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Wednesday, April 17, 2024

The long summer harms polar bears. They lose weight rapidly

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During the prolonged summer, polar bears in Hudson Bay have great difficulty finding food. Limited access to the ice makes it difficult for them to hunt seals, which form the basis of their diet. This results from observations made by scientists from Washington State University.

Climate change related to human activity is causing summers to become longer in the Arctic Sea region. Limited access to the ice cover at this time means that polar bears in Canada’s Hudson Bay have difficulty finding food and lose weight. These conclusions were reached by scientists from Washington State University who observed 20 polar bears for three weeks during the summer.

Why is sea ice so important? Because polar bears use it to capture their main food source – fat ringed seals (Pusa hispida) and mustachioed (Erignathus barbatus).

“Polar bears are not grizzlies in white fur”

Research conducted by experts from Washingon State University showed that bears lost an average of one kilogram of body weight per day. This contradicts optimistic theories that polar bears will be able to adapt to longer ice-free periods than before.

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Some experts said they would use similar strategies to their cousins, grizzly bears, which forage for land food and rest. Indeed, polar bears did this, but with little success.

– Neither strategy will enable polar bears to survive on land after a certain period of time. Even those that foraged for food lost weight just as much as those that rested, said Charles Robbins, director of the Washington State University Bear Center and author of the study published in February in Nature Communications. – Polar bears are not grizzlies in white fur. They are very, very different from them, he emphasized.

As researchers explain, an adult male polar bear can reach over three meters in length and weigh 700 kilograms, while a grizzly measures approximately 2.5 meters and weighs 350 kg. To maintain their enormous mass, polar bears eat mainly fat-rich seals, which they capture primarily on the ice.

Until now, little was known about how they behave on land. The answers were now provided by cameras and GPS sensors attached to 20 individuals, as well as weight measurements. “We found a wide variety of animal behavior and a wide range of energy expenditure associated with it,” said Anthony Pagano, the study’s lead author.

polar bearShutterstock

Many bears just lay there. By burning calories at a similar rate as during hibernation, they conserved their resources. Others foraged for food, eating bird carcasses, caribou, berries, seaweed and grass. Some individuals traveled long distances. However, their efforts did not pay off. “Terrestrial food provided an energy gain, but ultimately, the bears had to expend a lot of energy acquiring it,” Pagano explained.

Three individuals made long journeys in the water – one of the bears swam almost 200 km through the local bay.

Two found edible remains of a beluga and a seal in the water, but they failed to eat them while swimming and were unable to bring them to land.

Only one bear gained weight, and this was due to the remains of a large mammal being found on land.

The research focused on bears living in the Hudson Bay region, which will be the first to be affected by global warming. Since the late 1980s, the population of these predators in the area has declined by 30 percent. As summer lengthens, these animals are at risk of starvation and further population decline.

– As bears are forced to live on land earlier and earlier, the period in which they usually accumulate the energy they need to survive is shortening. As they stay on land longer and longer, they will likely become more and more hungry. This will especially apply to young individuals, Pagano emphasized.

polar bearShutterstock

Nature, The Guardian, PAP

Main photo source: Shutterstock



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