We generally open up the run so our girls can free range in the backyard. But yesterday we found a fairly large rat snake in the nesting box. The only way it could have gotten in would be to go into the run then up the ladder into the coop. So my question is, how do you prevent this? I feel like we need to keep the door open so the hens can go in and out to lay their eggs during the day, but I want to keep snakes and other predators out of the coop!