Social information used to elicit cache protection differs between pinyon jays and Clark's nutcrackers.

Behavioral plasticity can be described as the ability to adjust behavior depending on environmental information. We used a food-storing (caching) paradigm, during which individuals either ate or cached food under different conditions, to investigate whether they could adjust their caching behavior when observed by conspecifics and heterospecifics and which social cues they used to elicit these behavioral changes. We examined the location and number of caches made by two corvid species differing in sociality: highly social pinyon jays (Gymnorhinus cyanocephalus) and less social Clark's nutcrackers (Nucifraga columbiana). Although pinyon jays cached a similar amount of food across conditions, they allocated significantly more caches to areas less accessible to the observer. Nutcrackers, however, significantly reduced the number of seeds cached when another nutcracker was present in comparison to when they cached alone. Both species relied on different social cues to elicit re-caching: pinyon jays responded to the amount of time the observer spent close to the caching locations, whereas nutcrackers responded to the amount of time the observer spent pilfering their caches. The differences in cache protection behaviors and the social cues eliciting them may be explained by the species' social organization. Pinyon jays may only adjust their caching behavior when necessary, as they are often surrounded by other individuals. Being less social, Clark's nutcrackers reduce their caching when observed, as they have more opportunities to cache alone and may resort to additional cache protection when experiencing pilferage. Overall, our results provide insight into understanding how pressures associated with the social environment may influence foraging behaviors. Significance statement: To maximize resources, Corvidae will hide food for later consumption and seek out the hidden food of others. These birds also subvert this ecological game of "hide-and-seek" by re-hiding food that other birds know about. We demonstrate that two corvid species initiate "hide-and-seek" in response to different social information. Social pinyon jays re-hide their food after another bird approaches their hiding spots, a proactive response suited for species living in groups, in which attributing food theft to a specific individual may be difficult. Less-social Clark's nutcrackers re-hide food only after seeing another bird steal from them, a reactive response suited for species that typically have more opportunities for privacy when hiding food. We demonstrate corvids adapt to the risk posed by birds "seeking" their food, though which behaviors of the seeker are deemed risky differ between species and are shown to align with ecological demands. [ABSTRACT FROM AUTHOR]