A group of polar bears in south-east Greenland have adapted to hunt via blocks of freshwater ice from glaciers when sea ice retreats in the warmer months. This suggests the animals may be more resilient to climate change than we thought, although loss of sea ice remains the greatest threat to their survival.

Polar bears often hunt seals by waiting near holes in blocks of floating ice where their prey come up to breathe. Seals are also slower on ice than in water, giving polar bears an advantage. But this is being threatened by climate change and the resulting sea ice loss. As a result, the animals are projected to decline by 30 per cent over the next three polar bear generations, around 35 years.

“We provide evidence for a previously-undocumented and highly-isolated subpopulation of polar bears on the south-east coast of Greenland surviving in a special way,” says at the University of Washington in Seattle. “They survive in fjords that are sea-ice free for more than eight months of the year because they have access to glacier ice on which they can hunt.”

Laidre and her colleagues analysed genetic samples from polar bears that they tracked from 2015 to 2019, which they combined with data from previous studies. In their first discovery, they found a few hundred polar bears in south-east Greenland are the most genetically isolated of their species.

While tracking these animals, the team further discovered this genetically-isolated group hunts via floating blocks of freshwater ice, broken off from glaciers, for about 250 days of the year, when sea ice has melted. This probably enables the bears to live in the area, which has no sea ice for considerably longer than other polar bear habitats.

While this suggests all polar bears are more resilient than we previously thought, glacial ice is largely limited to the animals around Greenland and Svalbard.

“Glacier ice may help small numbers of polar bears survive for longer periods under climate warming, and may be important to prevent extinction, but it is not available for the vast majority of polar bears,” says Laidre.

“Climate action is the single most important thing for the future of polar bears. Most polar bears in the Arctic depend on sea ice.”

According to at the United States Geological Survey, the findings “offer a ray of hope that other refugia habitats may be available for polar bears to use, so that they can persist until greenhouse gas emissions are substantially mitigated and sea ice habitat is recovered”.

“But ensuring the long-term persistence of a [wild] population of polar bears is ultimately dependent on conserving their sea ice habitat. That will require mitigating greenhouse gas emissions.”

The genetically-isolated bears may have adapted to hunting via freshwater ice, but this doesn’t make them immune to the effects of climate change.

“I suspect the Achilles’ heel for this group of bears will be ongoing warming that negatively affects the ringed seal population in the area. If the ringed seals don’t have breeding habitat, the main prey of the bears may disappear,” says at the University of Alberta in Canada.

An extreme lack of sea ice in Canada this winter should serve as a “wake-up call” for the risk climate change poses to polar bears, say conservationists.

Ice normally starts building up across Hudson Bay in November, but the area has remained almost entirely ice-free in the face of temperatures 6°C above average. In the north-western part of the bay, ice extent . In an average year, 70 to 80 per cent of this part of the bay is covered in ice by this stage in the year.

That has left polar bears standing by the shore, waiting for the ice to form so they can hunt seals. Temperatures in recent days have begun dropping and the US . But the agency says the current low is “extreme” and, across the bay as a whole, second only to 2010 for this time of year.

“It’s very unusual. It’s very low,” says at WWF Canada. “I don’t think this is panic and everything is collapsing, but it’s indicative of the broader trend [of sea ice loss].”

Climate change has .

“It’s not good [for the bears],” says , an ecologist at the British Antarctic Survey. “The longer they don’t have sea ice, they get a gradual loss in condition. A lot will survive it [this year]. But it tips the balance towards stress-related mortality. Fewer will survive.”

Research suggests that almost all the world’s remaining 26,000 polar bears will be pushed to the edge of their fasting limits by the end of the century due to climate change. Laforest says that while bears in the high Arctic are currently doing fine, the sub-population in the Hudson Bay area are the canaries in the coal mine. 

“They are the first to go through these broad implications of climate change,” he says. “We need to take these warning signals for what they are. It’s a wake-up call.”

The remote nature of the region in which the bears hunt, and the cost of tracking them, means it will be hard to measure precisely what impact this year’s late freeze has on the animals. In the meantime, Laforest says there may be more human-wildlife conflict as hungry bears wander into Inuit communities in search of food. The late ice is also impacting people in the region, he says, as they cannot access their usual hunting grounds. 

The National Snow and Ice Data Center says the picture for the Arctic as a whole is mixed, with sea ice extent only the tenth lowest on record for November. On the Russian side of the Arctic, sea ice growth has been above average in the Bering Sea, trapping ships in ice and disrupting supplies to Siberian cities.

Being a polar bear is harder work than biologists thought. As the bears roam the Arctic sea ice hunting seals, they use more energy than expected. That has ominous implications for a future in which sea ice is ever scarcer.

of the US Geological Survey in Anchorage, Alaska, and his colleagues studied 9 adult female polar bears on the Beaufort Sea ice north of Alaska. They fitted the bears with collars carrying GPS trackers, accelerometers and video cameras. They also injected the bears with water labelled with stable isotopes of hydrogen and oxygen.

When the team recaptured the bears 8 to 11 days later, changes in the ratio of isotopes in their blood gave a measure of metabolic rate. The researchers could compare this with the bears’ activity and hunting success.

Researchers already knew that polar bears are inefficient walkers, but many assumed that they also saved energy by sitting quietly waiting for seals, and by reducing their metabolic rate when fasting. However, it seems these savings are small at best. The bears’ average metabolic rate during the study period was 1.6 times more than most previous estimates.

Not so thrifty

This means the bears must kill and eat more seals over the course of a year, to pay for this higher metabolic rate.

But as climate change melts ever more sea ice, the bears are likely to have to walk farther to find prey. “That has a cost, and the animal has to find the energy to do that – or take it out of growth, reproduction, or survival,” says polar bear biologist at the University of Alberta in Edmonton, Canada.

Though Pagano’s study focuses on just one population of polar bears, many of the other populations around the Arctic likely face the same challenges, says Derocher.

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Between 1870 and 2014, they found 73 cases of polar bears attacking a group of people or an individual, with 63 people injured and 20 people dead. Bears were acting in a predatory manner in most attacks, and it was male bears that were more often involved.

Encounters increasing