The octopus and the coconut

Tool use was once thought to be the preserve of human and a very small number of higher mammals. It is now well known that certain corvids will make extensive use of tools to obtain food. Now researchers have discovered an invertebrate that can be said to use a tool.

An octopus that ferries around coconut husks while “stilt-walking” with its extended arms is among the most primitive species yet found to use tools, research has suggested. Unsurprisingly the invertebrate in question is an octopus - the veined octopus from Indonesia has been observed stacking coconut shells thrown away by humans and then transporting them across the sea floor, using them as portable armour to protect against predators.

Scientists who first observed the behaviour while diving off the coasts of Bali and northern Sulawesi said it was one of the first documented examples of an invertebrate using tools. “I could tell that the octopus, busy manipulating coconut shells, was up to something,” said Julian Finn, a member of the study team from the Museum Victoria in Melbourne, Australia. “But I never expected it would pick up the stacked shells and run away. It was an extremely comical sight — I have never laughed so hard underwater.”

His colleague Mark Norman said the “stilt-walking” with coconut shells was a clear example of tool use, which is widely known among birds and primates but extremely rare in invertebrates such as octopuses. “There is a fundamental difference between picking up a nearby object and putting it over your head as protection versus collecting, arranging, transporting — awkwardly — and assembling portable armour as required,” he said.

The octopuses’ behaviour, details of which are described in the journal Current Biology, was observed during 500 hours of diving in Indonesia, during which the researchers watched 20 veined octopuses, of the species Amphioctopus margintus.

On four occasions, the scientists saw an octopus gather up several coconut shells, stack them, and then drape itself over them to pick them up. It would then extend its arms around the bulky cargo, and walk up to 20 metres with its load.

The shells, which had reached the sea floor as discarded human rubbish, were then employed as a shelter that could be carried around from place to place. It is qualitatively different from using rocks or empty shells as an impromptu hiding place, the scientists said.

The discovery of such tool use among octopuses suggests that it is quite a widespread form of animal behaviour. “Ultimately, the collection and use of objects by animals is likely to form a continuum stretching from insects to primates, with the definition of tools providing a perpetual opportunity for debate,” the researchers wrote.

This is utterly fascinating stuff. Previous research has proved the Octopus to be intelligent so this behaviour is perhaps not a huge surprise, still...