Estimating offspring production using capture-mark-recapture and genetic methods in red squirrels

Living on the edge: morphological and behavioral adaptations to a marginal high-elevation habitat in an arboreal mammal

Habitats are characterized by different local environmental conditions that influence both behavior and morphology of species, which can result in habitat-dependent phenotypic differences among animals living in heterogeneous environments. We studied three alpine populations of Eurasian red squirrels (Sciurus vulgaris), one living in a marginal high-elevation habitat at the edge of the species' altitudinal distribution, and two occurring in higher-quality habitats. Here, we investigated whether squirrels living in the marginal area differed in two morphological parameters (body size and body mass) and/or in the expression of four personality traits estimated with an open field test and a mirror image stimulation test (activity, exploration, activity-exploration and social tendency). Furthermore, we tested whether within-individual variance of the traits (behavioral plasticity) was higher in the edge habitat. Male squirrels in the edge habitat were smaller and weighed less than in the other study areas, while among females size-habitat relationships were less marked. These sex-specific patterns were explained by a strong association between body mass and reproductive success in female squirrels. Squirrels in the marginal habitat were more active, explorative and had a more social personality than in the other habitats. However, in contrast to our predictions, behavioral plasticity was smaller in the marginal habitat, but only for the trait exploration. Our results suggest that animals choose the habitat that best fits their personality, and that habitat-related differences in selective pressures may shape animals' morphology. This article is protected by copyright. All rights reserved.