Concealing of facial expressions by a wild Barbary macaque (Macaca sylvanus)
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Behavioural research on non-vocal communication among non-human primates and its possible links to the origin of human language is a long-standing research topic. Because human language is under voluntary control, it is of interest whether this is also true for any communicative signals of other species. It has been argued that the behaviour of hiding a facial expression with one’s hand supports the idea that gestures might be under more voluntary control than facial expressions among non-human primates, and it has also been interpreted as a sign of intentionality. So far, the behaviour has only been reported twice, for single gorilla and chimpanzee individuals, both in captivity. Here, we report the first observation of concealing of facial expressions by a monkey, a Barbary macaque (Macaca sylvanus), living in the wild. On eight separate occasions between 2009 and 2011 an adult male was filmed concealing two different facial expressions associated with play and aggression (“play face” and “scream face”), 22 times in total. The videos were analysed in detail, including gaze direction, hand usage, duration, and individuals present. This male was the only individual in his group to manifest this behaviour, which always occurred in the presence of a dominant male. Several possible interpretations of the function of the behaviour are discussed. The observations in this study indicate that the gestural communication and cognitive abilities of monkeys warrant more research attention.
KeywordsIntentionality Hiding Non-vocal communication Gestures Old World monkey
The authors are grateful to Bonaventura Majolo, Professor Mohamed Qarro, Julia Ostner, and Oliver Schülke for their support, and to the Haut Commissariat aux Eaux et Forêts et à la Lutte Contre la Désertification of Morocco for permission to conduct the research. We also wish to thank Juichi Yamagiwa, Joanna Setchell, Joanne Tanner, and several anonymous reviewers for useful comments on the manuscript. We thank Björn Rogell and Jonas Andersson for useful advice, and for assistance in the field we thank M. Madole, L. Maréchal, N. Marquez, J. Msindai, D. Thomas, S. Santos, and T. Smith. Financial support was provided to CY by the Max Planck Society, the Christian Vogel Fonds, and Georg-August University Göttingen through funds from the German Initiative of Excellence.
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