As Arctic sea ice keeps on melting, researchers noticed that polar bears are increasingly forced to swim for long and dangerous distances just to find food.
According to a study featured in the journal Ecography, polar bears have a concerning migratory response to climate change. The team monitored 100 bears in Hudson Bay and the Beaufort Sea between 2007 and 2012.
Results showed that the number of bears who perform life-threatening marathon swims has increased significantly over the past ten years.
In 2012, almost 70 percent of bears swam at least 49 km, accounting for a 25 percent increase in the number of bears who had to travel this long in 2004.
One of the more extreme cases occurred in 2000, and it features a female bear that went on record swimming almost 700 km in just nine days.
While her cub died on the journey, she made it thanks to an ice flow that could hold her weight and give her a place to rest. She also lost 20 percent of her body weight during this time.
But this has become an increasingly common phenomenon. According to study co-author, Andrew Derocher, a Canadian biologist, researchers have notice “some very unusual swimming events in the polar bears that they were following.”
This is not to say that polar bears are not capable swimmers, but they rarely prefer the open ocean as their permanent habitat. What’s more, bears at younger ages are not suited for long-distance swims, especially with the threat of hypothermia.
In the first couple of years of life, swimming for too long causes the young cubs – entirely dependent on its mother – to cool down, run out of energy, and simply exhaust themselves. This increases their risk of dying.
But at the same time, bears at the other end of the age spectrum are also at risk due to their poor health. Derocher said polar bears are designed “to walk on sea ice, not swim in the oceans.”
They’re not like seals or walruses that are well designed for swimming permanently. This strain on polar bears has driven the Beaufort population to a large decline; estimations show losses over 50 percent in the last decade.
It’s believed that the melting sea ice is the culprit for their dire situation. And their loss of habitat and food supply also prompts more bear-human run-ins. As Derocher puts it, “the problem for the bears is the rules are changing, and they’re changing very fast.”
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