Journal Article

Comparing cost, effort, and performance of environmental DNA sampling and trapping for detecting an elusive freshwater turtle

Katz, Aron D., Sperry, Jinelle H., Larson, Eric R., Pearce, Sarah E., Davis, Mark A., Sternhagen, Elizabeth C., Ecrement, Stephen M.

2024

Overview

Environmental DNA (eDNA) analysis is an effective and non‐invasive technique for surveying and monitoring rare, threatened, or endangered (RTE) species. Compared to conventional capture‐based sampling, eDNA analysis may offer a more cost‐effective approach for surveying RTE species, yet few studies have compared their cost‐efficiency—a critical consideration for conservation planning. We compared the costs, effort, and relative performance of aquatic eDNA sampling and conventional trapping for detecting the Alligator Snapping Turtle, Macrochelys temminckii Troost, 1835, in southwest Louisiana, United States. Environmental DNA was sampled quarterly over 1 year (2018–2019) at 19 streams, including three streams where M. temminckii presence had been previously confirmed via conventional trapping efforts (2012–2013). Water samples from each stream were analyzed using quantitative polymerase chain reaction (qPCR) to assess M. temminckii eDNA presence/absence. Time and costs (i.e., labor, travel, wages, and supplies) per detection via eDNA analysis and trapping were calculated and compared. Environmental DNA analysis documented the presence of M. temminckii DNA at two of the three streams where individuals had previously been trapped and yielded detections (qPCR amplifications) at 16 additional streams not previously sampled, expanding M. temminckii's documented distribution at our study sites by 84%. Environmental DNA analysis returned a detection rate (per site) 5.55 times higher than conventional trapping and was 18.7% less expensive. Our results provide evidence that strategically deployed eDNA surveys may be an effective and cost‐efficient approach for detecting freshwater RTE species. With eDNA analysis, additional resources can be invested toward expanding survey coverage and increasing sampling frequency, allowing managers to more effectively target subsequent intensive monitoring efforts. Successful integration of a new method into a standard management regime requires understanding both its relative efficacy and cost‐effectiveness when compared against conventional sampling methods. We successfully detected M. temminckii in Louisiana streams using both eDNA surveys and conventional trapping with eDNA surveys yielding 5.55 times higher detection rates, 40% fewer labor hours per detection, and 84% more streams surveyed per year than conventional trapping. Our results suggest that eDNA presents a promising and cost‐efficient technique for M. temminckii surveys.

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: alligator snapping turtle / Aquatic reptiles / Cost analysis / Costs / Creeks & streams / eDNA / Efficiency / Endangered & extinct species / Endangered species / Environmental DNA / Macrochelys temminckii / Monitoring / Polymerase chain reaction / quantitative PCR / Rare species / Sampling / Surveying / Surveys / Threatened species / Trapping / Turtles / Water analysis / Water sampling / Wildlife conservation