Wild vervet monkeys copy alternative methods for opening an artificial fruit
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Experimental studies of animal social learning in the wild remain rare, especially those that employ the most discriminating tests in which alternative means to complete naturalistic tasks are seeded in different groups. We applied this approach to wild vervet monkeys (Chlorocebus aethiops) using an artificial fruit (‘vervetable’) opened by either lifting a door panel or sliding it left or right. In one group, a trained model lifted the door, and in two others, the model slid it either left or right. Members of each group then watched their model before being given access to multiple baited vervetables with all opening techniques possible. Thirteen of these monkeys opened vervetables, displaying a significant tendency to use the seeded technique on their first opening and over the course of the experiment. The option preferred in these monkeys’ first successful manipulation session was also highly correlated with the proportional frequency of the option they had previously witnessed. The social learning effects thus documented go beyond mere stimulus enhancement insofar as the same door knob was grasped for either technique. Results thus suggest that through imitation, emulation or both, new foraging techniques will spread across groups of wild vervet monkeys to create incipient foraging traditions.
KeywordsField experiments Social learning Imitation Cultural transmission Primates Vervet monkeys
This project was supported by a Sinergia grant (CRSI33_133040) from the Swiss National Science Foundation to R. Bshary, C. P. van Schaik and A. Whiten, and by a SNSF personal grant of E.W. (P300P3_151187). We are particularly grateful to Kerneels van der Walt for permission to conduct the study in his reserve and Albert Driescher for his vital support in the field. The study was registered with Ezemvelo KZN Wildlife in South Africa and gained approval from the Ethics Committee of the School of Psychology and Neuroscience, University of St Andrews. We are grateful to all IVP field team for assistance in data collection during experimental sessions. Thanks to Andy Burnley for constructing the vervetables. We are grateful to Tina Gunhold for useful comments on the manuscript.
Video 1 Lift opening of the vervetable during demonstration phase (Baie Dankie group). (MPG 3544 kb)
Video 2 Slide to the right opening of the vervetable during demonstration phase (Ankhase group). (MPG 1748 kb)
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