It took one wolf to revive an entire forest ecosystem: The story of The Old Gray Guy

An excerpt:

In 1997, a lone wolf crossed an ice bridge that briefly connected Canada with the remote Isle Royale, which lies off the coast of Michigan in Lake Superior and is renowned for its rich biodiversity. His arrival revived the flagging fortunes of the wider wolf population, which had been hit by disease and inbreeding, and triggered cascading effects that improved the health of the overall forest ecosystem, a study in Science Advances showed Wednesday.

Here’s the whole story: https://www.sciencealert.com/it-took-just-one-wolf-to-revive-an-entire-forest-ecosystem