I was telling my friend Chris the other day that my dog, on the rare occasion when he has an accident and dumps inside, will try to hide it. He'll cover it up with dirty clothes, papers, or whatever he can find.
Chris was amazed that a dog, whose world revolves around smell, would learn that sort of behavior. "Hiding" poo doesn't get rid of the smell -- to the dog, the presence of said poo is still quite obvious. The only reason to hide the poo is to confuse silly humans, who have a less acute sense of smell.
I was kind of amazed, too, once I thought about things in that light. My dog is so smart.