Avian Theory of Mind and counter espionage by food-caching western scrub-jays (Aphelocoma californica)

Food-caching scrub-jays hide food for future consumption and rely on memory to recover their caches at a later date. These caches are susceptible to pilfering by other individuals, however. Consequently, jays engage in a number of counter-strategies to protect their hidden items, caching most of them behind barriers, or using shade and distance as a way of reducing what the potential pilferer might see. Jays do not place all their caches in one place, perhaps because unpredictability provides the best insurance against pilfering. Furthermore, after being observed by a potential pilferer at the time of caching, jays re-hide food in new places. Importantly, however, jays only re-cache food if they have been observed during caching and only if they have stolen another bird's caches in the past. Naive birds that have no thieving experience do not do so. The inference is that jays with prior experience of stealing others' caches engage in experience projection, relating information about their previous experience as a pilferer to the possibility of future cache theft by another bird. These results raise the intriguing possibility that re-caching is based on a form of mental attribution, namely the simulation of another bird's viewpoint.