a group including whales and dolphins. Aars said the bear, dubbed "Skadi" after a Norse goddess of snow, had probably swum closer to 100 km (62 miles) since the bear almost certainly did not swim the 74 km (46 miles) between the two points in an exact straight line. The bear covered the gap in about 24 hours, giving an average speed of 3-4 kmh -- about as fast as a person walking. The swim probably meant that two cubs, with Skadi when the bear was marked in the spring, had died earlier in the summer. Mortality rates among polar bear cubs are high. "We don't think cubs could swim that far -- they lose heat much faster than adults," Aars said. Cubs usually stay with their mother for about 2.5 years. The WWF environmental group said cubs were most at risk in a warming Arctic which could destroy cubs' dens. "If sea ice retreats from denning areas it will first become a problem for females with small cubs," said Tonje Folkestad of the WWF. An eight-nation report by 250 experts last year said that the Arctic was warming twice as fast as the rest of the globe and said that a buildup of heat-trapping gases from factories, power plants and cars was largely to blame. It said global warming could make the Arctic Ocean ice-free by the end of the century, threatening to wipe out species such as polar bears. Researchers say that the Arctic is warming faster than the rest of the globe because darker ground and sea water, once exposed, soak up much more heat than reflective ice and snow. --SP 2329 Local Time 2029 GMT
