Selective seasonal foraging behavior of herbivores on a Danish island demonstrated by <scp>DNA</scp> metabarcoding

Abstract Introduction Understanding how herbivores influence plant communities is critical for managing biodiversity and ecosystem functions, particularly in conservation areas undergoing restoration or rewilding, where free‐ranging large herbivores impact the vegetation development. Objectives Here we investigated the foraging patterns of two sympatric herbivores (Fallow deer: Dama dama and Mouflon: Ovis gmelini musimon ) in a protected biodiversity restoration site, the Danish island Æbelø, to assess their potential impact on the island's vegetation. Methods Through a year‐round environmental DNA metabarcoding diet survey, we evaluated seasonal foraging patterns and overlap. Subsequently, through a comparison with baseline vegetation survey data, we assessed diet preferences of the herbivores. Results The dietary niches of the Fallow deer and Mouflon overlapped greatly, with both species feeding on 69% of the detected plant genera. They shared a core diet dominated by graminoids with increased foraging on woody plants and forbs in summer and lower taxonomic richness in winter. Notably, soft grasses and woody species were consumed disproportionately to their availability, indicating selective foraging. Conclusion The foraging patterns suggest that the Fallow deer and Mouflon contribute to the suppression of tree regeneration on Æbelø, ultimately driving a shift toward grassland vegetation dominated by coarse graminoids, which is contrary to current management goals. As there is a minimum‐intervention management strategy on Æbelø, a more active management strategy could be considered to restore the island's original biodiversity.