Episodic-like memory during cache recovery by scrub jays

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Abstract
The recollection of past experiences allows us to recall what a particular event was, and where and when it occurred, a form of memory that is thought to be unique to humans. It is known, however, that food-storing birds remember the spatial location and contents of their caches. Furthermore, food-storing animals adapt their caching and recovery strategies to the perishability of food stores, which suggests that they are sensitive to temporal factors. Here we show that scrub jays (Aphelocoma coerulescens) remember 'when' food items are stored by allowing them to recover perishable 'wax worms' (wax-moth larvae) and non-perishable peanuts which they had previously cached in visuospatially distinct sites. Jays searched preferentially for fresh wax worms, their favoured food, when allowed to recover them shortly after caching. However, they rapidly learned to avoid searching for worms after a longer interval during which the worms had decayed. The recovery preference of jays demonstrates memory of where and when particular food items were cached, thereby fulfilling the behavioural criteria for episodic-like memory in non-human animals.