Drone video captured off the coast of Norway is teaching scientists about the cooperative hunting strategies used by the area's mammal-hunting orcas. The Norwegian Orca Survey (NOS) recently filmed a local pod catching and eating a harbour seal. 

The footage is certainly grisly (sensitive viewers be advised), but the NOS team emphasises that observing such behaviour is key to understanding social hierarchies within orca pods and the whales' use of local food resources.

The sighting is just the latest in a string of impressive killer-whale predations captured by drones this season. Last month, scientists in Russia filmed a pod hunting and eating a bowhead whale for the first time.

The video clips have drawn their share of viewer criticism, with some describing them as displays of "gratuitous violence" – a concern the NOS has addressed online. "We are providing our audience with our research and showing how things are," the team said in a Facebook response. "This is nature. Orcas are a top predator."

Killer whales elsewhere in the world – namely a group known as "Bigg's" (formerly "transient") orcas – have long been known to eat mammalian prey, but the behaviour was first documented in Norway only in 2014. Most of the killer whales that feed in local waters eat Atlantic herring. These fish-eating whale groups have been studied closely over the years, and are mostly seen in winter. That makes this summer sighting of particular interest to the NOS team. 

The pod featured in the video was not identified during the winter herring season, which suggests its members may be mammal specialists. The NOS drone studies, however, have also shown that some Norwegian orcas may be surprisingly unfussy eaters.

"We know a couple of groups from the herring season in Tromsø eat seals in the summer too," says the team, adding that other fish and seabirds seem to be on the menu as well.

Unique prey requires unique hunting strategies – and orcas are known to employ dozens of them. You'll notice that one whale in the footage uses its powerful flukes to stun and fling the harbour seal into the air before the prey is eventually scooped up by another pod member. This punting behaviour has been observed in other parts of the world too, and it's extremely effective on smaller marine mammals.

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"There is absolutly nothing bad with orcas consuming seals," add the researchers. "It's rather very interessting to see how they cooperate to do this."

One seal might not be enough to fill up multiple whale bellies, but as we've discussed before, sharing the meat provides a tactical advantage: giving each member a piece of the spoils helps to ensure the collective health of the pod, which translates into stronger defences against predators, healthier offspring and better foraging success in the future. 

And speaking of offspring – look closely at the footage and you'll see one of the adult females holding the seal meal steady while a juvenile pod member takes its turn at the table (featured at the end of this extended edit):

Similar behaviour has been observed in fish-eating orcas as well: mother whales have been known to hold salmon in their mouths while their young nibble bits of flesh.  

By the end of the day, this Norway pod had filled up on a bevy of seal meals – what we're seeing in the video above represents just a small part of the action observed by the NOS team. "This is a highlights reel," they explain. "There were about 20 [harbour seals] not having the best day."



Top header image: Miles Ritter, Flickr