In parts of the Arctic, polar bears are in decline as sea ice, which they depend on to hunt, disappears. That is not the case, however, on the Norwegian island of Svalbard, where bears have actually managed to grow more plump even as ice melts away.
Polar bears hunt by stalking sea ice in search of seals, but sea ice is shrinking across much of the Arctic, which is warming nearly four times faster than the world as a whole. Increasingly, ice forms later in the winter and melts earlier in the spring, which means bears spend less time hunting and more time fasting.
A study along the western edge of Hudson Bay, in Canada, found that, over the last half-century, the number of polar bears in the region dropped nearly in half, and the bears grew measurably smaller. The average female lost 86 pounds, the research found, while the average cub lost 47 pounds.
And yet, on Svalbard, polar bears are gaining weight. That is the finding of a new study of 770 bears on the remote Arctic island, which lies some 500 miles north of Norway in the Barents Sea. The region has seen a precipitous drop in sea ice since the early 1990s, adding about 100 ice-free days. And yet, since 2000, Svalbard polar bears have gotten bigger, boosting their reserves of fat, according to the research, published in Scientific Reports.
While the authors cannot say for certain how the bears are managing to thrive in a changing climate, they speculate on two possible causes. One is that seals are concentrating around smaller swaths of sea ice, making them easier to hunt. A second is that polar bears are feasting on a growing number of walruses and reindeer.
Walruses, targeted for their ivory, were nearly extirpated from the island in the early 20th century, but they mounted a recovery after Norway banned commercial hunting in 1952. There are now more than 5,000 on Svalbard. Reindeer were also hunted to the brink of extermination, but since Norway extended protections to the animals in 1925, their numbers have rebounded. Reindeer have recolonized their ancient grazing lands, researchers say, and now total around 22,000.
The island’s polar bears have taken notice. In 2020, scientists gathered the first evidence that Svalbard bears had begun hunting adult reindeer: a widely circulated video of a polar bear chasing a reindeer into the sea, killing it, and then dragging its body to shore. A follow-up study, based on that and other videos, found that across Svalbard, bears were increasingly targeting the ungulates. “This increase in hunting,” it concluded, “is probably linked to the reduced ice cover, with bears spending more time on land, and a growing reindeer population.”
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