May 25, 1993, Denali National Park, Alaska

The view on my left through the airplane window inspired me to put aside my work for a moment. The snow-capped peaks of the Alaska Range glistened in the bright sunlight, contrasting sharply with the dark blue sky. Below me, brown tundra dotted with melting snowdrifts covered the rolling foothills. Spring had finally arrived in Denali National Park, and although the land was still waking up, the animals responded in great anticipation.

I strained to see the scattered caribou below me, their mottled coats blended beautifully with the browns and grays of the gravelly hillsides and the last remnants of winter snow. The caribou trekked here from their winter range in the north to escape the hungry wolves that plagued them all winter. Here they hoped for solitude while they gave birth to the next generation. Here too, grizzly bears emerged from winter dens with appetites enhanced by a long winter of fasting and hibernation. Caribou calves would provide a great nutritional boost for a hungry grizzly bear, like the one I was searching for.

Between the sun shining through the large Plexiglas window and the engine heater working overtime, I was plenty warm inside the small, two-passenger airplane. The pilot sat in front of me, and thanks to the plane’s overhead wings, I had a clear view out both sides of the narrow fuselage. The tracking sheet on my clipboard indicated we should soon hear the radio signal of grizzly bear 662. I had spotted her here the week before, resting by her winter den with her two-year-old son.

We first captured 662 the previous year. At that time, we extracted a small, vestigial tooth, one that didn’t occlude with her other teeth and therefore had no use for biting or chewing. A thin slice from the root of that tooth, stained and mounted on a microscope slide, showed annual growth rings like those on a tree. We determined that she was seven years old at the time. The yearling male was probably her first offspring. She had done well for a young mother; only 16 percent of cubs in Denali survive to the age of two. Keeping her first cub alive into his third summer showed 662’s good instincts.

As the Piper Supercub banked left, I heard the repeating ‘beep’ of a radio transmitter. Veteran pilot Sandy Hamilton had good instincts too. He controlled the switch box that let us choose which of the two wing-mounted antennas we listened to. A strong radio signal on the left told us the bear was on that side. We headed up the center of the Straightaway Glacier and gradually started our descent.

I grabbed our topographic maps and studied them, tracking our current location while searching for 662. The bear’s radio signal led us up the glacier, then over to its east side.

Bear 662 had recently come out of hibernation and hadn’t eaten for almost seven months. When female grizzly bears in Denali enter their dens in late September or early October, they usually weigh around 300 pounds and average 25 percent body fat. By the time they emerge from the den in early May, they’re 100 pounds lighter and carry less than 10 percent body fat. When I had captured female bears in the spring, I could often feel the contours of their spine, three sides of each rib, and much of the pelvis. They felt like skeletons covered with furry hides. Needless to say, bear 662 was very hungry, and nothing would help her regain her strength like eating a young caribou calf with a belly full of mother’s milk.

“There she is, Sandy. She’s on the left side running down the gravel ridge that parallels the glacier. But she’s alone. Where’s her two-year-old?”

Nose to the ground as if following a scent, 662 frantically chased something we couldn’t see. Curious, we followed her from high in the air so that we didn’t disturb her. She gracefully loped for almost a mile, her long brown fur flowing like waves on a gentle sea. Suddenly, she dropped off the northeast side of the ridge into a small, gravel creek bottom. In one quick motion she seized a newborn caribou calf in her strong jaws. The calf’s mother, head up, ears erect, trotted away from the powerful predator. Still on full alert, the calf’s mother watched from a safe distance. Caribou rarely defend their calves, but her fidgety behavior belied great concern.

Sandy eased the airplane down so we could see better without a disturbing the bear. I wondered how long it would take the hungry female to eat an eight-pound calf.

“Sandy, there’s a wolf down there trying to steal the calf from 662!”

We don’t often see wolves and bears fighting. I quickly tuned my radio receiver to the bank of wolf frequencies. The wolf was wearing a radio collar; the signal indicated a female from the McLeod Lake pack. We detected two more radio-collared wolves about 100 yards to the north, and there could have been more without transmitters nearby.

Wolves are the primary predators of caribou and their calves. Caribou leave their traditional winter range and move to the calving ground to escape from the wolves. Wolves don’t usually discover the birthing caribou until well into calving season, which recently peaked. Looked like these wolves were right on time.

Female wolves in Denali average about 88 pounds compared to the typical 200 pounds of a spring female grizzly bear. After a long winter without food the bear should be hungrier and more determined than any wolf. This wolf apparently disagreed.

The wolf lunged at the bear several times, mouth open, trying to get a purchase on the young calf. The bear swiped back with strong forelegs and long claws. Still holding the calf in her mouth, the bear bluff-charged the tenacious wolf. The two sparred like seasoned prizefighters. Bear 662 frantically tried to eat her kill, but the wolf’s unrelenting attacks made it impossible.

Worried about the two-year-old, Sandy and I backtracked until we found the small male in the same place we first observed 662. He was running down the same ridge toward his mother and at least three very hungry wolves.

I’d heard stories of wolves killing and eating young grizzly bears. I wondered how they could brave the fury of a defensive mother grizzly bear. I thought I might soon find out.

The wolf continued to challenge the female bear but stayed out of range of her powerful paws. Sandy and I circled patiently, intrigued by the aggressive challenges of wolf and bear, and intent on learning the fate of the two-year-old.

When the young male finally arrived he careened off the ridge into the creek bottom, seemingly unaware of the presence or potential threat of the wolves. Then 662 did something perfectly logical that nevertheless took me by surprise. She dropped the calf and ran away from the pack of wolves. As her two-year-old followed her he too was drawn away from the wolves. The female wolf grabbed the calf, ran a quarter mile in the opposite direction, away from the bears, and devoured her quarry. I watched grizzly bear 662 and her two-year-old walk slowly up the hill away from the wolves. Her hunger for her son’s survival exceeded her appetite for food. Spring had indeed arrived in Denali, but the harsh realities of life in the subarctic, and the need for good instincts, continued.