I watched a show on animal planet about this. They said dogs do this out of instinct. If they were in the wild, it's to #1 make sure nothing is underneath them (bugs, snake etc) and #2 they make "the nest" bigger so as to fool other predators into thinking they are bigger than they are, to discourage an attack while sleeping. Smart little guys, huh?
__________________ Elizabeth    Harley Rita Scooter Bandit Peanut  |