Polar bears show better physical health now than they did 25 years ago, despite shrinking sea ice, new research reveals.
The well-being of these iconic white mammals, which live around the Norwegian island of Svalbard, has improved in the face of climate change, probably due to greater hunting opportunities.
Scientists were ‘surprised’ to discover that bears’ fat reserves have increased since 2000, even as sea ice levels decreased.
These findings, published in the journal Scientific Reports, contrast with previous observations that indicated a decline in the polar bear population throughout the Arctic.
Previous research shows temperature increases in the Barents Sea around Svalbard of up to two degrees Celsius per decade since 1980.
The Barents Sea polar bear population was estimated at about 2,650 individuals in a 2004 census, and it appears that this population has not decreased in size, although the reasons for this were unclear.
Therefore, Dr. Jon Aars, senior scientist at the Norwegian Polar Institute, together with his colleagues investigated the possible reasons for the stability of the Svalbard populations.
The team used data from 1,188 body measurement records of 770 adult polar bears taken in Svalbard between 1992 and 2019.
They compared changes in the body composition index (BCI), an indicator of fat stores and body condition determined by tape measurement, with the number of ice-free days in the region over the 27-year period.
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The research team found that although the number of ice-free days increased by about 100 during the study period, at a rate of about four days per year, the mean BCI of sampled adult polar bears actually increased after the year 2000.
“This indicates that fat reserves increased as sea ice levels decreased,” Dr. Aars said.
The researchers suggest that improvements in the body conditions of Svalbard polar bears could be attributed to the recovery of populations of terrestrial prey sources—such as reindeer and walrus—that were previously overexploited by humans.
They also believe that the loss of sea ice may have led one food source, such as ringed seals, to concentrate in smaller areas of sea ice, which could increase the efficiency of polar bear hunting.
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But Aars speculated that this trend could be unstable.
“Further reductions in sea ice could negatively impact Svalbard populations by increasing the distances they need to travel to access hunting grounds.”
“More research is needed to understand how different polar bear populations are adapting to a warming Arctic in the future.”
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