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.
Red squirrels live long lives compared to their size. The oldest squirrel in the wild was 10 years old, and the oldest in captivity was 9 years old. Their average lifespan is 5 years. However, red squirrels have difficulty surviving past 1 year old.