Yes, I know that P. Z. has already posted on it, but I think it deserves a bit fuller explication, for it’s the first reported instance of tool use in an invertebrate (reported in the news here, and at the journal Current Biology here). In this case the creature is the veined octopus, Amphioctopus marginatus, and the “tool” is a coconut shell that it uses as a protective home, just like a hermit crab uses another creature’s shell. What makes this real “tool use,” as opposed to what hermit crabs do, is that the octopus carries the coconut shell around with it, like an Airstream, and assembles the two halves into a protective hideaway. They’re smart little buggers. Here’s the (pardon me) meat of the story; I’ve put the direct links to the movies below:
Between 1999 and 2008, we undertook more than 500 diver hours (day and night) on subtidal soft-sediment substrates to 18 metres deep off the coasts of Northern Sulawesi and Bali in Indonesia. Over this period, we studied more than 20 individuals of the Veined Octopus, Amphioctopus marginatus (Figure 1). Octopuses were encountered in a range of behavioral states — emerged and active on the seafloor (Figure 1A); occupying empty gastropod shells, discarded coconut shell halves (Figure 1B) or other human refuse; or buried within the substrate (with or without accompanying shells; see Supplemental Movie S1 in the Supplemental Data available on-line with this issue). When flushed from shells by the observer, individuals quickly reoccupied the shells. On four occasions (three in Northern Sulawesi, one in Gilimanuk, Bali), individuals were observed to travel over considerable distances (up to 20 m) while carrying stacked coconut shell halves below their body (Figure 1C; Movie S1 ). For all instances of this behaviour, observing divers (JF, MN) remained static for up to 20 minutes at 1–2 metres from stationary octopuses, which emerged from the cover of one or two shells halves, arranged the shell(s) under the arm crown, and departed. Two shell-less octopuses were also observed to extract previously un-encountered coconut shells buried in the substrate, aided by jets of water to flush mud from shells (Movie S1 ).
To carry one or more shells, this octopus manipulates and arranges the shells so that the concave surfaces are uppermost, then extends its arms around the outside and walks using the arms as rigid limbs. We describe this lumbering octopedal gait as ‘stilt walking’ (see Movie S1 ). This unique and previously undescribed form of locomotion is ungainly and clearly less efficient than unencumbered locomotion (i.e. costly in terms of energy and increased predator risk compared with normal walking or the faster jet swimming escape; see Movie S2 ). While ‘stilt-walking’ the octopus gains no protective benefits from the shell(s) it is carrying as the head and body are fully exposed to potential predators. The only benefit is the potential future deployment of the shell(s) as a surface shelter (Figure 1B) or as a buried encapsulating lair (Movie S1 ).
The fact that the shell is carried for future use rather than as part of a specific task differentiates this behaviour from other examples of object manipulation by octopuses, such as rocks being used to barricade lair entrances . Further evidence that this shell-carrying behaviour is an example of tool use comes from the requirement of the octopus to correctly assemble the separate parts (when transporting two shells) in order to create a single functioning tool.
One of the scientists describes his reaction to the behavior, and I include it here because only an Aussie scientist, God love them, would describe it this way:
“I was gobsmacked,” said Finn, a research biologist at the museum who specializes in cephalopods. “I mean, I’ve seen a lot of octopuses hiding in shells, but I’ve never seen one that grabs it up and jogs across the sea floor. I was trying hard not to laugh.”
Figure 1 (from journal): Veined octopus, Amphioctopus marginatus. (A) Emerged on sand. (B) Using coconut shell halves assembled as shelter. (C) ‘Stilt-walking’ while carrying two stacked coconut shell halves (see Movie S1). Photos: M. Norman (A), R. Steene (B,C).
MOVIES: There are two of them at the journal site. Click the links below.
UPDATE: Neil notes in a comment below that he’s summarized several other cases of putative tool use by invertebrates.
Finn, J. K., T. Tegenza, and M. D. Norman. 2009. Defensive tool use in a coconut-carrying octopus. Current Biology 19:R1069-R1070