Intra-individual behavioural variability: a trait under genetic control
When individuals are measured more than once in the same context they do not behave in exactly the same way each time. The degree of predictability differs between individuals, with some individuals showing low levels of variation around their behavioural mean while others show high levels of variation. This intra-individual variation in behaviour has received much less attention than between-individual variance in behaviour and very little is known about the underlying mechanisms that affect this potentially large but understudied component of behavioural variation. In this study, we combine standardized behavioural tests to estimate intra-individual behavioural variance with a large-scale genetical genomics analysis to identify genes affecting intra-individual variability in an avian population. Our study shows that within-individual variance in behaviour has a direct genetic basis which is largely unique compared to the genetic architecture for the standard behavioural measures they are based on. We identify six candidate genes underlying variation in intra-individual behavioural variability many of which have previously been linked to behaviour and mental health. These findings demonstrate that within-individual variability in behavioural is a heritable trait in and of itself on which evolution can act.