mirim Kwon, chungbuk national university

Microbiomes are vital to wildlife health, yet the impact of reproductive strategies on ursid genital microbial environments is poorly understood. This study compared vaginal microbiomes of seasonally breeding Asiatic black bears (Ursus thibetanus; ABB) and year-round breeding sun bears (Helarctos malayanus; SB) to establish baseline data for reproductive monitoring and conservation.
Vaginal swabs were collected from ABB (n=3; one in South Korea, two in Laos) and SB (n=2; in Laos). Genomic DNA was analyzed via triplicate full-length 16S rRNA (V1–V9) sequencing (Oxford Nanopore MinION) and processed using the Emu algorithm and R.
Significant interspecies differences in microbial composition were observed (p=0.001). ABB was dominated by Firmicutes (72.2%), specifically Staphylococcus agnetis and S. schleiferi. SB showed higher Proteobacteria (35.8%) and Bacteroidota (24.8%), with Haemophilus influenzae and Porphyromonas detected. Notably, ABB individuals showed no significant microbial differences despite the geographical distance between South Korea and Laos.
ABB exhibited significantly higher alpha diversity (p=0.0039) and distinct beta diversity (p=0.001), suggesting a more complex, stable ecosystem. These differences may be associated with contrasting reproductive ecologies between the two species; however, the underlying hormonal and immunological mechanisms were not directly assessed in this study.
This study provides the first species-level reference dataset describing vaginal microbiomes in endangered bear species. These findings suggest that reproductive ecology may shape genital microbial communities in ursids and may support microbiome-based reproductive health monitoring in conservation programs. Given the limited sample size, these results should be interpreted as preliminary baseline observations. Further longitudinal and population-level studies incorporating hormonal and environmental variables are required to validate these findings.