Why you should care
Because scientists say this may have serious implications for polar bear populations.
If you grew up in the early aughts, or raised a kid during that time, you’re likely familiar with Dory’s cute ditty in Finding Nemo: “Just keep swimming, just keep swimming.” You know what’s not so adorable? Endangered animals that actually have to just keep swimming … and swimming …
Two-thirds of female polar bears in the Beaufort Sea have swum more than 31 miles at least once.
That’s roughly the length of 1,000 Olympic-size swimming pools, according to a study published in a recent issue of Ecography. The results were taken from data collected in 2012, which was, at the time, a record-low year for Arctic sea ice levels. Satellite links were used to track the movement of polar bears in the region, with the farthest-traveling bear swimming 249 miles in just nine days. “Swims are occurring more often,” said study author Nicholas Pilfold, a postdoctoral fellow at San Diego Zoo Global, “and moving farther from shore in the summer.”
This increase in swimming is due to reduced ice, which, scientists say, is due to climate change. When biologist and polar bear expert Andrew Derocher used to visit the Beaufort Sea above Canada’s Northwest Territories, ice rafts were common, and the bears spent most of their lives floating on the rafts and hunting seals, their preferred prey. Now the environment is more like Hudson Bay, Derocher says, and these furry Coca-Cola mascots are faced with a choice. They can ditch their rapidly melting homes for land, where fresh prey is scarce and many bears resort to picking at the rotting remains of whales or walrus, snagging the occasional bird egg or even eating grass. Or they can swim after their natural habitat, the next measly block of ice, an adventure that is “energetically expensive.” The strategy works for now, but eventually, global warming experts say, it won’t, as the ice breaks up even more.
A recent NASA study noted that thinning glaciers have been offset by heavy snowfalls, which has led to more ice in places like Antarctica. Whether or not that ice will also accumulate in places like the Beaufort Sea, though, isn’t clear. And tracking polar bears poses problems, some as goofy as trying to keep the GPS tracking collars on the skinnier bears, others as tragic as data being lost every time a bear dips into the water and doesn’t resurface. Efforts to study polar bears on the Canadian side of the Beaufort Sea have lagged, says Derocher, after local communities objected to further collaring. “Scientifically, I think we should be there,” he says, but the cultural and geopolitical barrier remains, meaning Canadians have to rely on Alaskan researchers instead.
Scientists know that polar bears are dealing not only with longer distances but also with more treacherous waters. Without ice rafts, there’s more space for waves to form. Typically, mother bears will go out of their way to keep their offspring from swimming, but that’s less of an option as ice continues to melt. “The peril is that if you’re a small cub without much body reserves, you’re not that buoyant,” Derocher explains. And for older bears? “It’s a lot different to tell a well-trained swimmer to do 20 lengths in a pool. Now try that with your elderly grandmother.”