By Daily Mail Reporter
Polar bear cubs forced to swim long distances with their mothers as their icy Arctic habitat melts have a higher mortality rate than cubs that didn't have to swim as far, according to a study.
Polar bears hunt, feed and give birth on ice or on land, and are not naturally aquatic creatures.
Previous reports have noted individual animals swimming hundreds of miles to reach ice platforms or land, but this is one of the first to show these swims pose a greater risk to polar bear young.
Polar bear cubs forced to swim long distances with their mothers as their icy Arctic habitat melts have a higher mortality rate than cubs that didn't have to swim as far
Researcher Geoff York, of World Wildlife Fund, said: 'Climate change is pulling the sea ice out from under polar bears' feet, forcing some to swim longer distances to find food and habitat.'
Mr York said this was the first time these long swims had been quantitatively measured, filling a gap in the historical background on this iconic Arctic species.
To gather data, researchers used satellites and tracked 68 polar bear females equipped with GPS collars over six years, from 2004 until 2009, to find occasions when these bears swam more than 30miles at a time.
There were 50 long-distance swims over those six years, involving 20 polar bears, ranging in distance up to 426miles and in duration up to 12.7days, they said.
At the time the collars were put on, 11 of the polar bears that swam long distances had young cubs - five of those polar bear mothers lost their cubs during the swim, representing a 45 per cent mortality rate, the study found.
Cubs that didn't have to swim long distances with their mothers had an 18 per cent mortality rate, the scientists said.
Mr York said: 'They're a lot like us. They can't close off their nasal passages in rough waters.
'So for old bears or young bears alike, if they're out in open water and a storm hits, they're going to have a tough time surviving.'
Under surveillance: Researchers used satellites and tracked 68 polar bear females equipped with GPS collars over six years, from 2004 until 2009
Two factors make it even harder for polar bear cubs to weather long periods in Arctic waters.
Steve Amstrup, a former scientist at the U.S. Geological Survey and now chief scientist at Polar Bears International, said: 'Young bears don't have very much fat and therefore they aren't very well insulated and cannot cope with being in cold water for very long.'
Because they are leaner than their parents, Dr Amstrup said, 'they probably aren't as buoyant so in rough water they'll have more difficulty keeping their heads above water.'
The Bush administration listed polar bears as threatened under the Endangered Species Act because of the decrease in their Arctic ice habitat. That decision survived a legal challenge last month, and this month, Canada listed polar bears as a species at risk.
The Arctic is warming faster than lower latitudes due to the accumulation of greenhouse gases in the atmosphere, and the melting of sea ice in summer accelerates the warming effect.
Arctic sea ice extent - the area covered by sea ice - in June was the second lowest in the satellite record since 1979, according to the National Snow and Ice Data Center.
The study is published as a paper which will be presented on Tuesday at the International Bear Association Conference in Ottawa.
source:dailymail
Polar bear cubs forced to swim long distances with their mothers as their icy Arctic habitat melts have a higher mortality rate than cubs that didn't have to swim as far, according to a study.
Polar bears hunt, feed and give birth on ice or on land, and are not naturally aquatic creatures.
Previous reports have noted individual animals swimming hundreds of miles to reach ice platforms or land, but this is one of the first to show these swims pose a greater risk to polar bear young.
Polar bear cubs forced to swim long distances with their mothers as their icy Arctic habitat melts have a higher mortality rate than cubs that didn't have to swim as farResearcher Geoff York, of World Wildlife Fund, said: 'Climate change is pulling the sea ice out from under polar bears' feet, forcing some to swim longer distances to find food and habitat.'
Mr York said this was the first time these long swims had been quantitatively measured, filling a gap in the historical background on this iconic Arctic species.
To gather data, researchers used satellites and tracked 68 polar bear females equipped with GPS collars over six years, from 2004 until 2009, to find occasions when these bears swam more than 30miles at a time.
There were 50 long-distance swims over those six years, involving 20 polar bears, ranging in distance up to 426miles and in duration up to 12.7days, they said.
At the time the collars were put on, 11 of the polar bears that swam long distances had young cubs - five of those polar bear mothers lost their cubs during the swim, representing a 45 per cent mortality rate, the study found.
Cubs that didn't have to swim long distances with their mothers had an 18 per cent mortality rate, the scientists said.
Mr York said: 'They're a lot like us. They can't close off their nasal passages in rough waters.
'So for old bears or young bears alike, if they're out in open water and a storm hits, they're going to have a tough time surviving.'
Under surveillance: Researchers used satellites and tracked 68 polar bear females equipped with GPS collars over six years, from 2004 until 2009Two factors make it even harder for polar bear cubs to weather long periods in Arctic waters.
Steve Amstrup, a former scientist at the U.S. Geological Survey and now chief scientist at Polar Bears International, said: 'Young bears don't have very much fat and therefore they aren't very well insulated and cannot cope with being in cold water for very long.'
Because they are leaner than their parents, Dr Amstrup said, 'they probably aren't as buoyant so in rough water they'll have more difficulty keeping their heads above water.'
The Bush administration listed polar bears as threatened under the Endangered Species Act because of the decrease in their Arctic ice habitat. That decision survived a legal challenge last month, and this month, Canada listed polar bears as a species at risk.
The Arctic is warming faster than lower latitudes due to the accumulation of greenhouse gases in the atmosphere, and the melting of sea ice in summer accelerates the warming effect.
Arctic sea ice extent - the area covered by sea ice - in June was the second lowest in the satellite record since 1979, according to the National Snow and Ice Data Center.
The study is published as a paper which will be presented on Tuesday at the International Bear Association Conference in Ottawa.
source:dailymail
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