Note from Con Slobodchikoff: This is a guest post by Randall Johnson, who has contributed a number of posts to this blog and to the Dog Behavior Blog.
In the 1866 classic, Toilers of the Sea, French writer Victor Hugo called it a 'devil fish' and described it as "disease shaped into monstrosity".
A little more than a century later, another famous Frenchman, oceanographer Jacque-Yves Cousteau, dedicated an entire book to the devil-fish and called it a "soft intelligence".
The subject of these two diametrically-opposed descriptions is the octopus, a mollusk which, along with squids and cuttlefish, is considered by marine scientists to be the most intelligent invertebrate.
Although biologists continue to debate the extent of their intelligence and learning abilities, numerous maze and problem-solving experiments have shown that the octopus has both long-and short-term memories, despite the fact that its brain contains far fewer brain cells and has a much simpler anatomical organization than that of the vertebrate brain.
Now, thanks to almost a decade of underwater research by Australia's Museum Victoria, the results of which were published in a recent issue of Current Biology, the octopus joins a growing list of animals that use tools, which not so long ago was considered to be an exclusively human trait.
Twenty veined octopuses (Amphioctopus marginatus) were filmed for a total of 500 diver hours between 1999 and 2008 off the coasts of Northern Sulawesi and Bali in Indonesia. During that time, four individuals were seen to collect discarded coconut shells that have become a regular feature of the sea bed in the study area and deftly remove accumulated mud and sediment. Then, they turned the shells over so the open side faced upward. If they'd collected two shells, they stacked one inside the other and spread themselves over the assembled shells, raised them up by stiffening their muscular arms, and quickly scuttled away using what researchers call "stilt walking".
The coconut shells are ultimately used as a protective shelter against predators in a part of the sea bed where there are few places for the mollusks to hide. If the octopus has one shell, it turns it over and crawls underneath. If, however, it secured two shells, it assembles them back into their whole coconut form and hides inside.
One of the researchers involved in the study, Prof. Tom Tregenza, an evolutionary ecologist at the University of Exeter, UK, says: "A tool is something an animal carries around and then uses on a particular occasion for a particular purpose.
He then equates the coconut-carrying octopus to people walking around with a closed umbrella.
"While the octopus carries the coconut around, there is no use to it - no more use than an umbrella is to you when you have it folded up and you are carrying it about. The umbrella only becomes useful when you lift it above your head and open it up. And just in the same way, the coconut becomes useful to this octopus when it stops and turns it the other way up and climbs inside it."
The researchers concluded that the collection and use of objects by animals is likely to form a continuum stretching from insects to primates [shades of Darwin!] and that the definition of tools will continue to provide fodder for ongoing debate.
Of course, the octopus is reputed to be intelligent, however one defines it. It's long been known capable of figuring out how to unscrew the top of a glass jar to access to the tasty crab inside.
More recently, some octopus species in the Indonesians waters, and at least one species in the Atlantic Ocean, have been shown to have exceptional camouflaging abilities by mimicking flounders in form, coloration, and swimming speed to avoid predators, who consider flounders too tough to tackle--literally.
Without a doubt, the octopus has any number of secrets yet to be revealed…and the ones that science has managed to penetrate will continue to motivate ongoing investigations into the capabilities of the ocean's mysterious "soft intelligence".
For readers who want to read the published paper, here is the citation:
Julian K. Finn, Tom Tregenza, Mark D. Norman. Defensive tool use in a coconut-carrying octopus. Current Biology, 2009.
A soundless video of a coconut-carrying octopus can be seen at: http://news.bbc.co.uk/2/hi/science/nature/8408233.stm
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