Obese Polar Bears of the Beaufort Sea

There is one population of polar bears that have an advantage that is theirs alone. Native people that harvest bowhead whales along the Beaufort sea provide remains for the bears to feast on. Polar Bears International is a conservation group that exists to protect the polar bear. This is their description:

in the Beaufort Sea, dozens of polar bears each year have developed a habit of gathering at the butchering sites of bowhead whales (Balaena mysticetus) that are killed by local Native people. The value of this alternate food is apparently great, as nearly every bear seen near whale carcasses in autumn is obese.

Torsten Bentzen is a graduate student at the University of Alaska Fairbanks. He was able to determine how much the bowhead whale contributed to the polar bear diet.

Using a technique called stable isotope analysis, Bentzen determines the relative percentages of whale and seal in the bears’ diet. If polar bears were feeding almost exclusively on seals, as most scientists expected, Bentzen’s blood analyses would have shown strong stable-isotope signatures for ringed and bearded seals and little if any whale.

What Bentzen saw was surprising. His preliminary results showed that bowhead whales may make up more than 10 percent of a Beaufort Sea polar bear’s diet. Biologists knew bears fed on the occasional bowhead carcass, but assumed the whales were an insignificant portion of their diet. Bentzen wondered if there could be enough whale carcasses to account for what his analyses was telling him.

"There are probably over 1,500 polar bears in the Beaufort Sea," said Bentzen, "so I estimated how many whales it takes to make up 10 percent of the diet of 1,500 polar bears and came up with less than 10 whales–definitely a doable number of whales to be available to polar bears" in that region. Source.

Bowhead whales are plankton eaters so the meat they supply is at the bottom of the food chain. This helps the polar bear avoid toxic build up compared to eating seals.

By hunting the Bowhead whale the Native people of Alaska provide an important source of food for the polar bear. With the help man the polar bears of Alaska are a plump lot.

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