A mother polar bear swam for nine days straight, covering 426 miles and losing her one-year-old female cub on the journey as she searched for ice in the Beaufort Sea, north of Alaska.
This was just one of the findings of a recent study that tracked the movement of female polar bears in the southern Beaufort and Chukchi Seas off the northern coast of Alaska. The study followed 68 female polar bears using GPS collars and satellite imagery between 2004 and 2009. Researchers identified 50 long-distance swims during the six year period involving 20 polar bears. Swims ranged in distance up to 426 miles and lasted up to 12.7 days.
Because their ice habitat is shrinking due to climate change, polar bears are continually being forced to find food by swimming vast distances to find sea ice. The long swims are strenuous on the bears and often fatal for their cubs. Eleven of the polar bears that were tracked during the study who swam long distances had young cubs at the time of collar deployment; when researchers saw them again, five of those mother bears had lost their cubs.
The study was authored by Anthony Pagano, a U.S. Geological Survey wildlife biologist, Geoff York, a polar bear expert with the World Wildlife Fund and zoologist George Durner. Results of the study were presented at the International Bear Association Conference in Ottawa, Canada on July 19.
“Climate change is pulling the sea ice out from under polar bears’ feet, forcing them to swim longer and longer distances to find food and habitat,” said York.
"This dependency on sea ice potentially makes polar bears one of the most at-risk large mammals to climate change," says Durner.