"The adaptable, omnivorous, diurnal Eastern Gray Squirrel is the native American mammal people most frequently see east of the Mississippi River. It prefers to den inside trees, but will construct large nests of leaves in the canopy if tree cavities are not available. An average of two to three blind, hairless young make up a litter. Litters are produced once or twice a year, in February and March and again in July through September. The young are weaned at eight or nine weeks, when their previously protective mother abandons them. In September, yearlings and some adults strike out to establish their own home ranges in a process called the ""fall reshuffle."" These home ranges are rarely more than one or two hectares in size. Successful as they are, Eastern Gray Squirrels live only 11-12 months on average, but some individuals have survived more than ten years in the wild. Factors affecting survival include the severity of winter, abundance of food, and parasites. One parasite, the mange mite, may cause enough hair loss to threaten survival through winter."

Links:
Mammal Species of the World
Click here for The American Society of Mammalogists species account