The Japanese macaque is an exceptionally intelligent and interesting primate living in Japan. They live in many different habitats like the cold temperatures of the Nagano Mountains and the temperate climate of Yaku-Shima Island. Also called the Snow Monkey, this primate is most famous for its time spent in the natural hot springs. These monkeys are also known for their ability to create new complex behaviors such as washing their food before they eat it.
The Japanese macaque is a medium-sized primate with a size ranging from 2-4 feet. They display the physical trait of sexual dimorphism, meaning that the male is generally much larger than the female. The weight ranges from 22-66 pounds.  The macaque has a pink or red hairless face that is surrounded by a yellow-brown beard. The rest of the body is covered with a layer of fur which tends to grow thicker in the winter.  The color of the fur can be brown, gray, tan, or have a mottled appearance with a darker coloring on the top of the head. The ventral surface of the body usually has a lighter color fur than on the back of the animal. Macaques also have a tufted tail that averages a size of about 7 to 9 cm. or about a quarter the size of the entire body length. They also have cheek pouches in which they store food as they forage. One of the more remarkable features of the Japanese macaque are the opposable thumbs. Like humans, macaques use these thumbs to manipulate objects with great precision and skill.
At approximately 3 years of age, the macaque reaches the age of sexual maturity. There is no specific time period or season in which the Japanese macaques mate, but the peak birth time periods are from May to September and April to July. These animals are polygynandrous, meaning that males and females can mate with several partners. The mate selection is dependent on the female's preference. The female considers the male's rank and tenure in the troop of monkeys. Also, interestingly enough, the female tends to avoid mating with a previous mate a second time. When the female discovers a male that she's interested in, the female will remain with one male and deny other male solicitation.
Once the female mates with a male, the female will undergo a pregnancy of about 5 to 6 months. This period will be very stressful and arduous on the mother. On the day of the birth, the mother will rest. She will avoid contact with other males and withhold from grooming, foraging, and moving. Her diet also changes from new leaves and shoots to fruit. Then the female will give birth to one infant, weighing about 500 grams on average. After the birth, the mother will eat the placenta immediately.
Parental Care and Infant Development
After birth, the infant is dependent on the parents for approximately 2 years when it is weaned. The male will huddle with, carry, and protect the young. However, the infant is most dependent on the female. The female forms a strong mother-infant bond with the child that lasts throughout their lifetimes. During this period of 2 years, the mother must carry, nurse, and protect the infant. The child will begin to toddle at 20 days. After the first month, the child will be able to climb. After 3 to 4 months, the child will go through a rebellious stage. This usually occurs when the child learns to ride on its mother back rather than clinging to her abdomen. Throughout this time period of parental care, the older siblings observe the mother and learn maternal behavior.
When the males reach the age of sexual maturity, they disperse to another troop. They continue joining other Japanese macaque troops throughout their lives. The females will generally stay in the same troop for their whole life. While the rank of the males are determined by strength and competitive ability, the rank of females is inherited from the mothers. The average life span in captivity for the Japanese macaque is 30 years, but their lives are most likely shorter in the wild.
These primates are found throughout Japan. They generally live in forested areas. There are four major areas of Japan where these monkeys live. Their northern limit is the northwest part of Honshu Island, where conifers and deciduous trees grow. Another region where they live is the Nagano Mountains, where the monkeys deal with the snow by using the natural hot springs. The third place is on the island of Oshima. In the northern habitats, the monkeys tend to migrate to different areas for the different seasons. The last area, which holds the largest population of Japanese macaques, is on the southern island of Yaku-Shima. Yaku-Shima has a habitat that is more temperate than the other habitats. The macaques from that island are classified in their own subspecies, M. fuscata yakui. That subspecies of macaques are classified as endangered based on a decreasing quality and size of the natural habitat.
The Japanese macaque eats foods ranging from leaves, fruit, seeds, insects, bark, small animals, leaves, and cultivated crops. These macaques are active during the day and like to sun themselves to conserve heat. They spend most of their time in the trees. Sometimes, they sleep in the trees to protect themselves from snow. 
The Japanese macaques have demonstrated extraordinary intelligent behavior. By imitation, these macaques have learned new and different behaviors. The members of a certain troop began washing their sweet potatoes after seeing a young female macaque take hers down to the sea to wash the sand off. This behavior was passed down through the generations of the troop and eventually evolved into seasoning the potato with sea water. The same young female macaque invented a way of sorting wheat from sand by putting them in water. This practice was adopted by her whole troop. Another interesting behavior of the macaques is their visits to the hot springs. In the cold Nagano mountains, the macaques can often be found relaxing in the natural hot springs to stay warm. The macaques have also come up with activities that are strictly recreational and unnecessary, such as playing with stones. They continue to invent new behaviors and practices that are adopted by the whole troop over time. Because each troop of macaques tends to have different social behaviors and diets, it seems as if each troop has established their own culture.
- Macaca fuscata Ed Tanhehco. University of Michigan Museum of Zoology: Animal Diversity Web.
- Are Japanese macaques threatened by neuroscience research? Ardith A. Eudey, David A. Hill, & Yasuyuki Muroyama. Nature Neuroscience.
- BBC - Science & Nature - Wildfacts - Japanese macaque Bbc.co.uk
- Japanese Macaque-Macaca fuscata Blueplanetbiomes.org
- Profile of Japanese Macaques by Masahiro Minami. Simon Fraser University.
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- Primate Factsheets: Japanese macaque by Kurt Gron. Primate Info Net.
- WAZA-World Association of Zoos and Aquariums-Virtiual Zoo by Peter Dollinger and Silvia Geser. World Association of Zoos and Aquariums.
- "Hot Tub Monkeys" Offer Eye on Nonhuman "Culture" Bijal P. Trivedi. National Geographic Channel.