What do you do if a large moose is charging you in deep powder? In the case of the skiers in the video below, shot in Gaspesia, Quebec, the answer is not very much, although clearly their options are pretty limited. Sierra can, however, offer some professional advice should you find yourself in the middle of a moose tête-à-tête, as happened to runner Sallie Shatz in Utah's Wasatch mountains. This advice from Matt Heid, author of the Appalachian Mountain Club's Best Backpacking Trips in New England.

"If a moose approaches you, it's generally trying to drive you off because it sees you as a threat. In most situations, retreat immediately."

Sadly, advice on moose encounters is at risk of becoming arcane, as moose populations in North America are in steep decline. The precise reason is not clear, although climate change is the most likely culprit.

Note: The first minute of the video is useful mainly for brushing up on your French. Otherwise you can safely skip ahead. 

PAUL RAUBER is a senior editor at Sierra. He is the author, with Carl Pope, of the happily outdated Strategic Ignorance: Why the Bush Administration Is Recklessly Destroying a Century of Environmental Progress.Otherwise he is a cyclist, cook, and father of two. Follow him on Twitter @paulrauber