At the beginning of the 20th century, and following long years of persecution, the wolf was completely eradicated from Yellowstone National Park (western United States). In the 1990s, fourteen gray wolves were reintroduced to the park. Today, there are 90 individuals. The reintroduction of the wolf had remarkable effects on the natural balance of the park: two years after the reintroduction of the animal, the number of coyotes had already dropped by 50%. Foxes, which are hunted by coyotes, have seen their numbers increase, helping to control the multiplication of rodents. And thanks to this, roots, seeds and insects from the park stopped being plundered, allowing the flora to regain momentum.