Effect of Social Rank on Gut Microbes and Their Metabolites of Greater Long‐Tailed Hamsters ( <i>Tscherskia triton</i> )

Although the effects of social rank on behavior and physiology are well established, their relationship with gut microbiota is not yet fully understood. We investigated how social rank affects physiological responses, gut microbiota, and metabolites in the greater long-tailed hamster (Tscherskia triton), a naturally solitary rodent. Dominant male hamsters displayed a "high-vigilance, metabolically activated" phenotype, characterized by increased aggression, elevated serum corticosterone (CORT) and serotonin (5-HT) levels, and activation of the paraventricular nucleus, a key regulator of the hypothalamic-pituitary-adrenal axis. In contrast, subordinates exhibited lower CORT and 5-HT levels, with increased activation of the arcuate nucleus (ARC), suggesting a more energy-conserving and stress-resilient phenotype. Social rank strongly shaped gut microbiota and metabolic output: dominants were enriched in energy-harvesting taxa (e.g., Limosilactobacillus and Alistipes) and had higher fecal queuine levels, a metabolite derived from gut microbiota. Conversely, subordinates were enriched in immunomodulatory taxa (e.g., Faecalibacterium and Butyrivibrio). These findings suggest that dominance in solitary species may be supported by coordinated host-microbiome interactions, which meet high energetic demands while maintaining stress resilience. This provides a novel framework for understanding the gut-brain-microbiome axis in social dominance.