Researchers from the Norwegian Polar Institute recorded the behaviour after large numbers of white-beaked dolphins became trapped under the ice sheet, surfacing for air at a small opening where they became easy prey for polar bears.
At least seven dolphin carcasses had been partially eaten by the bears.
In their report, the scientists report that one of the bears, who they described as “very skinny” but with a full belly, was seen covering a dolphin carcass with snow, after eating as much of the animal as it was able.
Dolphins usually don't travel to Svalbard in the early spring and may have been lured there because of higher-than-normal sea temperatures due to global warming.
Polar bears normally survive almost exclusively on a diet of seal and have never before been observed eating dolphin.
The polar bear population is rapidly declining as sea ice melts due to climate change. When there is less ice, there is less available food leaving polar bears vulnerable to starve.
Ian Stirling of the University of Alberta in Canada believes that incidents where polar bears find unusual prey will increase as hunting for seal becomes more difficult.
Polar bears are “willing to take and use anything possible when available", he told the New Scientist.