Into the Arctic National Wildlife Refuge, home of the last great migration on Earth

The grizzly bear appeared drunk, rolling around on the spongy tundra. He had just feasted on a freshly killed porcupine caribou, and now he lolled around, seemingly full and happy, blocking our path up the valley.

We crouched down and brought out binoculars. Meanwhile, hundreds of caribou continued their instinctive, ancient migration around the bear. Eventually, he moved on, and so did we — though the experience lingers in my mind.

This was the kind of wilderness encounter I'd hoped for when I planned a trip to the Arctic National Wildlife Refuge, in the remote northeastern corner of Alaska.

With 24/7 daylight and fast-changing Arctic weather patterns, this region presents challenges. The sun rarely sets. Mosquitoes swirl endlessly. Cold, snow and fog can descend, limiting views and hampering movement — of wildlife and visitors. We experienced all of that, and yet, our trip was overwhelmingly magical.

I have spent the past couple of decades sailing and exploring the ocean wilderness of the Northwest Passage, on routes in the icy Beaufort Sea that skirt the northern coast of Alaska. The continental shelf here extends some 100 miles out to sea, making these coastal waters shallow and dangerous for any vessel, but especially a deep-draft sailboat. As I twice swept past the Arctic refuge, about 25 miles away, all I could think about was what I was missing — and the wonders I would see if only I could stop and get my feet on the ground.

A decade later, I found myself 25 miles inland — deep in the refuge, 220 miles north of the Arctic Circle — setting up base camp in June with five other travelers. We scattered our tents in the greening landscape around a central cook area, where we stored food in closed containers to ward off bears.

We'd all met up in Fairbanks, an end-of-the-world town with fun restaurants, microbreweries and residents who clearly relish the outdoors. From there, we'd taken a small plane with regularly scheduled commercial service to Arctic Village, a scrappy place just outside the refuge inhabited mainly by indigenous Gwitch'in. Then we'd hopped on a bush plane, flew up and over the Arctic Circle, and landed on a remote stretch of land. It took two trips to get us all there; the plane can handle only three people with gear at a time. As if to accentuate the isolation, the airstrip is marked by caribou racks.

When the plane took off the last time, we watched it disappear. It would not return for eight days.

Arctic Treks, a longtime guiding company out of Fairbanks, led our trip. Although a guide is not required, the terrain, wildlife and logistics of the refuge are formidable. I welcomed the depth of knowledge and skills of our seasoned guide, Jeff "Country" Gillespie. And while my fellow travelers and I carried pepper spray in case of a bear attack, Country discreetly packed a weapon. The area is remote and can be dangerous.

Our hope was to catch the summer migration of the porcupine caribou herd within the 19-million-acre Arctic Refuge. Over 200,000 strong, their 1,500-mile migration represents the longest land-based mammal migration on the planet. Each summer, the caribou and their recently born calves travel en masse from the mountain range to the coastal plain, where food is plentiful and winds can keep the thick mosquitoes at bay.

Timing was tricky. Although each season the migration is unpredictable, last season's late spring cold and snow affected the herd's usual movement. They had already begun their descent from the mountains when a surprise snowstorm pushed them east. By the time we arrived, near the summer solstice, they had moved west in the vast open range. We had lucked into the migration.

We stayed at Arctic Refuge Base Camp at Sunset Pass and found the migration was all around us — thousands of caribou on the move.

Along with the caribou, grizzlies come to feast on the hoofed beasts. Wolf packs, too.

One day, I walked to a small bluff with a good vantage point. On the tundra, caribou became rivers of fur and antlers. Heat shimmered from the warming land, creating a mirage-like effect. Then I noticed my friends, about a mile away, shift their gaze toward me. Soon I understood why: A pack of arctic wolves was chasing caribou and headed in my direction. Just as I grabbed my camera, one wolf stopped, just 200 feet away, and stared straight at me. Unsure of how to respond, I resorted to my bear training. I got large, standing and raising my camera, with its big zoom lens, above my head. I talked to the wolf. And then the wolf returned its attention to the caribou.

We saw countless caribou, 14 grizzly bears, arctic wolves, golden eagles and more. Caribou, these massive, strong creatures, drive the entire ecosystem, from the grizzlies that feast on them to the smaller animals that clean up the messes to the eagles that prey on those small mammals.

The indigenous people of the region also rely on the caribou.

Many indigenous people living in communities surrounding the refuge depend on the caribou migration for sustainable hunting to provide food for their families. The tradition of balanced harvesting of animals has been taking place for multi-generations and thousands of years, whether it is bowhead whales from the Arctic Ocean or porcupine caribou from the Arctic Refuge.

On a high ridge overlooking the Arctic Coastal Plain, I sat with one of the trip participants, who happened to be the board chairman of the Alaska Wilderness League, Betsy Loyless. From our high perch, it was natural to talk about the glory of the Arctic Refuge and the migration it hosts. "It is not just our national treasure; it is an international treasure," she said.

When I was a young man I could only imagine what a wilderness looked like, especially in the vast expanse of Alaska. Through education about the American conservation movement and many outdoor experiences, I began to understand. We need wilderness to replenish our souls and remind us of our connections to undisturbed nature.

The Arctic National Wildlife Refuge, established in 1960, has been called the "American Serengeti." The analogy could not be more appropriate. The caribou migration is one of the world's greatest, and it takes place on one of America's great public lands.

I have spent much of my life traveling to the remote corners of the planet searching for the beauty and solitude of wild places. I am sorry it had taken so long to get to the Arctic National Wildlife Refuge. It is truly a remarkable, vast and unique wilderness.

David Thoreson is a climate and ocean educator, photographer and explorer; he lives in Okoboji, Iowa (davidthoreson.com).