Polar Bear Adults can swim but over 400 miles is ridiculous even for a good swimmer !!!!
In arguments over the impacts of climate change, some of the images commonly associated with those clashes have attracted skeptical critiques, perhaps none more so than those of polar bears forced to swim longer distances because their sea ice habitat is melting. Some skeptics point out that polar bears are born swimmers and that the worries of environmentalists are therefore overdone.
Now comes a new study from researchers at the United States Geological Survey and the World Wildlife Fund indicating, after tracking a small sample of bears wearing radio collars, that the swims have indeed grown longer over the last six years. Five of the 11 mothers swimming with cubs lost the cubs along the way, and one bear even swam about 427 miles to reach sea ice.
The study’s conclusions, that bears are swimming longer distances to get to the sea ice they use as a platform to catch seals, were in line with earlier work in the area, but its six-year duration gives it more heft. Scientists put global positioning system collars around the necks of 68 adult females to focus on swims of more than 30 miles.
The full text of the study, being presented at a meeting of the International Bear Association, is not yet available online, but the WWF published its abstract as part of a press release noting the results.
The mean distance of the bears’ swims was about 110 miles, usually from areas of intermittent ice floes to the main area of pack ice. As they swam, they expended more than twice the energy that they do on land or ice. “Despite the ability of polar bears to swim long distances,” the abstract said, “this behavior places them at risk of drowning and imposes greater energy expenditure,” which could affect their ability to reproduce.
The Fish and Wildlife Service’s decision to list the bear as threatened because of the impact of climate change on their habitat was upheld by a federal district judge three weeks ago; more recently, Canada identified the bear as a species at risk.
As my colleague Andy Revkin reported at his Dot Earth blog two years ago, 7 of the 19 subpopulations of polar bears in the Arctic are declining in numbers and only 1 is increasing.