the "big bad wolf" may be the most memorable and frightening of all the fairy tales told by the brothers grimm. that "grim" reputation actually produced a very real result in america in the early 20th century. wolves were wiped off the landscape-- trapped, poisoned, and hunted until there was not a single one left in the american west. the national park service brought wolves back to yellowstone park almost exactly 25 years ago, following a bitter debate between wildlife groups, who wanted them restored, and ranchers, who most definitely didn't. even today, the wolves of yellowstone stir strong emotions. but, as we first reported in 2018, they've also had an impact that almost no one saw coming. in the dead of winter, yellowstone park is a beautiful but forbidding place. howling wind, sub-zero temperatures, six feet of snow. just finding enough food to survive is a profound struggle for every animal. waterfowl, bison, elk, foxes, they all have to work for every morsel. yellowstone was the world's first national park, founded in 1872. and it remains one of the most visited-- millions of people