This is the second of a two-part series on the role of the gray wolf as a keystone species in Yellowstone National Park. To see what happened when wolves disappeared from the park's ecosystem, check out Part One.
In 1995, 70 years after the last wolf pack disappeared from Yellowstone National Park, scientists reintroduced 31 gray wolves back into the park to help control the elk population. In 1995, there were 17,000 elk in the park. Now, there are just 4,000. While a dwindling population in a species can be bad, in this case, it can be beneficial to the park's biodiversity.
The reintroduction of wolves into the park also helped improve the elk's gene pool. Only the strongest and most robust of the elk were able to survive and reproduce.
When wolves hunt elk, they don't eat the entire carcass. Once they're full, they go off and sleep with full stomachs. This leaves meat for scavengers like ravens, magpies, coyotes, and golden eagles. Bears, whose population numbers have been rising, also benefit from the leftover carcasses. Plus, bears now have more berries to feed on because they don't have to compete with a lot of elk anymore.
The trees and plants that had a hard time flourishing under the pressure of a large elk population are now thriving. Larger trees by the river now have stronger roots, which in turn strengthen the river banks. Song birds have made their return as well. This also means that beavers have returned, now that they have the resources they need to build their dams.
Wolves are what scientists call a keystone species for the Yellowstone National Park ecosystem. A keystone species is a species on which much of an ecosystem depends. Without this species, the ecosystem will undergo drastic changes and experience an imbalance. The ecosystem in Yellowstone perfectly illustrates the role of a keystone species and what happens when it disappears.
The reintroduction of the wolves resulted in a trophic cascade. A trophic cascade happens when a predator keeps its prey's numbers under control or changes their behavior. The organisms on the next levels of the food chain thus have a chance to thrive. The relationship between the wolves and the elk are another perfect illustration of this concept.
It's amazing how the disappearance and reintroduction of just one species can have such a domino effect in an ecosystem. It's also a lesson in how humans should be more mindful of our ecological impact. People in the 1920s didn't realize how much the extermination of wolves will impact the ecosystem in Yellowstone National Park. Now, the wolves are showing exactly how important they are in maintaining ecological balance.
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