I put an electric fense on my chicken coop. I went around the bottom and top with it. I use a solar powered electric fence zapper. also keep the door open 24/7 by placing several nite guard solar powered red flashing lights around the door. the light keeps predators away. Now I can free range my chickens. I do lose some during the day as they like to go into the woods and scratch in the leaves but not many.
Funny thing, the very day I put power to my coop, no sooner the sun went down came a very strong smell of skunk. Have not had any critters in my coop since I electrified it. I also grounded the fencing unit right to the coop wire.
I have had one black snake inside since I put juice to it. I believe it came thru a small hole in the house floor. If I fix that hole I imagine the juice will even keep snakes out.