|Navigation & learning|
|The general topic of locomotion is divided into sections of navigation & learning, considered here, and CRAWLING and JET PROPULSION considered elsewhere.|
Research study 1
Octopuses, like other animals, navigate by retracing specific routes, by orientating to features of the landscape, or a combination of both. An octopus’ suckers are extremely sensitive to chemicals and touch, and may be most used to navigate around at night, whereas vision may be more important during the day; Studies on daytime foraging by octopuses in the field show that homeward trips to the den do not retrace outgoing paths, suggesting either a good chemotactile memory of the habitat, full reliance on vision, or a combination of the two. The diagram on the Left shows the route taken by an Octopus vulgaris in Bermuda during 7 daylight excursions from its den. No equivalent information is yet available for night excursions for any species of octopus.
Laboratory studies on visual navigation in Octopus rubescens at the Seattle Aquarium, Washington reveal a quick ability to associate landscape objects with food and to orientate quickly to a “reward”-object if it is moved around in the habitat. In one experiment, an individual in its den is presented with a piece of plastic tubing containing a crab, sucker-contact with which will yield reward of a small shore crab Hemigrapsus oregonensis as food. On the first presentation the octopus comes out to investigate and gets a food reward (see Trial 1 in diagram on Right). On the following day the “reward”-tubing with crab is moved 90o counterclockwise. The octopus starts out, spots the tubing, goes to investigate, and gets its reward (see Trial 2). On subsequent days of testing, the octopus finds the “reward”-tubing, on one occasion (Trial 3) after first going incorrectly to the Trial 1 location from 2d previously.
The author does several other experiments using different types and configurations of landscape novelties and obtains similar results. In one such experiment, an octopus already experienced in finding the reward-tubing, is presented in successive daily tests with the “reward”-tubing placed between a larger black plastic box and a white dish. In half the trials the octopus orientates first to the black box, likely the most visually obvious of the objects, and then moves to the reward-tubing; in the other half, it goes directly to the tubing. The smaller visually less obvious dish is ignored. Overall, the study shows that octopuses can learn to orientate to visual landmarks and, like rats, have a working memory of where they have been.
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