Trust the octopus — which breaks all the rules for intelligence in a life form — to surprise us once again. The big blue octopus organizes fish to help it hunt:

Tracking 13 mixed-species hunting groups, Max Planck Institute behavioral ecologist Eduardo Sampaio and colleagues found a surprising level of sophistication in the way octopuses and fish hunt together in groups.

Analyzing footage from 120 hours of diving revealed different species contributed unique skills to the interspecies hunting party. The fish, such as the goatfish (Mullidae), perform the search, leading the group to areas of interest. But the big blue octopus (Octopus cyanea) determined when the hunt was on.

Tessa Koumoundouros, “Octopuses Team Up With Fish to Hunt, And Will Punch Them if They Act Up,” ScienceAlert, September 24, 2024

Unlike the fish, the octopus can work with stones where prey fish shelter. The fish get whatever the octopus drops, which apparently pays off for many of them.

From the open-access paper:

Day [big blue] octopuses, often considered solitary or at least asocial with conspecifics, can have a sophisticated cross-species social life without relying on previous interactions with conspecifics. This, to our knowledge, is unique in invertebrates and extremely rare in the animal kingdom.

Sampaio, E., Sridhar, V.H., Francisco, F.A. et al. Multidimensional social influence drives leadership and composition-dependent success in octopus–fish hunting groups. Nat Ecol Evol (2024). https://doi.org/10.1038/s41559-024-02525-2

First author Eduardo Sampaio from the Max Planck Institute in Konstanz told Helena Kudiabor at Nature News, “The octopus basically works as the decider of the group. There’s a sign that some cognition is occurring here, for sure.”

Enter the cheater…

One way the octopus needs some type of cognition is to deal with cheaters:

The octopuses also seemed to adapt and respond to different situations. In some groups, certain fish species — especially blacktip groupers (Epinephelus fasciatus) — were opportunistic, attaching themselves to the group without helping to find food. In some of these cases, octopuses would use their tentacles to ‘punch’ these opportunists in what seemed to be an attempt to punish them or get them to leave the group. Sampaio says that the team is interested in studying whether octopuses can recognize individual fish that have previously exhibited opportunistic behaviour.

“Octopuses and fish caught on camera hunting as a team,” September 23, 2024

Recognizing a new level of octopus smarts

A number of researchers have studied the puzzle of octopus intelligence. We typically expect intelligent life forms to be long-lived, warm-blooded, and social vertebrates like mammals or birds. But the octopus is a short-lived solitary invertebrate (cold-blooded, of course). Breaking all the rules, it is sometimes called the “second genesis” of intelligence.

In other words, researchers assume that animal intelligence generally evolved along the lines that, say, mammals and birds did. But the octopus’s intelligence seems to have a separate origin.

The basic idea Sampaio’s team noted — organizing groups of other species — is not unique, of course. Ant colonies, for example, may farm aphids. They transport the aphids to juicy leaves and protect them in exchange for the honeydew they secrete.

An ant colony, however, benefits from the hive mind, an algorithm-like way that the colony makes collective decisions. That is, no individual ant needs to figure it out; the ant needs only to obey the community algorithm, working alongside thousands of other ants.

The solitary octopus, by contrast, is developing and managing a system all on its own, which means that whatever intelligence is needed cannot be assisted simply by copying what other octopuses do.

Extended sensory system

The fish are functioning as an extended sensory system for the intelligent octopus. That’s not in itself unique either. Zebras and ostriches, for example, can work together on a predator warning system because zebras see better but ostriches smell better.

But both ostriches and zebras live in groups. So, again, they grow up learning and then replicating the system. The octopuses, by contrast — however they know how to do this — are essentially renting out their intelligence, handedness, and any other skills to the predator fish who, in return, track prey fish for them and eat the scraps. But still, what is the origin of the unexpected intelligence?

Doubtless, the octopus has more surprises in store — almost as if the sometimes too self-assured world of biology needed a shakeup.

You may also wish to read: Octopuses get emotional about pain, research suggests. The smartest of invertebrates, the octopus, once again prompts us to rethink what we believe to be the origin of intelligence. The brainy cephalopods behaved about the same as lab rats under similar conditions, raising both neuroscience and ethical issues.