As Arctic sea ice declines as a result of climate change, polar bears -- which traverse sea ice in search of seals, their primary prey -- are in some parts of their range being forced to forage for food on land.
Polar bears have long been known to eat the likes of berries, kelp and birds' eggs to supplement their diet, generally while waiting for sea ice to form in fall or after coming ashore when the ice breaks up in late spring. Now, there's evidence such behavior is becoming more common. Indeed, some bears may be going to extra lengths to procure the precious calories that a nest of bird eggs may provide: In 2010, scientists reported polar bears climbing rock cliff ledges to eat murre eggs in Canada; and the following year, tourists in the Russian Arctic saw a bear clambering down a cliff populated by guillemots, presumably with the same goal in mind.
However, although there has been some speculation that these alternative food sources may mitigate against the impacts of sea ice loss, most researchers have been far more cautious in reaching such conclusions; and a pair of new papers suggests that such caution is merited.
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In one, published in the journal Global Change Biology , scientists worked with local Inuit to study the interaction between polar bears and common eiders on Baffin Island. "Inuit are very in tune to this type of environmental change because they hunt eiders for meat, and collect eggs and down from their nests," said study lead author Cody Dey of the Great Lakes Institute for Environmental Research at the University of Windsor in Ontario. However, that traditional hunting may be at risk, Dey and colleagues wrote, because "our research suggests that eiders might nest in different locations to avoid polar bear predation, which could make it harder for local people to harvest eiders."
Dey and his co-authors further found that polar bear predation of eider nests is likely to increase over the next 25 years, and that a large percentage of the nests will be consumed by polar bears in years with earlier sea ice melt.
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