Octopuses filmed throwing things at each other, fish - even the cameras
Scientists have been left puzzled after footage caught rarely-seen footage of octopuses throwing silt and shells at one another, passing fish and even the video cameras.
The new research, published in the journal PLOS One, included footage of a female octopus repeatedly launch silt at a male trying to mate with her, with the male frequently ducking the attacks.
University of Sydney Professor Peter Godfrey-Smith, the study's lead author, said the octopuses on the receiving end of the attacks were often seen lifting up an arm, presumably in anticipation.
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Octopuses in Jervis Bay were filmed throwing shells and silt at one another. University of Sydney
Generally, females were more likely to throw than males.
Octopuses would also throw their remains of their meals and other materials away to clean their dens.
There was even a case where they hurled silt towards one of the researchers' cameras, and another two cases where throws hit fish.
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Females were more likely to throw than males. University of Sydney
Octopuses throw by gathering material in their arms, holding it in their arm web, and propelling it using their siphon – a funnel next to their head – sometimes as far as several body-lengths away.
The animals were filmed over 2015-2016 at a marine reserve in Jervis Bay.
Godfrey-Smith said it was hard to prove if the throwing was motivated by aggression.
"It is tempered by the fact that there are some things we have not seen. We have not seen an octopus who was hit by a throw 'return fire' and throw back," he said.
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Additionally, octopuses at the Jervis Bay reserve are relatively packed in, suggesting the violence could be a way of maintaining some personal space.
"Most throws do not hit others," Godfrey-Smith said.
"Only a minority of cases appear to be targeted."
He said it was "very hard" to know what their goals might be.
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