Introducing new cats to existing multi-cat households requires careful management to prevent welfare harm for both resident and incoming cats.
Multi-cat household introductions when done poorly create lasting welfare harm that is difficult to resolve once established. Cats that are introduced too rapidly and experience conflict develop fear associations with each other that persist indefinitely. The investment in slow, systematic introduction - weeks of scent swapping before any visual contact, gradual visual introduction behind barriers, and positive association building - prevents chronic conflict and the welfare harm it causes. The patience required is modest compared to the welfare benefit of a household where cats can coexist without chronic stress.