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Arctic Polar Bears Find Alternate Food Sources on Land

Sep 04, 2015 02:12 PM EDT
Arctic Polar Bears on Land
Arctic polar bears have found alternate food sources to compensate for not being able to hunt for seals during extended ice-free seasons.
(Photo : AMNH/R. Rockwell)

Polar bears may have found a solution for their difficulties in reaching seals when ice is thin or gone. A recent study suggests that these Arctic bears might turn to caribou and snow geese for food instead, when they can't hunt seals during long ice-free seasons. 

"Polar bears are opportunists and have been documented consuming various types and combinations of land-based food since the earliest natural history records," Robert Rockwell, a research associate in the American Museum of Natural History's Department of Ornithology, said in a news release. "Analysis of polar bear scats and first-hand observations have shown us that subadult polar bears, family groups, and even some adult males are already eating plants and animals during the ice-free period."

Previous studies estimated that by 2068 there would be a mass polar bear starvation as a result of the animals being separated from their sea-ice hunting grounds. This estimates however did not include the possibility of land food source. But Rockwell and Linda Gormezano, also a researcher from the American Museum of Natural History, did.

According to the release, Rockwell and Gormezano first computed the energy required from polar bears to offset any increased starvation. They then determined the caloric value of snow geese, their eggs, and caribou that live near the coast of the Western Hudson Bay. Their findings suggest that hungry polar bears will have plenty of food sources available during lengthening ice-free seasons.

While researchers are unsure exactly how this change in diet will take a toll on the polar bears, there have been reports of polar bears in the Canadian province of Manitoba hunting caribou using the same amount of energy that it normally takes to hunt seals.

The researchers noted that this may be because caribou and seals are similar enough in size that the polar bears would need to hunt for these large North American reindeer only as often as they usually would for seals.

"If caribou herds continue to forage near the coast of Western Hudson Bay when bears come to shore earlier each year, they are likely to become a crucial component of the bears' summertime diet," Rockwell explained.

According to their study, snow geese eggs in ground nests is another food source that would require a low energetic cost. The researchers noted that as long as geese have adequate food sources, they shouldn't experience any significant population effects from polar bear predation. 

Their study was recently published in the journal PLOS ONE. 

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