Polar bears can swim for days, covering hundreds of miles of open water at a time, accoding to new GPS tracking data. These long swims appear to be a response to declining summer sea ice in the Arctic.
Sea ice provides crucial habitat for polar bears, which hunt for prey, primarily seals, from it. But recent years of warming temperatures have brought significant declines in sea-ice cover over Arctic waters. Scientists worry this decline is causing bear cubs to drown on long swims and creating problems for walruses that also depend on the sea ice.
Over the course of six years, GPS collars to tracked 50 long-distance swims made by 20 adult female bears, some of which had cubs with them. The swims that were documented lasted from 17 hours to nearly 10 days and covered between 33 and 427 miles (54 and 687 kilometers) in the southern Beaufort Sea.
The frequency of the swims appeared to increase over the course of the study, which ended in 2009. Of the 20 adult female bears to make the long-distance swims, 12 had cubs when they were outfitted with a collar. Of the 10 recaptured a year later, six still had cubs with them. Learn more here.