A small octopus, about 15 cm (6 in) including arms, sandy brown with dark branching veins across the mantle and a bright yellow siphon. It lives on open sand and silt where there is nothing to hide in, which is the problem its behavior solves.
It carries a shelter with it. This octopus collects coconut half-shells, and where those are absent, bivalve shells or bottles, cleans them out with jets of water, and stacks them one inside the other. It then walks across the sand on two arms with the load held under the others - a stiff, comic gait known as stilt-walking - and when threatened, pulls the halves shut around itself like a clam.
That is genuine tool use, and it was the first case recorded in an invertebrate. The distinction matters: carrying an object that is useless while it is being carried, at a real cost in speed and exposure, purely for a benefit that comes later, is exactly what separates a tool from an opportunistic shelter. The 2009 paper describing it forced a rewrite of what cognitive scientists thought a mollusc could plan.
The rest is standard for the genus: crabs and bivalves for food, a clutch of very small eggs guarded by the female, and death shortly after they hatch. On a night dive on silty sand, a coconut shell that moves is the whole show.
- dark branching veins over the mantle and a bright yellow siphon
- carries shell halves or a coconut shell under its arms
- walks on two arms with the body held clear, a stiff stilting gait
- about 15 cm including arms, always on bare sand or silt
Why it's threatened
This species may be suffering from heavy fishing.
Threat classification from the IUCN Red List.
