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Thursday, December 29, 2011

Climate Change, Polar Bears and Cannibalism

Polar Bear at Indianapolis Zoo
 There has been quite a bit of talk recently about the polar bear and its struggle to survive in a rapidly changing Arctic Circle.  We now know that the melting polar ice caps are making it harder for the polar bear to successfully hunt for food so as a result, their territory is shifting more into overlap with the Grizzly Bear.  Hybrid bears that are a result of interbreeding between the two species are becoming more common.  As this process continues, many researchers speculate that the pure-bred polar bear may become a thing of the past.

As if this threat wasn't significant enough, there could be a new wrinkle to the polar bear struggle.  We know that historically summer and fall are a tough time for polar bears as some of the polar ice melts and makes it harder for bears to catch seals to eat.  During the roughest times, it has been documenting that occasionally an adult polar bear will resort to cannibalism to survive.  Usually this is limited to large males killing young cubs.  It is theorized that this practice serves a dual purpose.  The killing obviously provide food allowing the adult male to survive but by killing the other bears, it reduces the competition for the preferred food source - seals.

While cannibalism has been documented in the past, it was considered to be an uncommon practice.  Recent eyewitness accounts indicate a potential significant increase in polar bear cannibalism.  On three different occasions this year, researchers and nature photographers documented cases of polar bear cannibalism.  While these instances were during summer where it might seem logical due to poor food supply, in each case, the adult bear appeared to be fit, healthy and well-fed.  This fact could suggest that polar bear behavior is changing, possibly in response to the stress of lower preferred food supply caused by climate change.

Only time will tell if this is a shift in behavior or just one that we are now observing and documenting more often.  Either way, it looks like the polar bears' epic struggles will continue into the future.

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