Cache protection strategies of a non-social food-caching corvid, Clark's nutcracker (Nucifraga columbiana).

Clark's nutcrackers (Nucifraga columbiana), a non-social corvid, cache much of their food in order to survive periods of resource uncertainty. These caches are at risk as they are subject to pilferage from other animals including conspecifics. Potentially, nutcrackers can ensure the safety of these caches by keeping track of whether they have been observed making a cache and subsequently engage in cache protection strategies-strategies that have been shown by other members of the corvid family (e.g., scrub-jays and ravens). Behaviors including creating more caches, eating a higher proportion of seeds, and re-caching existing compromised sites have been shown in laboratory settings with social corvids and have provided preliminary evidence of the complex cognitive abilities of corvids. In the present study, Clark's nutcrackers are shown to engage in similar cache protection behaviors when observed by a conspecific. Furthermore, we show that these behaviors are a result of social, rather than associative, cues.