THE SEED-STORING CORVID CLARK NUTCRACKER LEARNS GEOMETRIC RELATIONSHIPS AMONG LANDMARKS

Many animals regularly return to particular locations such as hives, n ests, wintering grounds or cache sites. This ability clearly implies t hat animals possess information that allows them to find a route from their current location to their goal. However, the nature of this info rmation is, in many cases, unknown. One particularly important issue i s whether this information encodes at least some of the geometric rela tionships among real-world objects, which would meet a strict definiti on of a cognitive map(1,2). Are animals sensitive to such geometric re lationships? Although there is dear evidence that animals can learn ve ctors that represent a goal location in terms of absolute distance and direction to a landmark, there is little evidence of any ability to e xtract abstract geometric rules(3-8). Here we report data demonstratin g that the corvid Clark's nutcracker (Nucifraga columbiana) can learn to find the point halfway between two landmarks that vary in the dista nce that separates them. This learning is based on a general principle , as the birds correctly find the halfway point when the landmarks are presented with new distances between them. This demonstrates the abil ity to find a point defined not by the relationship between a goal and a landmark but by the relationship between landmarks. Further experim ents demonstrate that there were two distinct processes involved in lo cating the halfway point, the use of directional bearings to find the (hypothetical) line connecting the landmarks and finding the correct p lace along that line.