They are pernicious little buggers. Last year I had my chickens in a covered dog kennel. With 25 of them running around it took a while but I finally realized that they were disappearing. I moved them into the henhouse and put my game camera out. At about 10:30 a coon snuck in and spent some time cleaning up the feed before leaving through a small hole in the top which I had missed...bout 4 hours later he came back with two or three of his friends and they cleaned up all of the remaining feed.