How to

14 November 2016

How They Keep Warm: The Japanese Macaque

We’ve written about the crazy survival adaptations and techniques that some animals use to keep warm. From huddling penguins to blubbery seals, energy-converting polar bears to narwhal flipper heat exchanges, nature and evolution have spawned some truly impressive ways to fight off the cold in freezing climes. Whilst all these animals have to work hard to escape the icy clutches of winter, there are some that have a much easier time of it. Step forward, the Japanese macaque. Rather than spending millennia developing some fancy physical traits, or hibernating or migrating to escape winter, these monkeys simply, well, chill in a hot spring.

The Japanese Macaque, often simply known as the “snow monkey” is a monkey species native to northern Japan, where the snowy winters often drop below -15°C, and the are the northernmost (non-human) primate. They are known locally as Nihonzaru (Nihon 日本 "Japan" + saru 猿 "monkey") to distinguish it from other primates, but the Japanese macaque is very familiar in and widespread across Japan, so they’re often simply called “saru.”

The monkeys have a grey-brown furry coat that gets thicker as temperature decreases, with pink faces and butts and a stumpy tail. The average height & weight for males is 57cm and 11.3kg, and for females is 52cm and 8.4kg. They live both in trees and on the ground all across Japan, and are known for their long leap and great swimming ability.

This swimming ability is not the only thing the monkeys are noted for, and it comes in handy when they’re performing the role that gives them their biggest claim to fame, monkeying around in the natural hot springs of Japan:

As you can see, the monkeys are pretty good at chilling the hell out, appropriately so given that the main monkey hot spring spot is in Jigokudani, or Hell’s Valley, Nagano Prefecture, Japan. The area is so-named thanks to its craggy cliffs that spew forth steam into the winter air. The name, and the fact that the surrounding area is covered in snow for a third of the year, would make you think that this area could be hell for the monkeys. In fact, it’s much more like heaven.

The monkeys spend most of their days relaxing in the hot spring, whether grooming, playing, swimming, or just plain unwinding. It’s a far cry from the nightmarish winters some animals have to weather, and the monkeys can definitely consider themselves fortunate to live in such favourable surrounds.

It’s not just luck, however, as the Japanese macaque has been clever enough to adapt to its environment and take advantage of the local benefits. Indeed, the Nihonzaru is a clever monkey. They have been observed washing sweet potatoes to clean dirt off them, balling up wheat and submerging it before letting it rise for the same purpose, and making and throwing snowballs for fun. The macaques even develop regional accents, just like humans do.

Apparently, they can even use iPhones too!
However, this adoption of human behaviour is of some concern to zoologists, with the monkeys exposed to tourists and people across Japan and no longer fearing them, eating their trash and stealing harmful items, or even becoming dependent on human garbage. There were even reports of one trendy monkey making its home in central Tokyo for several months. Monkey see, monkey do.

Overall, despite the potential problems with human influence, the monkeys generally have it pretty good. It’s not like they have to pay monkey rent, and I’m sure many of us wouldn’t mind spending our winters chilling in a hot spring. It’s definitely one of the more relaxing ways we’ve seen animals keep themselves warm. You can pay them a visit at Jigokudani, maybe as part of a Asian winter trip, just watch out for snowballs and hold on tight to your phone!

Sam Franklin

With a master’s in Literature, Sam inhales books and anything readable, spending his working hours reformulating the info he gathers into digestible articles. When not reading or writing, he likes to put his camera to work around the world, snapping street photography from Stockholm to Tokyo. Too much of this time spent in Japan teaching English has nurtured a weakness for sashimi, Japanese whisky, and robot cafés.