August 15, 2005
Polar bear makes huge one-day Arctic swim
By Alister Doyle, Environment Correspondent
OSLO (Reuters) - Scientists have tracked a tagged polar
bear swimming at least 46 miles in just one day -- and maybe up
to 62 miles providing the first conclusive proof the bears can
cover such giant distances in the water.
Bears often roam thousands of miles in a year in search of
prey such as seals and there has often been anecdotal evidence
of lengthy swims, with bears turning up on remote islands or
across wide bays.
However, previously there had been doubts about whether the
bears had walked over ice part of the way or hitched a ride
"What's new this time is that we have data showing how long
the bear was in the water," Jon Aars, a researcher at the
Norwegian Polar Institute, said on Friday.
"This is the first time that such a long swim has been
documented by satellite telemetry for polar bears," the
The female bear, equipped with a satellite tracking device,
entered the water on the east of the Norwegian Arctic
island of Spitsbergen early on July 20, swam northeast and
re-emerged on the island of Edgeoya a day later.
A sensor on the bear's collar sent different signals when
it was in salty sea water compared to on land or on ice.
"This is an astonishing swim," Aars said, saying it showed
that polar bears could in many ways be classified as marine
mammals -- a group including whales and dolphins.
Aars said the bear, dubbed "Skadi" after a Norse goddess of
snow, had probably swum closer to 62 miles since the bear
almost certainly did not swim the 46 miles between the two
points in an exact straight line.
The bear covered the gap in about 24 hours, giving an
average speed roughly the same 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.