EFFECTS OF TEMPORAL AND SPATIAL VARIATION IN HABITAT QUALITY ON RED SQUIRREL DISPERSAL BEHAVIOR

Immigration patterns and the frequency of breeding dispersal in tree s quirrels are predicted to be related to the amount of temporal and spa tial variation in tree seed crops, their primary food supply. We studi ed Eurasian red squirrel, Sciurus vulgaris, dispersal patterns in a st able habitat with predictable food supply and a variable habitat with large temporal and spatial variations in food availability. In both ha bitats, we observed a male-biased immigration in spring and a female-b iased immigration in autumn. However, there were more adults among imm igrating red squirrels in the variable (66%) than the stable (31%) hab itat and large differences in the extent of site fidelity between the two squirrel populations. Multivariate analyses indicate that food ava ilability appeared to be the main factor affecting female dispersal be haviour. The data also suggest that female red squirrel dispersal patt erns 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 hig h in the stable habitat, whereas they appeared to track the movement o f females in the variable habitat. (C) 1997 The Association for the St udy of Animal Behaviour.