The role of partially consumed acorn remains in scatter hoards and their implications in oak colonization

Abstract

Past studies have revealed the benefits of rodent participation in the colonization process of oak species. Certain rodent species (Apodemus sylvaticus and Mus spretus) partially consume acorns, beginning at the basal part and preserving the embryo. Perea et al. (2011) and Yang and Yi (2012) found that during periods of abundance, the remains left after partial consumption continue to be present on the surface and are not transported to caches, given that they are perceived as leftovers. These remains, produced after several visits by the cache owner or by thieving conspecifics, also appear in the caches. If they are perceived as offal, they will not be attacked and may remain in these stores for longer periods, serving as resources for the cache builder. Our objective is to determine whether these remnants are perceived as offal by the rodent generating them or if the remains left by other rodents are considered offal. This is relevant in cases of theft, a common behavior of this species, if the thieving animals reject the remains. The results suggest that foreign remains and the rodents’ own remains are not rejected, but rather, they are consumed in preference to intact acorns. The intact acorns remain in the cache for longer periods and have a greater opportunity to germinate and emerge. Rodents prefer to consume foreign remains first. This may be due to the fact that, in case of shortage, it is considered advantageous to finish the reserves of a potential competitor before depleting one’s own reserves. Significance statement Rodents participate in the acorn dissemination process by constructing surface stores (caches). The rodent species studied here partially consumes acorns, beginning with the basal part and preserving the embryo located at the apical end. These partially consumed acorn remains are considered offal and remain in the caches for longer periods, serving as reserves for the rodent. Our objective is to examine whether these acorn remains are viewed as offal by the rodents. We have found that, to the contrary, they are consumed before intact acorns. Intact acorns remain in the caches for longer periods, assuming the role of reserves and taking on a greater capacity to germinate. This species of rodent differentiates between its own remains and those of others, first consuming the foreign offal. Therefore, their own offal remains in the stores for longer periods and may potentially germinate if the embryo is preserved. This behavior has been demonstrated by this rodent species.