identify proximate factors that influence variation in call rate and acoustic structure of meerkat close calls. Specifically, we investigated whether close calling behavior is associated with sex, age and rank, or stress hormone output (i.e., measured as fecal glucocorticoid metabolite (fGCM) concentrations) as individual traits of the caller, as well as with environmental conditions (weather) and reproductive seasonality. To disentangle the effects of these factors on vocal behavior, we analyzed sound recordings and assessed fGCM concentrations in 64 wild but habituated meerkats from 9 groups during the reproductive and non-reproductive seasons. Dominant females and one-year old males called at significantly higher rates compared to other social categories during the reproductive season. Additionally, dominant females produced close calls with the lowest mean fundamental frequencies (F0) and the longest mean pulse durations. Windy conditions were associated with significantly higher call rates during the non-reproductive season. Fecal GCM concentrations were unrelated to close calling behavior. Our findings suggest that meerkat close calling behavior conveys information regarding the sex and social category of the caller, but shows no association with fGCM concentrations. The change in call rate in response to variation in the social and ecological environments individuals experience indicates some degree of flexibility in vocal production.

Highlights

Vocal communication mediates many interactions between individuals in social species
By focusing on close calls produced in the foraging, context rather than on alarm calls produced under perceived predator threat, we aimed to minimize potential confounding effects from other components of an animal’s physiological stress response, allowing us to evaluate whether call rate and acoustic structure were associated with individual traits, weather conditions, reproductive seasonality, and fecal GC metabolites (fGCMs) levels
This study assessed the effects of individual traits, such as sex, age, body weight and social rank, and fGCM concentrations, as well as weather on the close call behavior of foraging meerkats during the reproductive and non-reproductive seasons

Summary

Introduction

Vocal communication mediates many interactions between individuals in social species. While acoustic properties that determine individual distinctiveness are genetically determined, other aspects of calls, such as those caused by physiological parameters [8], can be more or less flexible [9, 10]. Individual physiological [e.g. hormonal) states related to sex, age or social status [11,12,13,14] can be stable over long periods of time, but can change within short periods of time in response to e.g. reproductive state [11], social instability or environmental challenges, such as predation risk, food limitation and harsh weather conditions [15,16,17,18]

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Conclusion