Long before its establishment as a national park in 1872, Yellowstone was home to the gray wolf, as well as other large predators. But the relationship between human and wolf has always been a tense and complicated one. Predator control programs were developed and, by the mid-1900s, wolves had almost been entirely eliminated from the region and even the lower United States. The removal of even one strand of an ecosystem's complex web can have a ripple...