Otterly delicious: Spatiotemporal variation in the diet of a recovering population of Eurasian otters (Lutra lutra) revealed through DNA metabarcoding and morphological analysis of prey remains

Eurasian otters are apex predators of freshwater ecosystems and a
recovering species across much of their European range; investigating the
dietary variation of this predator over time and space therefore provides
opportunities to identify changes in freshwater trophic interactions and
factors influencing the conservation of otter populations. Here we sampled
faeces from 300 dead otters across England and Wales between 2007 and
2016, conducting both morphological analysis of prey remains and dietary
DNA metabarcoding. Comparison of these methods showed that greater
taxonomic resolution and breadth could be achieved using DNA metabarcoding
but combining data from both methodologies gave the most comprehensive
dietary description. All otter demographics exploited a broad range of
taxa and variation likely reflected changes in prey distributions and
availability across the landscape. This study provides novel insights into
the trophic generalism and adaptability of otters across Britain, which is
likely to have aided their recent population recovery, and may increase
their resilience to future environmental changes.