Young squirrels have milk teeth which are replaced by permanent teeth when they are between six and twelve months old. Eastern Gray squirrels are highly adapted for climbing trees and fatal falls are rare. Adaptations for climbing trees include tough curved claws, and the ability to reverse their hind foot 180 degrees to permit head first descent. Gray squirrels are excellent climbers and can leap considerable distances using powerful hindlimbs. Tails are used for balance when running and leaping between trees, and held over the back of a resting animal.
Females can have two litters per year, one from each breeding season.
Both sexes remain reproductively active throughout their lives. Female eastern gray squirrels have been known to produce litters as young as 5 months of age in the southern part of their range, but most do not reproduce until 1.25 years of age. An enlarged pink vulva is usually visible the day before the onset of estrus. Male eastern gray squirrels are sexually mature at 10 - 11 months of age. Functional testes descend in the scrotum from December to February and May to July, although testes may stay descended without spermatogenesis until October.