The Japanese macaque, commonly referred to as the “snow monkey,” is a primate species native to Japan, inhabiting environments from subtropical to subarctic forests. Their diet is remarkably varied, reflecting their ability to thrive across diverse habitats and adapt to available food sources throughout the year.
Primary Food Sources
Japanese macaques are omnivorous, consuming food items from over 213 plant species. Their diet predominantly consists of various plant parts, including foliage, fruits, seeds, buds, and bark. In some regions, like Yakushima Island, fruits, mature leaves, and fallen seeds form a significant portion of their intake.
Beyond plant matter, these macaques also incorporate animal matter into their diet, such as insects, fungi, and invertebrates. They have been observed eating crabs and bird eggs, particularly during winter months when other food sources may be scarce. This highlights their opportunistic feeding strategies.
Adapting to Seasons
The diet of the Japanese macaque undergoes significant shifts based on seasonal availability, particularly in colder regions. In northern deciduous forests, where leaves are absent for up to five months, macaques rely more heavily on stored fat and alternative food sources during winter. During this time, bark and buds of woody plants become a substantial part of their diet, especially in snowy areas like Kamikochi and Shiga Heights.
In contrast, warmer areas like Yakushima Island show a different seasonal pattern, with fruits being more prevalent in their summer diet and herbs increasing in winter. When preferred foods are scarce, macaques may resort to digging up underground plant parts like roots or rhizomes. Recent studies show them feeding on freshwater biota, including brown trout, riverine insects, and mollusks in winter, likely as a survival strategy.
Distinctive Dietary Behaviors
Japanese macaques exhibit several unique feeding behaviors. One notable behavior is food washing, observed in a troop on Koshima Island where a female macaque named Imo began washing sweet potatoes in river water. This behavior, initially aimed at removing sand, evolved to include dipping clean food in salty seawater, a practice that spread through the troop over generations.
Another interesting foraging strategy involves separating wheat from soil by throwing it into water and waiting for the wheat to float, a behavior also observed to spread culturally. Additionally, Japanese macaques engage in geophagy, the consumption of soil or clay, which may serve multiple functions. It is believed to alleviate digestive issues, such as forestomach acidosis, or supplement mineral intake in environments where certain nutrients might be scarce.