Conspecific presence, but not pilferage, influences pinyon jays' (Gymnorhinus cyanocephalus) caching behavior.

Caching species store food when plentiful to ensure availability when resources are scarce. These stores may be at risk of pilferage by others present at the time of caching. Cachers may reduce the risk of loss by using information from the social environment to engage in behaviors to secure the resource-cache protection strategies. Here, we examined whether pinyon jays, a highly social corvid, use information from the social environment to modify their caching behavior. Pinyon jays were provided with pine seeds to cache in two visually distinct trays. The cacher could be observed by a non-pilfering conspecific, a pilfering conspecific, or an inanimate heterospecific located in an adjoining cage compartment, or the cacher could be alone. After caching, the pilfered tray was placed in the adjoining compartment where caches were either pilfered (pilfering conspecific and inanimate heterospecific conditions) or remained intact (non-pilfering conspecific and alone conditions). The safe tray was placed in a visible, but inaccessible, location. Overall, pinyon jays reduced the number of pine seeds cached in the pilfered tray when observed, compared with caching alone. However, their caching behavior did not differ between the pilfering conspecific and the non-pilfering conspecific conditions. These results suggest that either pinyon jays were unable to discriminate between the pilfering and non-pilfering conspecifics, or they generalized their experience of risk from the pilfering conspecific to the non-pilfering conspecific. Thus, we report evidence that pinyon jays use cache protection strategies to secure their resources when observed, but respond similarly when observed by pilfering and non-pilfering conspecifics.