Let's start with the fact that Sherman's Fox Squirrel is restricted to Florida, so I think we can rule that out. There are two other subspecies of the Eastern Fox Squirrel in Mississippi. Bachman's Fox Squirrel, which occurs in upland areas across the state, has a black mask and white ears, nose, and paws. The Delta Fox Squirrel of the Mississippi River lowlands is sometimes glossy black, often with white appendages like Bachman's; and sometimes a grizzled, rusty color, with or without the black mask and white appendages. Wherever subspecies meet, there will be considerable individual variation across what is known as the "intergradation zone." I think you are in such a zone and that what you're seeing are Eastern Fox Squirrels exhibiting a color pattern representing the phenotype particular to that area, or maybe just a single individual. You haven't given any evidence that you've seen more than one of these animals. If you are seeing multiple individuals and no one else is, perhaps you really should cut back on the wine.