John McPhee: The Sledding Polar Bear

The polar bear is nothing if not athletic. Before he dens, or just after he emerges, if his mountains are covered with snow he will climb to the brink of some impossible schuss, sit down on his butt, and shove off. Thirty-two, sixty-four, ninety-six feet per second, he plummets down the mountainside, spray snow flying to either side, as he approaches collision with boulders and trees. Just short of catastrophe, still going at bonecrushing speed, he flips to his feet and walks sedately onward as if his ride had not occurred.

Coming Into the Country (1976)