It could be raccoons, dogs, cayotes, or foxes. More than likely it is dogs. My neighbors swear their dogs are sweet and wouldn't hurt anything, but when I catch one with a chicken in his mouth he just disappers. We also get a lot of dogs dropped off in the country when they are unwanted. Those dogs are always hungry. They come into my garage and tear open bags of feed to eat if they can't find anything else. They dissappear too.