When Eduardo Sampaio first saw an octopus coiled up and hit a fish, he said, “I laughed”. That was a problem because he was diving in the Red Sea and almost choking on his dive regulator.
While an octopus was previously seen curling one of its arms and explosively releasing it into an approaching fish, the context was new. The octopus that Mr. Sampaio was watching hunted for food alongside other marine animals and this was the first time anyone had seen an octopus haymaker being thrown during such behavior.
Mr. Sampaio and his co-authors published their observations of several octopus bullies in Ecology last week. They hope their research will help uncover the dynamics between these groups of animals that can balance their competing interests through subtle – and less subtle – negotiations.
Octopuses are known as solitary predators. But sometimes an octopus participates in an underwater hunting party and travels with fish of various species that are also looking for a meal. Studying this activity is part of Mr Sampaio’s doctoral thesis at the University of Lisbon in Portugal and at the Max Planck Institute for Animal Behavior in Germany.
Although the animals hunt together, Mr. Sampaio is careful not to call it cooperation. The group mechanics are not well understood, but the animals seem to be doing different jobs. While an octopus examines crevices in rock and coral, certain fish can patrol the ocean floor and others can wait in the water above. Some fish can only be moochers.
In other cases, however, fish can work more directly with octopus. Researchers have seen groupers and coral trout make a shimmering headstand over the spot when their prey is hiding in a crack. This headstand appears to signal mates, including moray eels or octopus, who then come over and use their flexible bodies to flush out prey.
During these hunts, Mr Sampaio said: “It is good for both the fish and the squid that the partner is there.”
However, sometimes the octopus wants a partner a little further away. That’s when it delivers a sill.
These blows are not common, says Mr Sampaio. He took about eight samples during three month dives in the Red Sea.
In some cases there was a clear reason for the aggression. An octopus threw a fish out of the way so it could catch prey. At other times it wasn’t immediately clear what a fish had done to deserve a wallop.
Perhaps launching a fish to the periphery of the hunting party brings a lesson on how not to steal from the squid. Another possibility is that punching can be a learned answer.
“The simplest explanation here is that the squid may have negatively linked loss of prey to tracking a fish,” said Alexandra Schnell, a comparative psychologist at Cambridge University who studies cephalopod intelligence rather than the Research was involved.
She also said she was not convinced that the squid and reef fish would work together during these multi-species hunts.
“There is no doubt that this is wonderful footage,” said Dr. Fast, but what is visible to the human eye in the Red Sea videos “is only part of the puzzle.”
Mr Sampaio is now analyzing these videos more closely. Like a forensic scientist reconstructing a crime scene, he builds 3D models of how all animals move within a hunting group. He wants to learn more about the network of interactions: who leads and who follows? Where does the octopus look for information? And does a well-placed stroke change a fish’s behavior?
Regardless of whether a fish gets the news or not, Mr Sampaio says he doesn’t think octopuses hit by chance. That’s because animals don’t mess around when it comes to food. “Your main drive is to eat,” he said. “When that comes into play, take off your gloves.”