In the beginning, would be trainers observed dogs in a pack. They recognized there was an Alpha dog that controlled the others by his behavior. He would stare, growl, nip, and bite, whatever it took to get them to do what he wanted. The mother dog with her young physically communicates to them what she wants. She prepares them for the world they live in, the physical world, the canine world.
Dogs communicate with each other by physical means, jumping, nipping, and biting