I have been visiting the Jigokudani Yaen-koen, one of Japan's many wild monkey parks, since 2007. And it was then, during my first visit, that I was able to create these intimate photographs of Japanese macaques resting in their own private onsen, or natural hot spring.

This photograph was taken on a very cold day around noon. It had snowed the day before—the last snow of that winter—and as a result many of the monkeys were congregated in the hot spring. There was hardly any wind, and a thick layer of fog was hanging above the onsen. This made it particularly difficult to focus on the animals, so I used a wider lens and worked with the monkeys closer to the