For nearly a decade, biologists at Wind Cave National Park have tracked elk movement through radio collars. While most collars are automatically released from the animals, some get hung up and elk must be shot to retrieve them.
There is an abundance of elk at the park. In fact, Wind Cave's elk population last winter was more than 900, even though the target is between 300-400.
"We brought in two helicopters and we chased about 389 elk from here, inside Wind Cave National Park into Custer State Park," Wind Cave National Park Biological Science Technician Duane Weber said.
In February, close to three-dozen elk were fitted with GPS-tracking radio collars, helping park officials better manage the population. It's found around 100 elk have returned.
"It took them about three months to find a spot where they could worry the fence enough so they they could slip through," Weber said.
The collars have a two-year life span and many are ready to be retrieved. While they're supposed to automatically unhook, some do not.
"We've radio collared over 300 elk with these GPS radio collars, and to date we've only had eight fail. So that's about a 2-3 percent failure rate on those collars," Wind Cave National Park Resource Management Chief Greg Schroeder said.
The radio collars that are used to track the elk cost upward of $2,500. But the real value is held in the information that they gather.
"All of the location data from that animal is stored on board with that collar, so if we don't get that collar back we get absolutely no data from that collar, whatsoever," Weber.
If the collars do fail, park officials will attempt to sedate the animals with tranquilizer darts. When that doesn't work, the animals are shot. But even in death, the elk still are used to help the herd.
"And at that point, we salvage every tissue and sample that we can and send it in to our diagnostic laboratory with our wildlife veterinarians down at Colorado State," Schroeder said.
Since the program began in 2005, a total of eight elk have had to be shot to retrieve the radio collars. The information gathered since then has helped park officials form their Elk Management Plan.