Spacing behaviour, kinship, and population dynamics of grey squirrels in anewly colonized broadleaf woodland in Italy

Eastern grey squirrels, Sciurus carolinensis, introduced to Britain and nor thern Italy are replacing the native Eurasian red squirrel, Sciurus vulgari s. We studied the pattern of colonization of a high-quality broadleaf woodl and by grey squirrels by means of livetrapping and radio-tracking. The stud ies started in July 1996, when six grey squirrels (four males, two females) first colonized the woodland, and lasted until November 1998, when densiti es exceeded those of the local red squirrel population. Grey squirrel colon ization was rapid, with a high proportion of adult and yearling females bre eding. Juvenile recruitment was also higher than in stable populations in B ritain. Adult survival was better in 1997 (83%) than in 1998 (47%), with pr edation accounting for 67% of losses in 1998. This indicates the effects of local predator communities on the colonization process. Densities of grey squirrels were moderate in 1998, with a maximum of 1.9 squirrels/ha and we expect density to increase further. Adult home range sizes were three to fo ur times larger than those of subadults, and male ranges were larger than t hose of females. Body mass was positively correlated with both total home r ange size and core-area size. Core-area size for adults was inversely corre lated with food availability. Juvenile female grey squirrels were philopatr ic, forming female kin groups, while most juvenile males settled outside th e mother's home range.