Often their nails are worn down and won't show in the track. A coyote will go for the throat to make a kill. It will rip out the heart, lungs and liver to eat. There has been one reported attack in Virginia. They are tough on the red fox population.
Foxes generally disappear when they arrive.
Early one morning three years ago, I was awakened by a sudden, ghostlike howl that was long, high-pitched and so piercing that it projected the pure and untamed sound of the the wilderness. It was the kind of experience that curls the hair on the back of your neck, and it was coming from what I estimated to be no more than 40 yards away. I had heard it before, during a visit to Arizona, so I immediately knew what it was, but that fact didn't still my heart. It was a coyote. This time I wasn't in Arizona, nor was I in the wilds of Maine or Montana.