Concerning dogs' hearing:

Our Yorkie Sugar will sometimes sleep in my Dad's desk chair when he's working at his desk. She'll often startle him by waking up barking (sometimes knocking her head on the underside of the desk, but she doesn't seem to even notice!) and demanding to be put outside. She'll run straight to a tree in the backyard and begin barking at a squirrel in the branches. How the heck did she know a squirrel was in the tree, especially if she was asleep? Did she actually hear the thing run up the trunk? Strange...