In May 2008 the Polar Bear was listed as a threatened species under the Endangered Species Act in the U.S. The most recognised threat to Polar Bears is ecological change as a result of global warming. Polar Bears live across Northern Russia, Alaska, Canada, Greenland and Norway, numbering around 22,000 bears. They depend on sea-ice to hunt and breed and spend much of their time at the edge of the ice pack, where they are most likely to find food. As sea ice recedes further and further from the coastline, Polar Bears are forced to swim farther in order to reach vital food sources, leaving them exhausted and vulnerable. Researchers at the U.S. Geological Survey in Alaska recently tracked a female bear who swam 685km for nine days in order to reach the ice floe. Read more: http://www.miamiherald.com/2011/02/02/2046963/polar-bears-long-swim-illustrates.html#ixzz1DZbFcE3I The following video from Ignatius G. Rigor at the University of Washington demonstrates the extent of ice loss in the Arctic: http://www.polarbearsinternational.org/polar-bears/maps-and-trackers/sea-ice-loss