Way -finding by Clark\u27s nutcrackers (Nucifraga columbiana) and humans: An assessment of the spatial information used during landmark navigation and the flexibility of some navigational systems

A large number of studies have shown that many motile organisms can use landmarks to navigate effectively in an environment. It remains unclear how landmarks are used during the navigational process, however. For example, much behavioral and neurobiological work remains to be done to examine (a) what is the nature of the spatial information that is encoded; (b) how this information is represented by the organism; and (c) do organisms have different ways of encoding, storing and retrieving the critical spatial information. The current set of studies have attempted to explore some of these issues. In one set of experiments nutcrackers were shown and then required to locate a goal that was buried in one of 15 test positions within a fixed landmark array. The position of the array and the test positions was fixed with respect to each other, but rotated and moved within an open-room during the experiment. In contrast to previous reports with pigeons, nutcrackers were able to use relative local cues from landmarks to accurately locate the hidden goal. Additionally, nutcrackers\u27 performance at different test locations suggested that birds may be using different combinations of landmarks to improve accuracy during search. Another set of experiments explored whether nutcrackers and humans can develop and use a cognitive map, an internal representation of the geometric relationships among landmarks, to assist them in locating a hidden goal. The results from these studies indicate that subjects did encode the position of landmarks relative to the testing environment, but did not appear to use the spatial relationships among the landmarks for moment-to-moment navigation. Rather landmarks in these studies appeared useful for the setting or determination of a compass bearing that was used during navigation. While these results do not eliminate the use of a cognitive map by some subjects, they do not confirm its existence, as other navigational mechanisms were available