What Do Polar Bears Do in Fall?

For polar bears across the Arctic, the arrival of fall presages a coming bounty, as waters begin to freeze, sea ice begins to form, and bears prepare themselves for a winter hunting on the ice.

In some parts of the polar bears’ range, such as the islands of the Canadian Arctic Archipelago, ice persists through the summer. But elsewhere, fall’s return prompts an uptick in activity as the bears anticipate the largely ice-free summer months finally giving way to an icy smorgasbord. 

With 20 populations of polar bears across the Arctic, there are 20 different stories as the bears adjust to different ice conditions. Following are some representative populations.

Norway’s Svalbard archipelago

In the Barents Sea, the bulk of the population spends as much of the year as possible on drifting sea ice, while a smaller number of bears – roughly 250 – remain on the coastal ice around Svalbard. During fall, says Jon Aars, senior scientist with the Norwegian Polar Institute, "The coastal bears have no choice, they have to stay on land, as there is no sea ice in most places on Svalbard from September until late in the fall.” Even when the ice does begin to form, these coastal bears remain close to shore at all times.

In the Svalbard region, sea ice is constantly being pushed away from shore by currents, and so, when summer arrives and new ice is no longer being formed, some of the so-called pelagic bears may find themselves trapped on or near land as the sea ice drifts away; come fall, they will be waiting anxiously for the ice to re-form so they can once more set out far from shore. Others, however, never leave the ice at all if they can avoid it.

“You can have pelagic bears in Svalbard or the Barents Sea that are on the ice 12 months a year,” explains Aars.

Southern Beaufort Sea bears

In the Southern Beaufort Sea, sea ice that traditionally stayed close to the northern coast of Alaska and Canada in summer now retreats hundreds of miles from shore. Bears in this region are forced to make a choice between following the ice over deep, less productive waters – where the hunting is less optimal – or remaining on land, where they are largely food-deprived. Among the land bears is a subset whose behavior is driven by a powerful attractant. They have discovered Inupiat subsistence whale hunts in communities like Kaktovik that provide them, says Geoff York, senior director of conservation for Polar Bears International, with “regular and predictable access to bowhead whale remains.”

Fall finds most of the bears in this population far out on the sea ice, where they seek to spend their entire year when possible. But as late fall extends the ice closer to shore, over more productive seal-hunting grounds, they follow it. Meanwhile, the bears that chose to remain on land wait for the ice to return.

Chukchi Sea bears

In the Chukchi Sea, a population shared by the U.S. and Russia, some bears are happy to spend at least part of their summers on Russia’s Wrangel Island, where walruses may gather in congregations 100,000 strong, giving those bears steady access to marine mammal prey. Additionally, says York, currents in the area are such that “Wrangel is a place where things tend to strand, be it wrecked boats that have blown off their moorings in Alaska or marine mammal carcasses.”

Even so, here too, the return of fall leaves bears ready and anxious to return to the sea ice where hunting is ultimately more productive and reliable. Alaska bears in this population await the freezing of coastal waters so they can rejoin the ice as it forms over productive continental shelf waters; on Wrangel Island, the return of fall historically sees the formation of an ice bridge from shore to the ice edge which grants bears relatively easy access to the riches of the frozen Arctic waters.

Churchill’s seasonal ice bears

Nowhere in the polar bear’s range is fall greeted with as much enthusiasm as in Canada’s Hudson Bay. There, sea ice melts completely in summer, forcing all the bears ashore during the warmer months. As soon as the temperatures begin to drop, the bears are on the move, keen to find food after weeks of fasting.

But even as the bears gather on the tundra along the shore of the bay, and even as the bay begins to freeze in November, they must still wait for the temperature to drop low enough and the ice to grow thick enough for them to head out and hunt.

“I imagine this time of year as if polar bears were starting to line up at a restaurant, waiting for the doors to open,” explains Alysa McCall, director of conservation outreach and staff scientist for PBI. “The ice starting to freeze is the equivalent of the restaurant’s doors opening. But the restaurant isn’t really prepared for the rush, and so the food doesn't all come out right away. So basically, freeze-up is great. The bears are stoked to get out on the ice, and they're going to find some food. But it can be slim pickings at first. Fall really isn't the best hunting time. So, it's not like they're immediately bouncing back to their original weight or getting all the food they need.”

As a result, early in the fall on Hudson Bay, bears can often be seen tentatively testing the first of the ice to see if it is thick enough to support their weight. And even when the ice forms near to shore, it can still take several weeks before it is thick and extensive enough to allow the bears to head out and focus on food.

“They really have to navigate carefully as the ice is freezing up,” explains McCall. "Plus, even as the ice is freezing, as long as there is still open water in the bay conditions can be quite stormy. So, it’s an exciting time for them, but it's still difficult.”

Fall sparring

For subadult and adult males in Hudson Bay, fall is time for sparring. As they await the ice, these male bears will tussle with each other on the tundra, behavior that exercises the muscles they need for hunting and also establishes both societal bonding and a hierarchy, as the bears determine which among them are the strongest. Although there have been scattered reports of sparring elsewhere, Western Hudson Bay is where by far the most sparring is observed.

 “The number one reason for that is that, because the ice melts completely and then re-forms in the fall, we see these large on shore gatherings of bears in Hudson Bay,” explains McCall. Plus, she adds, because so many researchers and tourists visit Western Hudson Bay because of the proximity of Churchill, Manitoba – the famous polar bear gathering place – “there are just more eyes on the bears here, so there are more people to see bears sparring. I do think it probably does happen in other parts of the Arctic when the circumstances are right.” She added that females may engage in sparring occasionally, although that hasn’t been confirmed.

Fall maternity dens

For one group of bears, however, fall does not present an opportunity to head back out immediately onto the ice. Fall is when pregnant bears separate themselves from the others and fashion maternity dens in the snow to give birth.  In Western Hudson Bay, bears curl up in peat dens that may be 200 years old and wait for snow to cover to seal them in and shelter them; in the Barents Sea, however, the islands of Svalbard that have historically been denning areas are no longer accessible due to a lack of sea ice. As a result, says Aars, it seems that more and more pregnant bears in that population travel on the sea ice to den in the archipelago of Frans Josef Land, “because they often don’t have sea ice around the traditional denning areas anymore.”

As other bears head out onto the ice and begin to gorge on seals, those females rest in the warm, dark dens, where they give birth in the winter and emerge with their cubs in the spring. They eat as much as they can in the spring so they can survive the summer shortfall and wait for sea ice to form anew the following fall, as the cycle begins again.

Kieran Mulvaney is a freelance writer who has written extensively about polar bears and the Arctic for publications including National Geographic, The Guardian, and The Washington Post. A native of Bristol, England, he lives in Bristol, Vermont.