I agree, Book of the Bitch by Kay White is excellent. Signs when a bitch is imminent (i.e. whelping within 24 hours) can include scratching up bed, panting, going off food and a drop in temperature. But not all bitches have read the book and some will pop out puppies with hardly any clues they are in labour . One of my GSD bitches was chewing large hunk of tripe, stopped eating, gave a couple of pushes and produced a pup