Dietary niche partitioning of threatened large ungulates in the desert of northwestern China

In resource-limited desert ecosystems, can sympatric large ungulates coexist stably, and how do they achieve coexistence? To address this key question, we used fecal DNA metabarcoding to investigate dietary niche partitioning among three threatened ungulate species—Przewalski’s horse (PH; <i>Equus ferus przewalskii</i>), Asiatic wild ass (AWA; <i>Equus hemionus</i>), and goitered gazelle (GG; <i>Gazella subgutturosa</i>)—in the Kalamaili Nature Reserve, a key hotspot for desert ungulates in China. The results showed that the two equid species were generalist feeders, whereas GGs were specialist feeders. The reintroduced PHs have not yet developed clear niche partitioning from the other two native wild ungulates. Both the widely distributed AWAs and GGs exhibited a significant positive correlation between dietary dissimilarity and geographic separation, with the GGs’ diet showing greater sensitivity to geographic variation. These two native species demonstrated patch heterogeneity in their dietary niches. They achieve resource partitioning by forming complementary niches across different resource patches, thereby enabling long-term, stable coexistence. The shared intermediate niche-width patches exhibited the highest competition intensity, indicating that this “middle-ground” of niche partitioning warrants further conservation attention. This research provides theoretical foundations for assessing the survival status of reintroduced species and for the conservation management of threatened species, while also emphasizing the importance of habitat protection.