NAGANO, JAPAN - DECEMBER 16: Japanese macaques, also known as snow monkeys, bathe in a hot spring at Jigokudani Monkey Park in Nagano Prefecture, Japan on December 16, 2016. Established in 1964, Jigokudani Monkey Park allows visitors to observe the monkeys in their natural habitat, as they bathe in the hot springs. (Photo by Daniel Cardenas/Anadolu Agency/Getty Images)

NAGANO, JAPAN -  DECEMBER 16: Japanese macaques, also known as snow monkeys, bathe in a hot spring at Jigokudani Monkey Park in Nagano Prefecture, Japan on December 16, 2016. Established in 1964, Jigokudani Monkey Park allows visitors to observe the monkeys in their natural habitat, as they bathe in the hot springs. (Photo by Daniel Cardenas/Anadolu Agency/Getty Images)