Polar Bears Are Swimming Themselves To Death As Sea Ice Melts

Ray Weaver
February 4, 2018

In 2014, researchers began strapping data recording equipment, including a camera, to a total of nine polar bears in south Beaufort Sea, Alaska. They attached Global Positioning System collars equipped with video cameras and released them back to the wild for 11 days to study how they forage.

With previous studies showing recent drops in polar bear numbers, survival rates and body condition, scientists said the new research suggests the species is facing an even worse predicament than was feared.

Over the course of the study, four of the nine seals did not reach that calorie level and lost a combined mass of 20 kilograms (44 pounds), which "reinforced the starvation lifestyle the polar bears have", Pagano said. "This study identifies the mechanisms that are driving those declines by looking at the actual energy needs of polar bears and how often they're able to catch seals", Anthony Pagano of U.S. Geological Survey, now a Ph.D. candidate at University of California, Santa Cruz and first author of the paper, said in a statement Thursday. And every additional mile that a polar bear has to traverse under its own power is that much more food the bear has to eat. A new study shows some polar bears in the Arctic are shedding pounds during the time they are supposed to be beefing up. And the high north where polar bears live has warmed faster than any other region on Earth, resulting in shrinking sea ice and a cascade of other environmental impacts.

"This was at the start of the period from April through July when polar bears catch most of their prey and put on most of the body fat they need to sustain them throughout the year", Pagano said. Even today, in the middle of the bitter cold Arctic winter, satellites show there is about 770,000 square miles less sea ice than the 1981 to 2010 median (That's an area larger than Alaska and California combined).

Our findings reinforce the physiological challenges that polar bears face as sea ice shrinks and becomes increasingly fragmented.

Nothing pulls at the heartstrings quite like a starving polar bear.

"Spring is the pupping season for the seals", said Dr. Bechshoft.

The researchers hypothesize that the bears' lazy hunting style - when it works - allows them to conserve energy, helping them survive through the summer months when food is scarce.

The GPS told them the distances the bears wandered, and the video camera recorded if the bears were successful in killing and eating prey.

"Every piece of evidence shows that polar bears are dependent on sea ice and if we don't change the trajectory of sea ice decline, polar bears will ultimately disappear". At the same time, a number of polar bear populations have been on the decline - for example, dropping by about 40 percent in the Beaufort Sea in the course of a decade.

By comparing the bears' blood samples before and after, they could calculate the amount of carbon dioxide that the animal had produced, and thus its metabolic rate.

Climate change is having dramatic effects on the Arctic sea ice, forcing polar bears to move greater distances and making it harder for them to catch prey. Polar bears hunt from the ice, often waiting for seals to pop out of holes.

So don't give up yet on the powerful polar bear.

Polar bears have been listed as a threatened species in the United States under the Endangered Species Act since May 2008, and the World Wildlife Fund lists polar bears as vulnerable to extinction, which is just one step above endangered. The study reinforces the understanding that polar bears are reliant on a diet of fat-rich seals to survive in the energetically-demanding Arctic.

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