Determinants, selection and heritability of docility in wild eastern chipmunks (Tamias striatus)

Many behavioural traits show important inter-individual phenotypic and genetic variation despite strong potential selection that should reduce this variability. Spatial and temporal heterogeneity in environmental conditions has been proposed to maintain such variation but empirical evidences supporting this hypothesis are still scarce for behavioural traits. Here, we analysed the repeatability and the ecological and individual factors that influence the expression of docility across different environmental contexts in wild eastern chipmunks (Tamias striatus) studied over a period of 10 years. We also estimated the heritability of docility and the patterns of viability selection acting on this trait for adults and juveniles. Docility was moderately repeatable among various contexts and was positively affected by age, was higher in males than that in females, was higher during the fall and decreased with population density. Heritability of docility was low at 0.17. We found disruptive selection for the survival of adults only, individuals more or less docile than average having a higher survival. Our study confirms that docility is both phenotypically and genetically variables and that disruptive selection might maintain the variability in this trait. Significance statement Documenting the factors allowing the maintenance of phenotypic and genetic variation of behavioural traits within natural populations is a central objective in ecology and evolution. Here, we studied a wild eastern chipmunk population over 10 years and recorded docility, a personality trait, on both juveniles and adults. We showed that docility was repeatable and that it was also heritable and influenced by different individual and environmental factors. Importantly, we also found that disruptive viability selection was acting on adult docility independently of environmental variations. Our results show that docility is both phenotypically and genetically variable and that patterns of selection acting on this trait can maintain personality heterogeneity across temporally varying environmental conditions in the wild.