Can partial acorn consumption be used as a strategy to avoid the depletion of caches during acorn pilferage?

Abstract

Cache pilferage by competing conspecifics is a very common hoarding behavior used by animals. Members of rodent communities use a wide variety of strategies to minimize this pilferage. In this work, we investigated one of these strategies. We observed that certain rodent species partially consume acorns, leaving the embryo intact. We investigated whether this strategy was used by Mus spretus Lataste 1883 (Algerian mouse) to avoid cache pilferage by competing conspecifics. Partially consumed acorn remains left in underground stores could be viewed as remains by competing conspecifics, and would therefore be rejected, preventing its consumption and pilferage. To test our hypothesis, we designed three experiments on the preference for intact acorns, acorns that had been partially consumed by the rodent itself or the remains from other competing conspecific rodents. The study verified whether the remains of partially consumed acorns were rejected. We verified that these remains are more highly valued than intact acorns or even the remains of the rodent’s own previous consumption, thus rejecting our hypothesis. Remains are not used as a strategy to prevent theft. However, preference for the remains of other rodents’ acorns could form part of an anti-theft strategy. If the acorn remains are used as a decoy to attract the attention of thieves to prevent the consumption of intact acorns, the intact acorns would be better preserved in the stores for longer periods of time. The remains were consumed before the intact acorns. We verified that rodents prefer the remains of other rodents’ acorns to their own, and even prefer them to intact acorns. This behavior may be part of a strategy to reduce other rodents’ reserves to avoid future competition by conspecifics.