Abstract
Socio-demographic factors, such as group size and their effect on predation vulnerability, have, in addition to intrinsic factors, dominated as explanations when attempting to understand animal vigilance behaviour. It is generally assumed that animals evaluate these external factors visually; however, many socially foraging species adopt a foraging technique that directly compromises the visual system. In these instances, such species may instead rely more on the acoustical medium to assess their relative risk and guide their subsequent anti-predator behaviour. We addressed this question in the socially foraging meerkat (Suricata suricatta). Meerkats forage with their head down, but at the same time frequently produce close calls (‘Foraging’ close calls). Close calls are also produced just after an individual has briefly scanned the surrounding environment for predators (‘Guarding’ close calls). Here, we firstly show that these Guarding and Foraging close call variants are in fact acoustically distinct and secondly subjects are less vigilant (in terms of frequency and time) when exposed to Guarding close call playbacks than when they hear Foraging close calls. We argue that this is the first evidence for socially foraging animals using the information encoded within calls, the main adaptive function of which is unrelated to immediate predator encounters, to coordinate their vigilance behaviour. In addition, these results provide new insights into the potential cognitive mechanisms underlying anti-predator behaviour and suggest meerkats may be capable of signalling to group members the ‘absence’ of predatory threat. If we are to fully understand the complexities underlying the coordination of animal anti-predator behaviour, we encourage future studies to take these additional auditory and cognitive dimensions into account.
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Acknowledgements
We would like to thank Tim Clutton-Brock for his support to work on the meerkat population of the Kalahari Meerkat Project and the owners of farms surrounding the reserve for allowing us to work on their land. We are thankful to Megan Price and Christele Borgeaud, as field managers, and the volunteers of the project for their help over the duration of the study. Thanks to Micheal Owren for Praat scripts, Roger Mundry for statistical support and for providing pDFA scripts, Katie Slocombe, Beke Graw, David Jansen and Manuela Cadilek for discussions and Amanda Ridley, Peter Bednekoff and two anonymous reviewers for helpful comments on the manuscript. The study was carried out under licenses issued by the Northern Cape Conservation Service and ethical committee of Pretoria University, South Africa. This work was funded by the University of Zurich.
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Communicated by P. Bednekoff
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ESM 1
Time frequency spectrogram and accompanying waveform showing two distinct tonal meerkat sentinel calls. Spectrogram window settings: FFT length = 512, Hamming window, window length = 0.05 s, bandwidth = 112 Hz, frequency resolution = 86 Hz, dynamic range = 70 dB. (DOC 45 kb)
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Townsend, S.W., Zöttl, M. & Manser, M.B. All clear? Meerkats attend to contextual information in close calls to coordinate vigilance. Behav Ecol Sociobiol 65, 1927–1934 (2011). https://doi.org/10.1007/s00265-011-1202-6
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DOI: https://doi.org/10.1007/s00265-011-1202-6