The bears start to move in October, when longer nights chill Hudson Bay and snow starts to fly. Along the stony western shore, they head north over the salt marsh toward Cape Churchill. Hunting season is about to begin, after a four-month fast since the annual ice breakup in July. Almost all summer the bears have been in "walking hibernation," sleeping in dens and occasionally wandering through a vast boggy lowland called Wapusk National Park, living mainly off their fat reserves.
But soon shoreline ice will form. By walking north, the bears know they will ﬁnd it and their staple prey—ringed seals—faster. In November when the ice usually thickens enough to walk on, hundreds of male bears and nonpregnant females roam far from shore, scanning and snifﬁng breathing holes of unwary seals. About 200 pregnant females remain behind, for Wapusk offers them excellent nurseries.
"More than half of Wapusk is peat bog, and some of the peat is 12 feet thick," says Cam Elliott, superintendent of Wapusk. "It's perfect for polar bear maternity dens. Females have dug more than 1,200 in the area, one of the largest concentrations in the world."
Land and ice are bound together for the polar bears of Wapusk, "white bear" in the Cree language. But the 4,431-square-mile park (nearly the size of Yellowstone and Yosemite combined) also holds plenty of other species. "It is the ecotone, the transition zone, between the boreal forest and the open tundra," says Andrew Derocher, a University of Alberta biologist who studies polar bears. "There are few places where polar bears, black bears, the occasional grizzly bear, moose, caribou, red fox, arctic fox, beluga whales offshore, and others overlap. The biological diversity of the area is huge." Almost 200 bird species breed here, or migrate through, including boreal owls, hawk owls, snowy owls, gyrfalcons, and peregrine falcons—a bonanza for bird lovers.
Yet visitors to the area, more than 15,000 a year, stay west of Wapusk, in or near the town of Churchill. Fewer than a hundred visitors a year have come to Wapusk since it was created in 1996, partly for the protection of the bears and their denning habitat. "The two areas are right next to each other, yet they're so different they might be two separate countries," says Elliott.
Simply put: The Churchill area, which lies along a bend of the coast running west from Cape Churchill, is underlain by bedrock near the surface, which makes it much ﬁrmer than Wapusk to the south (where the bedrock is deeper). So the Churchill area is terra ﬁrma, easier to walk on, drive on, even build a town on (they did). Since the retreat of the last continental glacier some 8,000 years ago, the land has been springing upward. This is some of the youngest land in Canada—and some of the soggiest. There are thousands of lakes and ponds in Wapusk. Bog, bog, bog. There is peat bog, or muskeg, dangerous if you take a misstep and fall into a muskeg hole. All of this is seasoned with an enormous and aggressive population of biting invertebrates.
In Wapusk there are no roads, no trails, no motels, indeed no tourist facilities of any kind. The terrain is too daunting, the bears too dangerous, and the liability too high for Parks Canada, Wapusk's overseer, in case of attack. A few people pay a thousand dollars (U.S.) an hour for a short helicopter flight in summer to view an unoccupied den, or visit a small temporary camp in the fall to watch the bears, or ride snowmobiles in late winter hoping to glimpse newborn cubs.
But these bears are in trouble. Hudson Bay polar bears, some of the southernmost in the world, are feeling the heat of global warming. The region is about two degrees (F) warmer in winter than 50 years ago. The bay's ice is breaking up in early July rather than late July, says Nick Lunn of the Canadian Wildlife Service. The earlier the ice disappears, the less time bears have to feed on seals. Pregnant females need to gain at least 200 pounds to sustain them through the long fast in their dens, where they may spend eight months. In the past they've been able to kill many seal pups being weaned by their mothers in early July. Now, with the ice melting sooner, the bears can't hunt and must forsake that nutrition. Such deprivation leads to fewer cubs surviving to adulthood.
"For every week that the ice is breaking up earlier, the bears are coming ashore more than 20 pounds lighter," says Lunn. He and his colleagues—including Derocher and Ian Stirling of the Canadian Wildlife Service—estimate that the bears are 15 percent smaller than they were 20 years ago. And Lunn says the latest census shows that in just ten years the bears' population has declined from 1,200 to less than 1,000. It doesn't seem like a temporary drop. "Until recently the numbers have been stable. The last two censuses, in the mid-1980s and mid-1990s, both showed 1,200 bears," says Lunn.
By 2050, southern Hudson Bay may be ice free year-round. Will Wapusk's bears move north? "There are already 2,000 polar bears in northern Hudson Bay," Lunn says. "The area probably can't take any more. The environmental changes in Hudson Bay are happening so fast that one day the bay may no longer be able to support polar bears."
Wapusk's bears will have to stay ashore longer and longer, marooned in the park created for them, watching and waiting for the ice. To the north the rest of the world's polar bears, about 25,000 of them, roam the Arctic. As the climate warms, what about them?