Dolphins. It's what's for dinner. At least for polar bears in the Svalbard archipelago, that is.

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This is the first time that polar bears have been observed feeding on white-beaked dolphins. Image: Samuel Blanc

Polar bears are seal-hunting specialists and dolphins aren't exactly a regular item on their menu – and yet scientists from the Norwegian Polar Institute came across not just one but several bears feasting on white-beaked dolphins during the course of their research in the Norwegian archipelago in the Arctic Ocean last year.

So what's going on here? It seems the dolphins had made a tactical error in venturing a little too far north too soon. "White-beaked dolphins are frequent visitors to Svalbard waters in summer, but have not previously been reported this far north in early spring. We suggest they were trapped in the ice after strong northerly winds the days before," the team explains.

It's likely that the bears managed to snatch and kill the trapped dolphins when the animals were forced to surface for air at small openings in the ice.

The team's first sighting took place back in April 2014, when an adult male bear was spotted with two dolphin carcasses. Having already munched his way through most of the first one, the bear was in the process of stashing the second (only partially nibbled) carcass for later, burying it under the snow, possibly in an attempt to hide it from hungry scavengers. 

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The first bear was spotted back in April 2014 while burying a dolphin carcass under the snow. Image: Jon Aars/Norwegian Polar Institute

Over the next few months, the researchers came across at least five other bears indulging in dolphin, all of them most likely members of the same doomed pod.

While this marks the first time the predators have been observed feeding on this particular dolphin species (Lagenorhynchus albirostris), the researchers note that polar bears are known for mixing it up when it comes to food. "Polar bears (Ursus maritimus) depend on sea ice, where they hunt ice-associated seals. However, they are opportunistic predators and scavengers with a long list of known prey species," they write. 

Seal-hunting specialists they may be, but that hasn't stopped the bears from having a go at eating other marine mammals, including seven different species of whale, the researchers add.

And this unfussy eating style could work in the bears' favour in future – especially as seal meals become harder to find and shifting ice cover puts newfangled prey on the menu. "An increase of white-beaked dolphins in areas where the sea ice shifts northward may, given the significant size of these animals, offer a new prey or carrion food source to bears in an environment where access to ringed seals and bearded seals may decline in future years," the team notes.

The findings are described in the journal Polar Research.

Top header image: longhorndave, Flickr