FOOD STORAGE IN GRAY JAYS - SOURCE TYPE AND CACHE DISPERSION

Animals that store food items in scattered sites must decide how to di stribute their caches in space. Our theoretical approach is based on t he assumption that such animals disperse their caches in a manner that maximizes the long-term rate of storage of recoverable (surviving) fo od items in the habitat. We investigate the cache-spacing behavior of theoretical scatter hoarders that encounter food sources differing in the energetic content of the items they contain. We then describe a fi eld experiment in which gray jays (Perisoreus canadensis) were present ed with both small- and large-item food sources. The jays compensated for source type by spacing larger-item caches more widely, a compensat ion that would tend to yield a high rate of storage of recoverable foo d energy over the long term and throughout the territory. Previous mod els do not adequately account for the observed patterns of cache dispe rsion.