Effects of spatial variation in food availability on spacing behaviour anddemography of Eurasian red squirrels

In heterogeneous habitats with limited resources, spacing behaviour will af fect individual variation in breeding success and density of populations, a nd is thus of general interest to ecologists. We investigated how red squir rels Sciurus vulgaris adapt their social organisation to fine-grained heter ogeneity in habitat quality, studying spacing behaviour, habitat use and po pulation dynamics in a forest in north Italy, characterised by a mosaic of high-quality (chestnut-pine) and poor-quality patches. We compared the data with those from more homogeneous broadleaf and mixed woodlands with simila r overall tree seed abundance ("stable" habitats). Squirrels lived at lower densities (pre-breeding density 0.39-0.58 ha(-1)) than in "stable" habitat s, although breeding rate was not reduced. Female breeding success was rela ted to being primiparous as yearlings, and increased with body mass and pro portion high-quality habitat in the home range. Persistency rate of females was as in stable habitats. It was higher than male persistency, but immigr ation and recruitment rates were male biased, resulting in even sex-ratio. All residents occupied high-quality patches, and no subadults established a permanent home range in poor-quality habitat. Home range and core-area siz e was typically larger in males than in females and a male's core-area over lapped those of other males and of females. Female core-areas were overlapp ed by males but not, or very little, by other females (intrasexual territor iality). Home ranges, or core-areas, were not smaller than in "stable" habi tats, nor did we find a higher degree of core-area overlap. We conclude tha t in patchy habitats dominant, resident red squirrels exclude dispersing an imals from preferred, high-quality habitat, producing a spacing pattern ref erred to as ideal despotic distribution, and that poor patches were only us ed temporarily by transient individuals, resulting in a reduction of densit y in comparison to populations in "stable" habitats.