Long-Distance Swims Are Increasing Mortality of Polar Bear Cubs

Rapid sea ice loss in the Arctic is forcing polar bears to swim ever-longer distances and is leading to greater mortality of their cubs, according to a new study. From 2004 to 2009, scientists from the U.S. Geological Survey and other institutions placed 68 GPS collars on polar bears in the southern Beaufort and Chukchi seas. During that period, 20 polar bears were forced to embark on long swims that averaged 104 miles and four days, with one bear swimming as far as 426 miles. Eleven of the 20 bears that made long-distance swims had young cubs, and the researchers found that five of those bears lost cubs during the lengthy swims — a 45 percent mortality rate. The study is the first to comprehensively document what many scientists had long suspected — that the steady loss of Arctic sea ice is shrinking the bears’ sea ice feeding platforms and forcing them to make long swims that drain their energy and increase cub mortality. “Climate change is pulling the sea ice out from polar bears’ feet,” said Geoff York, a co-author of the study and a polar bear expert with the conservation group, WWF. The paper will be presented tomorrow at the International Bear Association Conference in Ottawa, Canada.