"The eastern gray squirrel, or grey squirrel (depending on region), (Sciurus carolinensis), is a tree squirrel in the genus Sciurus native to the eastern and midwestern United States, and to the southerly portions of the eastern provinces of Canada. The native range of the eastern gray squirrel overlaps with that of the fox squirrel (Sciurus niger), with which it is sometimes confused, although the core of the fox squirrel's range is slightly more to the west.
A prolific and adaptable species, the eastern gray squirrel has been introduced to, and thrives, in several regions of the western United States. It has also been introduced to Britain, where it has spread across the country and has largely displaced the native red squirrel, Sciurus vulgaris. In Ireland, the red squirrel has been displaced in several eastern counties, though it still remains common in the south and west of the country.[3] There are concerns that such displacement might happen in Italy and that gray squirrels might spread from Italy to other parts of mainland Europe."