Effects of temporal and spatial variation in habitat quality on red squirrel dispersal behaviour

Immigration patterns and the frequency of breeding dispersal in tree squirrels are predicted to be related to the amount of temporal and spatial variation in tree seed crops, their primary food supply. We studied Eurasian red squirrel, Sciurus vulgarisdispersal patterns in a stable habitat with predictable food supply and a variable habitat with large temporal and spatial variations in food availability. In both habitats, we observed a male-biased immigration in spring and a female-biased immigration in autumn. However, there were more adults among immigrating red squirrels in the variable (66%) than the stable (31%) habitat and large differences in the extent of site fidelity between the two squirrel populations. Multivariate analyses indicate that food availability appeared to be the main factor affecting female dispersal behaviour. The data also suggest that female red squirrel dispersal patterns are an adaptive response to the predictability of food resources in space and time. Male dispersal behaviour seemed to be influenced by the distribution of the females. Their level of site fidelity was high in the stable habitat, whereas they appeared to track the movement of females in the variable habitat.