Wolves were systematically killed in the Yellowstone region and many other areas of the West beginning in the late 1800s. A concentrated effort between 1914 and 1926 finished the job - the last known wolf pack disappeared in 1926.
This video provides a highly educational overview of the important role an apex predator like the
North American gray wolf plays in maintaining a healthy ecosystem.
North American gray wolf plays in maintaining a healthy ecosystem.
Now, with the recent reintroduction of wolves back into Yellowstone in 1995, streamside shrubs and cottonwoods within the Lamar Valley are beginning to become more prevalent and taller, and were the focus of a second study in the same area. That study outlines how the fear of attack by wolves apparently prevents browsing elk from eating young cottonwood and willows in some streamside zones.
With the renewed presence of wolves, young cottonwoods and willows have been growing taller each year over on "high-risk" sites, where elk apparently feel vulnerable due to terrain or other conditions that might prevent escape. In contrast, on "low-risk" sites, they are still being browsed by elk and show little increase in height.
Traditionally, "keystone" predators such as wolves were known to influence the population of other animals that they preyed on directly, such as elk or antelope. What researchers are now coming to better understand is the "trophic effect," or cascade of changes that can take place in an ecosystem when an important part is removed.
