OOS 13-5 - Using environmental DNA to improve beaver-related restoration

The American beaver (Castor canadensis) is an iconic ecosystem engineer whose damming behaviors can contribute to the conservation of freshwater ecosystems under shifting climate regimes in the western United States. Beaver translocations to aid in restoration of aquatic habitat have been increasingly applied over the last decade. However, implementation has outpaced research and current understanding of beaver translocation success is limited by a lack of standard, sensitive monitoring methods. Additionally, there is a risk that invasive species or pathogen movement could occur during beaver translocation. Conclusions about the impact of beaver establishment on diversity are generally drawn from studies of single taxon or a subset of similar species, limiting our understanding of how beaver engineering impacts species diversity and species composition across diverse forms of life. Environmental DNA (eDNA) analysis is a flexible, sensitive tool with the potential to address these questions. We evaluated the use of eDNA for monitoring translocated beavers by pairing radio tracking with eDNA sampling. Further, we assessed whether beavers may move aquatic invasive species or pathogens by evaluating sets of eDNA samples collected from beavers throughout the translocation process. Finally, we studied the relationship between beaver dams and vertebrate communities in the Washington Cascade Range using eDNA metabarcoding at 17 beaver-dammed and 17 undammed paired sites. We found that eDNA sampling provided a rapid and sensitive means for detecting beavers, with high eDNA detection rates over 2 km downstream within a week of translocation. We reliably detected beavers in release systems through time, with positive detections occurring in >90% of samples collected downstream of confirmed beaver locations 1-3 months after initial release. Additionally, we found that translocated beavers may be exposed to fish pathogens, especially if held at fish hatcheries, but other target invasive species or pathogens were rarely detected during this process. From the metabarcoding study, we recovered 3.6 million reads from dammed sites and 5.3 million reads from undammed sites in a total of 98 eDNA samples. Our results thus far suggest that eDNA methods can accurately detect beaver presence at translocation sites or beaver distributions on the landscape, may provide powerful tools for assessing biodiversity associated with beaver engineering, and that consideration of pathogen exposure during the quarantine process may be important.