CHENNAI: A study finds that the gloomy octopus — its real name — is in the small club of animals that toss things at other members of their own species. It turns out that the urge to hurl something at an irritating neighbour is not confined to land animals. A study published on Wednesday in the journal PLOS ONE shows that octopuses of at least one species throw silt and shells, sometimes at one another. It’s a rare behavior in the animal kingdom, and the study is the first time it has been documented in octopuses.
While octopuses are intelligent, most species live largely solitary lives. But in Jervis Bay, Australia, unusually large numbers of one species — Octopus tetricus, better known as the gloomy octopus — gather at sites affectionately nicknamed Octopolis and Octlantis. Ideal denning conditions and abundant food attract the antisocial animals and force them into close quarters, where it’s common for them to poke, prod, grab and otherwise annoy one another. And that exasperation can lead to the deployment of projectiles as a potential manner of cephalopod conflict resolution.
Researchers observed this ballistic behavior while poring over more than 21 hours of video taken near octopus dens. Throwing was “not at all routine,” said Peter Godfrey-Smith, a philosopher of science at the University of Sydney in Australia and an author of the study. “But we were seeing it reasonably often.”
Though the researchers call the octopuses’ actions “throws,” Jervis Bay is not like a dodge ball court populated by eight-armed players; only in one case did an octopus fling a shell by straightening its arm the way a human would. There isn’t really a word for what the gloomy octopus does, Dr. Godfrey-Smith said. For instance, if an animal feels provoked by its neighbour, it will gather silt from the seafloor underneath its body and hold it there. When ready to fire, the thrower positions its siphon — the tubular organ used to pump water for swimming — underneath its body, which the study authors describe as an unusual stance. Then it will violently expel water to push the debris outward.
Octopuses are “very intelligent animals,” said Janet Mann, a biologist at Georgetown University who was not involved in the study. Given that they propel water to swim and some in captivity have been known to squirt water at people, it doesn’t surprise Dr. Mann that they can also use these aquatic jets to throw objects. “They use water as a tool,” she said.
While the existence of this octopus artillery is clear in photos and videos, whether throwers ever intend for their projectiles to hit another octopus is tougher to prove. To work this out, the team used its best data — where water quality was good and individual octopuses could be identified — to see if throws that hit other octopuses differed from throws that didn’t.
Don’t take it personally, the octopus is just done with that scallop shell. Dr. Godfrey-Smith said the researchers observed that debris that hit another octopus tended to be thrown from under the aggressor’s arms differently — slightly to the side rather than straight ahead. Additionally, the material thrown varied depending on context; when seemingly trying to strike another octopus, silt was the weapon of choice. But when a scallop shell was tossed, it seemed to be thrown like garbage being discarded after eating, and not like a projectile aimed at another octopus.
Incorvaia is a journalist with NYT©2022
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