Hunger threatens lives of polar bears with melting ice – 02/13/2024 – Environment

Some polar bears face starvation as Arctic sea ice melts. This is because they cannot adapt their diets to life on land, scientists have found.

The iconic Arctic species typically feeds on ringed seals that it catches on sea ice floes.

But as ice disappears in a warming world, many bears are spending more time on land, eating bird eggs, berries and grass.

However, animals lose weight quickly on land, increasing the risk of death.

The polar bear has become a poster child for the growing threat of climate change in the Arctic, but the reality of the impact on this species is complex.

Although bear numbers plummeted until the 1980s, this was mainly due to poaching.

With greater legal protection, the number of polar bears has increased. But rising global temperatures are now seen as the biggest threat.

This is because the frozen seas of the Arctic are essential for their survival.

The animals use sea ice as a platform to hunt ringed seals, which have high concentrations of blubber, especially in late spring and early summer.

But during the warmer months, many parts of the Arctic are now increasingly ice-free.

Other researchers, however, say the effect of climate change on polar bears will depend on location.

In the western Canadian province of Manitoba, where this study was carried out, between 1979 and 2015 the ice-free period in the region increased to up to three weeks.

To understand how animals survive as the ice disappears, researchers tracked the activities of 20 polar bears during the summer months over a three-year period.

In addition to collecting blood samples and weighing the bears, the animals were fitted with collars equipped with GPS and video cameras.

This allowed scientists to record the animals’ movements, their activities and what they ate.

In the ice-free summer months, bears adopted different strategies to survive, with some essentially resting and conserving energy.

Most tried to look for vegetation or berries or swam to see if they could find food.

Both approaches failed, with 19 of the 20 bears in the study having lost body mass, by up to 11% in some cases.

On average, the animals lost one kilo per day.

“No matter what strategy they tried to use, there was no real benefit to either approach in terms of being able to extend the period they could survive on land,” according to lead author Anthony Pagano of the U.S. Geological Survey in Alaska. .

“Polar bears are not grizzly bears that wear white coats,” says co-author Charles Robbins of the Washington State University Bear Center. “They are very, very different.”

Two of the three bears that went into the water found carcasses of dead animals, but spent little time eating as they were very tired from the effort.

“A subadult female found a dead beluga whale, took a few bites from it, but mainly used it as a rest buoy,” Pagano told BBC News.

“This really suggests to us that these bears can’t eat and swim at the same time.”

Key facts about polar bears

There are about 26,000 polar bears left in the world, most of them in Canada. Populations are also found in the USA, Russia, Greenland and Norway.

Polar bears are listed as vulnerable to extinction by the International Union for Conservation of Nature (IUCN), with climate change a key factor in their decline.

Adult males can reach around 3 m in length and weigh around 600 kg.

Polar bears can eat up to 45 kg of fat in one sitting.

These bears have a powerful sense of smell and can smell prey up to 10 miles away.

They are excellent swimmers and have been seen up to 100 km from the coast, and can swim at speeds of around 10 km per hour, partly due to their slightly webbed feet.

An intriguing finding of the study was that one bear gained 32 kg in weight.

Researchers believe that this bear, which spent much of its time resting and conserving strength, was lucky enough to stumble upon an animal carcass.

While previous research has outlined the challenges climate poses in the coming decades, this new work raises important questions about species’ ability to adapt.

However, other researchers say the impacts of climate change on polar bears would be different depending on their location.

“Polar bears are likely to disappear from areas where sea ice is lost in the future, but it’s difficult to say when and where,” says Jon Aars of the Norwegian Polar Institute, who was not involved in the study.

“Some areas will also have good conditions for bears many decades from now.”

“The area of ​​this study is one where conditions could be very difficult for bears in a short space of time if sea ice continues to disappear as predicted.”

The study was published in Nature Communications.