RACCOONS! We had an extremely hard time trapping and figuring out how he was getting in. Every time we would think we had safely caged the chickens in for the night, sure enough we would go out the next morning he had gotten more. He never got any that were in the coop, but we had cages (that had young chickens in them) in the "run" are that was all fenced in and he had gotten the young ones. He ended up getting a total of 13 :*( Our coop is connected to an out door run type thing and it is completely fenced in. The fence is even dug a few feet into thee ground to prevent digging animals in. It also has netting over the top so they didn't fly out. We finally caught him and had a video camera out there and found out how he was getting in. He was HUGE. And he could manage to get into the trap get the bait chicken we would set it in, and NOT set the trap off. My dad had to TIE the chicken to the back of the trap. What a bad experience. But we learned from it and now we know how to keep them 100% safe.