In a fight between a pipsqueak and a giant, the giant should win, right? Well, a battle between this underwater David and Goliath has revealed that sometimes the little guy triumphs. He just needs the right weaponry, a new study suggests.
The David in this case is the lobster krill. A small crustacean, it lives in the ocean. And instead of a slingshot, it’s armed with sharp pincers that can sometimes deter a Goliath: the gentoo penguin.
These penguins (Pygoscelis papua) live on the Falkland Islands in the remote South Atlantic. There, the birds nest in tall white grass. To eat, they trek some 800 meters (0.5 mile) from their colony to the sea. Jonathan Handley refers to the paths they take as “penguin highways.” Handley is a conservation ecologist. He studied these penguins while he was working for the Marine Apex Predator Research Unit (MAPRU) at Nelson Mandela University in Port Elizabeth, South Africa.
After spending a day or two feeding, the penguins return home along the same highways. Those predictable paths make a single penguin easy to find after its swim. So, in December 2013, MAPRU and Falklands Conservation launched a project to see what the penguins did while dining at sea. (Falklands Conservation is an organization that protects Falklands wildlife.)
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 explains. With a net attached to a long pole, the scientists would catch a penguin as it was headed out to sea. They marked 38 of them with the same type of animal marker that farmers use on sheep. They also strapped onto each of these penguins the equivalent of a GoPro camera before setting the bird loose. The team would then wait for the animal to return.
“You spend a fair few hours watching the highway, always with great anticipation,” Handley notes.
In all, the researchers retrieved nearly 36 hours of footage from 31 birds. They used that video to catalog what the penguins ate. Their diet included juvenile rock cod and other fish, lobster krill and adult squid. The video also turned up a surprise. It showed a gentoo swimming past a swarm of lobster krill. With each krill some 7 to 8 centimeters (about 3 inches) long, that should have been a big and easy feast. In fact, the bird ignored it. “Oh, that’s quite interesting,” the scientists thought at the time.
Then it happened again. And again. At that point, Handley says, “[We] realized we were onto something quite unique.”
Not only did the penguins avoid many of the large krill swarms, but sometimes these birds didn’t even manage to eat a single one of the crustaceans. A penguin would go in for the attack but fail.
The videos revealed some “epic fight scenes,” Handley says. In them, the lobster krill completely flared out their pincers and was able to use that pincer action to get away. That was enough, it seems, for the crustaceans to fight off the hungry penguins. And it’s pretty impressive, since the birds are some 10 times as long as the tiny krill.
That pincer flaring could explain why in open water the penguins tended to attack krill from below. It could also be why the birds seemed to avoid attacking the crustaceans on the seafloor as well as in krill swarms. There was just too much potential for injury.
Handley and his colleagues published their findings August 22 in Royal Society Open Science.
Just how much harm a lobster krill can do to a gentoo penguin remains unknown. However, Handley warns, the krill “can definitely give a nasty pinch when they want to.”