Hudson Bay is a large inland sea bordering three Canadian provinces and one territory, though technically the waters are considered the property of the Nunavut territory alone. At low tide, locals joke you can walk out along the sandy shore and find yourself standing in the northern territory. English explorer Henry Hudson, who built up his seafaring credentials near Greenland and Svalbard, discovered the bay in 1610 while searching for the fabled Northwest Passage, as was the thing to do if you were a brazen man with a penchant for exploration in the seventeenth century. But like his ambitious forefathers, he, too, was led astray. Mistakenly, Hudson believed he had discovered a route to Asia when he happened upon the large saltwater body smack-​dab in the middle of what would later become Canada. After three months of searching the bay’s edges, Hudson could find no outlet. By November, his ship was trapped in ice. He stubbornly demanded that his crew spend an abysmal winter on the shore of the bay before forging westward. (The polar bears were out on the ice by this point—​a small comfort.) Fed up with Hudson’s orders and the cold, the crew mutinied the following spring and set him and his teenage son adrift in a small shallop boat on the bay’s waters. No one ever heard from Hudson again.

Hudson Bay does not connect to the Northwest Passage, but it does eventually empty out of the aptly named Hudson Strait into the Labrador Sea, an arm of the North Atlantic Ocean. In late autumn, as Hudson and his crew unfortunately discovered, ice grows over the surface of the bay. Though this may have filibustered Hudson’s grandiose plans and led to his untimely demise, it’s also given rise to a unique population of polar bears that inhabit the bay’s shores. In other parts of the Arctic, sea ice may shrink in the summer but persists year-​round, and polar bears spend most of their lives on the ice, rarely coming ashore. (At least, this was the case before climate change entered our vernacular.) The sea ice of Hudson Bay, however, freezes and thaws according to the season. The region’s polar bears endeavor to stay on the ice as long as possible, but at some point they must decamp. During the summer and early fall, they bide their time on land as they wait for the ice to return. The patch of tundra around Churchill has become particularly populous with bears, in part because it’s the place where the sea ice breaks up last in spring and returns first in the fall. Migrating bears from around Western Hudson Bay are getting on and off the ice here, often passing through town as they do so.

Forced ashore for months at a time, there is little else to do but get to know the neighbors. Young male bears spar on the slushy shores to stave off boredom in late autumn. Others munch on kelp washed in by the tide. Pregnant females den in the soft peat banks of Wapusk National Park, the only place in North America outside of the Mackenzie River delta where all three species of bears—​black bears, polar bears, and brown bears—​mingle. Though grizzlies were thought to have disappeared from Manitoba, they began showing up again in Wapusk in the 1990s. Scientists believe the bears—​barren-​ground grizzlies—​are dispersing southward from Nunavut. Grizzlies have been seen in the park every year since 2008. For polar bears, the impermanence of ice means that they must pack on as much weight as possible during winter and spring when they can hunt blubbery ringed seals. A polar bear stomach can hold the food equivalent of as much as 20 percent of its body weight. Upon returning to land, the bears will fast for more than four months—​pregnant females for eight—​with rarely a pinniped in sight. Remarkably, during these lean months, a bear sheds about 2 pounds every single day until the ice returns.

Today seemed to be that day. In the twelve hours that had passed between me eavesdropping on the tourists’ conversations and heading out in pursuit of bears, the thick ice edge had connected to the shoreline. Nearly every single bear spotted on land yesterday had departed for the winter season, finally satisfied that the ice could support their tremendous weight. Though it was bad news for me, it was good news for the bears. In recent years, Hudson Bay has been freezing up later in the season, extending the bears’ tenuous fasting period. A sudden shift in weather patterns that week had spurred a surprisingly early freeze-​up, and the bears would have extra time to fatten up.

Trying to appear patient despite this bedeviling change of fortune, I took a seat next to Andrew Derocher, a towering Canadian with a gray-​streaked beard dressed in a puffed-​out parka that doubled his stature. Still, it was difficult to make out anyone’s physical characteristics under several layers of jackets, scarves, and toques. I was nearly as keen to meet Derocher as I was a polar bear. He was one of only a handful of scientists who had been studying polar bears before climate change hijacked the research agenda. Back in the mid-​1980s, while Derocher was working on his master’s of science, polar bears were doing well in Canada. It had been over a decade since the Canadian government began limiting the number of bears that could be harvested and restricting hunting permits to Indigenous people or to sport hunters with an Indigenous guide. (Canada is the only nation that still allows for the international export of polar bear hides and the only nation that permits the sport hunting of polar bears.) With these restrictions in place, many bear populations were recovering. “Our focus back then was just on basic ecology. We wanted to know about the lingering effects of the harvest and how many bears there were,” he told me as we rumbled over the tundra.