Polar bears have shifted to a diet of more land-based food in response to climate change and melting sea ice in the Arctic, new research finds. The results suggest that polar bears, at least in the western Hudson Bay area, may be slightly more flexible in the face of climate change than previously thought.
"We found they were eating more of what is available on the land," including snow geese, eggs and caribou, said study co-author Linda Gormezano, a vertebrate biologist at the American Museum of Natural History in New York.
Still, it's not clear that this foraging strategy can offset the negative impacts of climate change, with one scientist saying it is unlikely to make a difference for polar bear numbers.
Polar bears rely heavily on seals and other marine mammals for food. The white bears wait at gaps in the sea ice for their blubbery prey to surface, then pounce, according to the nonprofit conservation organization Polar Bears International.
When the sea ice melts, polar bears come ashore and eat a variety of foods, including mushrooms and berries, in addition to snow geese and other animals. [See Images of Polar Bears Feasting on Prey]
But global warming has reduced Arctic sea ice extent, especially in the late spring when polar bears fatten up on seal pups before moving to land. As a result, the U.S. Endangered Species Act has listed the majestic beasts as a threatened species, and the International Union for Conservation of Nature lists them as vulnerable.
In a 2013 study in the journal Polar Ecology, Gormezano and her colleagues took video of western Hudson Bay polar bears and caught them chasing, killing and eating snow geese.
Then, in a second 2013 study in the journal Ecology and Evolution, the researchers compared polar bear scat from modern times with an analysis conducted from 1968 to 1969, when climate change hadn't dramatically affected the habitat.
Back then, the scat contained fewer snow geese remnants compared to modern times, and the modern scat contained caribou and goose eggs not found in earlier specimens, suggesting the polar bear diet had changed.