Octopuses don’t always hunt alone — but their partners aren’t who you’d expect.
A new study shows that some members of the species Octopus cyanea maraud around the seafloor in hunting groups with fish, which sometimes include several fish species at once.
The research, published in the journal Nature on Monday, even suggests that the famously intelligent animals organized the hunting groups’ decisions, including what they should prey upon.
What’s more, the researchers witnessed the cephalopod species — often called the big blue or day octopus — punching companion fish, apparently to keep them on task and contributing to the collective effort.
Octopuses have often been thought to avoid other members of their species and prowl solo using camouflage. But the study suggests that some octopuses have surprisingly rich social lives — a finding that opens a new window into the marvels of undersea life. It’s an indication that at least one octopus species has characteristics and markers of intelligence that scientists once considered common only in vertebrates.
“I think sociality, or at least attention to social information, is way more deep-rooted in the evolutionary tree than we might think,” said Eduardo Sampaio, a postdoctoral researcher at the Max Planck Institute of Animal Behavior and the lead author of the research.
“We are very similar to these animals,” he added. “In terms of sentience, they are at a very close level or closer than we think toward us.”
To understand the inner details of octopus lives, researchers dived for about a month at a reef off the coast of Eilat, Israel, and tracked 13 octopuses for a total of 120 hours using several cameras. The team followed the octopuses for 13 hunts, during which they observed groups of between two and 10 fish working with each octopus.
These hunting groups typically included several species of reef fish, such as grouper and goatfish. The octopuses did not appear to lead the groups, but they did punch at fish to enforce social order — most often at blacktip groupers.
“The ones that get more punched are the main exploiters of the group. These are the ambush predators, the ones that don’t move, don’t look for prey,” Sampaio said.
Octopuses would also punch fish to keep the group moving.
“If the group is very still and everyone is around the octopus, it starts punching, but if the group is moving along the habitat, this means that they’re looking for prey, so the octopus is happy. It doesn’t punch anyone,” Sampaio said.
The researchers think fish benefit from such hunting groups because an octopus can reach into crevices where prey hides and root out lunch. The octopus benefits, they believe, because it can simply follow the fish to food, rather than perform what the researchers call speculative hunting.
“For the octopus, it’s also an advantage because it doesn’t need to sample or go around the environment,” Sampaio said. “You can just look at the fish.”