The Japanese macaque (Macaca fuscata), also known as the snow monkey, is a terrestrial Old World monkey species that is native to Japan. They are colloquially referred to as “snow monkeys” because some live in areas where snow covers the ground for months each year – no other non-human primate is more northern-living, nor lives in a colder climate. Individuals have brownish grey fur, pinkish-red faces, and short tails.
In Japan, the species is known as Nihonzaru (ニホンザル, a combination of Nihon 日本 “Japan” + saru 猿 “monkey”) to distinguish it from other primates, but the Japanese macaque is very familiar in Japan, so when Japanese people simply say saru, they usually have in mind the Japanese macaque.
The only place in the world where monkeys bathe in hot springs.
The Jigokudani Yaen-koen (altitude 850 meters) is located in the Valley of Yokoyu River sourced from Shiga-Kogen of the
Joshinetsu-Kogen National Park in northern part of Nagano prefecture. Because of the very steep cliffs and the steam coming off the springs in everywhere, ancient people called this valley ‘Jigokudani (Hell valley)’ .Also it is buried in snow almost one third of the year. Even that kind of severe environment here is a paradise on earth for monkeys to live in.
The troops of wild Japanese macaque (they are popularly known as snow monkeys) inhabit here naturally through the ages. Since the establishment of Jigokudani Yaen-koen in 1964, it has been a worldwide popular place for watching the bathing monkeys in a hot spring and for ecological observation of researchers or photographers, and some of them who visited here have accomplished certain results in the area.