New study of Svalbard's polar bears: "Completely different from what we expected," says researcher
Why are the polar bears on Svalbard doing so well?
The melting of ice in the Arctic affects wildlife on Svalbard. But some are coping better than others, a new study shows.(Photo: Geir Wing Gabrielsen / Norwegian Polar Institute)
But a new Norwegian study now shows that this is not the case for the polar bears on Svalbard. The bears there had maintained their weight – and then some – despite the loss of sea ice.
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"This was completely different from what we believed and expected," Jon Aars tells Science Norway. He is one of the researchers behind the new study, recently published in Scientific Reports.
Aars and his colleagues point to several possible reasons why Svalbard's polar bears appear to be doing so well.
Studied 770 polar bears
The researchers used measurements from over 770 adult polar bears taken on Svalbard between 1992 and 2019.
These measurements indicated how much fat the bears had on their bodies, which in turn says something about how well they are doing.
"Fat reserves are a really good buffer during hard times," says Aars. They give polar bears a very strong ability to cope, allowing them to survive for months without food.
Researchers examine and record the size of the jaw of a sedated polar bear.(Photo: Jon Aars / Norwegian Polar Institute)
Healthy and chubby
The researchers then compared changes in body fat with the number of ice-free days in the Barents Sea region over the 27-year period.
The results showed that the polar bears remained healthy and chubby.
Their numbers had not declined either. Despite significant ice loss in recent years, the population has stayed stable.
So why haven't rising temperatures and melting ice affected the polar bears on Svalbard?
To study polar bears, researchers must sedate them. In this photo, a sedated mother lies on the ice with her cub pressed close to her side.(Photo: Jon Aars / Norwegian Polar Institute)
Finding food on land
Aars and his team believe this may be related to the fact that polar bears have started to hunt on land.
While Canadian polar bears burned too many calories during land-based hunting and rapidly lost weight, Svalbard’s polar bears appear to have experienced the opposite effect.
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The key difference, researchers believe, is that Svalbard bears are actually finding enough food.
They are eating more reindeer, and there are plenty of eggs from common eiders, pink-footed geese, and barnacle geese.
"In some places, we've even seen polar bears climbing the mountainsides to take auk eggs. But that's probably rare," says Aars.
Barnacle goose eggs are now more vulnerable as polar bears can get to them.(Photo: Andreas Weith / Creative commons 4.0)
Common eider nests contain important food for polar bears on Svalbard.(Photo: Colin Seddon / Shutterstock / NTB)
Large carcasses
Over the past 20 years, walrus numbers around Svalbard have increased, which may also have helped the bears, according to Aars.
Polar bears rarely manage to catch them, but these large marine mammals sometimes die naturally.
"When that happens, there's a huge amount of food in those carcasses," says Aars.
Seals are the main reason polar bears depend on sea ice, since this is where seals live as well.
In recent years, polar bears have managed to catch harbour seals, one of two seal species found around Svalbard. They also feed on ringed seals.
"One idea we’ve discussed is that shrinking ice may actually make ringed seals easier for polar bears to catch. The seals simply have less space to move around," says Aars.
The researchers cannot draw firm conclusions yet, because the cause-and-effect relationships are still poorly understood.
"But taken together, these factors may help explain why polar bears on Svalbard have fared so well," he says.
Things could still get worse
Even though the polar bears have coped well with ice loss over recent decades, the researchers warn that there may be a tipping point.
"Further reductions in sea ice could harm the Svalbard population, partly because the polar bears would have to travel farther to reach hunting areas," says Aars.
This is what has happened with other polar bear populations, for example in Canada.
Aars and his colleagues therefore stress the need for more research to understand how different polar bear populations will adapt to a warmer Arctic in the future.
