Wolves Canis lupus, extirpated from the western U.S. before the mid-20th century, have made a rapid and surprisingly painless recovery because wild areas and prey populations remained abundant.

• 狼在二十世纪中叶就在美国西部灭绝了，但是目前由于有广阔的生存区域和丰富的食物，种群恢复很快。