Emerging infectious diseases are an increasingly common threat to wildlife. Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is an emerging infectious disease that has been linked to amphibian declines around the world. Few studies exist that explore amphibian-Bd dynamics at the landscape scale, limiting our ability to identify which factors are associated with variation in population susceptibility and to develop effective in situ disease management. Declines of boreal toads (Anaxyrus boreas boreas) in the Southern Rocky Mountains are largely attributed to chytridiomycosis but variation exists in local extinction of boreal toads across this metapopulation. Using a large-scale historic dataset, we explored several potential factors influencing disease dynamics in the boreal toad-Bd system: geographic isolation of populations, amphibian community richness, elevational differences, and habitat permanence. We found evidence that boreal toad extinction risk was lowest at high elevations where temperatures may be sub-optimal for Bd growth and where small boreal toad populations may be below the threshold needed for efficient pathogen transmission. In addition, boreal toads were more likely to recolonize high elevation sites after local extinction, again suggesting that high elevations may provide refuge from disease for boreal toads. We illustrate a modeling framework that will be useful to natural resource managers striving to make decisions in amphibian-Bd systems. Our data suggest that in the southern Rocky Mountains high elevation sites should be prioritized for conservation initiatives like reintroductions.

boreal_toad_bd_historiesEncounter histories for boreal toads and Bd at 83 sites in the southern Rocky Mountains. Data are for 10 visits for each species from 2001-2010. Encounters are coded as 1s when boreal toads or Bd were detected, 0s if these species were not detected, and "." if no survey was conducted.boreal_toad_bd_covariatesSite and survey covariate information for 83 study sites in the southern Rocky Mountains and 100 survey dates. Site covariates include: elevation, habitat permanence, whether other amphibian species had been detected at the site in the past, and which region the site is located in. The only survey covariate used was day-of-year that the survey was conducted on.