did everything i could to predator proof my chicken run, including hardware cloth two feet out and two feet up, around the entire run. my cluckers were good all summer, and so far they still are. today i found that some little thief has dug a 3" diameter hole from four feet outside the run, all the way into it! holes seem too big for mice, too small for groundhogs or fox, plus my chickens are unharmed. it's winter in the suburbs of philly so i don't think it's a snake. don't smell a skunk either. does anyone have a clue what might be doing this???