© Heather Angel
Japanese macaques - also known as snow monkeys - live further north than any other non-human primate. Snow covers the ground in Hell's Valley for four months of the year and temperatures often drop to -20 °C. Thermal pools - both natural and man-made - help the monkeys survive the harsh climate.
Snow monkeys are not only renowned for their love of hot baths, but for using tools and washing their food. In 1953, an 18-month-old female called Imo was spotted washing sweet potatoes to remove the mud before eating them. Ten years later the rest of the troop were also doing this, and had passed on the skill to the next generation. It was the first report of a learned tradition in a non-human species.
Comment: See also: US Military research site shows Arctic ice thickening over last 12 months