Wednesday, September 23, 2015
THE EVOLVING DIET OF POLAR BEARS
The wildlife highlight to any Arctic journey is witnessing a majestic polar bear in its natural habitat. Exceptional in the water, these beauties have been observed swimming hundreds of miles from land, likely aided by sheets of ice that serve as frozen rafts. Their iconic white polar coat enables these bears to blend in perfectly with their surroundings and at the top of the Arctic food chain, they are exceptionally well suited for hunting their primary food source; seals.
The plight of polar bears' disappearing habitat has been widely covered in the media, and the thought of these incredible animals becoming extinct is horrific. Yet new research suggests that polar bears might possibly be able to fulfill their dietary needs by turning to different prey. And in fact, they already are.
Linda Gormezano and Robert Rockwell from the American Museum of Natural History (AMNH) have conducted a study in the Western Hudson Bay, where the ice-free season is expected to expand from 120 to 180 days, during which 28-48% of adult bears are projected to starve unless their nutritional needs can be met. Caribou and snow geese are two possible prey alternatives to seals, and Rockwell and Gormezano have obverved polar bears hunting both. Calorically speaking, one bull caribou could fuel a polar bear for 27 days. Smaller food sources lke geese and eggs require more consumption, but the relative lack of effort needed to harvest them tends to offset this. In fact, polar bears seem to be excellent opportunitists from a dietary perspective, and have been known to snack on anything from berries to whale carcasses.
It is unclear what these observations mean for polar bear survival as a whole. Every habitat --Canada, Alska, Norway, Russia-- is unique and populations may or may not be able to adapt in the same way that Gormezano and Rockwell have seen in Western Hudson Bay. However, polar bears have been observed feasting on goose eggs also in Svalbard, and hunting walruses in the Bering Sea. So there is hope. And perhaps, more humans can also find inspiration to adapt and change their daily behavior to slow climate change, as our collective survival clearly rests on all of our ability to do so.
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