The Well-Armed Octopus: Shell-Throwing Behaviors Documented in Cephalopods

A Gloomy Octopus throws silt at another octopus as it approaches. For hitting fellow octopuses, silt is the projectile of choice. Credit: P. Godfrey-Smith *et al./PLOS ONE*

—via University of Sydney

A scientist at the University of Sydney and his colleagues have observed wild octopuses throwing silt, shells and algae underwater—sometimes hitting other cephalopods.

The research was published November 9th, 2022, in the journal PLOS ONE with the subjects being wild specimens of Octopus tetricus, the Gloomy Octopus, found in the subtropical waters of Eastern Australia and New Zealand. It is considered a member of the widespread Common Octopus, Octopus vulgaris, group.

Prof. Peter Godfrey-Smith, well-known cephalopod expert and author at the University of Sydney. Image: Dan Boud.

In one instance, the researchers watched a female O. tetricus octopus repeatedly launch silt at a male that had been trying to mate with her, with the male frequently ducking to avoid the hits.

Professor Peter Godfrey-Smith, the study’s lead author from the University of Sydney’s School of History and Philosophy of Science and Charles Perkins Centre who wrote Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness, said: “In some cases, the target octopus raised an arm up between itself and the thrower, just before the throw, perhaps in recognition of the imminent act.”

Debris throwing by *Octopus tetricus* in the wild: Panel A—Octopus (left) projects silt and kelp through the water (from video by Peter Godfrey-Smith); B–an octopus (right) is hit by a cloud of silt projected through the water by a throwing octopus (left; see SI for video of this event); C, D The mechanics of throwing behavior, C–shells, silt, algae or some mixture is held in the arms preparatory to the throw, mantle is inflated preparatory to ventilation during the throw, siphon at this stage may still be visible in its usual position projecting from the gill slit above the arm crown; D–siphon is brought down over rear arm and under the web and arm crown between the rear arm pair (arms R4 and L4), and water is forcibly expelled through the siphon, with contraction of the mantle, as held debris is released, projecting debris through the water column. Illustrations by Rebecca Gelernter.

Generally, females were more likely to throw than males.

After eating, a female Gloomy Octopus (left) tosses away empty shells. This requires an unusual position of the tube-shaped structure called the siphon, suggesting that the throw is deliberate. Credit: P. Godfrey-Smith *et al./PLOS ONE*

During observations, octopuses also threw the remains of their meals and other materials to clean their dens.

There was even a case where they hurled silt towards one of the researchers’ cameras, and another two cases where thrown “weapons” hit fish.

References

In the line of fire: Debris throwing by wild octopuses
Peter Godfrey-Smith, David Scheel, Stephanie Chancellor, Stefan Linquist, Matthew Lawrence
Published: November 9, 2022
https://doi.org/10.1371/journal.pone.0276482

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0276482#

The Well-Armed Octopus: Shell-Throwing Behaviors Documented in Cephalopods

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