What have eight legs, hunt among a group of fish and can throw a mean sucker punch?
According to research published in Ecology last week, the answer would be octopuses (yes, octopuses, not octopi—we asked).
Octopuses punch fish. Deliberately. Sometimes there's a reason, but other times, there's no discernible excuse. Researchers caught this behavior on video.
The first time researcher Eduardo Sampaio witnessed this phenomenon, he laughed. Normally that'd be fine but at the time he was underwater wearing scuba equipment.
"I almost choked on my regulator," he said in an interview with NPR's Morning Edition. "When I saw it for the first time, I just burst out laughing."
The octopus is typically a solitary creature, but sometimes an octopus might take part in a hunting party made up of fishes. A grouper's gestures, for example, can clue an octopus into the location of prey. Sampaio and his co-researchers were studying this mutually beneficial behavior when they came across an octopus punching fish while hunting.
Octopuses punch fishes. YES. OCTOPUSES. PUNCH. FISHES!!— Eduardo Sampaio (@OctoEduardo) December 18, 2020
Our new paper is out on @ESAEcology, showing that octos express this behavior during collaborative hunting with other fishes. This was probably the most fun I had writing a paper. Ever! (small 🧵)https://t.co/Vwg9BoaSUo pic.twitter.com/PIYuVXpM9t
Although researchers have observed octopuses punching fish before, the behavior happening in the context of a hunting party is new. And it can come suddenly, out of nowhere, Sampaio said.
"You can see there some punches are almost like a small boop," Sampaio said. "And the other ones that even the whole arm curls up and uncurls afterwards, you know, like the motion of a boxer doing a punch."
The punches are fairly rare, so it's not so easy to observe, he said. The research prompts many questions he said, like "Is there a species that the octopus prefers to punch?"
In some cases, the researchers were able to determine the reason the underwater bully decided to strike.
Sometimes it's a partner-control mechanism, Sampaio explained, to drive the fish away from the octopus' next meal. Or it can be to control where the fish is swimming. Or it can be a form of punishment, he said.
And sometimes the eight-legged creature just punches the fish — with no discernible incentive.
DAVID GREENE, HOST:
So what does an octopus do with its eight arms? Well, that is a question that's been interesting scientists. Two years ago, Eduardo Sampaio was studying octopuses off the coast of Israel. And he saw something surprising.
EDUARDO SAMPAIO: We saw one of them punch a fish.
LEILA FADEL, HOST:
That's right. He saw an octopus curl up a tentacle, then punch a nearby fish.
SAMPAIO: I just laughed out loud, like, underwater, and I almost choked on my regulator.
FADEL: Sampaio is a Ph.D. student at the University of Lisbon. He and a team of scientists worked to record the rare phenomenon.
GREENE: And this month, they have published their findings in the journal Ecology. Sampaio says the movements are just too deliberate to be accidental jabs.
SAMPAIO: You can see that some punches are, like, almost like a small boop. And other ones, even the whole arm curls up and uncurls afterwards, you know, like the motion of a boxer doing a punch.
FADEL: He says there are good reasons an octopus might want to knock some sense into a nearby fish, such as preventing the fish from taking prey away from the octopus.
SAMPAIO: The other possibility is that it could be punishment.
GREENE: Sampaio says this work brings up more questions than it answers, and that includes...
SAMPAIO: Is there a species that the octopus prefers to punch? Or another big question I have - could I take an octopus on in a fight? I'll let you decide.
(SOUNDBITE OF SONG, "OCTOPUS'S GARDEN")
THE BEATLES: (Singing) I'd like to be under the sea in an octopus's garden... Transcript provided by NPR, Copyright NPR.