Find some tin or scrap metal that makes a lot of noise and lay up against the piles so that they have to move it out of the way to access it. I keep all my wood behind a locked gate and have two dogs, so it is not a worry of mine...but if your stacks are close enough to your home that you can hear the 'clanging' of the metal, maybe that's better than nothing? This concept is used in Alaska to warn when bears get to drying fish used for dog sled teams... With that and good flood lighting, you should be set.