Black Friday Sale


Orcas seen in unique group ambush-and-kill attack on dolphins

By Bob Holmes

3 December 2015

New Scientist Default Image

They’ve definitely earned their name. Frighteningly effective hunting methods have become something of a speciality for a pod of killer whales off the coast of Patagonia, Argentina.

The pod became famous when some of them were spotted intentionally beaching themselves to capture baby sea lions, then refloating when the next wave rolled in.

Now the same pod has been seen tricking dolphins into an ambush. Orcas have been filmed hunting dolphins before, but never using such a complex group-hunting technique.


The ringleader in both cases is an adult female that researchers have named Maga. They watched from boats as the orcas – sometimes called killer whales, though they are more closely related to dolphins – encountered their prey then set up the ambush.

“It seems to be coordinated,” says Mariano Coscarella of Argentina’s National Scientific and Technical Research Council in Puerto Madryn. “Maga is within the group of killer whales following the dolphins, then she disappears.”

He thinks Maga swims ahead and waits for the unsuspecting dolphins, because the next time the researchers see her is when she suddenly head-butts one of the dolphins, throwing it into the air and injuring or killing it.

New Scientist Default Image

Just like chimps

Researchers have now seen the behaviour at least five times, including twice since Coscarella and his colleagues published their initial findings this summer. No one has looked for the behaviour in other orca pods, says Coscarella, but it would not surprise him if it were more widespread.

The technique is complex because the “catcher”, Maga, has to hide in order for the ambush to work. In practice, that means waiting quietly without echolocating while the pod drives the dolphins towards her.

“It takes coordinated behaviour, and really good knowledge of their environment. I think that makes this technique quite interesting,” says Coscarella. “They drive the prey towards a catcher, just as chimps do.”

Chimps famously go on coordinated group-hunting trips for red colobus monkeys, in which some individuals chase the monkeys towards others waiting to catch and kill them.

Cultural traditions

The only other mammals known to use such herding and ambush tactics are humans, which puts the orcas in a small and elite group, Coscarella says.

Most marine mammal biologists already think orca hunters are as sophisticated as any chimp.

They are known to pass hunting methods from generation to generation, resulting in the formation of cultural traditions.

Orcas in polar regions work together to make waves that wash seals off ice floes, while those in Australian waters are known to cooperate to separate humpback whale calves from their mothers. All this knowledge is culturally transmitted, says Jeff Higdon, a marine mammal biologist based in Winnipeg, Canada.

The Edison of orcas?

Herding and ambush hunting fits easily into this rich cultural repertoire. “Given the level of cooperation we see with these animals, it doesn’t terribly surprise me,” says Higdon.

So is Maga a Thomas Edison among orcas, unusually adept at invention? “It’s certainly possible,” says Higdon. “It’s clear that this pod has figured out some pretty amazing skill sets.”

On the other hand, says Coscarella, Maga may just be an older whale who’s been around for a while and picked up some skills along the way.

Journal reference: Aquatic Mammals, DOI: 10.1578/AM.41.2.2015.192

Read more:Orca invasion: Killer whales in a warmer world

Image credit: Kieke van Maarschalkerwaart