Experts stumped by bizarre behaviour of octopus caught on camera

Underwater cameras have captured octopuses throwing silt, shells and algae towards each other on the NSW south coast.

While scientists have speculated at what’s behind the strange behaviour, they’re far from settling on a definitive answer. Until now only primates, elephants, birds and mongooses have been known to fling objects at each other.

Sydney University’s Professor Peter Godfrey-Smith said the discovery “raises questions about octopus intelligence”. “(It’s) the closest we will come to meeting an intelligent alien,” he added.

Two images showing a before and after of an octopus throwing silt.
Octopuses have been filmed throwing objects at each other. Source: PLOS ONE / Sydney University

The octopuses were seen to throw objects at each other and even fish. They achieved this by accumulating items in their tentacles and then propelling them forward using water jets expelled from their bag-like bodies.

Here’s what else we know about octopus throwing:

  • Octopuses with a uniform colour threw more often and with more vigour

  • Throws appeared more aggressive when populations were more dense

  • Most throws did not actually hit other octopuses

  • A minority of cases are believed to be targeted

  • A female threw silt repeatedly at a male who tried to mate with her

Is the octopus behaviour aggressive?

Scientists set up GoPro cameras in 2015 and 2016 at a marine park at Jervis Bay for 20 hours, documenting the behaviour of 10 octopuses. They found females were more likely to throw objects than males.

In one video, a large octopus can be seen gently extending its tentacle towards another. In a sudden act of retaliation, the smaller one flings an arm full of silt, then retreats under the dust cloud.

Researchers are yet to determine whether the behaviour is aggressive, and are yet to document any victims “return fire”.

“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,” Professor Godfrey-Smith said.

Octopuses were also observed using their throwing skills to clean their dens. The findings have been published in the journal PLOS ONE.

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