Snow monkeys bathe in hot springs to relieve stress: study

April 4, 2018

Kyoto- Japanese macaques in Jigokudani valley, Nagano Prefecture, central Japan, take a dip in hot springs during the winter to relieve stress by warming themselves up, a research team has found.

The team including Rafaela Sayuri Takeshita, a researcher at Kyoto University's Primate Research Institute, made the finding through analyzing the excrement of the monkeys, which are famous for bathing in the hot springs at the Jigokudani Yaen-Koen park in the Nagano town of Yamanouchi.

A paper on the team's finding was published in an edition of the international journal Primates on Tuesday by the Japan Monkey Centre in Inuyama, Aichi Prefecture, central Japan.

As Japanese macaques, which are the world's northernmost-living monkeys and also known as snow monkeys, regularly soak in hot springs in winter, it has been assumed that they do so to warm themselves up.

On their analysis, the team said the results indicate that the snow monkeys bathe in the hot springs to reduce stress from the winter cold and raise the probability of their reproducing and surviving.

In 2014, the team observed the behaviors, such as the bathing time, of 12 female macaques aged between 5 and 24 in the birth season in spring, between April and June, and winter's mating season, between October and December.

It measured cortisol, a stress hormone, in the feces of monkeys that took a bath in the hot springs at least once a week and those that did not.

The cortisol concentration of monkeys that soaked in the hot springs in winter was some 20 pct lower on weekly average than those that did not bathe.

Breaking down the results in a statistical approach, the team discovered that the reduction of cortisol concentration was primarily attributable to the hot spring bathing.

Of the 12 monkeys that bathed in the hot springs in winter, eight gave birth in spring. Jiji Press