A gentoo penguin’s dinner knows how to fight back

In a fight between a pipsqueak and a giant, the giant should always win, right?

Well, a battle between an underwater David and Goliath has revealed that sometimes the little guy can come out on top. He just needs the right armaments. The David in this case is the lobster krill. And instead of a slingshot, it’s armed with sharp pincers that can sometimes fight off a Goliath: the gentoo penguin.

These gentoo penguins (Pygoscelis papua) live on the Falkland Islands in the remote South Atlantic, where the birds nest among tall white grass. To eat, they trek from their colony some 800 meters to the sea along what conservation ecologist Jonathan Handley calls “penguin highways.” He worked with these penguins while at the Marine Apex Predator Research Unit at Nelson Mandela University in Port Elizabeth, South Africa.

After staying at sea for a day or two hunting down their meals, the penguins return home along the same highways. Those predictable paths make it easy to find a single penguin after a swim. So, in December 2013, Handley and the MAPRU, along with Falklands Conservation, an organization that protects Falklands wildlife, began a project to see what the penguins did in the water.

The researchers started by setting up along one of the paths. “Then you wait really quiet, really low to the ground as the birds are coming past,” Handley says. With a net attached to a long pole, the scientists would catch a penguin as it was headed out to sea. Next, they’d mark the bird with an animal marker (the kind that farmers use on sheep), strap on the equivalent of a penguin GoPro camera and set the animal loose. Then, the team would wait for the bird to return.

“You spend a fair few hours watching the highway, always with great anticipation,” Handley says.

The scientists tagged 38 birds from two colonies, eventually getting nearly 36 hours of footage from 31 birds, which the team used to catalog what the penguins ate. Their diet included adult squid, juvenile rock cod and other fish, and lobster krill. Then the researchers noticed a gentoo penguin swimming past what could have been a feast — a swarm of lobster krill. “The first time,” Handley says, they thought “oh, that’s quite interesting.” Then it happened again and again. “[We] realized we were onto something quite unique.”

Not only did the penguins avoid many of the large swarms of lobster krill, sometimes the birds didn’t even manage to eat single crustaceans. A penguin would go in for the attack but fail.

The videos revealed some “epic fight scenes,” Handley says, in which the lobster krill flared out their pincers completely. That was enough, it seems, for the crustaceans to fight off penguins, some 10 times as long as the tiny krill. That behavior could explain why the penguins tended to attack krill in open water from below and to avoid attacking the crustaceans on the seafloor as well as in krill swarms, Handley and his colleagues report August 22 in Royal Society Open Science. There was just too much potential for injury.

Just how much damage a lobster krill can do to a gentoo penguin is unknown. However, Handley notes, the krill “can definitely give a nasty pinch when they want to.”