Female octopuses throw things at itchy males, and look, we totally got it

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When it comes to getting rid of an annoying parasite, sometimes subtlety isn’t enough. Sometimes it is enough to throw anything or everything at hand, bombarding the offender with shells and debris until he rushes to his hole.

OK, this approach is probably not great for humans. But for octopuses, it seems to work like a treat, according to new research.

In a site off the east coast of Australia, where such a large number of Sydney octopuses (Octopus tetricus) gather that scientists have dubbed the Octopolis region, scientists first observed octopuses throwing objects at each other in a heated argy-bargy scene in 2015.

Debris thrown by octopuses in the wild. (Godfrey-Smith et al., BioRxiv, 2021)

Now, they’ve determined that the flingers are mostly women – and they’re probably trying, at least in some cases, to keep men who are too in love away.

“Throwing of material by wild octopus is common, at least at the site described here. These throws are performed by picking up material and holding it in the arms, then expelling it under pressure,” researchers write in their pre-printed paper.

“The force is not transmitted by the arms, as in a human throw, but the arms organize the projection of matter by the throw … The throw in general is more often seen by women, and we have not seen only one hit (a marginal hit) of a throw by a male. Octopuses that were hit included other females in nearby dens and males that attempted to mate with a female thrower. “

A lot of animals throw debris at others, and there are many reasons to do so. It may be a threat or defensive behavior, or it may have to do with trapping prey. Most animals seen doing this, however, throw objects at other species, not theirs.

So, to find out why octopuses would like to throw shells, silt and algae at each other, a team of researchers led by science philosopher Peter Godfrey-Smith of the University of Sydney set out to observe the jet in action.

Using non-invasive GoPro cameras left behind, they recorded more than 100 cases of Octopolis residents throwing debris willy-nilly. The octopuses held equipment in their arms, then used their siphon to blow a jet of water that would blow the material up to several body lengths.

As they analyzed their recordings, the researchers noticed that there appeared to be two main types of throwing. The first was about housekeeping and keeping their cozy dens free from unwanted debris and food waste.

The second seemed a little more focused. Octopuses, determined to be (mostly) females, have been observed throwing gear at other octopuses during targeted attacks. Overall, shells were the most frequently fired object, at 55 instances recorded.

For 33% of those targeted throws, the thrown object actually hit the intended target, with silt being the best material for this task. The targets were either other nearby females or males attempting to mate.

In one notable case, recorded in 2016, a female octopus threw material at a male 10 times over a period of 3 hours and 40 minutes, hitting him five times. Interestingly, the octopuses that were hit by such ejecta did not attempt to retaliate, but sometimes attempted to duck down (although not always successfully).

Another, perhaps a little more controversial, explanation for this behavior could be that throws aren’t always necessarily targeted, but could be a form of temper tantrum due to frustration.

After several dramatic interactions, the researchers observed that one octopus was throwing objects in a way that did not appear to be directed at the other octopus. Given the difficulty of ascribing intention to animals, especially those that are as alien as octopuses, it is impossible to definitively conclude that this is the case.

Either way, it seems that the throw seems to be playing some sort of social role.

“Octopuses can thus definitely be added to the shortlist of animals that regularly throw or propel objects, and provisionally added to the shorter list of those who direct their jets at other animals,” the researchers write.

“If indeed targeted, these throws are directed at individuals of the same population in social interactions – the less common form of non-human throwing.”

The document is available on the pre-print website bioRxiv.


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