Whether an animal lives alone or with others has important implications for numerous aspects of an organism's biology. Social interactions and group living are integral aspects of some of the most exciting and intensely studied topics in behavioral biology, from the field of human psychopathology to investigations of cooperative behavior and reproductive suppression in animal societies. Understanding exactly how and why sociality evolves as an alternative to the more common trait of solitary living observed in many animals has become a topic of particular interest because growing evidence suggests that group living can incur a number of costs; for instance, animals that live in large social groups often experience an increased risk of exposure to parasites and communicable diseases compared to solitary species. This project endeavors to elucidate the ways in which social animals cope with the unique pressures associated with group living, particularly with regards to immune function, by comparing the variation in immune genes of closely related and ecologically similar species that differ in their social organization. To do this, the project uses newly developed, highly efficient laboratory procedures that allow sequencing of all active genes at the same time, thereby providing a very complete picture of immunogenetic variation. Characterizing the differences in immune genes between social and solitary species will provide insights into which genes are potentially responsible for allowing social animals - including humans - to cope with increased pathogen pressures as well as a further understanding of how disease resistance evolves and is maintained. Thus, by investigating the behavioral correlates of variation in genes found in all mammals, this work will inform current understanding of the mammalian immune system in general. This research will also provide opportunities for undergraduate involvement in research and training in both biology and bioinformatics