Unity is strength:octopuses socialize with fish to hunt together

Octopuses work in groups, each with a specific role, to hunt.Mullet and grouper are the closest "friends".

• Octopuses, together with various species of fish, create groups to facilitate hunting
• Anyone who doesn't help enough, or takes advantage of other people's work, is identified and hit
• It is not yet clear whether the octopuses remember which fish helped them

As the saying goes, unity is strength and octopuses, among the most fascinating animals present on earth know this well.In this story the protagonist is the Indo-Pacific octopus who teams up with various species of fish to capture prey more easily, while paying close attention to the crafty ones.In fact, anyone who tries to sneak in and take advantage of the group's work gets a nice tentacle blow.

Octopus and fish hunting companions

Even though they are generally solitary animals they can work together with different fish species to find prey and recognize group members who do not help in the hunt.This is the conclusion of a study focused on hunting packs characterized by the presence of an Indo-Pacific octopus (Octopus cyanea) and some species of fish such as the blue mullet (Parupeneus cyclostomus) and the Indo-Pacific grouper (Epinephelus fasciatus).Hunting groups, with this composition, had already been described for the first time in the 90s, but it was assumed that fish followed the octopus in the hope of eating some leftover or some prey that has escaped from his clutches.

Today, as he says Eduardo Sampaio, researcher at the Max Planck Institute for Animal Behavior in Germany, we know why they do it:“fish explore the seabed looking for potential prey and then they call the octopus to flush them out from the cracks.Furthermore, the octopuses attack those fish that wander around the school without helping, since they have understood that they are exploiting their work."

Fish look for prey, octopus hunts them down

The Indo-Pacific octopus, as its name suggests, is very common in this biogeographical region, in fact it is found everywhere from the Red Sea to Hawaii.His way of hunting is defined web-over. It basically wraps itself around objects, like rocks, forming a sort of bag with the membrane present between its tentacles, thus managing to trap small animals.When an octopus hunts alone it makes many web-overs in rapid succession, on the contrary, when it is in the company of fish it makes fewer but longer web-overs, sometimes even for more than a minute (according to a parallel study:when a web-over lasts for that long it's because the octopus has caught something). During 120 hours of diving in the Red Sea, Sampaio and his research group, recorded 13 such group hunts.Then they were record movements manually three-dimensional images of each member of the group so that you can be analysedthe statistically.The images, and the data, revealed that it is not only the fish that follow the octopus but the octopus also follows the fish.They also noticed that if a fish moves straight and fast towards a location it is a clear signal that there is something interesting.Not only that, if the octopus ignores this movement, the fish continues to swim back and forth until it gets its attention.

A punishment for those who exploit the work of others

As anticipated, the red mullet and the grouper are the octopus's closest "friends", but researchers have identified approx six species of fish who mix with octopuses.Each of them has its own skills and tricks:the mullet fish turned out to be the one more inclined to hunt, actively looking for prey and attracting the attention of the octopus more often, while the more cunning grouper he didn't struggle much.However, the octopus - a very intelligent animal - is difficult to deceive.In the various recordings it was observed the octopus strike to the sound of tentacle blows on 27 occasions the groupers were guilty of not having helped them and having exploited the group's work.In contrast, mullets were affected only 3 times.This, according to the researchers, is a possible sign of a sort of species-level recognition:you are a good and useful species for hunting you can remain in the group.It is still not clear whether the octopus remembers which fish was previously useful or not, it is a very difficult aspect to study especially because it is almost impossible to recognize one octopus from another without any sign of recognition.

The moral is therefore that it is not important whether you are a mullet or a grouper, the important thing is that you don't make the octopus angry!