Apparent Ophidiomycosis Alters Eastern Copperhead (Agkistrodon contortrix) Behavior and Habitat Use.

Pathogens not only cause mortality but also impose nonlethal fitness consequences. Snakes experience trade-offs associated with behaviors that combat disease but divert time and energy away from other critical activities. The impacts of such behaviors on fitness remain poorly understood, raising concerns amid the emergence of novel herpetofaunal diseases. Ophidiomycosis, caused by the ascomycete fungus Ophidiomyces ophidiicola, impacts free-ranging snakes across North America and has been implicated in declines of several imperiled populations. Although previous ophidiomycosis research has primarily focused on disease-related mortality, few studies have evaluated nonlethal impacts on snake fitness. To address this knowledge gap, we investigated the effects of apparent ophidiomycosis on the behavior, habitat use, and movement of snakes in central New Jersey, USA, from 2020 to 2021. Our focal species was the eastern copperhead (Agkistrodon contortrix), a state species of special concern with limited representation in the ophidiomycosis literature. Although we did not observe mortality in our study population, we found that copperheads with apparent ophidiomycosis (8/31 individuals) displayed significantly different thermoregulatory behaviors than snakes without ophidiomycosis. Specifically, individuals with apparent ophidiomycosis favored areas with less canopy cover, less rock cover, and more coarse woody debris. Our findings suggest that snakes with apparent ophidiomycosis select habitats conducive to initiating behavior-mediated fever, potentially facilitating recovery.