Grey squirrel 1
The eastern gray squirrel or grey squirrel (Sciurus carolinensis) is a tree squirrel native to North America. A prolific and adaptable species, the grey squirrel has been introduced to, and thrives in Britain, where it has spread across the country and has largely displaced the native red squirrel.
The grey squirrel is one of very few mammalian species that can descend a tree head-first. It does this by turning its feet so that the claws of its hindpaws are backward pointing and can grip the tree bark. They build a type of nest, known as a "drey", in the forks of trees and is a scatter-hoarder; it hoards food in numerous small caches for later recovery.