Navigation by spatial memory and use of visual landmarks in octopuses

This study begins to evaluate how octopuses navigate, and whether they can use visual landmarks. Paths of Octopus vulgaris were observed in the field as they foraged and responded to displacements. Octopus rubescens were trained to orient to a beacon in the laboratory, and response to its displacement was monitored. Octopuses foraged using chemotactile exploration but did not retrace their outgoing paths. Octopuses learned to orient to a beacon for a food reward, and oriented directly to it when it was moved 90 degree each day. When a three-landmark array was presented to one octopus it oriented first to the largest landmark, then to the beacon. It responded to movement of one or more landmarks suggesting both orienting to this conspicuous landmark and going to where the beacon ought to have been. The lack of disruption of octopuses' return home in the field by movement of an artificial landmark, the significant prediction of whether they would eat away from home by distance from the home, and their ease of return home when they were displaced by territorial fish, in combination with the lab data, suggested that octopuses can and do use a long-term memory of a visual landmark array.