The regeneration of the forests produced by the presence of wolves attracted bird species that had abandoned the park because they had no food source. The number of beaver also increased as the food source for beavers and the source for building beaver homes and dams was replenished. The beaver dam building explosion produced a new habitat for other animal species including otters, ducks, fish, reptiles, and amphibians. Weasel, badger, and other small animals grew in population. Bear populations grew because the bears had more food in the form of berries from the increased growth of plants and trees. Wolf competition with coyotes produced resurgence in the number of several species of rabbits, mice, and other rodents in Yellowstone. The rodent population brought more hawks and eagles back to the park.
The wolves actually changed the behavior of the rivers in Yellowstone. The rivers became narrower and meandered less. This reaction was in part a result of the number of beaver dams that were built by the increased beaver population. The major force that changed the rivers was the increase in the number of trees and plants. The trees and plants stabilized the banks of the rivers so that the size and shape of the rivers became fixed. The added vegetation prevented soil erosion so the rivers became deeper. Twenty years of study and research have shown that the reintroduction of wolves into Yellowstone National Park not only made plants and animals thrive but changed the geography of the park for the better. The reintroduction of wolves into Yellowstone National Park is one idea that produced tremendous ecological benefit and an unexpected change in landscape and geography. This one worked. The program shows that thinking men and women that are concerned with natural places can make a tremendous difference with the help of animals.