Wolves influence elk movements: behavior shapes a trophic cascade in Yellowstone National Park

Fortin and colleagues used step-selection functions to show that elk in Yellowstone altered their fine-scale movement decisions in response to wolf predation risk, avoiding risky habitats such as open valleys when wolves were present and thereby relaxing browsing pressure on aspen. By modeling each observed step against available alternatives, the study linked individual movement choices to a landscape-scale trophic cascade. Although focused on wolves and elk, the paper is a foundational demonstration and popularization of the step-selection framework now ubiquitous in carnivore and prey movement studies, including felid work. It showed that movement data could test how predation risk reshapes behavior and ecosystems, cementing step-selection analysis as a central tool for inferring how animals weigh habitat and risk step by step.