Selective social relationships are non-fundamental relationships occurring in group living species probably due to the benefits they entail. Partner preference is the selective social relationships for familiar individuals and has been evidenced in different species across the animal kingdom. In this study, I evaluated the partner preference in same-sex female and opposite-sex social relationships in guinea pigs (Cavia porcellus). I used a partner preference test with a three-chamber experimental apparatus in which the focal individual can freely interact and choose between a familiar, a novel individual or neither of them. My results showed a high sociality and preference for a familiar partner in opposite-sex relationships. Partner preference seems to be determined by the ecological and social conditions that the species is exposed to rather than to an evolutionary context.
