Researchers studying Octopus tetricus, the common Sydney octopus, have filmed the cephalopods picking up debris on their front arms and webbing and flinging it away from their bodies using water ejected from their siphon – the latter shifted between behind their arms for this purpose. . While the team says these “throws” appear to be used by the octopuses to clean the bed or to pull off the shells after eating, they have also recorded the creatures hitting other octopuses with material in what appear to be deliberate strikes . Professor Peter Godfrey-Smith, first author of the study at the University of Sydney, said the behavior was surprising, “Throwing – or advancing, or projecting – objects that have been gathered and held is rare in the animal kingdom. Propelling an object, even a short distance, under water is highly unusual, and also quite difficult to do,” he said. Writing in the journal Plos One, Godfrey-Smith and colleagues report how in 2015 they recorded more than 21 hours of video in Jervis Bay, on the south coast of New South Wales, Australia, using underwater fixed cameras, recording the behavior of around 10 octopuses . University of Sydney Octopus Aggression Research (2016) Both males and females were recorded performing ‘throws’. However, the group reports that the majority were from women, with two of them accounting for 66% of the hurling. Of the 102 discards, the team reports that 32% involved octopuses cleaning their dens, while 8% occurred after eating, with shells making up the majority of material scavenged by the creatures in these environments. However, 53% of recorded shots occurred within two minutes of one octopus interacting with another, whether fighting, mating or wrestling. These interactions also occurred in addition to another action, such as chamber cleaning, and tended to involve mud as the primary material. Additionally, the researchers note that 33% (17) of these throws involved the material hitting another octopus. It appears that such strikes may be deliberate. Among the evidence for this, the team found that octopuses that used an unusual combination of legs to hold the material, those that flew with strong force and those that were darker in color at the time of the throw were more likely to hit another octopus . “Previous work at this site found that darker colors are associated with more aggressive behaviors,” the team writes. While such strikes were generally by jets, in one unusual case the team reports that “a shell, at least partially, was thrown by straightening an arm and struck another octopus.” The team adds that recordings from 2015, as well as other footage, show instances of the cephalopods making multiple throws over a period of time, often hitting other octopuses in the process. In some cases, those in the line of fire were seen raising one of their arms before the shot in readiness – or raising the duck, either during or just before the throw. The group says it remains unclear why the octopuses would target others, adding that the footage did not show such behavior starting a fight or resulting in “return fire”, and in some cases, the throws were made at point blank range. Indeed, they write, it’s possible that octopuses are hitting each other simply as a result of interacting while in the process of other actions such as cleaning the den. But Godfrey-Smith suggested the strikes could have a purpose. “I think a lot of it is a bit like a ‘personal space’ claim,” he said. “In several cases, females threw material at male octopuses that were trying to mate with them… But in other cases, females threw and hit other females.”
