Female octopuses throw things at males that are harassing them

By Michael Le Page

The communal Sydney octopus (Octopus tetricus)

Nature Picture Library / Alamy

An investigation of footage of octopuses disconnected the seashore of Australia “throwing” shells and silt suggests that they intentionally people – and often deed – different octopuses. In astir cases, it is females that bash the throwing, often astatine males that are harassing them.

In 2015, Peter Godfrey-Smith astatine the University of Sydney and his colleagues filmed respective communal Sydney octopuses (Octopus tetricus) interacting astatine a tract successful Jervis Bay dubbed “Octopolis”. It is 1 of the fewer places successful the different sandy oversea bottommost wherever octopuses tin marque dens, truthful there are an antithetic fig of the animals in a tiny area.

The cameras captured fights, matings and an bonzer behaviour that the squad calls throwing. “It’s hard to cognize however champion to picture it,” says Godfrey-Smith.

The octopuses clasp silt, algae oregon objects specified arsenic shells nether their bodies successful their tentacles, past space their siphons and sprout a pitchy of h2o astatine the projectiles, propelling them up to respective assemblage lengths.

This throwing behaviour was known to beryllium utilized for discarding the remains of meals oregon for excavating dens, but the videos besides revealed galore instances wherever octopuses deed different individuals with thrown objects.

When Godfrey-Smith described this behaviour successful a 2015 talk, helium wasn’t definite whether they were intentionally targeting the different octopuses oregon conscionable accidentally hitting them.

Now the squad has much footage, and elaborate investigation has besides revealed differences betwixt the throws targeting others and those utilized for den clearing, suggesting the octopuses are so deliberately targeting others.

In 2016, for instance, 1 pistillate octopus threw silt 10 times astatine a antheral from a adjacent den who was attempting to mate with her. She deed him connected 5 occasions. “That series was 1 of the ones that convinced maine [it was intentional],” says Godfrey-Smith.

On 4 of these occasions, the antheral tried to “duck”, though helium didn’t ever succeed. In 2 cases, helium anticipated the throws from the female’s movements and started dodging earlier the silt was propelled astatine him.

When targeting others, the octopuses were much apt to propulsion silt than shells and the throws were besides much vigorous.

In addition, the throws utilized during den-building were astir ever changeable betwixt the beforehand 2 tentacles. When throwing astatine others, however, the octopuses sometime angled the propulsion betwixt the archetypal and 2nd tentacles connected the near oregon right. “That suggests a benignant of targeting,” says Godfrey-Smith.

On 1 occasion, the researchers did spot an octopus propulsion a ammunition astatine – and deed – different octopus by flinging it with a tentacle similar a frisbee, alternatively than by propelling worldly with its siphon.

While a fig of chaotic animals propulsion oregon propel things astatine different animals, only a handful, including chimpanzees, are known to people members of their ain species. “It’s beauteous rare. Especially uncommon is throwing of objects astatine different members of the aforesaid population,” says Godfrey-Smith.

On 2 occasions, an octopus deed a fish, though 1 of these collisions appeared to person been accidental. The animals besides seemed to people the camera connected occasion, hitting the tripod twice.

While the throwing appears to beryllium utilized arsenic a signifier of attack, the squad hasn’t seen immoderate targeted octopus respond by attacking oregon throwing things back. What’s more, immoderate throws that hap aft aggravated societal interactions aren’t directed astatine different octopus but into bare space, suggesting the animals mightiness beryllium venting their frustration.

In 1 case, aft a male’s advances to a pistillate were rejected, helium threw a ammunition successful a random absorption and changed colour.

The squad decided to merchandise the findings arsenic a preprint aft a insubstantial was released suggesting that polar bears sometimes usage rocks oregon lumps of crystal arsenic weapons during hunting, for lawsuit throwing rocks disconnected cliffs astatine walruses.

Reference: bioRxiv, DOI: 10.1101/2021.08.18.456805

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