A veined octopus uses shells to protect itself from predators.

Credit: Nick Hobgood

Related articles

• Octopuses capable of hand-eye coordination
• Antarctic octopuses wield icy venom
• World's oldest bling discovered
• Same-sex squids mate in the dark
• Can harmful relationships actually be beneficial?

SYDNEY: A species of octopus has been observed carrying coconut shells as armour - the first known case of an invertebrate using tools.

Julian Finn, a research biologist at Museum Victoria, said he was "blown away" the first time he saw the fist-sized veined octopus, Amphioctopus marginatus, pick up its portable protection and scoot away along the sea bed.

"We don't normally associate complex behaviours with invertebrates," said Finn. "And things like tool-use and complex behaviour we generally associate with the higher vertebrates: humans, monkeys, a few birds, that kind of thing.

Intelligent invertebrates

The use of tools is considered one of the defining elements of intelligence and, although originally considered only present in humans, has since been found in other primates, mammals and birds.

But this is the first time that the behaviour has been observed in an invertebrate, according to an article co-authored by Finn and published in the U.S. journal Current Biology.

Finn observed the octopuses over a ten-year period in Indonesia. When he first saw an animal carry its shell, he thought it might be just a freak example of wacky underwater behaviour.

"So over the 10-year period basically we observed about 20 octopuses and we would have seen about four different individuals carrying coconut shells over large distances," he said.

"There were lots that were buried with coconuts in the mud. But we saw four individuals actually pick them up and carry them, jog them across the sea floor carrying them under their bodies."

Thinking ahead

Finn said the animals - whose closest relative is a snail - were slower and more vulnerable to predators while carrying the broken shells, which they later used as shelters.

"They are doing it for the later benefit and that's what makes it different from an animal that picks up something and puts it over its head for the immediate benefit."

He said it was likely other animals would be discovered to exhibit similar behaviours.