What grizzlies want: the survival of North America's most fearsome predator depends on a fragile mix of seeds, berries, trout, moths, elk—and being left alone

Sierra, July-August, 2002 by Joe Kane

Here's something to ponder next time you board the StairMaster: On a frigid spring morning in 2001, down in the southeastern corner of the Greater Yellowstone Ecosystem, in a den tucked into the snowbound east flank of the 11,000-foot peak known as the Ramshorn, a deep-brown female grizzly called Number 128 awakens after a five-month nap. Though having stirred not even to pee, she has burned perhaps a hundred pounds of fat, or a quarter of her body weight. She's also gained some muscle. Through an effort no more arduous than a long snooze, what entered the den lard-swathed in November emerges a lean, mean fighting machine.

Well, almost. It will be another week before she's fully alert. She's had two cubs, which is impressive: On average, a grizzly sow produces offspring only once every three years. When the two little fuzzballs were born, weighing maybe a pound apiece, she roused herself just enough to lick them clean and plant them on her chest. Then she went back to sleep for three months. Nursing happily, the cubs managed to avoid getting crushed when Mom rolled over. They'll soon be hungry for solid food. So will she. She ambles into the sunlight, blinks, and sniffs the air. It's time for business: She must eat or die.

In its simplest and starkest terms, life for Yellowstone's "charismatic megafauna"--bears, wolves, moose, bison, elk--is about winter, a race against starvation. Stockpile calories in spring, summer, and fall, then hold on and hope your body fat outlasts the winter. Get stampeded by a snowmobile in December and every step spent fleeing for your life is one less step you'll have come April.

In her perfect world, 128 would commence feeding by ripping through the deliquescent carrion of winter-killed ungulate. But wolves were reintroduced to Yellowstone National Park in the mid-'90s, and she must contend with the Washakie pack. While she slept they nailed the easy pickings among the elk and bison herds. If she were a male, she might chase them off a carcass, but the wolves would kill her cubs. So might a male grizzly.

She's positioned nicely for live elk, though. Her home range is in the heart of a sagebrush-steppe corridor, rich in forage, that an enormous herd follows spring and fall between the low basin country near the Wind River Indian Reservation and the high range of the Yellowstone plateau. In a good year, she won't have far to travel for two of the remaining three foods that, with ungulates, constitute 80 percent of a typical grizzly's diet. Thick stands of whitebark pine grow all along treeline; come late summer, she'll raid the massive caches of tiny pine seeds hidden by red squirrels. From the talus slopes nearby, she'll dig out army cutworm moths, which are about 60 percent fat. She'll eat up to 40,000 of them a day, the energy equivalent of 70 Snickers bars.

Of the fourth major grizzly food, cutthroat trout, there have never been many in this corner of the Greater Yellowstone, but 128 is an omnivore by design, and adept at finding new food sources. A hungry grizzly will mosey 20 miles for a mere snack. She'll try almost anything that smells interesting, and stick with it if it proves out. Which is why Number 128 has developed a taste for dog food.

That's what worries Mark Bruscino, chief bear-management officer for Wyoming's Game and Fish Department. When there's a conflict between a human and a grizzly anywhere in Wyoming, it's up to Bruscino and his two deputies to resolve it. They love bears, but it is a simple fact of the job that if they can't find a way to keep a bear away from people and their flotsam--their pets, garbage, bird feeders, barbecue grills, pigs, chickens, you name it--they have only one option. In 2000, 22 Greater Yellowstone grizzlies died through human agency, the highest annual total since they were protected under the Endangered Species Act in 1975. From where Mark Bruscino sits in the spring of 20015, the future does not bode well for 128 and her cubs.

A lot rides on 128's humpy brown back. In 1850, some hundred thousand grizzlies roamed the Lower 48, mainly in the western plains. Today, there might be 1,100, though no one really knows, for they are solitary and elusive animals. For the most part they are concentrated in two areas--Glacier National Park, and the Greater Yellowstone, which is home to somewhere between 250 and 600 bears. While Glacier's grizzlies are free to wander deep into Canada, Yellowstone's are an island population, with no geographic connection to other grizzlies; whether the existing gene pool is sufficiently diverse to keep the bears viable for the next century is anybody's guess. Because grizzlies reproduce so slowly, it can take years before a population crash or inbreeding problems become evident. For perspective, consider this: Of all the barometers of grizzly health, of all the hundreds of factors critical to maintaining a stable long-term population, the foremost is the number of females of reproductive age. In Yellowstone, the loss of even half a dozen adult sows could tip the population into a downward spiral.