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.”
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Atlantic One of the world’s five oceans, it is second in size only to the Pacific. It separates Europe and Africa to the east from North and South America to the west.
behavior The way something, often a person or other organism, acts towards others, or conducts itself.
birds Warm-blooded animals with wings that first showed up during the time of the dinosaurs. Birds are jacketed in feathers and produce young from the eggs they deposit in some sort of nest. Most birds fly, but throughout history there have been the occasional species that don’t.
colleague Someone who works with another; a co-worker or team member.
conservation The act of preserving or protecting something. The focus of this work can range from art objects to endangered species and other aspects of the natural environment.
crustaceans Hard-shelled water-dwelling animals including lobsters, crabs and shrimp.
diet The foods and liquids ingested by an animal to provide the nutrition it needs to grow and maintain health. (verb) To adopt a specific food-intake plan for the purpose of controlling body weight.
ecology A branch of biology that deals with the relations of organisms to one another and to their physical surroundings. A scientist who works in this field is called an ecologist.
footage (in movies and videos) A term for the uncut or unprocessed motion pictures or video imagery taken by a camera. It takes its name from the fact that it took several feet of film to capture a few seconds of motion-picture photography.
juvenile Young, sub-adult animals. These are older than “babies” or larvae, but not yet mature enough to be considered an adult.
krill Tiny shrimplike crustaceans that live in the ocean and are the main food source of some whales.
marine Having to do with the ocean world or environment.
penguin flightless black-and-white bird native to the far Southern Hemisphere, especially Antarctica and its nearby islands.
predator (adjective: predatory) A creature that preys on other animals for most or all of its food.
prey (n.) Animal species eaten by others. (v.) To attack and eat another species.
sea An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.
squid A member of the cephalopod family (which also contains octopuses and cuttlefish). These predatory animals, which are not fish, contain eight arms, no bones, two tentacles that catch food and a defined head. The animal breathes through gills. It swims by expelling jets of water from beneath its head and then waving finlike tissue that is part of its mantle, a muscular organ. Like an octopus, it may mask its presence by releasing a cloud of “ink.”
swarm A large number of animals that have amassed and now move together. People sometimes use the term to refer to huge numbers of honeybees leaving a hive.
unique Something that is unlike anything else; the only one of its kind.
Journal: J.M. Handley et al. Behaviourally mediated predation avoidance in penguin prey: in situ evidence from animal-borne camera loggers. Royal Society Open Science. Published online August 22, 2018. doi: 10.1098/rsos.171449.