A D! Octopuses caught throwing things at each other
After eating, a female gloomy octopus (left) throws away empty shells. This requires an unusual position of the tubular structure called the siphon, suggesting that the throw is intentional.Credit: P. Godfrey-Smith et al./PLOS ONE (CC BY 4.0)
Octopus have been spotted for the first time throwing things at each other1.
Octopuses are known for their solitary nature, but in Australia’s Jervis Bay, the gloomy octopus (Octopus tetricus) lives in very high densities. A team of cephalopod researchers decided to film the creatures with underwater cameras to see if — and how — they interact.
When the researchers took the cameras out of the water, they sat down to review more than 20 hours of footage. “I call it octopus TV,” laughs co-author David Scheel, a behavioral ecologist at Alaska Pacific University in Anchorage. One behavior stood out: cases where the eight-limbed creatures collected shells, silt, or algae with their arms—then hurled them off, propelling them with water spouted from their siphon. And while sometimes it seemed like they were just throwing away debris or food scraps, sometimes it seemed like they were throwing things at each other.
The team found evidence that the octopuses were deliberately attacking each other. The throws that made contact with another octopus were relatively strong and often occurred when the thrower had a uniform dark or medium body color. Another clue: sometimes the octopuses on the receiving end would duck. Throws that made octocontact were also more likely to be performed with a specific set of weapons, and the projectile was more likely to be sludge.
A gloomy octopus throws sludge at another octopus as it approaches. For hitting fellow octopuses, sludge is the projectile of choice.Credit: P. Godfrey-Smith et al./PLOS ONE (CC BY 4.0)
“We couldn’t try to assess what the reasons might be,” Scheel warns. But throwing, he says, “can help these animals cope with the fact that there are so many octopuses around.” In other words, it’s probably social.
Tamar Gutnick, an octopus neurobiologist at the University of Naples Federico II in Italy, says the work opens a new door for research into the social lives of these famously smart animals. “The environment for these particular octopuses is such that they have this interaction between individuals,” she says. “It’s communication in a sense.”
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