Personality development in non-domesticated house mice evidence for a nutrition-dependent sensitive period early in life

Changing nutritional conditions pose challenges to developing organisms. Animals typically cope with such changes by adjusting their foraging, exploration or risk-taking behaviours. Notably, there exists considerable between-individual variation (‘animal personality’) in coping strategies. One dimension underlying such personality differences is whether animals cope actively or passively with stress. At present, we know little about how stress coping develops. Previous research found that house mice can adjust stress coping to food quality changes within three generations. However, understanding when during development such personality adjustments occur is crucial for understanding population dynamics in the wild. We tested experimentally how changes in food quality at different ontogenetic stages (fetus, newborn, weanling and late adolescent) affect personality development in non-domesticated cage-housed house mice (Mus musculus domesticus). Personality traits were assessed in the open field and the elevated plus maze at different ages (weaning, early adolescence, late adolescence and adulthood). We highlight two key findings. First, the fetal life stage is a sensitive period for stress coping in response to experiencing decreases in nutritional quality. Second, experiencing an increase in nutritional quality may slow the age-related switch towards a passive stress-coping strategy. Our study contributes towards understanding the complex relationships between development, nutrition and personality.