Orcas in Russia filmed hunting a bowhead whale for the first time

With their large skulls and powerful bodies, bowhead whales are capable of breaking through sea ice at least seven inches thick. But even these powerful animals are no match for Russia's mammal-eating orcas.

This incredible hunt was filmed during the Western-Okhotsk Beluga population assessment, a 2016 expedition led by Dr Olga Shpak, a marine biologist with A.N. Severtsov Institute of Ecology and Evolution, the Russian Academy of Sciences and Marine Mammal Council

Earlier this month, we featured footage of the so-called "sea wolves" taking down a minke whale – and like that impressive clip, the recent sighting is thought to be the first of its kind.

Bowheads can reach an impressive 75-100 tons, and while this eight-metre individual isn't fully grown, it's not a calf as some have suggested.

"It is a weaned juvenile," writes Shpak, who has done extensive work on bowhead whales in the Okhotsk Sea, where this hunt took place. If this youngster were indeed a calf, we'd expect to see a mother nearby, but Shpak says no other big whales were in the vicinity. "We were there since the very start of the attack."

Orcas have long been known to eat bowhead meat: interviews with Inuit hunters have revealed that roving pods in Alaska readily target bowheads, and Shpak and her colleagues have encountered the aftermath of such predatory behaviour in Russia, too. During a three-week survey in 2016, six orca-dispatched bowheads were found in the area, and local sailors reported another two. But aerial footage of these hunts has eluded the FEROP team until now.

The highlight reel you see above represents just a fraction of the effort required for a kill of this nature. According to Shpak, it took the orcas over an hour to finish the job. "By 'these' I mean a family, which has definitely polished its skills," she explains, adding that a bowhead calf would have made a significantly easier target, requiring "just a few rams and rides".

For those of you wondering about the colour of the water, this isn't quite the bloodbath it appears to be. Some blood (the very red patches) can be seen in the video, but the milky-brown cloud surrounding the animals is just silt. The bowhead was killed in a shallow bay, with mud and debris easily stirred up by the orcas' large flukes.

Killer whales are known to feast on the protein-rich tongues of their rorqual prey, and that taste preference was captured in all of its grisly splendour during the event. A small calf even entered the bowhead's mighty muzzle beside its mother for a chance at the spoils:

Fatty blubber also makes for a choice cut, but it's common for orca pods to leave much of their hard-won meals behind. That might seem like a waste, but these leviathan leftovers benefit many other predators – sometimes even terrestrial ones.

On the other side of the world, receding pack ice in the Canadian Arctic has allowed orcas to move into new territory in recent years. Some scientists are concerned that the predators' expanded foraging grounds could be problematic for other marine life. A recent study conducted in Hudson Bay and nearby Foxe Basin, however, suggests there may also be a silver lining: polar bears are beginning to scavenge the bowhead carcasses that wash up – headless and tooth-raked – after local orcas have had their fill.

"The increasing abundance of killer whales and bowhead whales in the region could be indirectly contributing to improved polar bear foraging success despite declining sea ice habitat," write the authors.

It's certainly not a cure-all, but the extra food source could bring a bit of relief to some polar bear populations during the lengthening ice-free season. This is similar to what we've seen on Alaska's Barter Island, where polar bears regularly supplement their diets with whale meat left behind by traditional hunters: