I was trying to remember if I'd told this story on here before - but if so - I'm gonna tell it again, lol. Years ago my dh had brought home some young-ish feral hogs. It was gonna get really cold one night and there was no good shelter where they were penned. I planned to make a "U" shaped shelter out of hay bales and cover it with a piece of plywood. I took three bales of hay to their pen and went back inside to warm up. A couple hours later I went out to finish building the shelter and was amazed at what they'd done. They had dug themselves a cave, basically. It was probably 4 x 4 ish and oval shaped. They had dug out the hole and took the dirt and banked it on the north side against the wind. They had also broke open the hay bales and used that to build up the north side a little higher and took the rest of the hay and lined their hole. The way they had constructed the side to the north gave it a little overhang that they got under. They were truly as snug as a bug in a rug, lol. I didn't worry about them for the rest of the winter. I just occasionally threw them another bale of hay to shore up their shelter with. Smart critters!