An emergent disease reduces survival of mature female eastern diamondback rattlesnakes (Crotalus adamanteus), a key demographic for a slow-lived species.

Survival of mature females disproportionately contributes to population stability via recruitment. Thus, risks of population imperilment increase when females face novel selection pressures that reduce survival. We used radio telemetry to monitor adult female (n = 23) eastern diamondback rattlesnakes (Crotalus adamanteus; EDBs) for one year, and demonstrate, for the first time, that clinical signs of fungal disease (consistent with ophidiomycosis, caused by the fungal pathogen Ophidiomyces ophidiicola; Oo) reduces survival in a free-ranging snake. Dormant season (i.e., late fall/winter) body condition was positively associated with survival. Annual survival (i.e., 68%) was the lowest currently on record for the focal species. Our results suggest that fungal disease poses a critical threat to vulnerable North American snake populations. While additional research is needed to characterize dynamics between disease pathology and demographic trends, we recommend careful consideration of disease risks when designing ophiological research experiments and the prioritization of appropriate biosafety practices.