The prairie vole (Microtus ochrogaster) has become a classic model for studying social monogamy. In this species, mated pairs form a bond and the father often helps care for offspring (paternal care).
For decades, researchers have investigated the behavior, hormones, and neurobiology of pair bonding of these small rodents, largely from laboratory populations. However, research in the wild has found that not all prairie voles form pairs; sometimes voles will abandon their nest and seek other mates, termed the “wandering” type. This variation in pair bonding in nature, as well as the effects of abandonment on the offspring, is a focus of Dr. Alexander Ophir’s research group at Cornell University.
Prior work from this group has found that there are consequences of paternal abandonment. Vole offspring that were raised by the mother alone have a greater stress response to social isolation. When these single-parented young reach adulthood, they are slower to form pair bonds themselves and they groom their own offspring less than voles that were raised by both parents. While there are clear effects of paternal presence, it was unclear what factors influenced the voles when they were young. Single and paired mothers usually behave similarly towards their young.
Dr. Jesus Madrid, a postdoctoral researcher in the Ophir laboratory, and Travis Covitz, an undergraduate student, began investigating whether the offspring receive cues from the mother beyond behavior. Because maternal milk delivers biological materials to offspring – nutrients, proteins, hormones, and even vesicles carrying RNA – they tested whether removal of the father from the nest right after birth altered the mother’s milk composition. The results were stark: out of the approximately 500 proteins identified in vole maternal milk, 255 of these proteins differed in concentration in the milk of partnered mothers compared to the milk of mothers whose mate had been removed. Dr. Madrid then looked into the function of the genes associated with these proteins and found that many of them were related to growth factors, developmental factors, and immune defense. He suggests that maternal milk may be influencing the offspring adaptively for an environment where the father is absent, which could signal differences in resources and social dynamics.
Dr. Madrid will present this work at the Annual Meeting of Society for Integrative and Comparative Biology in Atlanta, Georgia in January 2025.