For much of the twentieth century, gray wolves were missing from Yellowstone National Park. By the 1920s, hunting, trapping, and poisoning had eliminated them from the region. Without wolves, elk populations grew very large. Elk browsed heavily on young trees near rivers and streams, which caused erosion and reduced habitat for beavers, songbirds, and fish. The ecosystem became unbalanced.
In 1995, wildlife managers reintroduced wolves to Yellowstone. Fourteen wolves from Canada were released into the park, followed by more the next year. The return of wolves quickly set off a chain reaction known as a “trophic cascade.” Wolves hunted elk, and as elk numbers and behavior changed, streamside vegetation like willow and aspen began to recover. With more trees, beavers built dams again, which created wetlands that supported fish, amphibians, and birds. Other predators, such as bears and coyotes, also adjusted their behavior in response to wolves.
The story of Yellowstone’s wolves is not without conflict. Some ranchers outside the park feared that wolves would kill livestock. Wildlife managers set up programs to compensate ranchers for losses and tracked wolf packs with radio collars. Debates continue, but many scientists and visitors see the return of wolves as a success for conservation and ecosystem health.
Today, Yellowstone is one of the best places in the world to watch wild wolves. Tourists come with spotting scopes, hoping to glimpse packs on the move across valleys or hear their howls echo through the mountains. The reintroduction shows how human decisions can shape ecosystems—for better or worse—and how carefully managed actions can sometimes repair past mistakes.
1. What happened in Yellowstone after wolves were eliminated in the 1920s?
2. What is a “trophic cascade” as described in the passage?
3. Which change followed the recovery of streamside vegetation?
4. Why did some ranchers oppose the return of wolves?
5. How did wildlife managers respond to ranchers’ concerns?
6. Which statement best describes the main idea of the passage?
7. Why is Yellowstone considered a special place to view wolves today?