Longest polar bear swim – distance

The longest recorded distance for a swimming session by a polar bear Ursus maritimus is 687 km, accomplished by an adult female during 232 continuous hours (9.67 days) of swimming, through chilling waters of only 2-6°C in the Beaufort Sea, north of Alaska and northern mainland Canada. This epic swim was recorded by a team of researchers from the US Geological Survey, whose findings were published by the scientific journal Polar Biology in January 2011. The polar bear had been fitted with a GPS tracking collar, and had made her record-breaking swim in search of food during the period between her initial capture in late August 2008 and recapture in late October 2008. Moreover, the study also found that after doing so, she then intermittently swam and walked for a further 1,931 km on the sea's ice surface. Tragically, her one-year-old cub accompanying her did not survive the journey, perishing en route, unable to complete such an extensive continuous swimming session.

Polar bears typically swim between land and sea ice floes and thence between ice floes in order to hunt seal prey. However, research has shown that owing to extensive summer melts that have typically occurred since the mid-1990s in the Beaufort Sea, polar bears inhabiting this region have had to swim further and further as the number of available floes upon which to land has dramatically decreased.

The marathon swim of the collared polar bear was so energy-costly that she lost 22 per cent of her total body fat while accomplishing it. In total, the study tracked 68 adult females from 2004 to 2009.

Five of the 11 that had cubs before they began their lengthy swims had lost them by the time that they were observed again on land by the team, representing a 45.5 per cent mortality rate and starkly showing the negative impact of such swims upon cub survival.