What is the purpose of a dog's shaking himself out when he doesn't seem to have a reason to (i.e. he hasn't gotten wet or dirty)? Lefty is always shaking himself out--when he gets up from a nap, before we go for a walk, after we go for a walk, on his way from one room to another, etc... I've never known a dog to do this as often as he does. Does it serve any purpose other than to get things out of their fur?