A six-year study has found that polar bears are capable of swimming great distances when foraging for food, an increasingly critical skill as Arctic sea ice declines in summer. Using GPS collars attached to 52 adult females in the southern Beaufort and Chukchi seas from 2004 to 2009, scientists from the U.S. Geological Survey (USGS) found that about a third of the bears — including some with cubs — completed swims greater than 30 miles. Writing in the Canadian Journal of Zoology, the scientists found that in the case of 50 long-distance swims, the bears traveled an average of 96 miles, swimming from one to 10 days; one bear swam 220 miles. While such stamina will become increasingly important for polar bears as a warming climate makes resting on summer sea ice a less available option, the researchers expressed concern that traveling such great distances takes a greater energy toll on the animals. The study sample was too small to draw conclusions about the fate of entire populations, and it is unclear whether such long swims are a new behavior.