Thursday, September 17, 2015

Some Polar Bears Will Survive Global Warming

credit: R. Rockwell
Condemned to mass starvation by mid-century due to global warming disrupting their seal hunts ,according to recent research, polar bears may be able to find a way out of the man-made dilemma. Researchers from the American Museum of Natural History say that polar bears near Hudson Bay are adapting to land-based prey to replace seal meat they usually require. Ice-free seas will last two months longer than those of the 1980s requiring the bears to change their hunting behavior. Scats and first-hand observations show subadult polar bears, family groups, and some mature adult males are eating plants and animals during the longer ice-free summers.  Calorie calculations show that there is enough calories in snow geese, their eggs, and caribou to feed polar bears stuck on the coast. Bears in Manitoba have been seen ambushing caribou with the same techniques they use to hunt seals. Since adult caribou are about the same size as an adult seal, bears would only need to hunt them as often as they usually would hunt seals.

The exact energetic cost of polar bear hunting land prey is not yet known however; nowhere in the scientific literature is it documented that polar bears are shifting to a terrestrial diet in general. Caribou herds continue to forage near the coast of Western Hudson Bay, and are apparently unaware of the bears changing hunting behavior. Snow geese eggs are a good source of protein and require little effort to take from their ground nest. Snow geese are know to endure egg predation by polar bears, but in a study published in April, scientists observed fewer than thirty bears within populations of 900 to 2500 individuals consuming terrestrial foods such as eggs. Further, starving polar bears with a higher energy requirement will have to compete with other predators such as brown bears that are already adapted to surviving on scarce Arctic food sources. So some polar bears will survive the heating of the Arctic, if they live in an abundant ecosystem and are opportunistic. Many more will not. The chief scientist for Polar Bear International agrees with the scientific consensus that without greenhouse gas mitigation the polar bear will be extinct by the end of the century.