A classic example is a cat watching a stray outside a window, becoming highly aroused, and then attacking a housemate cat or the owner who approaches. In dogs, redirected aggression may happen when an excited dog behind a fence lunges at a dog on the other side and then bites the person holding the leash. Redirected aggression can seem unprovoked because the trigger is not always obvious to the observer. It can seriously damage relationships between housemate pets, sometimes requiring a careful reintroduction process. Prevention involves identifying arousal triggers, blocking visual access to them when possible, and avoiding interacting with a highly aroused animal until it calms down. Never reach toward a fence-fighting dog or interrupt an agitated cat with your hands.