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What is the context of this research?

Japanese macaques inhabiting the high-altitude site JMP, in Nagano, Japan, display a unique behavior among primates during winter: hot spring bathing. Such HSBB is thought to be beneficial for thermoregulation and stress reduction. However, there are cases where hot springs facilitated transmission of heat-resistant parasites in humans. At the same time, non-heat resistant parasites may be limited by HSBB. For example, several lice are known to thermo-orient and be susceptible to high temperatures.

However, studies linking HSBB with parasites have never been conducted in nonhuman primates. Neither have there been any studies linking HSBB with other symbiotic organisms, such as gut microbiome, which provides crucial support system against harmful intestinal infection.

What is the significance of this project?

Previous work on Japanese macaque HSBB explored basic aspects of the behavior to understand its function. Other ecological implications related to parasitism and gut microbial communities have not been addressed. Thus, ours will be the first study of its kind to tackle such questions and expand our knowledge of this intriguing behavior. It is also worth noting that HSBB has been linked to health risks in humans globally, so given the close proximity between macaques and humans at the site, our results should help inform park management about any potential risks related to the behavior to help mitigate any chance of bidirectional exchange of pathogens between monkeys and visitors. In addition, this study will help further our understanding of infectious disease ecology in Japanese macaques.

What are the goals of the project?

Our research aims to investigate the effects of HSBB on parasitism and gut microbiome in Japanese macaques.

This is a field study that will be conducted over two winters and one summer. Sixteen adult female macaques will be selected as subjects. Instantaneous sampling will be used to record behavior of focal individuals. Fecal samples will be collected from focal individuals and later examined for parasitic intestinal protozoa and gut microbe community structure.

Generalized linear mixed-modeling framework will be performed for modeling the effects of bathing on our response variables (intestinal diversity and abundance, gut microbe diversity, etc.) while controlling for variables such as the reproductive state, dominance rank and age of each macaque, among other things.