Dogs may bark at delivery drivers, urine mark on walks, and become reactive behind fences. Cats spray urine, scratch prominently placed objects, and may aggressively confront new cats introduced into the home. Birds can become fiercely protective of their cage, and fish establish territories around caves or plants in the aquarium. Territorial behavior intensifies with intact (unneutered) animals, insufficient space, and poor introductions of new pets. Management strategies include neutering or spaying, gradual introductions using scent swapping and visual barriers, providing enough resources (food bowls, litter boxes, perches) to reduce competition, and positive reinforcement training for calm behavior around perceived boundary threats.