In the early 1900s, cougars were killed as part of predator control in the parkl and likely eradicated along with wolves in the 1930s. However, cougars naturally recolonized by the early 1980s. From 1987 to 1996, the first cougar ecology study was conducted in Yellowstone National Park. The research documented population dynamics of cougars in the northern Yellowstone ecosystem inside and outside the park boundary, determined home ranges and habitat requirements, and assessed the role of cougars as a predator. Of the 88 cougars that were captured, 80 were radio-collared.