Octopuses are not known for their sociability. Yet although they are typically solitary creatures, it appears that octopuses are willing to team up with other species when dinner is on the line—as long as they’re the ones in charge, of course.
This surprising behavior was discovered by researchers observing big blue octopuses (Octopus cyanea, also known as the day octopus) in the Red Sea. The researchers, from the Max Planck Institute of Animal Behavior in southern Germany, recorded 120 hours of underwater footage of a big blue octopus teaming up with various fish species to track down prey, typically smaller fish, crabs, shrimp, or mollusks.
In all of the interactions, it was obvious that the octopus was the boss, while the fish played supporting roles by exploring rock crevices and locating potential food sources, then alerting the octopus of their discovery. The researchers called the octopus “the decider of the group,” though one might also describe it as a bully. When the helper fish weren’t doing much helping, but rather hovering around waiting for the octopus to find food, the octopus would punch them with one of its eight limbs.
Some species appeared to be more helpful than others. Blue goatfish (Parupeneus cyclostomus) were more likely to identify prey and successfully alert the octopus, while blacktop groupers (Epinephelus fasciatus) did a lot of waiting around and were frequently punished with jabs and punches from the octopus. The researchers also observed some aggressive interactions between the fish species, but never towards the octopus, which appeared to make all of the decisions about where the group would hunt.
An unlikely alliance:
- The fish appeared to help the octopus save energy during the hunt so that it didn’t need to wrap its body around rocks as frequently when trying to trap prey. Typically, big blue octopuses use a technique called speculative hunting where they float along a reef, stopping at rock crevices as often as once every seven seconds in the hopes of encountering prey inside.
- While promising, numerous questions about the hunting process remain. It wasn’t clear from the video footage whether the octopus and the fish could recognize each other, or whether the octopus intentionally sought out certain species to hunt with. The researchers also wondered to what degree the octopus and fish could communicate. Famous for their color-changing abilities, they theorized that the big blue octopus might alter its hue to warn freeloading fish that they would soon be on the receiving end of a punch.
- Contrary to popular belief, an octopus does not have tentacles. Its eight limbs are actually arms (though some marine experts say it's more accurate to describe them as six arms and two legs).
