Fecal DNA Metabarcoding and Microhabitat Analysis Reveal Summer Resource Differentiation Between Sympatric Forest Musk Deer and Siberian Roe Deer

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How sympatric species with similar ecological requirements partition resources to reduce competition is a key question in community ecology. We tested whether forest musk deer ( Moschus berezovskii ) and Siberian roe deer ( Capreolus pygargus ) exhibit resource differentiation despite their sympatric distribution. This study was conducted in the Huanglong Mountains, China, using fecal DNA metabarcoding and microhabitat surveys. The largest numbers of fecal detection sites for both ungulate species were recorded in deciduous broad-leaved forest. Fecal detection sites attributed to forest musk deer had larger trees and higher herb species richness than those attributed to Siberian roe deer. Although the measured microhabitat characteristics at fecal detection sites showed substantial overlap between the two species, the observed overlap differed significantly from the null expectation. Dietary analyses revealed they collectively consumed 173 plant genera. Tree taxa had the highest relative read abundance in forest musk deer samples (62.18%), while shrub taxa dominated Siberian roe deer samples (51.94%). Siberian roe deer exhibited a significantly broader trophic niche than forest musk deer. Overall dietary overlap between the two ungulates was significantly different from random expectation. Species identification based on fecal morphology achieved only 70.40% accuracy. These findings support dietary differentiation and reveal interspecific differences in microhabitat characteristics measured at fecal detection sites, whereas habitat-specific use, selection, or preference could not be inferred. Additionally, we emphasize the necessity of molecular confirmation in sympatric ungulate studies. Protecting frequently detected dietary plants such as Morus and Quercus may benefit forest musk deer, whereas the potential importance of large trees and understory structure should be evaluated through standardized use-availability studies.