Catching a Fox in a cage trap can be very difficult if its not set up properly. The trap needs to be set up in a way the animal has no choice but to go in. If the Fox is going through a gap in chicken wire to get into the coop. set the trap up on the other side of the opening so when the animal comes in. It goes straight into the trap. If a Fox can avoid a cage it most likely will. They are weary and cautious creatures.