Influences of Affiliative Behavior in a Socially Monogamous Mammal

Abstract

All animals engage in aspects of social behavior at some time in their lives, whether through mating, territory defense, or more complex sustained cooperative behaviors. Therefore, the study of social behavior allows researchers to understand the large variability in the affective valence, length, and biological relevance of interactions among dyads or groups of conspecifics. This dissertation examines several aspects of social behavior (such as space use metrics and the number and strength of social contacts) across populations of a socially monogamous mammal, the prairie vole (Microtus ochrogaster). Throughout this research, I aim to understand and clarify the external and internal influences of among- and within-individual variation in close social contact behavior. Traditional methods of recording social behavior in small mammals, including live trapping and radio-frequency identification (RFID), are unable to track direct interactions or the day-to-day temporal dynamics of social relationships. Therefore, in Chapter 2, I first developed a novel biologging method to improve the temporal resolution of social behavior data collected in field settings with populations of small mammals. I compared the social behavior of free-living prairie voles as recorded by proximity loggers that detect direct interactions, live trapping, and RFID. I found that the use of proximity loggers for collecting social contact data increased the resolution of data (measured as the number of observations of an individual, social contacts recorded, and the strength of those social contacts) beyond that collected through traditional methods. In addition, I found that the proximity loggers recorded information consistent with patterns of spatial and temporal overlap among voles, as measured by live trapping and a passive monitoring technique. I conclude that the accessibility of proximity loggers for studies of behavior in small mammals offers a promising method for improved understanding of their social behavior and its dynamic nature. In Chapter 3, I used live trapping and a passive monitoring technique to investigate influences on social behavior in prairie voles. I compared the non-mutually exclusive hypotheses that aspects of the social environment drive social affiliation among individuals, that abiotic aspects of the physical environment drive social affiliation among individuals, and that individual traits of each vole drive their social behavior. I found that aspects of the social environment—specifically, adult sex ratio and adult population density—most reliably predicted metrics of social behavior for my study populations of prairie voles. My results indicate that aspects of demography and sociality are most influential on patterns of close social contact in this species, rather than seasonal factors. These findings add clarity to our understanding of prairie vole social behavior and help explain the behavioral variation that has been observed among populations of prairie voles for decades, by directly comparing the hypothesized influences of close social contact behavior. Finally, in Chapter 4, I explored the effects of laboratory breeding on outcomes of field studies, during which laboratory-bred animals are released into semi-natural enclosures. Despite finding quantifiable differences among the groups of founding voles used to populate the enclosures for our studies, I found only weak evidence for differences in their natural behavior. Instead, my findings are consistent with environmental influences on social behavior. These results demonstrate that, in contrast to laboratory studies of inbred animal strains, differences in laboratory breeding colonies do not significantly alter the outcomes of enclosure studies.