For threatened polar bears, the climate change diet is a losing proposition

For polar bears, the climate change diet is a losing proposition, according to a new study.

As Arctic sea ice shrinks due to climate change, many polar bears are forced to shift their diets to land during parts of the summer. A study looking at Hudson Bay Polar Bears tries to find out if they can keep up their roll poly figure, which is what it takes and found that a huge number of them drop the pounds no matter what they do they to try to raise beef. weight.

Some bears get a lot of food — berries, eggs, seabirds and even caribou antlers — but it takes so much effort, so many calories are burned trying to eat, that they lose weight and expend more energy than they take in. in, according to a study in Tuesday’s journal Nature Communications.

Other bears go into a semi-winter phase, don’t do much, but they also lose the pounds, so it doesn’t work either way, said study author Anthony Pagano, a U.S. Geological Survey wildlife biologist. United.

​​​​Researchers found that 19 of the 20 bears studied lost an average of 47 pounds (21 kilograms) over three weeks after being studied in research that monitored their calorie intake, using energy and respiration in the wild. That’s losing about 7% of their body mass on average in just 21 days, according to the study.

Polar bears try to keep their weight up during the summer after spring when they feast and fatten horribly. In the Hudson Bay area where researchers studied, polar bears have been without sea ice on land for three weeks longer than in the 1980s, Pagano said.

Polar bears usually eat high-fat seals based on sea ice, near where the seals are. Hunting is especially good in the spring when seal pups are weaning and easy pickings for polar bears before they learn to swim off the ice, Pagano said.

Last September, when Arctic sea ice hit its annual low in September, there was about 1 million square miles (2.6 million square kilometers) less sea ice than the same time in 1979, according to the National Snow and Ice Data Center. The United States Fish and Wildlife Service lists polar bears as a threatened species “due to the loss of their sea ice habitat”.

“This paper clearly shows that polar bears cannot adapt to the pace of change in the Arctic and that the bears are using everything they already have to stay alive,” said University of Alberta biologist Andrew Derocher, who was not part of the research. , but called it extremely elegant and insightful.

“This is a concern because of course it raises the question of when the individual bears will run out of energy,” Derocher said. While research shows that some of the bears will be fine, “other bears were basically on the edge where they could starve to death.”

Overall, it shows that polar bears are unlikely to be able to adapt to living on land, Derocher said.

When polar bears have sea ice, they feast on seals. Not just the seals, but their fat. About 70% of a polar bear’s diet while on ice is fat, said study co-author Karyn Rode, a USGS wildlife biologist.

“They have the highest fat content diet of any species in the world,” said Rode.

University of Washington biologist Kristin Laidre, who was not part of the study team, said, “Polar bears need sea ice to feed on – this is how they get access to their primary prey (ice seals). They evolved from grizzly bears to survive on a high fat marine diet and have an amazing ability to eat and digest lipids.”

To find out what happens on the ground, a joint team of US-Canadian biologists attached video to the bears’ collars, fed the bears a type of water that allowed their calorie intake and expenditure to be tracked and returned them to the wild to look at it.

The bears were very popular for food. All but one of them ate grass and kelp, 10 of them feasted on berries, eight of them feasted on bird carcasses, a third of them chewed on bones and four of them ate caribou antlers, with bird, rodent and rabbit eggs as well. eaten.

But the bears had to spend a lot of energy in their efforts to fill their bellies. On average they traveled 58 miles (93 kilometers) to put one young female in 233 miles (375 miles) in three weeks.

“This paper adds to a growing body of evidence that polar bears cannot sustain themselves on land as we continue to lose sea ice due to climate warming,” said Laidre, who chairs polar bear specialist group for the International Union for Conservation of Nature, the international organization that monitors the status of endangered species.


Associated Press journalist Stephanie Windeler from London assisted.


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