Keeping treasure safe: Eurasian red squirrels cache valuable food far from the food source with low canopy cover

Scatter-hoarding animals decide their food hoarding location by assessing food quality and pilfering risk. Previous studies have proposed two non-mutually exclusive hypotheses; the optimal density model (ODM) and the habitat structure hypothesis (HSH). The ODM proposes that animals utilize low cache density to protect their valuable caches by transporting food far from food sources. The HSH proposes that animals utilize predation risk to protect their valuable caches by hoarding food in open areas. Here, we investigated the hoarding behaviours in Eurasian red squirrels Sciurus vulgaris by experimentally providing high-quality (walnuts) and low-quality (acorns) food, to examine if they follow ODM or HSH. Compared to acorns, squirrels hoarded walnuts in places further from the area where food was provisioned and in areas with low canopy cover. These results agree with both ODM and HSH, providing the first evidence that hoarding behaviour in Eurasian red squirrels is shaped by multiple factors.