The reintroduction of a top predator changed Yellowstone. wolves were absent for 70 years. When brought back the entire population of animals changed for the good, the geography of the rivers was stabilized and the vegetation increased. A 5 minute video: - https://aeon.co/videos/how-the-return-of-just-66-wolves-rejuvenated-yellowstone-s-entir... - Comment: Well worth watching. Everyone has to eat is neatly shown.