Octopuses, fish cooperate to hunt and punish intruders: NPR

The Red Sea, located between northeastern Africa and the Arabian Peninsula, is teeming with life, including octopuses and more than a thousand species of fish.

Every day the goal of these creatures is the same.

“Anything smaller than them that can fit in their mouths, they will try to eat,” he says. Eduardo Sampaioa behavioral biologist at the Max Planck Institute for Animal Behavior in Konstanz, Germany.

He was intrigued by the descriptions of different species of fish hunting together in large schools among the coral reefs. “It’s not just one octopus and one fish,” Sampaio says. “We’re talking about one octopus and five, six, seven, eight, nine, ten completely different fish.”

For many years, the hierarchy of these groups was not clear. But in a new study published in the journal Natural ecology and evolutionSampaio and his colleagues argue that these creatures share leadership when making hunting decisions.

“This kind of very complex dynamic, which we think only arises in complex societies, we can find in the wild, even among animals that are not related to each other,” he says.

Shared leadership benefits everyone.

Before this study, Sampaio says, the consensus among researchers was that the octopus (specifically, a species called the diurnal octopus) did all the work, and the fish—usually various species of goatfish—parasitized the others.

“So the octopus will do its job, which is to hunt on its own. The fish will feed on the prey that the octopus catches, taking advantage of the situation,” he explains.

But Sampaio says he drew these conclusions largely from looking at the situation from the surface. He wondered if there was something more complicated going on. So he decided to dive in to find out.

“We can actually use multiple cameras, reconstruct everything in 3D, and try to figure out who is following whom throughout the habitat,” Sampaio says.

But this approach has its challenges, of course. “You have to find the octopus, which is an animal that has evolved not to be found,” he says. “And when you find it hunting, you have to get used to it enough that it continues hunting as if you weren’t there, and doesn’t try to escape.”

After a month of diving, Sampaio managed to record three or four hours of catching these mixed-species groups.

“I immediately realized that these groups weren’t just following the octopus, because you could clearly see that they were moving in a stop-and-go pattern,” he says. “And when this stop happens, the fish always start moving in search of prey.”

Later analysis confirmed the sophistication of their collective hunting.

“The fish explores its environment and finds prey,” Sampaio says. “Then the octopus chooses between the options the fish presents— [the octopus] “The octopus moves in there, flushes out the prey. Then the whole group moves in with the octopus.”

The fish present potential targets to the octopus, and the octopus chooses the target it wants. The creatures divide roles and share leadership, Sampaio says.

Feeding is done on a first-come, first-served basis, but with repeated hunting, everyone in the group eventually gets food. The result, Sampaio says, probably helps the fish, “because they can reach prey that would otherwise be inaccessible because they can’t reach prey in crevices.” Prey that the octopus can easily flush out. This teamwork seems to benefit the octopus, which feeds more than it would alone and with much less effort.

Intruders better stay away.

But any good party has its attackers. In this case, the blacktip sea bass waits and watches. “As soon as they see their prey, they move and try to catch it,” Sampaio says.

But these black-tipped fish pay a heavy price for their exploitation. About half the time they spend in the group, the octopus hits them. When Sampaio first saw this, he burst out laughing.

He says the octopus also hits other fish if they are unable to do their job or if the group remains still for too long. “Then this leads to more movement in the group, and then the octopus stops hitting.”

Sampaio also noticed that some species of fish attack other fish that did not contribute to the catch. “So they also understood that this species here is taking advantage for free,” he says.

But the fish didn’t hurt the octopus. Sampaio doesn’t think it’s because the octopus is stronger, but rather “the fish seems to understand that if the octopus goes away, no one gets anything.”

oceanographer Kelly Benoit BairdMary Louise, of the Monterey Bay Aquarium Research Institute, who was not involved in the research, says the study was carefully conducted, though she would like to see what happens when there are no people around using autonomous robots or cameras to film the groups.

“It’s hard to put a diver in the water at night and see if this would happen at other times of the day,” she says. “And it’s hard to do that when a storm is coming.”

However, Benoit Bird is still excited about what octopus and fish fishing groups can offer people.

““We can learn about alternative perspectives on what leadership might look like when we think about how to structure organizations or build teams to achieve better outcomes,” she says.

And maybe punches shouldn’t be allowed, she says.