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Cameras mounted on polar bears have captured the fine line between feast and famine that characterizes bear life. In a study published Thursday in the journal Science, researchers found that polar bears burn more calories while hunting than previously believed.

Why it matters: Some populations of bears — including these bears on the Beaufort Sea — are in decline. As the Arctic warms and sea ice melts, bears will have to travel farther each hunting season. This study provides a baseline that will help researchers understand the impacts of climate change on polar bears in the future.

What they found: Polar bears are ambush predators. They hide near holes in the ice, waiting for seals to come up for a breath. Then, they pounce. Researchers had previously thought this method helped bears save energy, but this study shows that may not be the case. In an 11-day period, an unsuccessful bear could lose up to 10% of its body mass, while a successful bear could gain the same amount.

“We certainly didn’t expect to see such dramatic changes in body mass over such a short period of time,” study author and U.S. Geological Survey biologist Anthony Pagano tells Axios.

What they did: Researchers placed GPS collars, cameras, and metabolic trackers on 9 different female polar bears. A few bears were tracked each year, from 2014-2016. The cameras and collars stayed on the bears for an average of 11 days.

Why they did it: There are few studies of bears in their natural habitat. Seminal research was conducted by Ian Sterling decades ago, while he sat on a cliff and watched bears hunt. That, says Pagano, is the foundation that much polar bear behavioral research is based on. The bears that roam the sea ice of the Beaufort Sea are more mysterious. They’re difficult for scientists to study or follow. Since different populations of bears are responding differently to climate change, it’s important to know how their behaviors and metabolic needs vary across regions.

Go deeper

16 mins ago - Politics & Policy

Vaccinations, relief timing dominate Sweet 16 call

Sen. Joe Manchin (D-W.V.) speaks during a news conference in December with a group of bipartisan lawmakers. Photo: Caroline Brehman/CQ-Roll Call, Inc via Getty Images

Vaccine distribution, pandemic data and a cross-party comity dominated today's virtual meeting between White House officials and a bipartisan group of 16 senators, Senator Angus King told Axios.

Why it matters: Given Democrats' razor-thin majority in both chambers of Congress, President Biden will have to rely heavily on this group of centrist lawmakers — dubbed the "Sweet 16" — to pass any substantial legislation.

Progressives pressure Schumer to end filibuster

Senate Majority Leader Chuck Schumer. Photo: Win McNamee / Getty Images

A progressive coalition is pressuring Chuck Schumer on his home turf by running a digital billboard in Times Square urging the new majority leader to end the Senate filibuster.

Why it matters: Schumer is up for re-election in 2o22 and could face a challenger, and he's also spearheading his party's broader effort to hold onto its narrow congressional majorities.

4 hours ago - Health

U.S. surpasses 25 million COVID cases

A mass COVID-19 vaccination site at Dodger Stadium on Jan. 22 in Los Angeles, California. Photo: Mario Tama/Getty Images

The U.S has confirmed more than 25 million coronavirus cases, per Johns Hopkins data updated on Sunday.

The big picture: President Biden has said he expects the country's death toll to exceed 500,000 people by next month, as the rate of deaths due to the virus continues to escalate.

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