A professional trainer is required if your usually well-mannered and well-behaved fur ball starts growling at everyone unprovoked, including you. Training can fix and control the aggression pets display towards people or when someone approaches their toys or food using professional training methods, such as positive reinforcement. For instance, dogs communicate via barks. They bark to show excitement, hunger, or as a warning in case of potential danger, but excessive barking or growling points to availing the services of expert pet trainers.