In part one, we discussed the extreme unlikelihood of your human biomass being incorporated into the food web by a hungry grizzly, how with a bit of care and common sense, backpacking in Yellowstone is actually quite safe. In fact, grizzlies – and black bears, too – are highly adapted extremely flexible omnivores. Wherever they live, they are opportunists, capable of adapting to local or seasonal situations as mother nature and meteorology dictate. Of course, bears are big. In the Greater Yellowstone grizzlies can weigh up to 600 pounds, but usually are somewhat smaller. However you look at it, though, that’s a lot of bear-mass to maintain and nourish.
Generally speaking Yellowstone Griz eat more meat (mostly non-human) than bears of most other grizzly populations. Boars tend to eat more meat than sows with cubs because for the sake of safety, sows with cubs avoid dead meat that could create a conflict with other bears, especially adult boars. There are a couple of reasons for the relatively high level of carnivorous behavior. For one thing, the cold relatively dry climate of Greater Yellowstone produces fewer berries than, for example, the wet woods of Glacier Park or the moist temperate mountains of coastal British Columbia. Most important, though, Yellowstone’s high dry climate is ideal for producing huge herds of ungulates that thrive upon the abundant grasses, sedges and succulent forbs. For most of the year grizzlies don’t often succeed in catching/killing healthy adult ungulates such as elk or moose. But these animals are vulnerable when they’re at their weakest, at the end of the long Greater Yellowstone winter. In the early spring after a particularly severe winter, there’s also plenty of winter-killed ungulate carrion to feast upon. And newborn calves and fawns are a particularly tantalizing treat that’s not too tough to secure during a brief post-birth window of time. Add Yellowstone’s famous restored wolf population to the mix, and there’s even more year-round protein for bears. That’s because grizzlies will often challenge wolves for fresh wolf-killed meat, and the grizzly usually wins. By the way, if you come upon a carcass, leave immediately. Pronto. Do not hesitate, do not wait to see if a Griz has claimed the dead elk. Bears are funny about their food; they defend it, and you do not want to be what they are defending it from.
Nonetheless, most grizzlies in most places – including Yellowstone – more often than not, feed upon green plants, insects, roots and berries. Historically, spawning cutthroat trout were a major seasonal food source in Yellowstone, as were the rich nutritious seed nuts of the whitebark pine. But as Bob Dylan sang, “the times they are a’ changin’.” Next blog, we’ll look at how grizzlies are altering their culinary habits in response to human-induced environmental change. And in our fourth and final installment of this series, we’ll consider what may lie in store for grizzlies in the Greater Yellowstone Ecosystem of the not too distant future.