Spatial proximity is a factor that facilitates the formation of social relationships. Here, I evaluated whether spatial proximity promotes the development of low-cost relationships and whether these favor the formation of cooperative relationships (high-cost relationships). To do this, I used 23 guinea pigs distributed in six enclosures controlling for familiarity between group members. The experiment consisted of three treatments that were evaluated in three phases.In treatment A individuals could freely interact in a shared foraging arena;In treatment B individuals were forced to share the foraging arena and in the control group, individuals were not allowed to share. The results suggest that spatial proximity facilitates the development of low-cost foraging relationships. The strength of foraging relationships increased over time, a phenomenon that was more evident when individuals were allowed to freely decide whether toshare space with other individuals. Additionally, pairs that form strong foraging relationships were more likely to develop high-cost relationships. In conclusion, spatial proximity, especially voluntary proximity, promotes the formation of low-cost social relationships, and these in turn favor the formation of cooperative relationships.
