This looks like a fox with mange.  Mange is a torturous disease for foxes, who get it from domestic dogs.  This little guy has lost a lot of hair in his tail, that's why he doesn't look like a fox should.  

You may be able to save him from a slow painful death by  leaving out a chicken laced with the medication that kills mange.  Speak with your veterinarian about what to do. 

ECN