I've been pretty lucky as a large flock owner. Over the last few years I've only lost a few hens and I've dispatched numerous raccoons, a couple of possums, and one skunk (which I hope to never trap again). My flock is currently in the 80 range, but it is decreasing by the day. Here is the scoop.... My coop is built raised 1 foot above the ground using concrete footings. The base is skirted with welded wire on two sides and plywood on the other two sides to keep chickens from going under and laying eggs there. The floor is pressure treated plywood. The walls and ceiling are built like a house. 2 x4 framing with plywood sandwiching insulation. I have windows covered with 1/4 inch hardware cloth. Pop door is pretty heavy and we have a lip that prevents it being pushed up from the bottom on the inside. It could be pushed up from the bottom on the outside with some skill, but once the predator got in, it would be stuck inside. I have checked and checked and I cannot find any holes or cracks in the coop other than a very slight (1/8") gap between 2 of my floor boards. There is a hole about the size of a quarter at the corner of one window. I have found that something has dug under the coop on the two plywood sides, but again, my floors are wood so getting underneath is not a benefit. I lock up my flock at dusk, as early as I can get them all in. Then in the morning when I come out to let them out, I find a pile of feathers and blood by one of the corners of the coop. I suspect a raccoon and have a trap set, but each morning the trap is sprung with bait still inside and another chicken is gone. I really cannot figure out how it is getting in the coop. The last two nights it got 2 hens each night. edited to add pics to title.