A portion of the study on the elk in Custer State Park, South Dakota, utilizes a helicopter crew. The helicopter crew will go in first and dart some cow elk, then return and pick up the researchers. When the researchers reach the sedated cow elk, they fit them with implants and radio collars to track their movement, and when they calve in the spring the researchers then also radio collar the calves.
This year after tranquilizing one cow elk, the pilot told the researchers they wouldn't believe it but a mountain lion was trying to make lunch out of one of the drugged animals. Actually it was very believable though, as this is exactly what happened last year.