Science had predicted the exact opposite. Yet as global warming continues to melt Arctic sea ice, polar bears in Svalbard are now fatter and in better condition than they were in the 1990s. Between 1992 and 2019, researchers weighed and measured 770 adult bears and found a significant increase in body fat. The finding is striking, given that the sea-ice platforms the bears rely on to hunt seals have shrunk dramatically.
The explanation appears to lie in a dietary shift. The bears have diversified their menu, increasingly preying on land-based animals such as reindeer and walruses.
Published in Scientific Reports, the study surprised scientists because it challenges prevailing expectations about the immediate effects of climate change on Arctic wildlife.
“The fatter a bear is, the better,” lead researcher Jon Aars of the Norwegian Polar Institute told the BBC. Fat reserves provide energy and insulation and allow mothers to produce rich milk for their cubs. Still, Aars admitted he had expected to see declining body condition given the substantial loss of sea ice.
Walruses, protected in Norway since the 1950s after being hunted nearly to extinction, have rebounded in number and now represent a new, calorie-rich food source. “There are many more walruses today,” Aars noted. It is also possible that shrinking ice areas concentrate seals into smaller spaces, making them easier for bears to hunt.
Despite the encouraging short-term results, researchers urge caution. John Whiteman of Polar Bears International says the improvement is likely temporary. As sea ice continues to retreat, bears will need to travel farther to reach hunting grounds, expending more energy and depleting their fat reserves. Other studies have already shown that more ice-free days reduce the survival of cubs and vulnerable females.
Elsewhere in the Arctic, the outlook is far less positive. Of the 20 recognized subpopulations, some are already in decline. In Western Hudson Bay, Canada, population decreases have been directly linked to rising temperatures. The long-term picture remains clear: polar bears depend on sea ice to survive. If ice loss continues unchecked, their populations will ultimately decline.
