During years of dives in Indonesian waters, biologists Julian Finn, Tom Tregenza and Mark Norman observed veined octopuses (Amphioctopus marginatus) collecting coconut-shell halves, cleaning them with jets of water and carrying them across sandy and muddy seafloors. Some journeys reached up to 20 metres. The team documented the behavior in 20 octopuses and recorded four instances of shell-carrying.
The animals moved with the shells held beneath their bodies, extending their arms over the edges and walking on the tips of their limbs. The researchers called this “stilt-walking.” It was a slow and exposed way to travel, especially since octopuses can otherwise escape quickly by jet propulsion.
The purpose became clear at the end of a journey. An octopus would place itself inside one half and, when it had two, position the other over its body to create an enclosed shelter. It held the pieces together with its suckers. On open seabeds with few natural hiding places, the shells offered a portable refuge that the animal could assemble when threatened.
In a paper published in Current Biology on December 15, 2009, the researchers described the behavior as defensive tool use. Unlike a hermit crab, which remains protected inside its shell while moving, the octopus carried the coconut halves without gaining protection until it assembled them at its destination. That separation between carrying an object and using it later was central to the team’s interpretation.
The scientists suggested that the behavior may have developed from octopuses using large mollusc shells found naturally on the seafloor. Discarded coconut shells from coastal communities could have provided another durable, stackable material. The study did not establish when the behavior began or show that human waste caused it. Nor does the observation prove that the octopuses consciously planned for future use; the scientific definition of tool use remains debated.
The finding added to evidence of the varied ways cephalopods interact with their surroundings. In this case, the octopuses collected, transported and assembled objects to meet a defensive need, turning discarded shells into temporary shelters.
Sources: Xataka.