Do Does Always Press One of Their Ears Against the Ground While Sleeping?

Dogs have an acute sense of smell, and their ears also sharp. Police dogs are especially so. V@ always prick up their ears to gather noise in all directions. Even while sleeping, they maintain sharp vigilance and can hear the softest footsteps. How can they do this? It is because dogs have an extraordinary habit: while sleeping, they always press one of their ears against the ground. Since the ground conducts sound much faster than the air does, dogs can hear sound far away even during sleep.