Research suggests that certain octopuses deliberately throw objects like silt, sand, and shells at other octopuses.
21 hours of film of Octupus tetricus, the common Sydney octopus, has captured over 100 instances of individuals gathering debris in their arms and then launching it away with a burst of water from their siphon — an organ octopuses also use to help them swim and steer.
While many of these “throws” appear to be used for cleaning out the octopuses’ den or chucking away shells, 53% of the 102 throws were made within two minutes of a previous interaction with another octopus, such as fighting, grappling, or even mating. About a third of those throws hit the other octopus. On a few occasions, one octopus would notice where the other was aiming and would duck out of the way.
“The throwing — or propelling, or projecting — of objects that have been gathered and held is rare in the animal kingdom. To propel an object, even for a short distance, under water is especially unusual, and also quite hard to do,” Professor Peter Godfrey-Smith, the primary author of the study, said.
Octopuses are generally solitary and territorial creatures and have even been known to cannibalize one another. However, they are exceptionally intelligent animals — they have an unusually high brain-body ratio, although their brains are dispersed throughout their arms rather than located solely in their heads. Octopuses are capable of using tools and engaging in complex problem solving — octopuses have even been known to escape aquariums, contorting their bodies so they can slip through even the smallest cracks; a 600 lb octopus can slip through a hole the size of a quarter.
Octopuses are also able to modify the shape, color, and texture of their bodies to a remarkable degree, often as camouflage to avoid predators or ambush prey. Some researchers believe this variation in color could also reflect variations in mood or function as a kind of social signaling.
“Earlier work at this site has found that darker colours are associated with more aggressive behaviours,” the team write. Octopuses that hit other octopuses with projectiles were usually darker in color than most were when performing a normal “throw”; they also tended to hold the projectile differently and throw it with more force, further suggesting that the strikes were deliberate.
Throwing behavior is rare, however — while individuals of both sexes were observed lobbing various objects, two females accounted for 66 of the 102 total throws.
Furthermore, despite the seemingly aggressive nature of the behavior, none of the strikes escalated to a full blown fight between the animals or provoked any “return fire.”
“I think quite a lot of it is a bit like an assertion of ‘personal space,’” Godfrey-Smith said. “In quite a few cases, females have thrown material at male octopuses who have been attempting to mate with them … But in other cases, females throw and hit other females.”
The footage was collected in Jervis Bay, off the coast of New South Wales, Australia, by stationary cameras.