Rabu, 02 Mei 2012

GPS trackers reveal polar bears can swim non-stop for up to 10 days

GPS trackers reveal polar bears can swim non-stop for up to 10 days

By Eddie Wrenn

PUBLISHED: 10:13 EST, 2 May 2012 | UPDATED: 10:24 EST, 2 May 2012


Polar bears are capable of swimming vast distances, with one endurance swimmer travelling 220 miles in a non-stop marathon over 10 days.

The bears were tracked as part of a study, published in the Canadian Journal of Zoology, which tracked 52 female polar bears in the southern Beaufort Sea off Alaska.

Between 2004 and 2009, a period of extreme summer-ice retreat, about a third of those bears made swims exceeding 30 miles in distance - and many others swam at least 90 miles or more.

English Channel? No problem: Polar bears in the study were seen swimming distances of 90 miles without any problems - and some bears went a lot further

English Channel? No problem: Polar bears in the study were seen swimming distances of 90 miles without any problems - and some bears went a lot further

A total of 50 bears recorded ultra-marathon swims - an average of 96 miles (155 km) each.

But king of the swimmers was one bear, who was able to swim nearly 220 miles (354 km). The duration of the long-distance swims lasted from most of a day to nearly 10 days.

The bears' movements were tracked using GPS collars. All the animals in the study were females because male polar bear necks are too thick for GPS-equipped collars.

Many of the polar bears in the study had young cubs with them, and it appears that at least some of the cubs - which were not collared - might have been able to keep up with their mothers in the water, USGS officials said.

The scientists were able to track 10 of the studied bears within a year of collaring and found that six still had their cubs.

Anthony Pagano, a USGS scientist and lead author of the study, said: 'These observations suggest that some cubs are also capable of swimming long distances.

'For the other four females with cubs, we don't know if they lost their cubs before, during, or at some point after their long swims.'

While the demonstrated long-distance swimming ability is likely a good thing for polar bears, scientists were concerned about the animals expending too much energy in their efforts to travel across open water, the USGS statement said.

Researcher Oakley said that the bears would not have needed such a long swim in the past, as sea ice would have provided a float for them

Researcher Oakley said that the bears would not have needed such a long swim in the past, as sea ice would have provided a float for them

Karen Oakley, a supervising biologist at the USGS Alaska Science Center, said the study sample was too small to draw conclusions about the fate of the entire polar bear population, which in 2008 was designated as threatened and granted Endangered Species Act protections because of rapid warming in their Arctic habitat.

She said: 'It's just very interesting that in fact they can swim long distances, and cubs can swim long distances.

'Do all the cubs that attempt to swim these long distances survive? We don't know.'

The researchers said they did not know whether such long-distance swimming is a new behavior.

The technology to track long-distance bear swims accurately was not available in the past, Oakley told Reuters.

She said: 'The GPS technology, which is relatively new, is what allowed us to really do the actual in-depth analysis of this.'

But polar bears probably lacked the opportunity or need to make such long swims in tha t part of the Arctic in the past.

In past decades, polar bears were always able to rest on available floating summer sea ice, she said. 

She said: 'These long distances of open water didn't use to exist in the southern Beaufort Sea.

'Did they swim these really long distances? Well, they didn't have to because they weren't there.'

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