Seasonal Diet Variation in Reintroduced Milu (Elaphurus davidianus) Revealed by DNA Macrobarcoding: Implications for Biodiversity Conservation

Understanding seasonal dietary shifts in reintroduced herbivores is essential for conservation, yet detailed patterns for Milu (Elaphurus davidianus) in wetland habitats remain underexplored. This study applied high-throughput sequencing to fecal samples collected across four seasons in Tianjin Qilihai Wetland, identifying 43 plant species from 24 families. Significant seasonal differences were detected in relative read abundance. At the family level, Poaceae dominated spring, significantly exceeding all other seasons; Asteraceae and Cyperaceae were highest in summer, with Cyperaceae also surpassing winter and spring; Amaranthaceae peaked in autumn, higher than spring and summer; and Celastraceae prevailed in winter. At the species level, Phragmites australis was overwhelmingly consumed in spring; Lactuca indica and Bolboschoenus planiculmis peaked in summer; Euonymus japonicus dominated winter; and Suaeda salsa was highest in autumn, exceeding spring. These compositional shifts reveal a strategic transition from a specialized diet focused on high-quality resources in spring–summer to a broad-spectrum diet including woody plants, legumes, and cultivated species in autumn–winter. Overall, Milu exhibit substantial dietary plasticity, a key trait underpinning reintroduction success, and our findings provide empirical evidence to guide adaptive forage management in wetland reserves.