This sad but mesmerizing clip of a dog painstakingly burying a dead pup will leave you with little doubt that dogs mourn and that their compassion runs deep. Watch as the self-appointed gravedigger stumbles upon the dead animal and spends more than three minutes spreading sand over the carcass with its nose. Are we watching a mother administering last rights to her dead puppy? A random pooch doing a good deed? We're not sure. What we do know is that this solemn, heart-wrenching moment will melt your heart and boost your respect for the unwritten rules of the animal kingdom.