Scratching Our Heads: Rethinking Social Anxiety in Vervets (Chlorocebus aethiops)
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Numerous conflicting results exist in the primate literature regarding the role of dominant individuals in creating conditions of social anxiety. Self-directed behaviors (SDB) have been used as an indicator of increased anxiety in primates to examine the effects of social stimuli such as dominance and association. This study recorded SDB from 11 free-ranging female vervets in the semi-arid Klein Karoo region of South Africa for a total of 468 focal hours to determine whether anxiety was influenced by the hierarchical rank of, and degree of association with, neighboring monkeys. Associates were dyads that spent long periods of time together, i.e., proximity sociality index scores in the top 40% of all scores, and nonassociate dyads spent very little time together, i.e., scores within the bottom 40% of all scores. Rates of SDB were significantly higher when dominant neighbors were nonassociates vs. associates. The rate of SDB when neighbors were dominant associates vs. subordinate associates did not differ. These findings indicate that anxiety is influenced to a greater extent by the degree of association with neighboring monkeys than by hierarchical rank. Measurement of multiple social variables can elucidate the relative contributions of the variables to changes in SDB and demonstrate how the variables interact, thereby providing a more comprehensive understanding of conditions leading to changes in social anxiety.
KeywordsAssociation Dominance Self-directed behavior Social anxiety Vervet
We thank Mark and Sarah Tompkins for permission to work on their property. Dr. Parry Clarke, Nicola Forshaw, April Takahashi, Nicole Whale, and David McCaffrey provided valuable assistance in the field, and many stimulating discussions. Louise Barrett, Peter Henzi, and 2 anonymous reviewers provided valuable feedback on an earlier version of this manuscript. I also thank Caroline Mullins for her assistance with this project and Bruce Raphael for the title. This project is funded by NSERC (Canada), NRF (South Africa), and UNISA grants to L. Barrett, S. P. Henzi, and L. Brown.
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