Q: I’m often hiking above treeline. At what altitude is it okay to not hang a bear bag? If that is never okay, how do you suggest securing food above treeline without a bear canister? —Katie Robinson, via email
A: Just like you, bears love to get high—above treeline. Witness the efforts of grizzly bears in Glacier National Park, who climb up into the peaks to get at army cutworm moths hiding under talus in late summer. Black bears travel above treeline less often, but they won't hesitate to break altitude barriers to get at huckleberries and other sweets (I've seen nine of my brethren doing it above or near treeline in Olympic NP in a two-day period).
In short, if you're going above treeline in bear country, you should still bring a bear canister. Store it several hundred yards away from camp. If you can find additional obstacles (like a deep crevice or a rocky promontory that requires a little climbing), consider stowing it there, where I might have a tougher time getting at it. If no such obstacles are around, at least keep it far from camp and hidden if possible.
If you still refuse to take a canister, you're taking big chances. You can attempt to conceal your food in several layers of large, odor-blocking Ziploc bags and take the same precautions to hide it far from camp and in hard-to-get-to places. But even plastic bags allow for some odor permeation, meaning I could still find your food. In fact, grizzly bears in Denali have learned how to raid these types of food caches.
To be safe, bring the canister—plenty of new, lightweight options exist. Or camp in designated sites with bear lockers. Otherwise, you risk losing your food, habituating me to it, and getting me killed, and nobody wants that.
Got a question for the bear? Send it to firstname.lastname@example.org.