Cache protection strategies by western scrub-jays (Aphelocoma californica): hiding food in the shade.

In the presence of conspecifics, food-caching western scrub-jays (Aphelocoma californica) implement a variety of strategies to reduce the chances of cache theft. This experiment aimed to determine whether the jays could exploit an environmental variable, the level of ambient light, to reduce the transfer of visual information to potential pilferers. Each jay was allowed to cache non-degradable food in two trays, one of which was well lit, whereas the other was in shadow. In some trials the birds cached in private and in others they were observed; however, they always recovered their caches in private. When observed the jays preferentially cached in the shaded tray, whereas both trays were used equally when caching in private. By caching in shaded sites, the quality and transfer of visual information available to the observer may be reduced, thereby making the location of cache sites less certain. These results suggest that western scrub-jays may selectively cache in the shade as a strategy to reduce the chance of cache theft by observing conspecifics.