Scientists Discover Marine Mafias Led by Eight-Armed Dons

Octopuses are well known as loners of the sea. They’ve got plenty of reasons to live alone, after all. It allows them to better avoid predators. It means they don’t have to compete with each other for food. And they can stake out larger territories if they don’t have to share. A new study published this month in the journal Nature suggests, though, that not all of the eight-limbed cephalopods work alone.  

Imagine a gang of fish, roaming around a coral reef in search of tasty prey. At the center of the band is a leader. It's an Octopus cyanea, or big blue octopus. It directs the fish as they hunt. It even lashes out to punch any fish that it thinks isn't working hard.    

“If the group is very still and everyone is around the octopus, it starts punching," Eduardo Sampaio told NBC News. He's a researcher at the Max Planck Institute of Animal Behavior. "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." 

The octopus and its fish-gang have a social and symbiotic relationship, experts say. That means both parties get something good from it. The octopus relies on fish to hunt down prey. If the prey dares to hide in a place the fish can't reach, the octopus uses its tentacles to drag it out.    

Sampaio’s team observed group hunts dozens of times as they tracked 13 octopuses through 120 hours of video footage. They noticed that only larger octopuses formed gangs. That led the team to believe the behavior is learned over time, not something they're born with.       

Reflect: Describe a time when you saw or learned about an animal acting in an unexpected or surprising way. 

Gif of octopus punching fish from GIPHY.