DNA metabarcoding shows strong potential for investigating diet and niche partitioning in the native European otter (Lutra lutra) and invasive American mink (Neovison vison)

Dietary studies play a fundamental role in ecological research through revealing the feeding ecology of key species, the degree of resource overlap between species, and reconstructing complex trophic networks. Morphological faecal analysis can be time-consuming, and accuracy hinges on possessing the necessary expertise to identify both the predator and its prey. Conversely, faecal DNA metabarcoding can provide species resolution data at greater spatiotemporal scales for the vast majority of prey items, regardless of prey size, type, and integrity or lack of hard components. We explored the potential of DNA metabarcoding for investigating diet and niche partitioning between the native European otter (Lutra lutra) and invasive American mink (Neovison vison). Otter spraints (n = 171) and mink scats (n = 19) collected from three sites (Malham Tarn, River Hull, and River Glaven) in northern and eastern England were screened for vertebrates using a two-step PCR protocol to amplify the 12S ribosomal RNA (rRNA) region, followed by High-Throughput sequencing on an Illumina MiSeq. Our results show that DNA metabarcoding of otter and mink faeces using vertebrate-specific primers is suitable for dietary assessment, and could be applied to other vertebrate carnivores. When upscaled across multiple habitat types, DNA metabarcoding should greatly improve future understanding of resource use and niche overlap between these mustelids.