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.
NONNATIVE INVASIVE TREE SQUIRRELS The Eastern gray squirrel and Eastern fox squirrel are nonnative invasive species of concern in the state. While their effects on Oregonâs ecosystems are not fully understood, there is enough evidence to consider them a threat to native squirrel populations.estern gray squirrel The western gray squirrel (Sciurus griseus) is the stateâs largest native tree squirrel. It has a creamy white belly and silvery gray fur, and ranges in length from 19 to 24 inches including the tail which is a bushy gray with black hairs.