Seven-centimetre-long lobster krill look like easy prey for 90-centimetre-tall gentoo penguins, but they don’t go down without a fight. Cameras mounted on the penguins to study their hunting behaviour reveal that the krill fight back with their tiny pincers – and they often succeed in deterring their attackers.
Jonathan Handley of Nelson Mandela University in Port Elizabeth, South Africa, and colleagues attached cameras and depth recorders to 38 gentoo penguins in the Falkland Islands as they set out on foraging trips early in the day. “We were hoping to discover what’s happening in the underwater lives of these birds,” says Handley.
The footage showed the penguins hunt lobster krill and small fish, and occasionally larger fish and squid. The penguins usually attack while ascending from deeper water, so that their prey is easily visible against the light sky.
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On a number of occasions, lobster krill avoided capture by defending themselves with their pincers. “That was a unique finding that we weren’t really expecting,” says Handley.
Groups of lobster krill also defended themselves successfully by forming tightly clustered swarms. When penguins approached these swarms, they weren’t able to pick off any individuals.
Unlike African penguins, which were filmed hunting in groups in a recent study, there was no sign of cooperative hunting among the gentoo penguins.
The lobster krill’s defensive strategies show we can’t assume that when there’s lots of prey available, there will be plenty for penguins to eat, says Handley.
Royal Society Open Science
