Abstract
In the UK, the native European otter (Lutra lutra) and invasive American mink (Neovison vison) have experienced concurrent declines and expansions. Currently, the otter is recovering from persecution and waterway pollution, whereas the mink is in decline due to population control and probable interspecific interaction with the otter. We explored the potential of DNA metabarcoding for investigating diet and niche partitioning between these mustelids. 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 high-throughput sequencing. Otter diet mainly comprised aquatic fishes (81.0%) and amphibians (12.7%), whereas mink diet predominantly consisted of terrestrial birds (55.9%) and mammals (39.6%). The mink used a lower proportion (20%) of available prey (n = 40 taxa) than the otter and low niche overlap (0.267) was observed between these mustelids. Prey taxon richness of mink scats was lower than otter spraints and beta diversity of prey communities was driven by taxon turnover (i.e. the otter and mink consumed different prey taxa). Considering otter diet only, prey taxon richness was higher in spraints from the River Hull catchment and beta diversity of prey communities was driven by taxon turnover (i.e. the otter consumed different prey taxa at each site). Studies using morphological faecal analysis may misidentify the predator as well as prey items. Faecal DNA metabarcoding can resolve these issues and provide more accurate and detailed dietary information. When scaled up across multiple habitat types, DNA metabarcoding should greatly improve future understanding of resource use and niche overlap between the otter and mink.
Highlights
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 (Martínez-Gutiérrez et al 2015)
Faeces were ostensibly identified as otter spraints (n = 206), mink scats (n = 9) and red fox (Vulpes vulpes) scat (n = 1)
Fish community data for Malham Tarn were obtained through environmental DNA metabarcoding verified by fishery owners (Hänfling et al 2020) and from fish surveys detailed in Eldridge (2016)
Summary
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 (Martínez-Gutiérrez et al 2015). Smaller prey are less likely to be recovered from faeces, prey components may be fragmented or damaged beyond recognition and prey components from related species can be morphologically similar. These issues individually or combined can prevent species-level identification for various taxa, especially fishes (e.g. closely related cyprinids) and birds (Britton et al 2006, 2017; Shehzad et al 2012a; Krawczyk et al 2016; Berry et al 2017; Smiroldo et al 2019; Traugott et al 2020)
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