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Birds of a feather fish together – if they’re . By doing so they catch more food while expending less energy.

African penguins were believed to forage in groups, but nobody had ever seen them hunt underwater. To find out how they catch common fish in their habitat, like schools of sardines and anchovies, of Nelson Mandela Metropolitan University, South Africa, and colleagues attached cameras to 12 of the birds.

On most dives the penguins pursued single fish, but sometimes they teamed up for bigger rewards. Groups of penguins were seen herding schools of fish towards the surface, corralling them into a “bait ball”. Any fish trying to escape would peel off from the group, making them easy prey. The penguins’ plumage – black on the back, white at the front – probably makes it difficult for the fish to see them coming from below.

The researchers calculated how efficient the penguins were by dividing the number of fish caught by the time spent foraging. When hunting a school of fish as a group, penguins were 2.7 times as efficient as when they attacked on their own.

Foraging in groups can be beneficial in different ways. At the simplest level, animals like swordfish , killing more fish this way. At a more sophisticated level, creatures like dolphins communicate and coordinate their activity.

Penguins aren’t cooperating like dolphins, but they may be more advanced than swordfish, says McInnes. At the surface, they communicate to find other birds and synchronise their dives.

“This study provides the first evidence that penguins are actively interacting with other individuals to enhance hunting efficiency,” says at the National Institute of Polar Research, Japan. He says other penguins may do the same, but we don’t have evidence yet.

African penguins are an endangered species – the . Overfishing of their prey is thought to be a factor.

It’s likely that this decline will make it harder for the remaining penguins to get enough food, says McInnes. “If they benefit from group foraging and there are less birds at sea, it’s harder to find other penguins to benefit them when they’re foraging.”