Seasonal and Environmental Influences on the Gut Microbiota of South China Tigers (Panthera tigris amoyensis)

In ex situ conservation, gut bacteria and fungi play a crucial role in maintaining the intestinal microecological balance of the gut, and disruptions in this system may negatively impact host health. The South China tiger (<i>Panthera tigris amoyensis</i>) is a critically endangered tiger subspecies currently surviving under human-managed care and captive breeding programs, with only a small number of individuals remaining. Disruption in the gut microbiota, particularly the proliferation of pathogenic bacteria, can be fatal for cubs. This study analyzed the composition and seasonal changes of the gut bacterial and fungal communities of South China tigers in captive and semi-released environments during the winter of 2023 and the summer of 2024, using 16S rRNA and ITS high-throughput sequencing. The results showed that the dominant gut bacteria were Bacillota, Actinomycetota, Fusobacteriota, Pseudomonadota, and Bacteroidota. The abundance of Bacillota decreased in summer and was slightly lower in captive tigers than in semi-released tigers. Fungal communities were dominated by Ascomycota, with a negative correlation observed between Ascomycota and Basidiomycota. The abundance of Ascomycetes was lower in summer but significantly higher in semi-released tigers than in captive ones. Diversity analysis revealed no significant effects of the season or the environment on bacterial α-diversity, and fungal α-diversity was also not significantly affected by seasonal variation. However, microbial diversity increased under semi-free-range conditions, with fungal richness significantly higher than in captive environments (<i>p</i> < 0.01). Principal coordinate analysis (PCoA) based on Bray-Curtis distances revealed significant differences in the community structures of both bacterial (Adonis, R² = 0.2364, <i>p</i> = 0.001) and fungal (Adonis, R² = 0.1542, <i>p</i> = 0.001) communities across different seasons and environments. These findings provide valuable insights into the health management strategies and ecological adaptation of South China tigers.