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.
Lifespan/Longevity. Southern flying squirrels in the wild can live to 5 or 6 years old. In captivity they have been known to live up to 10 years. Most flying squirrels probably die in their first year of life.