From Eurasiareview.com:

After wolves were reintroduced to Yellowstone National Park in the mid-1990s, some scientists thought the large predator reestablished a ‘landscape of fear’ that caused elk, the wolf’s main prey, to avoid risky places where wolves killed them. This fueled the emerging idea that predators affect prey populations and ecosystems not only by eating prey animals, but by scaring them too.

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