The reason I've read is that it's a leftover from when they lived in the wild, and it would help make sure they don't lay down on top of something dangerous, li

The reason I've read is that it's a leftover from when they lived in the wild, and it would help make sure they don't lay down on top of something dangerous, like a snake or ant colony. It would also make since to do it before pooping since they're going to be in a vulnerable position.