What this actually means for the structure of the foot is a question that is still being researched today. It would seem that an accessory navicular is commonly related to pes planus. Frederick Kidner, in 1929, first theorized that the presence of an accessory navicular could be the cause of pes planus.
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.
At this time, they begin to disperse. Young of the late summer litters may remain with the female during the winter. Sexual maturation takes place during the following spring or summer. Mean life expectancy for a gray squirrel at birth is 1-2 years; the average life span of an adult is closer to 6 years. Records for maximum life span are 12 years in the wild and 20 years in captivity. Predators: The typical predators of small to medium-sized mammals prey upon gray squirrels.