Before and After Wolves

Restoring wolves to Yellowstone after a 70-year absence as a top predator – especially of elk – set off a cascade of changes that is restoring the park’s habitat as well.

Yellowstone Without Wolves (1926-1995)

Elk over browsed the streamside willows, cottonwoods, and shrubs that prevent erosion. Birds lost nesting space. Habitat for fish and other aquatic species declined as waters became broader and shallower and without shade from streamside vegetation, warmer.

Aspen trees in Yellowstone’s northern valleys, where elk winter, were seldom able to reach full height. Elk ate nearly all the new sprouts.

Coyote numbers climbed. Though they often kill elk calves, they prey mainly on small mammals like ground squirrels and voles, reducing the food available for foxes, badgers, and raptors.

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 stream sides, where it can be harder to escape attack.

Regarding aspens the number of new sprouts eaten by elk has dropped dramatically. New groves in some areas now reach 10 to 15 feet tall.

Concerning 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 vegetation have begun to stabilize 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.

Regarding 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.

Note: Hunters were upset because of the lessened number of elk which depicts a long history of the battle over resources including food sources.

Source: Chadwick, D. Wolf Wars: Once Protected, Now Hunted. (March 2010 issue of National Geographic).