One night years ago, biologist Albert Manville drove to a garbage dump near Lake Louise in Alberta’s Banff National Park.

The site was unfenced back then, and grizzlies often came to rummage for leftovers. Manville was watching a bear feast on a hefty scrap of meat when he noticed movement toward the edge of his car’s beaming headlights. It was a wolverine, staring intently at the bear and the meat. What else could it do? It weighed maybe 30 pounds; the grizzly weighed several hundred.

“Then all at once the wolverine ran up and bit the bear right on the butt,” Manville says. “The grizzly whirled and swiped with a paw, but the wolverine was already racing around to