Hi, We use the deep-litter method, and this is our first winter with our chickens. We buried 6x6s in the ground, built the henhouse on top and used hardware cloth (something like that - metal, 1/4") all under the letter. The coop is completely covered - top to bottom and the hardware cloth is buried a good 18" underneath. I thought I made a great fortress for our girls (and roo). We have found 3 holes in our henhouse so far. We would cover one up and another one would appear. I found a trail through the snow into the woods on the other side to one of the holes. This hole is big enough to fit a tennis ball in it. What could be making these holes? I think it's too big for a mouse and I'm afraid to think what else it could be. How on earth did this/these critters get in?? We stuck foil in the holes for now and will find out how they got in when we clean it out in the spring. In the meantime, I now take their food out at night to deter any other visitors. Thanks.