Captured on camera: Octopuses hunt in groups with fish and punch them to "enforce law"

Scientists have caught Octopus cyanea (O. cyanea, otherwise known as big blue or day octopuses) exhibiting rather astounding and highly humorous behaviour when hunting for prey. The present research documents octopuses recruiting fish in an organised social system to hunt and if they don’t comply they get punished with a little bop on the head.

Habitat and behaviour

O. cyanea can typically be found in areas of the Indo-Pacific region, namely, shallow reef environments surrounding Hawaii, the Red Sea, and East Africa. Areas of craggy coral reefs are ideal for this animal, providing them with to hide, rest, and hunt for food in cracks and crevices. The species is considered to be a solitary animal employing camouflage to ambush prey, actively stalking prey, and using a webbing technique to envelop a section of reef (acting as a net) and trap prey.

How to irritate an octopus during a hunt

While the scientific community believes O. cyanea to be a solitary hunter, their research captures a social hunting behaviour, one enlisting the skills of generalist species of fish (or those that eat mollusks, fish, and crustaceans) such as the blacktip grouper, blue goatfish, and cornetfish.

A month-long study of octopus behaviour was conducted by researchers who used several cameras to track 13 octopuses over five days (or 120 hours) in situ at a reef astride Eilat, Israel. They saw groups of two to ten fish interacting with each octopus across 13 hunts. Software was used to process the video, track the motions of each animal, and produce 3D renderings.

This research showed which animal led the group and the proximity of the animals to one another. According to the findings, blue goatfish would frequently forage ahead of other fish, leading the search, but if the octopus wasn't following right away, the fish would slow and wait for the octopus.

Although the O. cyanea did not actively lead the group, the octopuses appeared irritated, administering a punch to fish that stayed close and did not keep moving on the hunt. This observation suggested that the octopuses were enforcing the law and were doing the decision-making during the hunt.

The researchers believe that the octopus benefits from interacting with the fish because it simply needs to look at them and follow as opposed to searching and exerting effort on its own. The fish are likely to benefit from having the octopus on side because its flexible, nimble body allows it to flush out prey from extremely small crevices that the fish would otherwise not reach.

Questions remain, such as whether the day octopus has a preferred fishy companion to go hunting with, but until they are answered, we can certainly sit back and enjoy this intriguing and rather amusing social behaviour.

News reference

Sampaio, E., Sridhar, V.H., Francisco, F.A. et al. Multidimensional social influence drives leadership and composition-dependent success in octopus–fish hunting groups. Nature Ecology and Evolution (2024).