When we first moved into our "very" old house with a limestone foundation I couldn't figure why there were always pieces of limestone laying on top of the water heater. It doesn't take much to knock if off anyway but one day, for some reason, I was folding clothes on the washer. Mind you this room is basically a cave as there are no windows. Rocks started to fall on the water heater from where the furnaces was vented out. I thought I bet that's a mouse so I crawled up on the washer and came face to face with two garder snakes. Exit room! My husband told me would should let them live they will eat the bugs. Not in my house. So after he evacuated them he took a flash light and looked into where they were and told me by the amount of snakes skins it looked like they had been in there awhile. The foundation got fixed soon after. Our 3 hens are hard on the baby snakes and baby mice and they have 12 more baby chicks to help them.