National Geographic : 2010 Mar
Young aspens Willow Willow flycatcher Elk Raven Grizzly bear Pronghorn Beaver Green-winged teal Wolves Yellowstone cutthroat trout Boreal chorus frog YELLOWSTONE WITH WOLVES 1995 PRESENT ELK population has been halved. Severe winters early in the reintroduction and drought contributed to the decline. A healthy fear of wolves also keeps elk from lingering at streamsides, where it can be harder to escape attack. ASPENS The number of new sprouts eaten by elk has dropped dramatically. New groves in some areas now reach 10 to 15 feet tall. COYOTES Wolf predation has reduced their numbers. Fewer coyote attacks may be a factor in the resurgence of the park's pronghorn. WILLOWS, cottonwoods, and other riparian vege- tation have begun to stabi- lize stream banks, helping restore natural water flow. Overhanging branches again shade the water and welcome birds. BEAVER colonies in north Yellowstone have risen from one to 12, now that some stream banks are lush with vegetation, especially willows (a key beaver food). Beaver dams create ponds and marshes, supporting fish, amphibians, birds, small mammals, and a rich insect population to feed them. CARRION Wolves don't cover their kill, so they've boosted the food supply for scavengers, notably bald and golden eagles, coyotes, ravens, magpies, and bears.