Behavioral sex differences in the developmental emergence and selectivity of partner preferences in prairie voles.

Convergent evidence across foundational and clinical research has demonstrated the expansive functions and health consequences of adult pair bonding. For decades now, study of the socially monogamous prairie vole (Microtus ochrogaster) has provided valuable mechanistic insights into the neuromolecular substrates that enable adult pair bond formation and maintenance. Despite this rapidly growing literature, substantially less is known about the lifespan development of pair bonding behavior and the organization of the monogamous brain. To characterize the age at which prairie voles are capable of pair bonding, we tested if male and female prairie voles between juvenile and adult stages of development could exhibit an other-sex partner preference after 48 h of cohabitation. We found that females paired by early adolescence (P31-36) preferred to huddle with their partner over a novel male conspecific, but this selective social preference was not observed in males until adulthood (P60+). Further, the degree of preference for the pair bond partner was greater in females compared to males, suggesting that there is a robust sex difference in the developmental onset and strength of pair bonding in this species. Identifying the typical developmental trajectories of sex-specific pair bonding behavior will enable novel inquiries into the neuroscience and endocrinology of age-specific social attachments.