I don't think it's cruel at all. I used to live in Oregon and there's a cycle with deer and mountain lions. The deer get over populated and the lions eat well. This eventually causes the mountain lions to become over populated and there aren't enough deer to sustain their population so eventually a lot of them start dying of starvation. After the mountain lion population goes down, the deer population goes back up and the cycle repeats. To to control this the local wildlife services track and tag the deer and mountain lions and figure out how many deer hunting permits should be issued each hunting season. This keeps the deer population steady and that keeps the mountain lion population stead as well. If cats and dogs were in the wild again, they would have to compete with other wid animals and go through the same cycles.