I lost 4 birds earlier in the season to raccoons, even though I used hardwire cloth and sturdy lumber, the predators managed to pull the chickens UNDER the tractor! I even lost a 10 week old turkey! I tried laying 2x6's around the edges, and about 10 other ideas until I finally gave up and went NUCLEAR. I decided to electrify the tractors. Obviously the big constraint with using electric on a chicken tractor is the problem with grounding. I solved this problem by simply tethering my tractors to my existing electric fence around my garden. So basically I run a dog run cable from my fence around the garden and then move the tractors around the garden like a racetrack. See the pics attached: So far it has been about 4 months without a single loss. I really like this system and would highly recommend it to anyone with a predator problem. The tractors roll VERY easily and you don't have to drag additional mesh, wood or other blocking devices around, all you need to do is keep the tractors within 40' or so of an existing electric fence. If I didn't have any electric fencing, I would install a small section just for this. Totally worth it!