In 2009, scientists discovered something extraordinary in Indonesian waters: small octopuses that collect scraps and coconut shells and walk with them on the seabed, sometimes up to 20 meters. That way of moving was so uncomfortable that the animals came into contact with their predators. Until researchers discovered what the coconuts were transported for. The discovery turned out to be one of the most surprising observations about the intelligence of invertebrates.
A sight that is hard to believe. Over the course of nearly a decade, biologists Julian Finn, Tom Tregenza and Mark Norman spent nearly 500 hours diving in Indonesian waters from the Lembeh Strait to Bali. They were studying the marbled octopus (Amphioctopus marginatus), a small species that lives on sandy and muddy bottoms, when they began to observe strange behavior.
Some specimens dig up coconut halves, clean them with water jets and carefully place them under their bodies. Then they picked up the shells and started walking. Norman admitted that he found the scene so funny that he had a hard time containing his laughter underwater without flooding his diving mask.
Twenty octopuses and inexplicable behavior. The researchers studied 20 specimens and documented four cases where they carried shells for distances of up to 20 meters. Some carry a single half, others stack two like nest bowls. To move, the animal extended its arms on its extremities, lifted the shell, and advanced on the tips of its limbs, in a movement that scientists call stilt-walking, literally walking on stilts.
The technique was particularly odd because octopuses can escape quickly using jet propulsion, but carrying these objects forced them to move slowly and stay in contact with predators. At first glance, they were risking enough to carry something that seemed to be of some use to them.
Until they discovered what they wanted the coconut for. The explanation appeared when the researchers observed what happened at the end of the path. The octopus accumulates the shell, enters one half and, if it has two, keeps the second on its body until it forms a protective sphere. From the inside, it holds the two pieces together using its suction cups, turning two simple plant remains into a closed shelter.
It was highly effective in the sandy bottoms of Indonesia, which lack rocks and natural hiding places. The creature can move across completely open terrain and when a threat arises, sets up a small fortress in an instant. What seemed an unreasonable burden was, in reality, a portable shelter.
That changed the detailed investigation. Octopuses were already known for their ability to hide in rocks, use shells, or modify their environment, but transporting coconuts introduced a fundamental difference. As they walked half-stacked, they afforded them no protection: the advantage came later, when they gathered for shelter.
That delayed utility led Finn, Tregenza, and Norman to interpret the behavior as a form of tool use, an ability long associated primarily with humans, other primates, and certain birds. In fact, the discovery was published on December 15, 2009 in the scientific journal Current Biology under the title Use of protective equipment in coconut-carrying octopuses. The study became a reference to tool use among invertebrates, although it was not the first documented case of this entire animal group.
Why it’s not like a hermit crab. Comparisons with hermit crabs explain why this behavior was so unique. These crustaceans use empty shells as permanent protection and stay inside them when they move, so that the object always performs its function. The marble octopus, on the other hand, carries shells without protection during the journey and uses them only when it needs to build a shelter.
This separation between transporting an object and later using it was the central rationale for researchers to classify the behavior as tool use. However, it is important to note that the scientific definition of a tool is still a matter of debate, and observing future utility does not in itself prove that the animal consciously plans like a person.
Humans were able to provide them with the perfect ingredients. The researchers proposed that this behavior may have originated from the use of large mollusc shells that are naturally available on the ocean floor. Over time, coastal communities in Indonesia began discarding the halves of coconuts that ended up in the water, providing the octopus with a robust, easily transportable alternative.
The shells had an additional advantage: they could be nested inside each other and later combined to form a closed shelter. The hypothesis is plausible, although the work does not reveal when the behavior began or whether human waste is its source. Amazingly, in any case, an object abandoned by our species can become a protective resource for others.
An intelligence that did not need to resemble human intelligence. Because the 2009 discovery adds an important piece to our knowledge of cephalopods, a group of molluscs whose evolution diverged from vertebrates millions of years ago. Despite this evolutionary distance, octopuses have complex nervous systems and show remarkable abilities to explore objects, solve problems, and adapt to new situations.
Indonesia’s documented behavior has shown that they can collect, transport, and integrate elements of the environment to address a defensive need, although this does not allow for the characteristics of conscious planning for our future. The paradox is that the clumsiest movement in the entire sequence revealed precisely its sophistication: those octopuses walking slowly across the ocean floor as they found a way to carry with them something that was scarce there, a safe place to hide.
Picture | Noobgood
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