For a good reason, many people like to call their German Shepherd dogs "ground sharks". Usually, biting is a sign of the dog being overstimulated and losing control of his bite force The Dogfather German Shepherd Shirt. A common cause of dogs biting or acting aggressively towards owners is resource guarding, which means dogs growling or biting if someone comes near or tries to get food or toys from the dog or tries to give the dog a treat. dog out of the resting place. German Shepherds will protect their owners without proper training. German Shepherds are very loyal to their owners and can become possessive of their owners fairly quickly.