A team of researchers believes a warming Arctic climate has caused polar bears to start eating dolphins, prey the animals have been recorded attacking.

According to Agence France-Presse, authors of a study published in the journal Polar Research detailed the first instance they witnessed in April 2014. The scientists said dolphins do not usually head north in the Norwegian Arctic until the warmer months, but that has changed due to warmer winters and decreasing ice sheets.

"It is likely that new species are appearing in the diet of polar bears due to climate change because new species are finding their way north," study lead author Jon Aars, of the Norwegian Polar Institute, told AFP.

Aars described a dolphin he saw poke its head through a hole in the ice sheet, which was likely the best time polar bears have to catch their newfound prey.

"Even if they saw the bear, the dolphins did not necessarily have any other choice," he told AFP of the dolphin. "We think that he tried to cover the dolphin in snow in the hope that other bears, foxes or birds would have less of a chance of finding it. Maybe to be able to eat it a day or two later, once he had digested the first one.

"I don't think that this signifies a great upheaval in the diet of the carnivores.

"It's just that the polar bear is coming into contact with species they have not been used to meeting until now."

Past studies have indicated polar bears' diet will be hit hard by climate change, as they will not be able to adapt to land-based foods like some of their relatives. Aars and his team noted the polar bears they observed appeared thin and their study indicates they are doing whatever they must to survive.