Understanding and quantifying the feeding behavior of large carnivores is crucial for determining their functional roles within ecosystems. This involves evaluating both their top-down effects on prey populations and their interactions with sympatric carnivore species. In this study, we employed DNA metabarcoding to investigate the dietary composition of three sympatric large carnivores (snow leopard Panthera uncia, wolf Canis lupus, and brown bear Ursus arctos) in the Sanjiangyuan Region (SR) of the Qinghai-Xizang Plateau, with a focus on seasonal variations and interspecific competition. Analysis revealed 16, 11, and 17 prey species in the diets of snow leopards, wolves, and brown bears, respectively. Domestic yak (Bos grunniens) was the most frequently detected prey item in the diets of both snow leopards (Relative Read Abundance; RRA = 25.42%) and wolves (RRA = 52.29%), whereas brown bears primarily consumed plateau pikas (Ochotona curzoniae; RRA = 43.10%) and Himalayan marmots (Marmota himalayana; RRA = 19.88%). Although high dietary niche breadth overlap was observed between snow leopards and wolves (Ojk = 0.76) and between snow leopards and brown bears (Ojk = 0.79), potential interspecific competition may be mitigated through differential prey selection and varying consumption intensities. The relatively low dietary overlap between wolves and brown bears (Ojk = 0.32) implies that these two species likely coexist by partitioning tropic resources. Seasonal fluctuations in dietary niche breadth and overlap among snow leopards and wolves align with predictions from the classic optimal foraging theory (OFT). Moreover, the substantial proportion of livestock found in the diet of these large carnivores indicates the presence of significant human-carnivore conflict in the SR. Combined with previous findings, our results support the hypothesis that the abundance and size-class availability of ungulate prey are key factors enabling the sympatric existence of these three apex predators.

Keeping healthy status is the primary condition in endangered captive breeding of alpine musk deer (Moschus chrysogaster, AMD), and that captive breeding program is beneficial to the ex-situ conservation and wild population recovery of musk deer. Therefore, regulating the health status of captive musk deer is the premise of musk deer resource utilization. Meanwhile, gut microbiota is essential for host health, survival and environmental adaptation. However, the changes of feeding environment and food affected the composition and function of gut microbiota in musk deer. Here, 16S rRNA was used to reveal the composition and function variations between wild and captive AMD. Wild AMD had higher alpha diversity of gut microbiota, with higher relative abundance of phylum Firmicutes, and dominant genera UCG-005, Christensenellaceae R7 group, Monoglobus, Ruminococcus, and Roseburia, which conducive to the wild AMD more effective absorption and utilization of nutrients, stability of intestinal microecology, and adaption to complex natural environment. Captive individuals had higher metabolic functions, with higher relative abundance of phylum Bacteroidetes, and dominant genera Bacteroides, Rikenellaceae RC9 gut group, NK4A214 group and Alistipes, which contributed to the metabolic activities of various nutrients. Furthermore, 11 potential opportunistic pathogens in captive AMD were higher than those in wild AMD, with higher enrichment of disease-related functions. Compared with wild populations, captive musk deer had a higher risk of intestinal diseases. The results can provide a theoretical basis for healthy breeding of musk deer, and a guidance for evaluating the health status of wild release and reintroduction of musk deer.