You may have seen a recent viral video that showed a polar bear in the throes of suffering. The beast seems to be in the final hours of its life—its legs wobbling under its weight, its pupils widened in pain, its yellow fur hanging loosely off its bones—as it gnaws on trash, lays down, and shuts its eyes.
Paul Nicklen, the conservationist who shot the video, said he hoped the haggard bear would reveal the true face of climate change. “When scientists say bears are going extinct, I want people to realize what it looks like,” he told National Geographic. “Bears are going to starve to death. This is what a starving bear looks like.”
Millions of people saw the clip—and polar-bear researchers added some caveats. “It is what a starving bear looks like for sure, because I’ve seen some,” Ian Stirling, a research scientist emeritus with the Canadian government, told me. “Now, we don’t know if that bear was starving to death, or if it was suffering from something else, without doing a proper necropsy. But it certainly looked like it was starving.”
Whatever the fate of that one bear, many more will soon look much like it. New research, published this week in the journal Science, shows that bears are even more vulnerable to undernourishment than once thought. Polar bears have higher daily energy demands than other apex carnivores, the paper finds, and they may need to eat every few days to avoid burning into muscle mass.
Fittingly, this new research comes with some startling video of its own. As part of the study, scientists recorded hundreds of hours of footage from small cameras strapped to polar bears, giving the team a unique “bear’s-eye view” into the animals’ lives. They witnessed solitary bears in the wild as they are rarely seen: hunting, swimming, mating, and just having fun.
The new video provides a trove of useful data for scientists even as the research confirms what they have long known: As global warming steadily reduces the amount of sea ice in the Arctic, bears will miss opportunities to snag their favorite prey—fatty, calorie-rich ringed seals—and many will weaken and starve.
Of course, you cannot just strap a GoPro to a polar bear. Anthony Pagano, a research biologist at the U.S. Geological Survey, learned that early, when a first attempt at this experiment went awry.
Pagano works at the agency’s Alaska Science Center in Anchorage. He studies polar bears that live in the south Beaufort Sea, the part of the Arctic Ocean that meets the state’s northeastern coast. Beaufort Sea polar bears are among the first of the species’ subpopulations to see population reductions due to climate change.
Every year, the roughly 900 bears in the region endure a cycle of plenty and want. Arctic sea ice reaches its maximum area by March, stretching all the way down to Alaska’s north coast. For the next few months, the bears chow down, hunting in the fertile and shallow waters of the continental shelf. They become fat and happy. But as June turns to July, summer heat causes the ice to recede, and the bears follow the ice into the Arctic basin, where there are fewer seals. They may fast for weeks at a time. At last, in late September, the ice begins to recover, and sometime in the next few months—during the long night of Arctic winter—the bears return to their feeding grounds.
Scientists believe that the early springtime is of crucial importance to the bears, as it’s when they build up their fat reserve before the hungry summer. In April 2013, Pagano and his colleagues set out to better understand the bears’ springtime habits. They located two female bears by helicopter, tranquilized them from the air, and tagged them with both a GPS tracker and a GoPro-style video camera. About 10 days later, they tranquilized the bears again and recovered the footage.
Except there wasn’t any. The camera’s battery had encountered its first Arctic night—during which temperatures can regularly reach -20 degrees Fahrenheit—and promptly conked out. It wouldn’t have been able to see anything, anyway, as a slab of ice had encrusted the lens. Regular cameras wouldn’t be able to stand up to the Arctic. Pagano needed a custom job. He spent the next few months working with Mehdi Bakhtiari, an engineer at the company Exeye, who specializes in making custom wildlife cameras.
By the next spring, he had four new wildlife cameras that could endure the Arctic conditions. Pagano and his team began a lengthy experiment. Every April, they would fly out, find a female bear without cubs, and subdue it. Then they would lift the animal above the ice surface with a tripod, weigh it, and run some blood tests. They also outfitted it with a GPS tracker, an accelerometer, and one of the new cameras.
Between eight and 11 days later, they would find the bears again, recover the cameras, and run more tests. After successive runs in April of 2014, 2015, and 2016, they had hours of footage from nine bears.
This video alone represented a major achievement in polar-bear research. “We don’t get to observe these animals much at all,” Pagano told me. Bears spend most of their lives out on the ice, alone; and they can attack humans who get too close. So scientists haven’t known—and still don’t know—what the day-to-day life of a polar bear is like.
So the team’s footage—days of film of polar bears just being polar bears—was something special. The cameras showed bears spending hours of their day sitting near gaps in the sea ice, waiting for a seal to surface to breathe. The footage caught bears trying to sneak up on seals who were sunning themselves on the ice. It displayed, even more peculiarly, a bear trying to catch seals by swimming beneath the ice.
“One bear was throwing chunks of ice in the water,” Pagano said. The animal seemed to lift up a piece of ice above its head, stand on its hind legs, and chuck it into the water. “She did this repeatedly,” he told me. “It’s not clear why that individual was doing that.”
Even more spectacularly, the team got to glimpse the polar-bear courting and breeding process. Courting?, I asked Pagano. Do the males bring fish to the females or something?
He paused. “Usually the males would simply harass the females until they would acquiesce,” he said. “It varied depending on the individuals, for sure. But most typically the bears would follow and harass the females—and the females would try to get them to create some space, would vocalize at the male and paw at the male—but the male would harass and dog the female until she gave in.”
The cameras faced to the front, so researchers couldn’t verify every instance of mating. “But in some instances, I could see shadows on the ice, shadows on top of the female,” Pagano said. “Which was, yep, quite interesting.”
Most importantly, these observations let scientists count how many seals each bear was able to catch. They paired this information with other data: the bears’ blood test data, their starting and ending weight, and their movement as recorded by GPS and accelerometer. By comparing all those figures with data from a captive polar bear at the San Diego Zoo, they could measure the bears’ metabolism rate—how fast the bears burn through energy.
The bears burn calories fast, and everything comes down to how many seals a bear can catch. The most successful bears were able to snag a seal every day or two. Over the week and a half they wore the cameras, those bears gained up to 44 pounds, or 10 percent of their preexperiment body mass. But bears that missed out on seals were equally punished. Four of the nine bears shed up to 40 pounds of body mass during the same length of time—and at least one had started burning away its lean muscle.
“This highlights the feast-or-famine lifestyle of these animals,” said Pagano, who estimates that Beaufort bears in the springtime must eat an adult ringed seal every three days to maintain a healthy weight. “They’re highly dependent on being able to catch seals to meet energy demands. And since the ice is breaking up earlier every year, it’s reducing their opportunities to catch these seals.”
Polar bears, the study found, have a higher metabolic rate than apex predators that live on land, like lions, hyenas, or black bears. They burn energy at the highest end of the range scientists had previously simulated—especially when “sitting and waiting” for seals to surface at a gap in the ice.
The research also reinforces the general principle that marine mammals, like polar bears, burn energy faster than their terrestrial brethren. This suggests something about how polar bears became marine in the first place: Their evolutionary predecessors must have found seals to be so efficient (or delicious) that eating them was worth the high caloric costs of living on the sea ice.
This new data will help scientists better track polar-bear populations. “You can build better [population] models knowing what the feeding requirements are for these animals,” said Øivind Tøien, a research scientist at the Institute of Arctic Biology who was not involved in the study. “It provides very solid data for the management of the polar bears. That’s important.”
He thought that the number of animals observed—nine bears, over three years—allowed for a robust finding. He praised the arduousness and robustness of the study. “You can’t just walk up to a wild polar bear and say, ‘Okay, I’d like to inject you with deuterium,’” he said. “And then you really can’t come back a few days later and say, ’Okay, I’d like to take a blood test now.’”
One of the few scientists who had last observed polar bears this closely is Stirling, the retired Canadian government ecologist. In the 1970s and 1980s, he found ways to successfully observe polar bears on Hudson Bay. Some of his studies were the first to warn that climate change could endanger polar bears across the Arctic.
“I think the study itself is very interesting,” he told me of the new paper. “It doesn’t give us anything new on the big picture, because we’ve had good data now for 20 or more years that the loss of sea ice is causing lots of problems for polar bears. But the understanding they have of some of the physiological mechanisms are very interesting and valuable, particularly to physiologists.”
He cautioned that polar bears in the Beaufort Sea may not resemble groups elsewhere in the world. “There are 19 different subpopulations of polar bears—and the ecological circumstances that each lives in are its own,” he said. “The Beaufort Sea is different. It’s the only population where—even in good times—females didn’t breed for the first time until they were at least five years old. Breeding starts at age four everywhere else. You have to be a little careful expanding [this finding] too far.”
But the Beaufort Sea bears—and the once-thriving bears of Hudson Bay, where Stirling first studied—make for good case studies because they have already suffered so much due to the loss of sea ice. Long-term studies have found that the number of polar bears in both regions is decreasing, as is the amount of body fat on each animal. Mothers have lower birth rates, and the number of cubs who survive infancy is falling as well. “Those areas are giving us a pretty good idea of what we can expect in other areas as things continue to warm,” said Stirling.
Some bears may already be taking extraordinary steps to survive. A series of GPS-collar studies have found that polar bears sometimes swim for days at a time at the end of the summer, when sea ice is at its lowest and bears are in the least productive waters. One bear was tracked as it swam more than nine days across the Arctic Ocean without stopping to sleep. Another study, published recently in the journal Polar Biology, found that the metabolic costs of those multi-day swims are also extremely high.
“Putting the two studies together does suggest that polar bears are simply walking a finer line energetically than we thought, so things like long-distance swims could be even more detrimental than previously supposed,” said Blaine Griffen, a biologist at Brigham Young University who led the swimming study, in an email. “These swims may reflect bears that are searching for food, but it is difficult to know why any particular animal chooses to make a single decision.”
The sea ice will continue to melt, and bears will continue to take catastrophic steps to save themselves. If carbon pollution continues unabated, then models suggest that the Arctic Ocean will lose all of its sea ice every summer by about the year 2050. (It will form again every winter through at least 2100.) The math here is simple and cruel, as Arctic sea ice exists in a linear relationship with the amount of greenhouse gas in the atmosphere. The average American emits enough carbon to melt about 645 feet of summer sea ice every year.
And as the ice melts, and breaks up earlier every year—shortening the springtime feeding season—more bears will starve. Polar bears do not have a natural predator in the wild, so most bears already die of old age, illness, or starvation.
“It’s very easy for people to understand,” said Stirling. “A warmer climate means less ice, bears need the ice to hunt the seals, less ice means they don’t get as much time to hunt seals, and that’s bad.” Tøien agreed: “If Arctic ice disappears, and you have an animal that is capturing their prey on the ice, and depends on that ice—it’s obvious what’s going to happen.”
For all the research, for all the delightful bear cams, for all the effort to save the species, there is only one step that can permanently protect the polar bear. “If climate change continues unabated, we unfortunately will likely see many more images of starving polar bears in years to come,” said Griffen, the Brigham Young professor. “The only viable, long-term solution to staving off the effects of climate change for polar bears, and for other species (including us), is to reduce greenhouse-gas emissions.”
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