The status of most species in the Rocky Mountains is unknown, due to incomplete information. European-American settlement of the mountains has adversely impacted native species. Examples of some species that have declined include western toads, greenback cutthroat trout, white sturgeon, white-tailed ptarmigan, trumpeter swan, and bighorn sheep. In the United States portion of the mountain range, apex predators such as grizzly bears and wolf packs had been extirpated from their original ranges, but have partially recovered due to conservation measures and reintroduction. Other recovering species include the bald eagle and the peregrine falcon.