The use of environmental DNA (eDNA) in biological monitoring of the Natterjack toad (Epidalea calamita)

Abstract: Environmental DNA (eDNA) is a promising new tool in the field of conservation management, which can contribute to non-destructive species determination as well as improved data on species occurrence. Still, it is important to gain knowledge on how eDNA works compared to conventional monitoring methods in order to evaluate the detection efficiency. In this study, I have investigated the use of eDNA as a compliment to the traditional survey methods used in Sweden’s national biogeographical monitoring of the red listed Natterjack toad (Epidalea calamita). E. calamita occurs in 4 different counties, Västra Götaland having a large viable population distributed on small islands in Kattegat. In Skåne, Blekinge and Halland, where the species is not considered common, it occurs in a much wider range of habitats such as coastal rock-pools, heath meadows and gravel pits. The difference in population status and county, have resulted in two slightly different survey and sampling methodologies. The study demonstrates that eDNA proved to be a useful tool for species identification and species occurrence. The assurance of species identification and low amount of potential false positives and negatives, provide justification for the usefulness of eDNA in the national monitoring of E. calamita. However, difference in results between counties indicates that there is a need for site-specific protocols to assure the most reliable results for all counties.