Personality Traits in Rhesus Macaques (Macaca mulatta) Are Heritable but Do Not Predict Reproductive Output
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There is growing evidence that behavioral tendencies, or “personalities,” in animals are an important aspect of their biology, yet their evolutionary basis is poorly understood. Specifically, how individual variation in personality arises and is subsequently maintained by selection remains unclear. To address this gap, studies of personality require explicit incorporation of genetic information. Here, we explored the genetic basis of personality in rhesus macaques by determining the heritability of personality components and by examining the fitness consequences of those components. We collected observational data for 108 adult females living in three social groups in a free-ranging population via focal animal sampling. We applied principal component analysis to nine spontaneously occurring behaviors and identified six putative personality components, which we named Meek, Bold, Aggressive, Passive, Loner, and Nervous. All components were repeatable and heritable, with heritability estimates ranging from 0.14 to 0.35. We found no evidence of an association with reproductive output, measured either by infant survival or by interbirth interval, for any of the personality components. This finding suggests either that personality does not have fitness-related consequences in this population or that selection has acted to reduce fitness-associated variation in personality.
KeywordsAdditive genetic variance Behavioral tendencies Fitness Quantitative genetics Reproductive success
We thank Bonn Aure, Jacqueline Buhl, Monica Carlson, Sam Larson, Elizabeth Maldonado, Heather Sherwin, and the Cayo Santiago Staff for research support. We thank Greg Blomquist and John Pearson for statistical advice and assistance, and Amanda Melin and two anonymous reviewers for helpful comments on the manuscript. The authors were supported by NIMH grants R01-MH089484 and R01-MH096875, an Incubator Award from the Duke Institute for Brain Sciences. L. J. N. Brent was supported by fellowships from the Natural Sciences and Engineering Research Council of Canada (NSERC), the University of Roehampton, and the Duke Center for Interdisciplinary Decision Sciences. The CPRC is supported by grant 8-P40 OD012217-25 from the National Center for Research Resources (NCRR) and the Office of Research Infrastructure Programs (ORIP) of the National Institutes of Health.
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