Willows grow where the wolves prowl in Yellowstone

In Yellowstone's Lamar Valley, bison congregate in the summer and graze not only on grass but also on willow, cottonwood and aspen. These bison are eating willows in the foreground, while in the background some emerging willow thickets are visible. Credit: Luke Painter, Oregon State University

Wolves may be engineering the Yellowstone ecosystem by helping the growth of tall willow trees in Yellowstone National Park. Since their reintroduction in 1995, gray wolves (Canis lupus) have caused a number of cascading effects on the Yellowstone ecosystem such as a decrease in elk (Cervus canadensis) numbers. A new study shows that this elk reduction, which feed on tree saplings among other vegetation, has contributed to the growth of taller trees. “Wolves didn’t do it all by themselves,” said the study’s lead author Luke Painter, a wildlife ecologist at Oregon State University. “Other predators and hunters also affected elk, but this would not have happened without the wolves.”

Read more at Oregon State University Newsroom.