Museum Victoria’s Julian Finn and Mark Norman have recorded the first case of tool use – sophisticated behaviour generally limited to mammals and birds – in an invertebrate.
The Veined Octopus, Amphioctopus marginatus, uses foreign objects for shelter, which is common in octopuses and is not itself considered tool use. However the Veined Octopus goes a step further and prepares, manipulates and carries coconut shells up to 20 metres to reassemble its shelter elsewhere.
Julian and Mark spent more than 500 hours diving in Indonesian waters to observe and film these animals. They watched octopuses dig out coconut shells from the ocean floor, empty shells with jets of water, stack two empty shells hollow-side up, and carry the shells in a unique gait they call ‘stilt-walking’. This series of actions is among the most complex ever recorded in an octopus.
The Veined Octopus probably evolved this behaviour using clam shells as shelter. However once humans began discarding large numbers of coconut shells, they inadvertently created a steady supply of lightweight octopus tools.
Download the Coconut-carrying octopus video
Julian and Mark’s paper 'Defensive tool use in a coconut-carrying octopus' was co-authored by Tom Tregenza. It was published in the journal Current Biology on 15 December.
David’s point reflects one of the ongoing debates in the literature on tool use – when does a behaviour start to become tool use? He highlights a number of examples of invertebrates picking up objects in their environment and using them for building – something octopuses also do (see ref in our article). Even more impressively, some species of ants encountering sugar solutions will pick up masses of absorbent soil and use these to soak up the solution for transport back to the nest (also cited in our article). However, the reason we argue that the behaviour of this octopus is unique is that it carries the coconut shells around in such a way that they provide no benefit during transport, and then uses them when they will be beneficial. This is distinct from collecting a rock and then putting in front of a burrow or collecting a piece of soil to soak up liquid because these behaviours appear to occur only in response to a specific stimulus of the need to build a den or the presence of a liquid food source. In contrast, the octopus seems to carry shells, much as we might carry an umbrella – in anticipation of them being useful in the future. We fully accept that this distinction is a subtle one – this is an inevitable feature of these sorts of semantic debate – nature has a seamless continuum of behaviours whereas language is constructed to reflect our love of putting things in pigeon-holes.
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Thanks for that interesting anecdote, Max! We'll pass it on.
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