Wolves, elk, and groves of tall, mature aspen trees dot the wildlife-rich Lamar Valley in the northern region of Yellowstone National Park. Young aspen are beginning to flourish in some of these groves. What is missing from this picture are the middle years for Yellowstone's trees: aspen that sprouted in the last several decades, not the last several years.
A new study by Oregon State University biologists William Ripple and Robert Beschta explains those missing years by investigating the interconnectivity of species in Yellowstone. Wolves were eradicated from Yellowstone in the 1920's and reintroduced in 1995. The wolves not only predate on the elk, but introduce a "fear factor"-they scare them away from browsing on new aspen shoots. This Bio Bulletin highlights the dynamics of this ecosystem, which, even though protected, is still susceptible to declines when a key species is removed.