Both juvenile and adult animals display stable behavioural differences (personality), but lifestyles and niches may change as animals mature, raising the question of whether personality changes across ontogeny. Here, we use a wild population of red squirrels to examine changes in activity and aggression from juvenile to yearling life stages. Personality may change at the individual level (individual stability), population level (mean level stability), and relative to other individuals (differential stability). We calculated all three types of stability, as well as the structural stability of the activity–aggression behavioural syndrome. Within individuals, both activity and aggression scores regressed towards the mean. Differential stability was maintained for activity, but not aggression. Structural stability was maintained; however, the activity–aggression correlation increased in squirrels that gained territories later in the season. These results suggest that personality undergoes some changes as animals mature, and that the ontogeny of personality can be linked to environmental changes.
DingemanseN.J.Van der PlasF.WrightJ.RealeD.SchramaM.RoffD.A.Van der ZeeE.BarberI. (2009).
Individual experience and evolutionary history of predation affect expression of heritable variation in fish personality and morphology. —
Proc. Roy. Soc. Lond. B: Biol. Sci.276:
Measuring individual differences in reaction norms in field and experimental studies: a power analysis of random regression models. —
Methods Ecol. Evol.2:
Slow explorers take less risk: a problem of sampling bias in ecological studies. —
Low heritabilities, but genetic and maternal correlations between red squirrel behaviours. —
J. Evol. Biol.25: