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Octopuses punch fish and sometimes do it out of spite, study shows

Rob Waugh
·Contributor
·3-min read

Watch: Why some angry octopuses punch fish

As if octopuses weren’t strange enough already, new research has shown that they “punch” fish - and sometimes seem to do so out of spite.

Researcher Eduardo Sampaio, of the University of Lisbon in Portugal, observed octopuses as they hunted alongside fish (something the two creatures do regularly).

Sampaio and his colleagues saw octopuses lashing out, sometimes in a similar way to diners “elbowing their way” up to the buffet – prior to grabbing food (prey).

But at other times, it was less clear why the octopus had hit the fish – and the researchers suggest it is sometimes done purely out of spite.

“Octopuses punch fish,” says Sampaio. “They express this behaviour during collaborative hunting with other fish.

Octopuses punch fish, the researchers discovered (Eduardo Sampaio)
Octopuses punch fish, the researchers discovered. (Eduardo Sampaio)

Read more: Octopus arms ‘make decisions on their own, without the brain’

The research was published in the journal Ecology.

Sampaio said: “Octopuses and fishes are known to hunt together, taking advantage of the other's morphology and hunting strategy. Since multiple partners join, this creates a complex network where investment and payoff can be unbalanced, giving rise to partner control mechanisms.

“We found different contexts where these punches occur, including situations where immediate benefits are attainable, but most interestingly in other contexts where they are not!”

Sampaio and his team watched octopuses interacting with other fish species in the Red Sea including tailspot squirrelfish, blacktip and lyretail groupers.

The researchers found that the “directed explosive arm movements” occurred in several different contexts.

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The researchers say that in most cases, the action is followed by an attempt to retrieve prey.

“The octopus performs a swift, explosive motion with one arm directed at a specific fish partner, which we refer to as punching,” scientists wrote.

“From the octopus’ perspective, punching serves as a partner control mechanism, the nature of which is dependent on the ecological context of the interaction.”

But in some cases, the octopuses attack fish without there being any immediate benefit.

The attack is either motivated by spite, or to “bully” the fish into co-operating in future, the researchers say.

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The researchers write, “Other events show that punching is not always followed by an attempt to retrieve prey, indicating it also occurs in the absence of immediate benefits.

“In the first one, benefits are disregarded entirely by the octopus, and punching is a spiteful behaviour, used to impose a cost on the fish regardless of self-cost, e.g. after defection (stealing prey) by a usually collaborative partner.

“In the other theoretical scenario, punching may be a form of aggression with delayed benefits (i.e. direct negative reciprocity or punishment), where the octopus pays a small cost to impose a heavier one on the misbehaving partner, in an effort to promote collaborative behaviour in the following interactions.”

Watch: Here’s how octopuses use their tentacles to taste