Habitat-dependent effects of personality on survival and reproduction in red squirrels

Abstract

Abstract: Variation in intrinsic (body mass, reproductive condition) and extrinsic factors (habitat quality, spatio-temporal variation in food availability) can affect the costs and benefits of personality traits. Relationships between personality and fitness components can vary with changes in population density and/or habitat quality. Here, using capture-mark-recapture data of individually marked Eurasian red squirrels (Sciurus vulgaris), we explored whether indices of boldness and exploration are correlated with local survival in either of the sexes and with a measure of reproductive success in females, under different conditions of food availability. PCA scores derived from the number of captures (trappability) and number of different traps where an individual was captured (trap diversity), in the first 1 or 2 years of presence, were used as indices of personality (boldness and pure exploration). The relationships between boldness and local survival differed between habitats in both sexes. Bold squirrels survived better than shy ones in Norway spruce forest, while in the other two study areas (Scots pine or mixed spruce-fir forest), survival was lower for bolder squirrels. Pure exploration behavior was negatively correlated with local survival in all habitats and in both sexes. Female reproductive success increased with body mass and decreased with the tendency to explore, a relationship consistent across habitat types. Bolder females did not have a reproductive advantage in years of poor food availability. We suggest that costs and benefits of boldness vary with spatio-temporal differences in availability of high-quality food resources which may help to maintain variation in personality in red squirrels in heterogeneous landscapes. Significance statement: Differences in personality among individuals can affect their survival or reproductive success. We investigated the relationship between personality traits and fitness components in Eurasian red squirrels under different food availability. We scored boldness and exploration using indices derived from capture-mark-recapture data. Bold red squirrels survived longer than shy ones in spruce forest where food availability varied strongly between years. Instead, in mixed forests with more stable food supplies, shy individuals survived longer. Heavy females produced more litters in their lifetime than those with lower body mass. Explorative squirrels were more likely to die young and to produce no or few litters, independent of the habitat they lived in. Our results suggest that variation in personality traits within populations of Eurasian red squirrels was maintained by changing fitness benefits in relation to habitat type in pulsed resource systems.