Seals swim in a cold blue abyss. White paws paddle through the icy water, giving chase. Finally, morsels of frozen, skinned seal float into view as the hunter gnaws down on her meal.
It’s the first glimpse of life on Arctic sea ice through the eyes of a polar bear.
Footage released earlier this month by the U.S. Geological Survey has proved a technological breakthrough, says Todd Atwood, a biologist who leads the USGS Polar Bear Research Program. But it took a while to happen.
Harsh Arctic weather and freezing temperatures in 2013 had thwarted previous attempts at collecting video from a wild polar bear’s perspective, draining camera batteries and icing up lenses as the bears moved in and out of the water.
But with the help of Mehdi Bakhtiari, one of the engineers who helped develop National Geographic’s Crittercams, Atwood and University of California, Santa Cruz doctoral student Anthony Pagano were able to attach specialized, durable collar cameras to four adult female polar bears in northern Alaska’s Prudhoe Bay this April.
The collars, which remained on the bears for between eight and ten days, collected an estimated 160 hours of footage. And biologists have only just begun to dissect the film.
“It was like a kid unwrapping a Christmas present,” Atwood said of watching the videos for the first time. “Just total excitement.”
Yet the footage has much larger implications than just an up-close-and-personal view of the bears. Pagano is hoping to use the film to better understand polar bears’ changes in body motion—also known as energetic rates—in response to declining sea ice in the southern Beaufort Sea.
Measuring Motion in the Ocean
In addition to sporting a weather-resistant video camera, each collar comes equipped with a sort of fitness tracker, known as an accelerometer. The device measures changes in body motion, recording movement in three dimensions and at very high frequencies. It can tell when a bear is resting, walking, swimming, or hunting seals. And while the cameras stay on the bears for just eight to ten days, the accelerometer will record data for up to a year.
“That’s really where the camera collars came in,” explained Pagano. “It allows us to calibrate these accelerometers with the video information of the wild bear’s [movement].”
In other words, researchers can match up the behavioral data from the camera footage with the movement readings from the accelerometers to determine which activities give off particular frequencies. And they can extrapolate that data to cover the entire year without having to retrieve more video.
“We can start to understand how bears are behaving differently in the summer when sea ice is receding to the north, versus in the winter when sea ice is fairly similar to what it’s been historically,” said Pagano.
One of Pagano’s top goals is to examine how often polar bears are catching seals—and how that might be changing. When sea ice is hundreds and hundreds of miles offshore, are bears still actively hunting and catching seals? Or are they conserving their energy by waiting for seals to return to shallow water? Pagano aims to find out.
While there has been significant research looking at polar bear population ecology and conservation, less has been published on their behavior.
Polar bears are typically viewed as ambush predators, meaning they don’t spend a lot of time chasing prey animals. So when Atwood and his team sat down to pore over the footage, they were surprised to see one polar bear follow a seal through its hole, diving and resurfacing multiple times.
Another unexpected scene showed a polar bear repeatedly dunking a frozen piece of seal in the sea, like a person might dunk a cookie in milk.
“We’re not sure what [that] means at this point,” said Atwood. “It looks like it could have been playing with the food, or it could [have been] dunking the food to thaw it out and make it a little bit easier to eat.”
Over the past 15 years, scientists have witnessed increased ice fragmentation and reduced summer ice coverage. The upshot has been that polar bears are coming to shore more often than they used to and are spending more time swimming in the summer.
“All these things might affect their energetics, and ultimately [their] population dynamics,” explained Atwood.
Researchers plan on returning to the field next spring to collar more bears and gain insights into their enigmatic lives in one of the world’s least forgiving environments.
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