Primates are quite the problem-solvers and the snow monkey (Japanese macaque Macaca fuscata) was recently found to be no exception. In times when food is hard to come by, these animals will take to the water, scooping out brown trout to stay alive. The curious behavior was recently reported in a paper published in the journal Scientific Reports.
Snow monkeys are native to the main islands of Japan (except for Hokkaido) where snowfall is common in the northernmost regions. The wintery blanket can get so dense, in fact, as to make finding their favorite foods much harder. Winter is no time to be running out of calories, so the snow monkeys have adapted a novel way to find grub.
To confirm how Japanese macaques from the Chubu Sangaku National Park in Japan were surviving overwintering in such a nutritionally baron environment, researchers took to scooping up poop samples. Using metabarcoding, they were able to determine that the macaques were indeed subsidizing their diet with freshwater animals, including brown trout, mollusks, and aquatic insect larvae and nymphs.
Despite being one of the coldest regions in the world, the groundwater-fed streams at the Chubu Sangaku National Park continue flowing all winter long. This is due to the fact that they maintain a constant water temperature of about 5 °C (41 °F) so never reach freezing.
The fecal analysis supports the theory that in the winter, when food is scarce, the Japanese macaques will hunt along the edges of pools and streams snatching up some of the aquatic animals they find. The alternative winter diet likely emerged as the monkeys’ unique habitat keeps waters free-flowing even in the coldest months of the year.
“Japanese macaques have a wider winter home range when food resources are scarce, but Kamikochi lies in a deep valley where they cannot cross the mountains,” said lead researcher Alexander Milner, Professor of River Ecosystems at the University of Birmingham in a statement.
“Larger populations create additional stress for surviving winter, but an abundance of groundwater upwellings and hot spring inputs from active volcanoes ensures many streams flow without ice cover allowing easy access to the monkeys... the Kamikochi area may be the only environment in Japan where the topographical, geological, and meteorological conditions allow Japanese macaques to supplement their winter diet in this way.”
Japanese macaques are also famous for bearing the brunt of the winter months from the warmth of hot springs, a behavior that’s found to relax them as well as keeping them warm.