Zoologger: Cultured killer whales learn by copying

Zoologger is our weekly column highlighting extraordinary animals ? and occasionally other organisms ? from around the world

Species: Orcinus orca
Habitat: throughout the world's oceans ? humans are the only mammal to range further

Big and strong predators are dangerous enough, but clever ones are the worst. There's nothing more annoying than realising you've been outwitted in the seconds before you're disembowelled.

Killer whales are some of the smartest predators on Earth. They can climb onto beaches to catch sea lions, stun fish by slapping them with their tails, and create waves to knock seals off ice floes.

That might be because they learn from each other. They are one of the few animals that can imitate behaviours that they haven't seen before, and they are ferociously quick students.

See more in our gallery: "Marine lessons in becoming a killer"

Whaling on seals

Despite their name, killer whales are actually dolphins ? albeit rather large ones. Populations in different areas are quite dissimilar, and genetic evidence suggests that there are actually several species.

A key difference between populations is that they target different prey, using different techniques. In the Crozet Islands in the Indian Ocean, whales strand themselves on beaches to hunt southern elephant seals. In Patagonia, they hunt sea lions in the same way.

Beaching oneself on purpose is unusual, and it takes young killer whales years to get the hang of it. Even at five or six years old, they often need their mothers' help to get back off the beach.

Around the Antarctic Peninsula, Weddell seals are the prey of choice. These often rest on ice floes, so the whales form teams up to seven strong and swim towards the ice floe, beating their flukes. This creates a large wave, which can tip up the ice floe and topple the seal into the water.

Killer whales off Norway have a totally different approach. They herd herring into densely-packed balls. Ordinarily this protects the fish as it makes it hard to pick out individuals to target, but the whales get around this defence mechanism by slapping the ball with their tails, stunning some of the fish.

Do what I do

These different styles of hunting could well be cultural: learned behaviours that are shared by members of a single killer whale population. Jos? Abramson of the Complutense University of Madrid in Spain and colleagues have found that captive killer whales are excellent at imitating each other.

They studied three killer whales living in an aquarium in France. In each test, they instructed one of the whales to imitate an action that another was performing. Each whale learned the "do that" command within 20 attempts.

Once the whales knew what "do that" meant, Abramson instructed them to imitate 15 behaviours that they already knew, such as slapping the water with their pectoral fins. They were also asked to imitate four that they had never seen or attempted before, such as barrel rolls. The whales took no more than eight attempts to imitate a familiar behaviour, and even the new behaviours never took more than 16 tries.

That's impressive, but Abramson's whales might not be representative. Their trainers have taught them lots of tricks, so they may be unusually good learners. Such "genius" animal behaviour can be misleading.

Nevertheless, the whales' imitative skills could help explain why different groups use such varied strategies. As soon as one whale develops a new hunting technique, the others will quickly pick it up. If that's what's going on, killer whales join bottlenose dolphins in a small group of marine mammals that have cultural traditions.

Journal reference: Animal Cognition, DOI: 10.1007/s10071-012-0546-2

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