Animal behavior

... A small octopus on the seafloor was busy manipulating two halves of a discarded coconut shell. The researcher assumed the animal was going to hide inside one of them. Which would have been ordinary. Octopuses hide inside things constantly. Empty shells, bottles, pipes, anything with a cavity ...

What the octopus did instead was stack the two shell halves like nested bowls, position itself on top of them, extend its arms rigidly around the outside, and walk away across the sand carrying the whole assembly with it ...

There is no immediate benefit to the animal while the shells are being carried. Whatever benefit they provide arrives later, once the octopus has stopped moving.

At the destination, the animal inverts the top shell over the bottom one, climbs inside the resulting sphere, and pulls the closure shut around itself, leaving only a small gap for water flow. The two shell halves, now assembled, function as a small hardened chamber inside which the otherwise-defenceless octopus is completely protected from view and from most physical attack. When the animal decides to move again, it disassembles the shelter, re-stacks the halves, and stilt-walks away ...

The specific reason the coconut behaviour has been treated as tool use, rather than as ordinary shelter use of the kind hermit crabs perform every day, sits in the details of how the shells are handled. A hermit crab lives inside its shell continuously. The shell is part of its ongoing life. The veined octopus does something different. It picks up the shell halves at one location. It carries them, at real energetic cost and with no immediate benefit, to somewhere else. It assembles them into a functional shelter only at the point where the shelter is actually needed. Which means the animal is, on the standard definition operating in the cognitive literature, using foresight. It is acquiring an object now for a benefit it anticipates receiving later ...

The small pink-veined octopus ... carrying its little portable house, continues to disturb the previously comfortable assumption that this kind of behaviour belonged only to warm-blooded animals with backbones.

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