In January 1995, fourteen wolves were brought from Canada in wooden crates and released into Yellowstone National Park to replace the population killed off by 1926, and the question of whether they have changed the course of the park's rivers, as popular science videos viewed by tens of millions claim, has now become one of the most contested debates in ecology.

In January 1995, fourteen wolves were brought from Canada in wooden crates and released into Yellowstone National Park to replace the population killed off by 1926, and the question of whether they have changed the course of the park's rivers, as popular science videos viewed by tens of millions claim, has now become one of the most contested debates in ecology.

The first eight wolves arrived through the Roosevelt Arch on the morning of 12 January 1995, in a horse trailer escorted by two park service patrol cars. The wolves had been live-trapped in three different packs in Jasper National Park and the surrounding wilderness of Alberta, Canada, weighed, fitted with radio collars, and flown south. Wyoming Farm Bureau Federation lawyers had obtained a stay from a federal appeals court before the plane land…