Springtime high in the Rockies, where the calendar reads May 9, but it’s snowing in rattling bursts of graupel. After snow-shoeing for hours up a tilted, twisted drainage in Montana’s Gallatin Mountains, south of Bozeman, I emerge into the headwaters cirque and stagger to where a cluster of researchers, led by Wildlife Conservation Society biologist Bob Inman, are gathered around three holes bored into the snow.Nobody seems to think the climb has been exhausting except me. Wolverine researchers are freakish in their ability to cover punishing vertical terrain—and yet their subject routinely eludes them. “A wolverine will climb up an avalanche chute, climb up over a cornice, belly-slide down the other side, and keep running,” says Tony McCue, then a field biologist on the crew. “They’re so fast in covering their habitat, we just can’t catch up with them unless they’ve decided to stop.”Inman, McCue, and the rest of the team fervently hope a wolverine has stopped...