Partial Consumption of Acorns by Some Rodents Leads Their Relationship with Oaks Species Towards Mutualism

Abstract

Numerous interactions between plants and animals vary in their outcome between predation and mutualism. Depending on the costs and benefits, the relationship is placed at one end of the scale or the other. A thin line separates both interactions. Acorn consumption by rodent species has been considered a predation relationship. Rodents consume acorns, which is a cost to oaks species as they are prevented from colonizing new places. The aim of this study is to show that part of the costs allocated to depredation due to loss of acorns cannot be allocated to costs. Some attacked acorns are partially consumed, but preserve their embryo and are not lost as they can germinate. This behavior, preserving the embryo, is observed in certain species. We will attempt to verify whether the behavior of conserving the embryo shown by some rodent species during partial consumption of acorns is intended to bring their relationship with oaks species closer to mutualism. To do this, we studied and compared the behavior of two acorns-consuming rodent species (Apodemus sylvaticus and Mus spretus) with another species that has never used this type of resources (Microtus arvalis), during acorns consumption. The results show that only two acorn-consuming species preserved the embryo, and not by species that are incorporating acorns into their diet. Species that have consumed acorns since ancient times show embryo-acorns preserving behavior. These species (Apodemus sylvaticus and Mus spretus) start consuming the acorns at the basal part, away from the embryo, at a higher energy expense, but they assume it because the mutualistic relationship they seek provides them with food guarantees in the future. This behavior is the contribution made by mutualistic rodents to maintain their relationship with oaks plants within the term of mutualism. Both species benefit from the relationship. Plants seeds are successfully transported to and germinated in suitable places and rodents obtain nutrients and the possibility of providing their offspring with future resources. The species not using acorns as food (Microtus arvalis) behaves as a predatory. The most convenient way for it to open the acorn is to devour the embryo, thus posing a threat to oak species.