Placement, Retrieval, and Memory of Caches by Thirteen-Lined Ground Squirrels

Mechanisms governing placement and retrieval of scatter hoards were investigated in 13-lined ground squirrels ( Spermophilus tridecemlineatus ). The squirrels used several placement tactics, including relatively deep burial of seeds, avoidance of prominent objects, and cryptic placement, which would reduce chance discovery by competitors but that might also increase the difficulty of retrieval for the hoarder. Nevertheless, scatter hoards were unfailingly retrieved within a day or two after placement, despite experimental elimination or displacement of local sensory cues emanating from the sites. Artificial caches placed close to true caches were not discovered, indicating that recovery attempts were quite precise. These results imply that 13-lined ground squirrels rely heavily on spatial memory for retrieval and are the first experimental demonstration of the importance of memory for cache recovery in a natural population of mammals.