CSU professor and Wildlife Conservation Society scientist Joel Berger holds up two costume bear heads in his gear closet.

Courtesy of Joe Mendoza/Colorado State University Photography

Colorado State University professor and Wildlife Conservation Society scientist Joel Berger is familiar with extremes. He's worked on some of the world's highest mountains, in some of its lowest temperatures, to study some of the animals most vulnerable to climate change.

To do that he uses a fairly, well, wacky, research tactic: He dresses up as a polar bear to study musk oxen. The oxen are the largest land mammals in North America, and as climate change pushes more and more polar bears to hunt on land, Berger wants to find out how the oxen will respond to a new potential predator.

The odds of watching an actual encounter in the wild are remote, so Berger simulates it—donning a Styrofoam head and a body suit, and plodding through deep snow on all fours to approach the burly musk oxen.

The scientist talked to Colorado Matters about his unusual techniques and his latest book, "Extreme Conservation: Life at the Edges of the World."