It acts as a rudder when the animal jumps from high places, as a warm covering during the winter, as a signal to other grey squirrels indicating an individual's mood, and perhaps as a sun shade. The fur is thicker and longer in winter. The fur colour is grey or black and may change with the seasons. Black individuals are generally a glossy uniform black all over, but the species may show all shades of gradation between black and grey. A litter may contain both black and grey individuals.
Signs There are typical signs that grey squirrels inhabit an area.
The gnawed husks and shells of nuts, especially acorns, hickory nuts, walnuts, beechnuts, and pecans, can be found littering the ground around the base of a tree where the squirrels have been feeding. In winter small holes in the snow or ground indicate where squirrels have been digging to find nut caches buried earlier in the year. When the squirrel bounds across the ground the tracks are paired, hindprints slightly ahead of the foreprints. This bounding stride may be as much as 1 m if the animal is in a hurry. A noticeable sign of the presence of the grey squirrel is the large leaf nest, or drey.