Yellowstone’s bears are beginning to stock up on much-needed nutrients in preparation for hibernation, as our Institute students have been observing in the field. Earlier this month, participants on an Old Times on the Grand Tour program spotted a large male grizzly feasting on a bison carcass at LeHardy’s Rapids, while Essential Yellowstone participants observed black bears munching on whitebark pine seeds on Dunraven Pass. The seeds of whitebark pine are a high-energy food rich in fat, carbohydrates, and protein, and are one of the most important food sources for bears this time of year.
Though bears spend most of their time feeding, they’re especially food-focused during the period in autumn known as “hyperphagia,” where they may gain up to three pounds per day. Along with carrion and whitebark pine seeds, bears may feed on pondweed root, grasses and sedges, huckleberries, dandelions, ants, and army cutworm moths before heading into the den for the winter.
Bears in the Greater Yellowstone Ecosystem generally re-emerge from hibernation when temperatures warm up and food is available, typically between March and early May.