It's not easy to swim 109 miles when you're starving to death. It's not easy either to try to survive when you're losing body weight at a rate of 2. 2 Ib. a day. And it might be the hardest of all if you're anursing mom and your calorie intake has dropped so low that you can no longer produce the milk you need to care for your young.
As a new paper in Nature Communications reveals, all of those challenges and more are facing the world's polar bears, thanks to disappearing sea ice in our warming world, denying the animals a plat form that they need to hunt for seals. If the trend isn't reversed(扭转) soon, the estimated 26, 000 polar bears in the wild could start to lose their hold on survival before the middle of this century.
The researchers followed 20 different polar bears in Manitoba, Canada, from 2019 to 2022, fitting them with GPS trackers and video collars and periodically tranquilizing(麻醉) them to analyze their blood, body mass. and daily energy consumption. "The polar bears in Hudson Bay are probably at the edge of the range at which they can survive right now, " says Anthony Pagano, a research biologist with the U. S. Geological Survey and the lead author of the paper. " Most of the modeling work suggests that around 2050, they are going to be on land and away from their primary habitat on the ice.
According to the study, the data gathered was troubling. Weight loss varied among bears, with the daily loss of 2. 2 Ib. representing an average; some of the subjects dropped up to 3. 75 Ib. every 24 hours.
The bears are efficient hunters when they've got the purchase of ice beneath them, but they are clumsy when they are going after seals and trying to swim at the same time. That leaves them searching on land for foods they would not ordinarily eat and getting little payoff for their efforts. Polar bears are feeding on ducks, geese, and eggs. Other foods on the desperate bears menus include berries and other vegetation. None of that food is as calorie-rich as seals
