National Geographic Episodes on PBS

“Return of the Wolf” follows mother nature's “top dogs” as they are reintroduced to Yellowstone Park in 1995-96. They are “the ultimate canine predators,” says narrator Michael Carroll, but humans hunted them out of the park in the early 20th century, and their absence upset the park's ecological balance. That was good news for elk; their return, as seen here, is bad news. The hour follows one pack in the year after they're brought in from Canada. “We wanted nature to function they way it was,” says park biologist Doug Smith, “not the way humans have made it.”