Investigating the Efficiency of Environmental DNA (eDNA) for Detecting Terrestrial and Semi-aquatic Mammals

Broadhurst, Holly

Abstract

The global decline of terrestrial and semi-aquatic mammals creates an urgent need for accurate information on species distributions for effective conservation efforts. Environmental DNA (eDNA) has emerged as a reliable, non-invasive, and novel approach for monitoring mammalian communities, aiming to enhance biodiversity assessments. Based on a literature search between 2012 (where the first extant mammals were detected using eDNA) and 2023, we found 94 articles characterizing terrestrial and semi-aquatic mammals. We provide insights into the global application of eDNA methodologies, including the challenges and prospects of its widespread implementation (including the regional disparity in its application), serving as a broad guide for researchers and stakeholders. We emphasize the importance of reliable eDNA data in comparison to more traditional monitoring methods and encourage further research to enhance the sensitivity and reliability of eDNA.
Exploring the efficiency of eDNA compared to traditional surveying methods is important to validate it as a reliable monitoring method. We used eDNA metabarcoding in Assynt, North-West Scotland, to explore seasonal variations in species richness and detection probabilities compared to camera trapping across summer and winter. eDNA metabarcoding consistently detected red deer and small mammals and camera trapping provided a temporal aspect which aided in the detection of European otter and badger. The synergy of both methods offered a more holistic understanding of species presence and distribution, but other eDNA approaches may be necessary to detect elusive carnivores.
To enhance the detection of these elusive carnivores such as otter (Lutra lutra) using eDNA, we compared a single-species digital droplet polymerase chain reaction (ddPCR) assay with eDNA metabarcoding and traditional spraint surveys across 60 sites in England. Spraint surveys recorded otter signs at 51 out of 60 sites, and otter eDNA was detected in 48 sites using ddPCR and only five sites using metabarcoding. We found that ddPCR outperformed metabarcoding in otter detection, exhibiting higher probabilities and sensitivity, even at low DNA concentrations. The comparison underscores the benefit of utilizing a single-species approach for detecting elusive carnivores such as otters using eDNA in combination with spraint surveys.

Citizen scientists have become integral participants in conservation projects, and the expanded use of eDNA engaged them in the sample collection process. We trained ten conservation volunteers to collect eDNA samples for mammal detection across two rivers and a beaver enclosure. We assessed volunteer motivations, experiences, contributions and validated collected samples with a direct comparison of results. Citizen scientists exhibited high motivation for participating, developed innovative sampling approaches, and expressed a strong understanding of eDNA techniques after training. Their involvement resulted in the detection of 20 mammal species, surpassing the 16 species identified by researchers. Beyond scientific outcomes, volunteers expressed satisfaction in contributing to meaningful scientific knowledge, demonstrating the broader impact of citizen science on local biodiversity surveys.
Our research highlights the effectiveness of eDNA in mammal monitoring, with important implications for conservation efforts. Combining eDNA with traditional methods and involving citizen scientists not only enhanced species detection but also fostered valuable knowledge exchange and community engagement. These findings contribute to an enhanced understanding of mammalian communities, providing a foundation for informed conservation strategies in the face of global declines.

Citation

Broadhurst, H. (2024). Investigating the Efficiency of Environmental DNA (eDNA) for Detecting Terrestrial and Semi-aquatic Mammals. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Jan 25, 2024
• Publicly Available Date: Jan 27, 2026
• Keywords: Citizen science, Conservation, Environmental DNA, Mammalian communities Mammals, Metabarcoding, Semi-aquatic, Terrestrial
• Award Date: Jan 26, 2024