Unrecovered nuts may sprout and grow into trees. In this way, squirrels help ensure continual forest growth. Grays are probably the wariest of Pennsylvania's squirrels. Hawks, owls, foxes and tree-climbing snakes occasionally kill young squirrels, but adults are not easily taken. A maximum life span for a wild gray squirrel could be 10 years or even longer, but few live more than two or three years.
Grays live in nests and dens.
They build leaf nests in trees near good food supplies in both summer and fall, the leaf nests are cooler than tree dens, they're about 12 by 16 inches and are built of twigs, leaves, grass, bark and other plant materials. Tree dens are often in cavities where limbs have broken off or in deserted woodpecker holes, usually 40 to 60 feet off the ground. Resident squirrels gnaw back the outer tree bark that, in time, would otherwise seal off den holes. Gray squirrels breed in late winter or early spring. The young are usually raised in tree dens and nursed by their mother for 5-7 weeks.