The Only Monkeys That Soak in Hot Springs to Lower Their Stress: Japan’s Bathing Monkey Mystery

The Only Monkeys That Soak in Hot Springs to Lower Their Stress: Japan’s Bathing Monkey Mystery

Humans love spas, sauna bathing, hot baths; after a cold day what could be better? Japan has a famous troupe of wild monkeys that also love a relaxing soak in the country’s hot springs, and after delighting tourists for decades, scientists have decided to finally sort out the behavioral particulars of this fascinating trait.

What they found was that monkeys not only use the hot springs for warmth in their frigid winter environment, but that they serve to bring down the levels of stress hormones in the monkeys’ brains.

Near the site of the last Winter Olympics lies the town of Nagano. Here ,Japanese macaques exhibit a strange behavior.

Bathing monkeys is a more common sight in India and China, but only in Nagano have monkeys been recording bathing in hot water.

Other macaques live further north than Nagano, so it’s clear the species is adapted to cold weather, however despite the fact that the local environment is filled with natural hot springs, the 140° F water temperature is too hot.

Nearby hotels use cool water to bring that scalding temperature down to one that guests find enjoyable, and in 1963, a female monkey was found relaxing in one such pool.

Eventually it caught on, and the monkeys became a nuisance and a health hazard; so a park was built nearby where the monkeys had exclusive access to several 104° pools.

Having obvious use as a therapy for the cold, recent tests have aimed to determine whether there was any other driver of this novel behavior.

Perhaps unsurprisingly, considering primates’ strong social bonds, a stress hormone called glucocorticoids, which is known to be elevated by cold weather, were considerably lower in the animals’ fecal matter after periods of bathing.

Rafaela S.C. Takeshita from the University of Kyoto admitted that spending so much time watching the macaques relax in the hot springs rubbed off on her.

“I confess that during my research, many times after, I jumped into one of the hot springs pools,” she told the New York Times, adding that it was the humans-only pool.