Those Arks and Tractors can be difficult. I think your actual biggest risk, especially in daytime, just might be a dog, but any of those you mentioned could be a threat.
I'll mention an apron instead of burying the wire. The idea is that you lay a section of wire horizontal around the outside of the coop or run, having it attached to the bottom of the fence. The predator goes up to the wire, starts digging and hits the wire. They don't know to back up and start digging over. 18" is usually a good width.
Of course, those aprons laying on the ground would make it real hard to move the Ark. You could maybe build them in a way you could tie them up off the ground when you move it. Another possibility would be to build separate panels that could be moved independently. Maybe rip a 2x4 then put that back together with the edge of the wire clamped in between the two sections. Drill some holes in the 2x4 that will fit over bolts in the Ark, than attach with washers and butterfly bolts. Allow the wire to overlap on the corners when you lay them down.
Good luck!
