abstract: Zoos are a unique collection-based institution with deep roots in the social structure of modern society. From their beginnings as elite menageries to display power or wealth, they have evolved into public institutions committed to providing exemplary animal care, and recreational and educational opportunities for visitors. More recently, zoos have developed a series of significant conservation programs and partnerships around the globe, efforts that have proved vital to saving endangered species such as the Arabian oryx (Oryx leucoryx) and California condor (Gymnogyps californianus), among other species. Intrinsic to the development of modern zoo designs are the interwoven concerns of naturalism and animal welfare. Animal welfare, in particular, has become the paramount responsibility for professionally run zoological institutions as they seek to become centers of conservation and education without compromising animal wellbeing. Animal welfare and naturalism (understood as a design feature in zoo exhibits) are typically harmonious objectives, but these goals have occasionally clashed in implementation. While animal welfare and naturalism are defined in various (and not always consistent) ways in the literature, in-depth interviews of leading professionals and scholars in the zoo community and multi-dimensional case studies of exemplary, accredited institutions (including the Phoenix Zoo, the San Diego Zoo, Woodland Park Zoo and Arizona-Sonora Desert Museum) provide unique insight into the shifting meaning of these terms and how welfare and naturalism have and continue to shape the development of modern zoo enclosures. This study concludes by suggesting a possible future trajectory for innovative and alternative zoo designs that incorporate both animal welfare and naturalism without sacrificing either goal. / Dissertation/Thesis / Masters Thesis Biology 2017