NORTH AMERICAN BEAVER (CASTOR CANADENSIS) DETECTION WITH ENVIRONMENTAL DNA: INFORMING SAMPLING DESIGN FOR CONSERVATION AND MANAGEMENT

The engineering activities of North American Beaver (Castor canadensis) contribute to the biodiversity of aquatic and riparian systems, provide water impoundments on the landscape, and create refugia from wildfires. Beaver activities also can result in conflict with other land uses. Beaver relocation is increasingly being applied as a tool for reducing these conflicts while restoring freshwater habitats in places where beavers are not currently active. These beaver conservation and restoration efforts require knowledge of existing beaver distribution on the landscape. Although beaver often leave visible markings of their behavior, current occupancy is not always discernable using visual surveys. We investigated the utility of environmental DNA (eDNA) detection methods for surveying and monitoring North American Beaver in 2 regions of Washington state. We conducted paired visual and eDNA surveys and tested 3 different sample-collection and filtering methods (grab samples processed using a hand pump, point sampling with the Smith-Root eDNA Sampler Backpack, and transect sampling using the Sampler Backpack). We also evaluated hypotheses of abiotic factors influencing eDNA detection. We found that eDNA sampling was effective for detecting North American Beaver at sites with and without visual signs of their presence. Beaver were highly detectable using eDNA and the most efficient and effective method of eDNA sample collection was point sampling with the Smith-Root eDNA Sampler Backpack; however, the tradeoff with cost may make hand-pump methods more suitable for some projects. Our results show that eDNA analysis can be an effective tool for the detection and monitoring of beaver and useful for relocation and management programs.