Octopuses have been captured on camera throwing silt and shells at one another, according to new research.
Large numbers of Octopus tetricus, also known as the common Sydney or the gloomy octopus, gather in Jervis Bay, Australia, known as Octopolis due to the bountiful hunting conditions that attract the usually lone, anti-social creatures.
After analysing more than 24 hours of underwater video footage taken at the sites in 2015 and 2016, researchers from the University of Sydney were stunned to see the cephalopods throwing algae, silt and shells through the water - seemingly at other octopuses.
Although they noted 102 instances of throwing among roughly ten individuals, two females were the biggest chuckers, making 66 per cent of the throws, which tracks with past research that found female octopuses throw objects at males when they're feeling harassed.
Individuals of both sexes with darker-coloured skin threw with more force and were more likely to hit another octopus.
Lead scientist Professor Peter Godfrey-Smith said: "Octopuses that displayed uniform colour (dark or medium) threw significantly more often with high vigour, while those displaying a 'pale and dark eyes' pattern threw more often with low vigour."
The scientists state that this is the first time they have documented the behaviour in octopuses. The octopuses' motivation for throwing remains a mystery.
Professor Godfrey-Smith speculates that the behaviour arises out of a desire for their personal space.
"Most throws do not hit others," he said. "Only a minority of cases appear to be targeted... I'd speculate that a lot of the targeted throws are more like an attempt to establish some 'personal space', but this is a speculation, it's very hard to know what their goals might be."