I don't worry about the zombie apocalypse. So I don't worry about what would happen to the cats if it happens. I worry more about what would happen in the here and now if they go outside. We have coyotes, packs of dogs, bears, hawks, snakes who would all be happy to dine on nice tasty kitties. My neighbors regularly lose cats, rabbits, guinea pigs, chickens, ducks, geese etc to the wildlife.