On personality, energy metabolism and mtDNA introgression in bank voles

Consistent interindividual differences in behaviour, or animal personality, are emerging as an important determinant of a wide range of life history traits and fitness. Individual behaviour, however, may be constrained by between-individual variability in energy metabolism and may become unstable owing to intrinsic and extrinsic stressors. Here we tested the relationship between personality and physiology using wild-caught bank voles, Myodes glareolus, that varied according to mtDNA type (original or introgressed from Myodes rutilus). Personality traits and their within-individual consistency were assessed using an open field test and basal metabolic rate (BMR) was measured in an open-flow respirometer. A significant relationship was found between individualsʹ consistent (repeatable) personality trait (principal component analysis score reflecting individual differences in proactivity) and their consistent (repeatable) residual BMR (body mass corrected); however, this association depended on mtDNA type and sex. Particularly, the males with original mtDNA showed a positive relationship between proactive behaviour and BMR, which supports the increased-intake model, stating that BMR is positively related to the capacity to engage in costly behaviours. However, this relationship was disrupted in introgressed males, and showed a negative trend in females, suggesting the alternative compensation model. According to our findings, it is likely that consistent differences in behavioural patterns and mtDNA types promote variation between individuals in energy metabolism.