Polar Bears Struggling to Catch Enough Seals to Meet Energy Demands

Jo Lloyd
February 2, 2018

"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.

"You're talking a pretty unbelievable amount of mass to lose", said U.S. Geological Survey wildlife biologist Anthony Pagano, lead author of a new study in Thursday's journal Science.

While those Arctic ocean bears need ice in order to hunt for food during the spring, global warming is dwindling the blanket of ice across the locale.

Collars attached to the bears documented the animals' location and activity levels over a period of eight to 10 days, while metabolic tracers tracked how much energy the bears expended.

On average, the bears needed almost 12,325 kilocalories per day - 1.6 times more energy than previously thought. Measurements showed those animals lost 10 percent or more of their body mass.

"We were surprised to see such big changes in body masses, at a time when they should be putting on bulk to sustain them during the year".

This is where there's still a lot of work to be done, the WWF 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".

Millions have seen the heart-wrenching video of a polar bear clinging to life, its white hair limply covering its thin, bony frame.

Though polar bears are known to live a "feast or famine" lifestyle, in which their weight fluctuates considerably, the creatures should have been gaining weight during the period studied, rather than losing it.

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. For more than a decade, San Diego Zoo Global's researchers and its US and Canadian partners have focused on contributing to science-based conservation strategies, to preserve and understand wild populations of polar bears. The bears, therefore, are ending up burning more energy during the summer as they are fasting until the ice returns in the fall.

Every year in the Beaufort Sea, the sea ice begins to retreat north in July.

For now, the study demonstrates that bears' energy demands are likely higher than expected-meaning they require more food to survive than previously thought-and that failure to catch seals can result in rapid, significant weight loss.

"That [number] tells us a lot about modelling into the future what's going to happen with the bears". The recorded data-informed that, polar bears have a higher metabolism capacity.

"They're far more successful doing this than any other method of hunting", Pagano said.

In the long run, climate change "will result in smaller bears that produce fewer cubs and that have lower survival rates", Blaine Griffen, a Brigham Young University biology professor who wasn't part of the study said in an email.

Adult female polar bear part of a recent study shown wearing a Global Positioning System video-camera collar on the sea ice of the Beaufort Sea.

"We found that polar bears actually have much higher energy demands than predicted".

The research could help explain some of the population declines scientists have observed in the Beaufort Sea region over the last decade or so.

Polar bears hunt from the ice.

According to the World Wildlife Fund, polar bears spend more than 50% of their time hunting and are successfulless than 2% of that time.

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