It is probably true, as the Jigokudani Yaen-koen ‘wild snow monkey park’ website says, that there are many notable aspects of the lives of these Japanese macaques, other than the fact that they bathe in thermal springs. But, really, if s difficult to imagine what. This is the place where – in 1963 – a young female macaque called Mukubili first went into one of the springs to retrieve some soya beans, and found the 43°C temperature of the water was preferable to the sub-zero one of the chilly mountain air.

The practice soon spread, first to younger monkeys, then to all those in the area, and since then the monkeys have featured in dozens of natural history documentaries and been snapped by thousands of professional wildlife and enthusiastic amateur photographers. They are primate superstars. Even before this extraordinary cultural shift in behaviour, the monkeys were record-breakers – humans excepted, they are the most northerly living primates in the world, and in this part of Honshu island, as they endure temperatures as low as -15°C in winter and high as 23°C in summer.