Snow monkeys soak in hot springs to warm up … and boost their health! Image via Eliot Herman. Used with permission.
Japanese macaques, or snow monkeys, famously soak in hot springs to stay warm in freezing winters. A team at Kyoto University said on January 20, 20206, that they studied macaques at Jigokudani Wild Snow Monkey Park over two winters. They wanted to see if hot spring bathing does more than just keep them cozy. And, indeed, it does! The researchers found soaking in warm waters also influences the monkeys’ parasites and the tiny organisms living in their digestive systems, which play a key role in shaping their health.
The team published the study in the peer reviewed Springer Nature journal Primates on January 19, 2026.
A hidden ecosystem inside every monkey
Researchers observed female macaques at the park over two winters. They compared individuals that bathed regularly with those that did not. The researchers looked at the monkey and also those things that live inside and on the monkey. Therefore, they tracked the monkey’s behavior, checked for parasites such as lice (tiny insects that live in fur) and analyzed gut bacteria.
Scientists use the term holobiont to describe an animal and all the microbes and parasites living with it. So you can think of these monkeys as not just one organism but a whole ecosystem.
Subtle changes with meaningful effects
The results revealed small but important differences. Bathing monkeys showed changes in their lice distribution. This suggests hot water may disrupt parasite activity. In the gut, overall bacterial diversity was similar. However, some bacterial types were more common in non-bathing monkeys. And, surprisingly, sharing hot springs did not increase parasite infections. Bathing monkeys did not show higher parasite levels.
Behavior shapes health
These findings show that natural behaviors can shape health in subtle ways beyond their immediate purpose. In this case, hot spring bathing does more than help monkeys stay warm. It also affects the parasites and microbes living on and inside them. Even small shifts in these communities may play a role in shaping overall health. As lead author Abdullah Langgeng of Kyoto University explained:
Behavior is often treated as a response to the environment, but our results show that this behavior doesn’t just affect thermoregulation or stress: it also alters how macaques interact with parasites and microbes that live on and inside them.
The study also points out that, by analogy, behaviors in other species — including human cultural practices such as bathing — can influence microbial exposure. It challenges the assumption that sharing water necessarily increases disease risk, at least under natural conditions.
Snow monkeys as social spa users
Snow monkeys live in large family groups and are the only wild primates known to use hot springs regularly. At Jigokudani, these monkeys walk through deep snow to enter pools that can reach nearly 104° F (40° C). Because it can drop below freezing in winter, the hot springs are a toasty treat. As Langgeng said:
Hot spring bathing is one of the most unusual behaviors seen in nonhuman primates.
The habit is learned socially rather than instinctive. Observations show young monkeys often mimic older group members, particularly their mothers. Furthermore, participation varies with age, sex and social rank. Adult females and juveniles tend to bathe more often. Meanwhile, adult males and lower-ranking monkeys bathe less frequently or remain on dry ground. Because the hot springs are limited in size, dominant individuals may spend more time soaking, while others wait their turn or avoid the pools.
How the hot spring baths began
The tradition of bathing in hot springs began in the early 1960s, when a young monkey at Korakukan, a traditional inn in the Jigokudani Valley, reached into an outdoor bath, likely drawn by food dropped into the water. Other monkeys began entering the hot springs to follow the example of human guests and soon realized the warm water was very comfortable in the freezing winter conditions. Gradually, more monkeys joined in, creating a social norm within the troop. Consequently, the behavior became so consistent that in 1964 a dedicated hot spring pool was built for the monkeys. Of course today this area is known as Jigokudani Monkey Park.
How snow monkeys avoid getting cold
Do snow monkeys feel cold after their bath? We have towels and hairdryers, but they don’t! Well, unlike humans, who sweat to regulate temperature and lose heat rapidly when exposed to cold, snow monkeys have relatively few sweat glands and do not rely on sweating. This means they do not experience sudden drops in body temperature after leaving the hot springs.
Their thick winter fur provides excellent insulation. Moreover, their bodies are adapted to extreme cold. Capillary vessels at the ends of their limbs constrict in low temperatures, reducing heat loss from hands and feet. These adaptations allow snow monkeys to step onto snow with bare feet or leave the hot springs without risk of frostbite or sudden chilling.
A healthy, steamy dip
So while humans debate the benefits of hot baths and spa days, snow monkeys seem to have figured it out. For them, a soak in a hot spring is not just a way to stay warm. It’s part of a lifestyle that shapes their health, one steamy dip at a time.
Special thanks to our friend Eliot Herman, who captured all these amazing images and happily shared them with us. Visit his Flickr page here.
Bottom line: Snow monkeys stay warm in hot spring baths. These baths also affect their parasites and gut microbes. It’s a cozy way to get a health benefit!
Read more: Orphaned bonobos can develop social skills and empathy
Read more: Female bonobos rule the bonobo kingdom. Girl power!
The post Snow monkeys bathing in hot springs get health benefits first appeared on EarthSky.
from EarthSky https://ift.tt/poUBqaf
Snow monkeys soak in hot springs to warm up … and boost their health! Image via Eliot Herman. Used with permission.
Japanese macaques, or snow monkeys, famously soak in hot springs to stay warm in freezing winters. A team at Kyoto University said on January 20, 20206, that they studied macaques at Jigokudani Wild Snow Monkey Park over two winters. They wanted to see if hot spring bathing does more than just keep them cozy. And, indeed, it does! The researchers found soaking in warm waters also influences the monkeys’ parasites and the tiny organisms living in their digestive systems, which play a key role in shaping their health.
The team published the study in the peer reviewed Springer Nature journal Primates on January 19, 2026.
A hidden ecosystem inside every monkey
Researchers observed female macaques at the park over two winters. They compared individuals that bathed regularly with those that did not. The researchers looked at the monkey and also those things that live inside and on the monkey. Therefore, they tracked the monkey’s behavior, checked for parasites such as lice (tiny insects that live in fur) and analyzed gut bacteria.
Scientists use the term holobiont to describe an animal and all the microbes and parasites living with it. So you can think of these monkeys as not just one organism but a whole ecosystem.
Subtle changes with meaningful effects
The results revealed small but important differences. Bathing monkeys showed changes in their lice distribution. This suggests hot water may disrupt parasite activity. In the gut, overall bacterial diversity was similar. However, some bacterial types were more common in non-bathing monkeys. And, surprisingly, sharing hot springs did not increase parasite infections. Bathing monkeys did not show higher parasite levels.
Behavior shapes health
These findings show that natural behaviors can shape health in subtle ways beyond their immediate purpose. In this case, hot spring bathing does more than help monkeys stay warm. It also affects the parasites and microbes living on and inside them. Even small shifts in these communities may play a role in shaping overall health. As lead author Abdullah Langgeng of Kyoto University explained:
Behavior is often treated as a response to the environment, but our results show that this behavior doesn’t just affect thermoregulation or stress: it also alters how macaques interact with parasites and microbes that live on and inside them.
The study also points out that, by analogy, behaviors in other species — including human cultural practices such as bathing — can influence microbial exposure. It challenges the assumption that sharing water necessarily increases disease risk, at least under natural conditions.
Snow monkeys as social spa users
Snow monkeys live in large family groups and are the only wild primates known to use hot springs regularly. At Jigokudani, these monkeys walk through deep snow to enter pools that can reach nearly 104° F (40° C). Because it can drop below freezing in winter, the hot springs are a toasty treat. As Langgeng said:
Hot spring bathing is one of the most unusual behaviors seen in nonhuman primates.
The habit is learned socially rather than instinctive. Observations show young monkeys often mimic older group members, particularly their mothers. Furthermore, participation varies with age, sex and social rank. Adult females and juveniles tend to bathe more often. Meanwhile, adult males and lower-ranking monkeys bathe less frequently or remain on dry ground. Because the hot springs are limited in size, dominant individuals may spend more time soaking, while others wait their turn or avoid the pools.
How the hot spring baths began
The tradition of bathing in hot springs began in the early 1960s, when a young monkey at Korakukan, a traditional inn in the Jigokudani Valley, reached into an outdoor bath, likely drawn by food dropped into the water. Other monkeys began entering the hot springs to follow the example of human guests and soon realized the warm water was very comfortable in the freezing winter conditions. Gradually, more monkeys joined in, creating a social norm within the troop. Consequently, the behavior became so consistent that in 1964 a dedicated hot spring pool was built for the monkeys. Of course today this area is known as Jigokudani Monkey Park.
How snow monkeys avoid getting cold
Do snow monkeys feel cold after their bath? We have towels and hairdryers, but they don’t! Well, unlike humans, who sweat to regulate temperature and lose heat rapidly when exposed to cold, snow monkeys have relatively few sweat glands and do not rely on sweating. This means they do not experience sudden drops in body temperature after leaving the hot springs.
Their thick winter fur provides excellent insulation. Moreover, their bodies are adapted to extreme cold. Capillary vessels at the ends of their limbs constrict in low temperatures, reducing heat loss from hands and feet. These adaptations allow snow monkeys to step onto snow with bare feet or leave the hot springs without risk of frostbite or sudden chilling.
A healthy, steamy dip
So while humans debate the benefits of hot baths and spa days, snow monkeys seem to have figured it out. For them, a soak in a hot spring is not just a way to stay warm. It’s part of a lifestyle that shapes their health, one steamy dip at a time.
Special thanks to our friend Eliot Herman, who captured all these amazing images and happily shared them with us. Visit his Flickr page here.
Bottom line: Snow monkeys stay warm in hot spring baths. These baths also affect their parasites and gut microbes. It’s a cozy way to get a health benefit!
Read more: Orphaned bonobos can develop social skills and empathy
Read more: Female bonobos rule the bonobo kingdom. Girl power!
The post Snow monkeys bathing in hot springs get health benefits first appeared on EarthSky.
from EarthSky https://ift.tt/poUBqaf
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