For group living species, social bonds serve to regulate many of life’s challenges, including gaining access to and defending resources (e.g., shelter and mating partners). However, with heterogenous environments and everchanging individual needs, the quality of social bonds often varies. Despite this widely acknowledged plasticity, little is known about the long-term regulation of social bonds. This dissertation investigates how social context impacts the formation and maintenance of pair bonds in the socially monogamous prairie vole (Microtus ochrogaster) and the underlying neural mechanisms modulating bond plasticity. Additionally, I explore the neurobiological shifts associated with socio-contextual changes, providing a foundation for further investigation into the mechanistic regulation of bond plasticity. In chapter 2, I show that the socio-contextual change associated with the onset of motherhood (i.e., offspring presence) results in pair bond plasticity. Additionally, in chapter 2 I show that activity of the nucleus accumbens (NAc) – a neural structure important for pair bond formation – regulates affiliative behavior well after the bond formation stage. Critically, NAc activity has also been implicated in the formation of the maternal bond. This overlap in neural mechanisms creates a potential for altered pair bond regulation during the formation of the maternal bond. In chapter 3, I characterize how the onset of motherhood impacts the expression of a suite of genes implicated in the regulation of the pair bond. These data reveal evidence consistent with altered gene expression within key regions of the pair bonding brain (e.g., NAc), signifying a potential disruption of the molecular mechanisms modulating pair bonds after the onset of motherhood. Finally, in chapter 4, I show support for the preference to bond hypothesis by demonstrating that female socio-contextual history (previously bonded or not) does not influence a male’s decision to form a pair bond. I hypothesize this male preference to bond resembles a life-history stage-specific behavioral tactic that maximizes reproductive fitness. Altogether, this dissertation provides novel insights into the regulation of social bonds by considering their expression within and across life-history stages. Furthermore, this research highlights the importance of investigating the neurobiological regulation of how multiple bonds are expressed simultaneously.