The intelligent octopus
ISLAND CONSERVATION - 18.01.2010
For once, the lowly octopus or zourit was in breaking news headlines around the world: Clever octopus builds a mobile home, Tool Use Found in Octopuses, Coconut-Carrying Octopus Stuns Researchers, Coconut shell shelter for “smart” octopus, Aussie scientists find coconut-carrying octopus, Octopus snatches coconut and runs… There was fierce competition among newspapers and websites to find the most attention-grabbing headline.
Even the French-language media were at it: Pieuvre qui déplace une noix de coco, Une pieuvre au comportement inédit, La pieuvre a du coco! …
The reason for the screaming headlines and hysterical broadcasts was an article that appeared in the scientific journal Current Biology on December 15 with the more sedate title Defensive tool use in a coconut-carrying octopus. A team of scientists had discovered, during research in the waters around Indonesia, that the veined octopus collects coconut shells on the seabed and carries them around to use later as protective shelters. If it has only one half-shell, it turns it over and hides underneath. If there are two half-shells, the octopus makes them fit together so that it can hide inside a shelter that looks like a whole coconut.
Tool use
This is the first documented case of an invertebrate (an animal without a backbone) using a tool. The three scientists – Julian Finn and Mark Norman of Museum Victoria in Australia, and Tom Tregenza from the University of Exeter in the U.K. -- point out in their paper: “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.” The researchers believe that the veined octopus originally used large empty bivalve shells, similar to those of the giant clam or benitye, and then switched to kafoul koko discarded by humans as these became more abundant.
I, for one, am not surprised at the discovery of tool use by octopuses. From childhood I have been fascinated by these animals - which are molluscs, by the way, and therefore related to “seashells” and snails. I would examine the catch of octopus hunters and watch in wonder the complex patterns of colour change along the tentacles and over the rest of the body.
Later I learned that these are brought about by the contraction and expansion of special cells, known as chromatophores, in the skin of the octopus – a mechanism that enables it to take on the colour of its surroundings for camouflage. Then there is the way an octopus propels itself - especially when escaping from danger - by squirting a jet of water from its mantle or bonnen. But, more importantly, since the first half of the twentieth century scientists have found out just how intelligent octopuses are.
In one set of experiments, an octopus that had attacked a crab shown with a square and received an electric shock rapidly learned not to attack when this situation appeared again, while continuing to attack crabs shown alone. During other research it was discovered that the common octopus is able to open transparent glass jars closed with a plastic plug and containing a live crab. It removed the plug and seized the crab in one single move. And, in an example of learning by observation, untrained octopuses observed conditioned or trained ones (demonstrators) perform the task of selecting one of two objects that were presented simultaneously and differed only in color. After being placed in isolation, the observers, in a similar test, consistently selected the same object as did the demonstrators.
Mating
Something else that makes octopuses such endearing creatures is the courtship and displays – flirting, in human terms – by the males before mating. This can involve elaborate postures and changes of colour and texture. A male octopus has a specially modified third arm – usually the third right one – that it uses to titillate the female and insert a sperm packet inside her oviduct. After laying, she stops feeding and spends all her time tending her eggs and cleaning them by squirting jets of water onto them.
One report, published in 2005, claimed that the annual catch of octopus in Seychelles is approximately 50 tonnes. According to another, 27 tonnes were landed in 2003. It would be interesting to see more detailed studies on our octopus populations.
In his book Underwater Seychelles, published in 1972, Al Venter wrote: “Most of the octopuses you will come into contact with will be found to be shy, reticent creatures, more anxious to disappear into the haze than befriend you.” My last encounter with an octopus was at Port Launay. It was a small one, and it was resting against a granite boulder at the very edge of the bay. I stood there for long minutes, the heat of the sun on my back and the gentle murmur of the surf all around me. I sent out my own mental tentacles of acknowledgement, in a manner of speaking, to the little zourit pressed against rock, almost exactly the same colour as its background. It didn’t budge. I don’t think it was trying to befriend me. Perhaps it was relying on its effective camouflage. Or maybe it was intelligent enough to perceive that I was not a threat and there was no need to jet off “into the haze”.
The Island Conservation Society promotes the conservation and restoration of island ecosystems.
by Pat Matyot