Study links snow monkeys’ hot-spring bathing to microbiome shifts

Japanese macaques at Japan’s Jigokudani Snow Monkey Park may be getting more from winter hot-spring bathing than warmth alone. In a new study published January 19, 2026, in Primates, Kyoto University researchers reported that female monkeys that regularly bathed showed differences in lice distribution and some gut bacterial genera compared with non-bathers, while rates of gastrointestinal parasite infection did not appear to increase. The work, based on observations and fecal sampling collected across two winters from 16 adult females, adds a microbiology and parasitology layer to a behavior already known to support thermoregulation and reduce cold-related stress. (pubmed.ncbi.nlm.nih.gov)

Why it matters: For veterinary professionals, the study is a useful reminder that behavior can shape the “holobiont,” or the host plus its associated microbes and parasites, in selective ways. The findings suggest shared bathing environments don’t automatically translate into higher endoparasite burden, at least in this wild primate setting, and they reinforce the idea that husbandry, social behavior, and environmental exposure can all influence microbial and parasite patterns without producing obvious disease signals. (pubmed.ncbi.nlm.nih.gov)

What to watch: The next step is whether follow-up work can link these subtle microbiome and ectoparasite shifts to measurable health, immune, reproductive, or welfare outcomes in wild or managed primates. (pubmed.ncbi.nlm.nih.gov)