Australia’s ‘Gloomy Octopuses’ have been caught throwing things. Sometimes at each other.
Underwater footage, from Jervis Bay in New South Wales, shows Gloomy Octopuses (Octopus tetricus) throwing debris. Occasionally the material – mainly silt, shells and algae – was aimed at other octopuses, and even the camera recording them.
Throwing is an uncommon behaviour in animals, an activity only observed in a handful, including elephants and chimpanzees.
Twenty-four hours of footage gathered during 2015 and 2016 captures around 100 octopus throws among a group of roughly ten of the animals. Ninety throws were by females, and eleven by males.
On 17 occasions, octopuses threw material which actually hit another octopus, often with ‘high vigour.’ In two cases, the throw hit a fish. Twelve meanwhile were directed at the camera.
One female octopus was recorded throwing 17 times in the space of an hour, with nine throws hits on other octopuses (who sometimes ducked or raised their arms in the direction of the thrower).
The gloomy octopus is common in Australian and New Zealand waters.
Having gathered their ammunition, octopuses hurled their material by using a jet of water from their siphon (a tube-shaped structure that can eject water at speed) to propel it between their arms. Throwing under water requires greater force than throwing through air, and the octopuses often managed to throw their material several body lengths away.
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Given the octopuses had to move their siphon into an unusual position to perform the throws, the researchers believe the behavior was deliberate.
The study by Australian and US researchers is the first-time throwing behaviour has been reported in octopuses. The research is published in PLOS One.