Disease dynamics vary spatially and temporally in a North American amphibian

Local environmental conditions are a primary factor influencing chytridiomycosis, an emerging disease caused by the fungus Batrachochytrium dendrobatidis (Bd) that has affected over 200 amphibian species worldwide. In North America, seasonality and regional habitat differences predict considerable spatial and temporal disease variability, yet the sparse and opportunistic nature of most studies have provided insufficient data for understanding regional Bd epidemiology. We present a five-year field study that reveals spatial and temporal Bd dynamics across Lithobates yavapaiensis populations in Arizona, USA. Two populations showed no Bd infection or mortality, ten populations showed winter Bd infection, and five populations experienced winter mortality. Infection intensity decreased over winter sampling seasons, whereas mortality and infection prevalence did not change over time. Frogs dying from chytridiomycosis were significantly larger and had significantly higher infection intensities than survivors. We conclude that conserving L. yavapaiensis and other native amphibians requires protection and management of riparian ecosystems to promote populations large enough to survive winter cycles of chytridiomycosis.