Monogamy in a Moment: How do Brief Social Interactions Change Over Time in Pair-Bonded Zebra Finches (Taeniopygia guttata)?

Research on monogamy has largely focused on marked behaviors that are unique to pair bonded partners. However, these marked behaviors represent only a subset of the pair-directed behaviors that partners engage in; the influence of pair bonding on mundane or subtle social interactions among partners remains largely unknown. In this study, we describe the changes that occur during brief social reunions (or greets) over the course of pair bonding in zebra finches. We quantified pair-directed behavior during 5-min reunions from three stages of pair bonding: initial pairing (between 4 and 72 h), early pairing (1-2 weeks), and late pairing (>1 month). These social interactions were operationalized in multiple ways. First, we quantified the overall activity levels (call and movement rates) for both the male and female. Overall, females were more active than males, but for both males and females calling activity was highest at initial pairing. We quantified behavioral coordination between partners in two ways: (1) similarity in call and movement rates between partners and (2) temporal synchrony of calls and movements between partners (via sliding correlation coefficients of time-stamped calls and movements). Overall, there were no effects of pairing stage on behavioral coordination. Finally, we used principal component analyses to disentangle behavioral coordination from the activity levels of the male and female. These results contribute to a growing line of evidence that male and female zebra finches differentially contribute to social dynamics and highlight the influence of pair bonding on the development of social dynamics. Furthermore, our preliminary analyses raise the hypothesis that behavioral coordination during the earliest phases of pairing is modulated by the extent and nature of prior experience. Overall, while behavioral coordination is clearly important for many salient interactions such as duetting, courtship displays, and biparental care, the significance of mundane social interactions for monogamous partnerships remains largely unknown.