Clarks Nutcracker Number Operant

Clark’s nutcrackers (Nucifraga Columbiana) cache tens of thousands of pine seeds in several thousand cache sites in the fall. The birds later retrieve a large proportion of these nuts during the winter to use as energy for survival. A large body of past work has focused on nutcrackers’ spatial cognition and their ability to recover seeds from their hidden caches. However relatively little is known about numerical cognition in nutcrackers, and birds more broadly. It is possible that food caching birds, in particular, may need a strong sense of numerosity to keep track of the number of seeds retrieved from their caches. Past work from our lab (Tornick, Callahan, & Gibson, 2015) has shown that nutcrackers spontaneously discriminate the larger of two quantities of pine seeds. Nutcrackers continued to do so even when the sets being discriminated were larger, unlike many other animals that have been tested using similar procedures. However, it was unclear in that work if the birds could use features other than number to make their discriminations. In the current set of studies, we tested the same birds from our previous study using artificial stimuli in a laboratory to better control features other than number. Nutcrackers were able to make fine discriminations of two quantities when controlling for factors like surface area. We speculate that nutcrackers impressive numerical abilities may be correlated with their dependence upon cache recovery.