Polar bears forced off melting sea ice will not find enough food to replace their current diet of fat-laden seals, researchers say in a conclusion that contradicts studies indicating bears may be benefiting from bird eggs, berries, and other land food sources. Karyn Rode, a USGS wildlife biologist and lead author of the paper published yesterday in Frontiers in Ecology and the Environment, aimed her study at research documenting bears feeding on land, which could increase their chance for survival as receding summer sea ice prevents seal hunting. But not everyone agrees with her findings. Robert Rockwell, a population biologist and ecologist, has conducted research at western Hudson Bay for 47 years. "These bears are changing their behavior," he said. "It's got to benefit them some. If you eat the eggs from 40 nests, then you just consumed the same number of calories as if you ate a seal."
Land food such as berries can be abundant for polar bears but low quality, Rode counters, adding that eggs from ground nests are higher quality but limited. Polar bears on land also face competition for food from Arctic foxes, birds, and grizzly bears. "This paper establishes in no uncertain terms that polar bears are very unlikely to be able to make a living on land, and that if we don't save the sea ice, polar bears will indeed be gone," said co-author Steven Amstrup. Adds Rodes, "In western Hudson Bay, where more high-quality terrestrial food (birds, bird eggs, and caribou) may be more readily available than in most other Arctic landscapes, survival rates and population size have declined with increasing time spent on land despite terrestrial foraging."