Estimates Of Eastern Hellbender (Cryptobranchus Alleganiensis Alleganiensis) Occupancy And Detection Using Two Sampling Methods

Environmental DNA (eDNA) is a non-invasive survey method that is an increasingly popular alternative for detecting rare aquatic species. Although recent studies have demonstrated the efficacy of eDNA in detecting the presence of aquatic species, the factors affecting eDNA detection deserves substantial attention. Further, there is great variability between aquatic systems and study species. We used hellbender salamanders (Cryptobranchus alleganiensis) and occupancy modeling to investigated the factors affecting the probability of occupancy and detection for eDNA survey and traditional survey methods. We collected eDNA via water samples, conducted exhaustive traditional hellbender surveys (i.e. snorkeling, rock-turning), and characterized instream habitat three times at each of the 25 sites. Both survey methods yielded similar detection estimates, but eDNA surveys detected hellbenders at 20% more sites. Hellbenders were more likely to occur at sites with increased substrate sizes and larger catchments. Detection estimates for traditional surveys were highest at sites with larger individuals and populations. Environmental DNA detection estimates were most affected by eDNA concentrations on the filter and the amount of sand at a site. This project expands upon the current knowledge of eDNA detection by demonstrating the importance of accounting for factors affecting the detection of eDNA such as substrate composition.