The Fox Squirrel, Sciurus Niger, is the largest species of tree squirrel native to N. The most common Squirrel in my area by far. There ins't a thing you can do about them. They're tenacious survivors.
The silver fox is a melanistic form of red fox. Melanism is when the animal's coloring is much darker than normal. Interestingly, fox squirrels, who have brownish body fur and reddish tummy fur also have a melanistic form that resembles this.