Tool use is generally considered a sophisticated behaviour that is limited to mammals and birds. However, australian scientists discovered that some octopuses carried coconuts to later use as shelter. This unusually sophisticated behaviour for an invertebrate animal was published last week in the journal of Current Biology.
Cephalopods (octopuses, squid and cuttlefish) are widely regarded as the most intelligent of the invertebrates. Not only do they have their dramatic and complex colour and shape change abilities, recent observations show unexpected behavioural flexbility and the capacity to physically manipulate their environment.
Recently, Australian scientists observed soft-sediment dwelling octopuses carrying around coconut shell halves assembling them as a shelter only when needed. Whilst being carried, the shells offer no protection and place a requirement on the carrier to use a novel and cumbersome for of locomotion whereby the octopus sits on top of the shells and extends its arms around the outside and walks using the arms ar rigid limbs.
This ‘stilt walking’ is a unique and previously undescribed form of locomotion. It is much more costly in terms of energy and increased predator risk compared with normal walking or the faster jet swimming escape. The only benefit is the potential future deployment of the shell(s) as a shelter or as a ‘buried encapsulating lair’ (see movie).
The authors argued that this sophisticated behaviour is a form of defensive tool use, which has not been shown before in invertebrates. Although invertebrates have often been documented to manipulate objects, such as rocks being used to barricade lair entrances, this is the first proof of invertbrates actually using objects for future use rather than as part of a specific task.
Finn, J.K., T. Tregenza and M.D. Norman. (2009) Defensive tool use in a coconut-carrying octopus. Current Biology 19(23): R1069-R1070. (15 December 2009)