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.
Quick Answer. According to the University of Michigan, the African grey parrot has an average life expectancy of about 45 years in captivity. Some live to be as old as 60. In the wild, the life span is about 23 years. Keep Learning.