Snow monkeys, also known as the Japanese macaque, are native to many of the main islands of Japan. These fluffy creatures are the most northern-based non-human primate out there, meaning they have some cold temperatures to put up with. Many live in the Japanese Alps, where in the winter months’ snow cover limits much of their summer food supply. To make matters worse, the deep valley the monkeys reside in means no escape from these harsh conditions. The macaque is forced to have to look elsewhere in their environment to make up for the depleted food source.
A new study by The University of Birmingham has uncovered where this alternative food comes from. Thanks to active volcanoes in the area, temperatures in flowing streams are at a constant of around 5˚C. This means many tasty snacks can still survive in the water, such as brown trout. The snow monkeys take advantage of these fish, pulling them out of the water to feast upon with their sharp claws.
It was previously unknown exactly how the monkeys gathered their food in the cold, though scientists have guessed these primates fished for a while. Alongside some documentary footage from the BBC, Japanese macaques have been seen grabbing dried-up fish in the summer months. Clues also lie in the fact that closely related species also hunt freshwater marine life year round.
The paper, published in Scientific Reports, confirmed the theory by analyzing fecal samples from streams. Shallow pools along the edge of the water where the snow monkeys are thought to fish acted as the perfect poo collectors! Lead researcher Alexander Milner discussed the humorous events which transpired when carrying out the experiment to ZME science: “We did collect in March when the Kamikochi area is open again to visitors as it is one of the most visited National Parks in Japan – we got some strange looks from tourists as we were collecting the snow monkey poop. Also, we used a tracer dye to follow the groundwater and got the dose wrong and turned a whole stream purple for 30 minutes which certainly created a surprised look from tourists standing on a bridge where the stream went under.”
From these samples, the wintertime diet could be analyzed through what remains were in the feces. It was uncovered that alongside fish, river-based insects and molluscs were also part of the food supply they can get their hands on in the cold conditions. The discovery of aquatic insects such as nymphs and larvae being involved in their diet is an ecological first!
Source study: Scientific Reports – Winter diet of Japanese macaques from Chubu Sangaku National Park, Japan incorporates freshwater biota