In an effort to determine what is causing the decline of the Custer State Park elk in South Dakota, elk are darted and studied. One unfortunate elk became a quick and easy dinner for a mountain lion. The Rapid City Journal  has a write up about the incident. A more extensive article about the elk herd decline .
"It was a nice sunny day, and I guess that lion was sitting out there sunning itself when an elk staggers up and tips over," said Gary Brundige, resource manager in Custer State Park. "Well, what's any top-of-the-line predator going to do in a situation like that?" It killed the elk and prepared to have dinner.