Researchers have documented a group polar bears with a taste for dolphin. It's the first time bears have been recorded eating the marine mammal.

The first instance was documented in 2014. Researchers with the Norwegian Polar Institute came upon a polar bear with two dead white-beaked dolphins. The scientists believe the bear caught the two dolphins the same way bears catch seals, by waiting for specimens trapped under the ice and in need of oxygen to emerge through a hole in ice.

Because the bear found himself with more than he could consume in one sitting, he froze the dolphin in a pile of snow for later eating -- a technique researchers say is rarely employed by polar bears. In the barren and hostile ice fields of the Arctic, it's unusual for predators to find themselves in possession of excess food.

After the initial sighting, scientists witnessed at least five other bears picking at the dolphin carcasses. But researchers aren't necessarily surprised by the behavior. Being almost always hungry, polar bears are rather opportunistic predators, and will eat a range of species.

"They will eat any marine mammal given a chance," researcher Jon Aars told the NewScientist. "The bigger surprise was that the dolphins were entrapped before they could migrate south for the winter."

Researchers believe the dolphins were enticed north by warmer than usual waters and subsequently blown off course.

"We suggest they were trapped in the ice after strong northerly winds the days before, and possibly killed when forced to surface for air at a small opening in the ice," scientists wrote in their new study on the phenomenon, published in the journal Polar Research.