Polar Bears More Vulnerable to Starvation than Previously Thought

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. A new study now shows that polar bears more prone to starvation than they were previously believed to be.

A group of researchers from the U.S. Geological Survey and other institutions weighed and monitored the blood of track nine female polar bears near the Beaufort Sea last April. The researchers continued to monitor the polar bears over a span of 10 days using radio collars. According to the study published on Thursday in the journal Science, the dwindling ice caps are taking its toll on the polar bears.

As their habitats shrink, polar bears are having to swim further away from land in their search for food. Polar bears mostly prey on ringed seals, and the pups are easy prey in the spring. However, the scientists found that the polar bears burned more energy than they were able to take in from their prey.

The research was conducted during a time when the polar bears were supposed to be putting on weight so that they could later have cubs, feed those cubs, and survive the winter. Polar bears hunt from the ice, often waiting for seals to pop out of holes. Other times, the polar bears will swim after the seals. With less ice, polar bears are having to travel more and swim more often, which results in the bears using more energy.

The data collected showed that many of the polar bears ran on an energy deficit, and the metabolic rates, which is the amount of energy their bodies need to function, averaged more than 50 percent higher than previous studies predicted. Five of the bears lost weight and four of them lost 2.9 to 5.5 pounds a day. One bear lost 51 pounds in just nine days.

For now, the findings of the study demonstrates that polar bears require more food to survive than previously previously predicted, and the failure to catch prey will result in rapid, significant weight loss. “This is kind of the initial step, and the next step will be to see how energy expenditure is changing seasonally and how changing ice conditions are ultimately impacting the energy expenditure of these bears,” lead author of the study, research wildlife biologist Anthony Pagano said.  Further research will be needed to fully understand the impact of what is happening to the polar bears.