Polar bears can survive ice melt by choosing new food sources

Polar bears may survive climate change by switching to alternate food sources like caribou and snow geese when they can't hunt for seals during ice-free periods, a new study has found.
The research is based on new computations incorporating caloric energy from terrestrial food sources and indicates that the bears' extended stays on land may not be as grim as previously suggested.
Researchers found that land-based food sources like caribou, snow geese, and eggs might provide enough calories for bears to avoid starvation.
"Polar bears are opportunists and have been documented consuming various types and combinations of land-based food since the earliest natural history records," said Robert Rockwell, from the American Museum of Natural History.

"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," Rockwell said.
Previous studies have predicted mass polar bear starvation by 2068, when annual ice breakup is expected to separate the bears from their sea-ice hunting grounds for a consecutive 180 days each year - creating ice-free seasons that will last two months longer than those in the 1980s.

However, those estimates assumed no energetic input from land food sources.
The new study computed the energy required to offset any increased starvation and then determined the caloric value of snow geese, their eggs, and caribou that live near the coast of the Western Hudson Bay in US.

Researchers found that there likely are more than enough calories available on land to feed hungry polar bears during the lengthening ice-free seasons.
Although the exact energetic cost for a bear to hunt geese and caribou is uncertain, polar bears in Manitoba have been reported ambushing caribou with the same energetically low-cost techniques they typically use to hunt seals.
The similar size of these two prey species means that bears would need to hunt for caribou only as often as they would usually hunt for seals, the researchers said.
"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 said.

The eggs of snow geese are another food source for bears, and the energetic cost of obtaining eggs in ground nests is exceedingly low, the researchers said.
Scientific consensus holds that the rapidly melting circumpolar ice reserves will increasingly prevent polar bears from hunting the seals on which they currently depend.
Nevertheless, these observations of one population along the Western Hudson Bay show that bears marooned on land might, where the conditions are right, stave off starvation by turning to alternate food sources.
The study was published in the journal PLOS One.