A visit to the Nagano area would not be complete without seeing the Japanese Snow Monkeys in Jigokudani Monkey Park (地獄谷野猿公苑 Jigokudani Yaen Kōen) in Yamanouchi Town, Nagano Prefecture – near Iiyama and Togakushi. The Monkey Onsen is located in the valley of the Yokoyu River which is part of the Joshinetsu-Kogen National Park. Despite its relatively remote location, roughly 90,000 visitors trek through the woods of Nagano each year to see Jigokudani Wild Monkey Park. Visitors base themselves in nearby Kanbayashi Onsen, Shibu Onsen or Yudanaka Onsen
The large population of wild snow monkeys go to the valley during the winter foraging elsewhere in the national park during the warmer months. The main onsen bath was constructed specifically for use by the monkeys. The monkeys descend from the steep cliffs and forest to sit in the warm waters of the onsen, and return to the security of the forests in the evenings. The monkeys are all free-ranging; their numbers move in and out of the valley depending on the season. In winter, when food is limited, monkeys congregate in and around the pools for warmth and the daily supply of barley and soybeans. However, they are still sometimes sighted even in the summer as they take occasional baths. Some would say that this is because they are lured by food thrown into the pool by park wardens.
The name Jigokudani, meaning “Hell’s Valley”, is due to the steam and boiling water that bubbles out of small crevices in the frozen ground, surrounded by steep cliffs and dense forest. Jigokudani is as nearly as far north as it gets for monkeys (the furthest extreme being the Shimokita Peninsula at the northern part of the Honshu island). No primate, with the exception of humans, is known to live in a colder climate. And it does get cold here—snow covers the ground for four months of the year, and winter temperatures average 14ºF (-10º).
The story goes that in 1963, a young female monkey clambered into a hot spring to collect soybeans that were floating on the surface of the water. The behaviour was copied by others in the troop, and soon it became common for the monkeys to retreat to the hot pools when the harsh winter arrived. Naturally the tourists followed soon after.