A bear canister is a bear-resistant container used to protect cached supplies from being broken into by bears or other large and determined animals. It serves the same purpose as a bear box in protecting cached supplies from being broken into by bears or other large and determined animals in campgrounds or other outdoor environments.
Bear canisters come in different sizes that can used for shorter or longer trips. While bear canisters can add a little weight and be a little unwieldy in some backpacks, they are required in some national parks and forests such as the Yosemite National Park (High Sierra, California), Inyo National Forest (High Sierra, California), Sequoia-Kings Canyon National Park (High Sierra, California), Olympic National Park (Washington State), and are also required by the New York Department of Environmental Conservation (Adirondack State Park).
The goal in preventing bears from getting access to food is twofold, to prevent loss of food and to prevent bears from developing a taste for and becoming dependent upon human food sources. They say that a fed bear is a dead bear due to bears due to how quickly bears can crave and become dependent on human food sources.