Analysis of sucking octopuses off the coast of Australia with throwing shells and sediments suggests that other octopuses are being deliberately targeted – and are often found. In most cases, these are the females they ejaculate, and the males often harass them.
In 2015, Peter Godfrey Smith, a philosopher of science at the University of Sydney, and his colleagues photographed a number of common Sydney octopuses (Octopus tetricus) as they interacted in Jervis Bay, a site dubbed “Octopolis.” This is one of the few places in places where octopuses are sandy on the sea floor, they can make nests, so there are an unusual number of animals in a small area.
The cameras caught a brawl, mating, and odd behavior the team calls throwing. “It’s hard to know how best to describe it,” says Godfrey Smith.
Octopuses hold sediment, algae, or things like shells under their bodies in their arms, then bend their straws and shoot a jet of water at the projectiles, folding them to lengths of several bodies.
This use of tossing behavior has been known to throw up food scraps or dig nests, but the videos have also shown many examples where octopuses hit each other with discarded objects.
When Godfrey Smith described this behavior in a 2015 conversation, he wasn’t sure if they were intentionally targeting other octopuses or accidentally hitting them.
Now the team has multiple shots, and a detailed analysis has also shown the differences between targeting each other and cleaning the nest, suggesting that the octopuses intentionally target each other.
In 2016, for example, a female octopus dumped sediment 10 times on a male from a nearby nest trying to mate with him. The male was hit five times. “That series was one of the ones that convinced me it was intentional,” says Godfrey Smith.
Of these, four times the male tried to bend over, but not always. In two cases, he expected to be driven away by the female’s movements and began to dribble before the sediment drove him.
When the octopuses targeted each other, the shells were more likely to fling sediments than the shells and the throws were stronger.
In addition, the throws used in the construction of the nest were almost always fired between the two front arms. However, when the octopuses flung each other, the octopuses sometimes rolled them between the first and second arms to the left or right. “It’s kind of a sign,” says Godfrey Smith.
On one occasion, researchers saw an octopus throwing a projectile—and hitting it—on another octopus, throwing it with one arm like a flying saucer rather than throwing a substance propelled by its siphon.
While many wild animals throw or drive objects at other animals, only a handful, including chimpanzees, are known to target their own species. “It’s very rare. It’s especially rare to throw things from the same population with things,” Godfrey Smith says.
Twice, an octopus hit a fish, although one of the collisions seemed accidental. Occasionally, the animals seemed to point the camera and hit the stand twice.
While the throw seems like a form of attack, the team didn’t see any of the thrown octopus react with an attack or throw objects. Moreover, some of the throws that occurred after a strong social interaction targeted not another octopus but the empty space, suggesting that the animals might fill in their frustration.
In one case, after the female refused the approach of the male, the male threw a shell in a random direction and changed its color.
The team decided to publish the findings after publishing a research paper, indicating that polar bears sometimes use rocks or nuggets as weapons, such as by throwing stones at walruses.
(Source: New World)
The video below shows octopuses fighting when shells can be used as weapons.
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