Scat-Tered Evidence. Understanding the Diet of Forest-Associated Mammalian Mesopredators in a UK Peatland Ecosystem.

Peatland ecosystems and the unique biodiversity they support are under risk from multiple stressors, including changes in species interactions. Land use changes that lead to increases in the density and activity of mammalian mesopredators such as red fox () and pine marten () could be particularly detrimental to vulnerable peatland species such as wading birds (). However, our understanding of predator-prey interactions in the context of land use change remains limited, because most published evidence is correlative. In contrast, DNA metabarcoding of scats can reliably identify both the host and the prey consumed, thereby clarifying the role of consumption in species interactions. In this study, we collected scats from areas of open peatland and non-native forestry on peatland across the Forsinard Flows Nature Reserve, part of The Flow Country UNESCO World Heritage Site in Scotland. We focused our collections during the wader breeding season of 2023. Following DNA extraction and metabarcoding, we found that diets of foxes and pine marten were made up of small mammals (e.g., and ), non-wader bird species, and frogs. By frequency of occurrence, birds formed a substantial part of the pine marten diet (50%), while red deer carrion and pine marten (or their scat) were key food resources for foxes (46% and 50% respectively). Surprisingly, wading birds were absent from our samples, challenging the assumption that forest-associated mammalian predators actually prey on waders in adjacent peatland. DNA metabarcoding may be crucial to understanding the trophic and non-trophic interactions that govern recruitment and habitat use of vulnerable native species in remote and complex landscapes.