As wildlife populations across the globe experience dramatic declines, the resulting shrinking population sizes often lead to inbreeding, which can severely threaten the health and long-term survival of a species by exposing harmful genetic mutations. Understanding exactly how mating between closely related individuals causes these negative health impacts, known as inbreeding depression, is a critical challenge for evolutionary biologists and conservationists striving to design effective wildlife management strategies. To address this fundamental issue, this project investigates a unique, extensively documented population of wild house mice that has been isolated in a natural barn environment for over twenty generations. Researchers will combine more than two decades of observational data on mouse behavior, physical development, and survival with advanced genetic sequencing of thousands of individuals to map exactly how inbreeding affects physical traits and social networks. Ultimately, by revealing the hidden genetic costs of inbreeding and exploring whether animals naturally alter their behavior to avoid it, this research will provide vital scientific justification and practical tools to guide wildlife conservation efforts, while also contributing broadly to our understanding of genetic diseases. This project advances NSF's priorities in Biotechnology. The core objective of this research is to comprehensively characterize the phenotypic, genetic, and behavioral consequ