Octopuses are fascinating models for understanding the evolution of complex behaviors. Two-thirds of their brain cells are spread out inside their arms, meaning that each one can operate independently. The cephalopods change their texture and shape at will — an effective trick for hunting prey or hiding from predators. Octopus also cooperate with other predatory fish when they hunt. New research reveals that the inner-workings of this interspecies collaboration is not without surprises. 

Many different species exhibit collaborative behavior in nature. Groupers and reef fish often hunt with octopuses to cover more gorund. They understand gestures from other fish which helps the group capture prey. Now for the first time, researchers captured footage of octopuses punching fish. Sometimes, seemingly, for no apparent reason.

Researchers studying cooperative hunting events filmed these interactions off the coast of Egypt. While observing different Octopus cyanea collaboratively hunting, they noticed these punches. Specifically, the octopus would aim at a fish and strike them with an explosive motion. These punches targeted different species of fish, suggesting this behavior serves an important function. 

When an octopus punches a fish, it exerts a small amount of energy while hindering an individual fish's hunt. The fish then might lose their position within the hunt, may lose out on a prey opportunity or might even be kicked out of the group. The octopus clearly has the better end of this bargain, allowing it to control which individuals it hunts with. The researchers observed cases where the octopus would quickly grab the prey after punching a fish. Curiously though, sometimes it did not gain any immediate advantage from these punches. 

The authors hypothesize that in these cases, the octopus might be punching out of spite to punish a hunting partner that cheated in the past. Alternatively, this aggression might serve to deter fish from non-collaborative behavior. This behavior may stem from complex cognitive or emotional pathways. This research provides another indication that the octopus brain, though drastically different than ours, is capable of complex behavior and cognition.