Observational spatial memory in Clark's nutcrackers and Mexican jays

Abstract

Recent work has demonstrated that pinyon jays, Gymnorhinus cyanocephalus, can remember the locations at which they have seen conspecifics cache food. Pinyon jays are both highly dependent on cached food and live in large social groups. To examine the importance of food caching and social living for observational spatial memory, Clark's nutcrackers, Nucifraga columbiana, and Mexican jays, Aphelocoma ultramarina, were tested on the same spatial memory tasks as used with pinyon jays. Clark's nutcrackers are highly adapted for caching food and live alone or in family groups, and Mexican jays are non-specialized cachers that live in highly structured groups. In these experiments, Clark's nutcrackers performed poorly at relocating caches they had seen conspecifics create. Observer nutcrackers were significantly more accurate than expected by chance at one but not two days after cache creation. Caching nutcrackers were more accurate at recovering caches than were observers. In contrast, Mexican jay observers performed at above-chance levels on both intervals after cache creation and were as accurate during cache recovery as were caching Mexican jays. These results suggest that observational spatial memory could be common among corvids and that its degree of development may be influenced by group living.