Factors influencing the use of multiple landmarks by Clark\u27s nutcrackers (Nucifraga columbiana)

Clark\u27s nutcrackers live at high elevations across western North America. Nutcrackers store tens of thousands of pine seeds in thousands of cache sites every fall. The pine seeds then serve as the nutcracker\u27s primary food source through the winter and spring. Experiments both in open aviaries and the laboratory have shown that nutcrackers use visual landmarks to relocate caches of stored food. Nutcrackers use distance and direction information from those landmarks in relocating caches. The experiments of this dissertation investigate how the distance and direction information from landmarks influences how nutcrackers encode those landmarks in relation to a cache or goal location. The first experiment tested how the distance of landmarks from a goal affects how an array of landmarks is encoded. The results demonstrate that both relative and absolute goal-landmark distances are important in spatial search. When the closest landmark of an array was very close to the goal, nutcrackers were only accurate in probe tests with that landmark. When the closest landmark of an array was more distant, nutcrackers were accurate in probe tests with multiple landmarks from the array. The remaining experiments of the dissertation examine how direction of landmarks from a goal affects nutcrackers\u27 encoding of an array of landmarks. Results showed that nutcrackers are able to use both relative and absolute bearings from landmarks to encode a goal location. The nutcrackers encoded all five landmarks of an array, although not to the same level of accuracy. The ability to use absolute bearings from landmarks also affected how the array was encoded. Subsequent experiments were performed by training a single group of nutcrackers to an array of three distant landmarks to further examine how goal-landmark geometry affects encoding of an array of landmarks. While some predictions were met, it is also apparent that other cues such as the geometry of the experimental environment are also important in spatial encoding