Implications of Drought and Ranavirus on an Amphibian Community in the Great Smoky Mountains National Park

The Great Smoky Mountains National Park is an epicenter of amphibian biodiversity in North America. Over the last 18 years, amphibian die-off events due to the pathogen, ranavirus, have been documented at Gourley Pond in the Cades Cove region of the Park. The goal of my study was to determine if ranavirus was present and having negative impacts on the Gourley Pond amphibian community. During my study (2016 – 2017), a significant drought occurred, allowing me to investigate possible interactions between ranavirus and drought. In 2016, I documented ranavirus persisting in three post-metamorphic amphibian species (Lithobates sylvaticus = 8.9%; Ambystoma maculatum = 1.6%, and Notophthalmus viridescens = 1.2%); however, after extended drought, ranavirus was not detected in 2017 despite extensive sampling. The drought conditions resulted in an insufficient hydroperiod for larval development of several amphibian species, and nearly complete recruitment failure both years. I documented a 39 – 99% decrease in catch-per-unit effort for five common amphibian species between 2016 and 2017. My results provide evidence that ranavirus can persist in the post-metamorphic amphibian community; however, if the pathogen is not amplified in the aquatic environment by highly susceptible larvae, its prevalence may drop below ecologically relevant levels after one year of wetland drying. My study also found that insufficient hydroperiod at Gourley Pond could be having negative impacts on the amphibian community. If these conditions persist, the U.S. National Park Service (NPS) should consider implementing conservation strategies which extend the hydroperiod at Gourley Pond, such as installing wetland liners or diverting nearby Sea Branch to the site. At a minimum, I recommend low-intensity monitoring of the hydroperiod, amphibian community, and ranavirus prevalence to inform future management decisions. I also found public visitation to Gourley Pond is high (ca. 10 trail passes per day), suggesting that humans could play a role in translocating ranavirus from the site if the pathogen re-emerges. If ranavirus is detected in the future at Gourley Pond, the NPS should consider informative signage about the pathogen and restricting access to the site