And then there were three.
Michigan's unique wolf population is on the brink of dying out. In the early 1900s, a group of moose made their way to Isle Royal National Park, a remote, forested island in the middle of Lake Superior, via an ice bridge. For the next few decades the moose flourished, their population limited only by the amount of food on the island.
Then, in the 1940s, a group of wolves found their way over. Since 1958, researchers have closely monitored the wolf and moose populations as part of the longest ongoing predator-prey study in the world.