Macaca fuscata
Japanese macaque
(Also: snow monkey)

Japanese macaques are found in the forests, highlands, and mountains of Japan.

Japanese macaques range through the forested mountains and highlands of Japan. They occupy the northernmost regions of any nonhuman primate and are subject to large seasonal variation in climate, as is typical of northern latitudes. In the central and northern parts of Japan, temperatures can range from -15 C in the winter to 23 C in the summer. These large swings in temperature may explain why Japanese macaques have different home ranges in different seasons.

Wada (1980)

Japanese macaques average 522.8 mm in length in females and 570.1 mm in males. Average female mass is 8.4 kg and 11.3 kg in males. They are known for their hairless red faces, and their thick, furry coats. Pelage is usually ranging from gray to brown or mottled. During the winter months, these coats grow very thick. Like humans, all macaques have opposable thumbs that they use to manipulate objects. (Gron, 2007)

Most macacques can life to be about 30 years of age in captivity, although their lives are shorter in the wild. It is reasonable to assume that M. fuscata is like other members of the genus in terms of longevity.

Japanese macaques live in "troops," usually made up of 20 to 30 individuals, but sometimes including over 100. A major constraint on troop size is food availability. Each troop is lead by a dominant male, the Alpha male. Japanese macaques have strong social bonds, especially among females.

Japanese macaques are seldom aggressive, and display social interactions such as grooming one another and sharing the jobs of bringing up the young. Not only are infants raised by adults other than their parents, but males and females have nearly equal roles in caring for the young.

Koyama (1967), Sprague (1992)

Communication in all macacques is varied and complex. Because they are social creatures, there is much for them to communicate. Macaques typically use some combination of visual signals (facial expressions and body postures), vocalizations, and physical contact (play, grooming, mating, etc). In addition, some species of macaques emit chemical signals which indicate estrous. It is reasonable to assume that Japanese macaques are fairly typical of their genus with respect to communication.

Japanese macaques are primarily frugivorous. However, they also eat seeds, young leaves and flowers, insects, and tree bark. The variety of their diet is in part due to seasonal changes in the abundance of food. The central and northern regions of Japan experience large climate changes from season to season. In the spring and summer, young leaves, flowers, and shoots are eaten; while in the fall, mostly fruits are consumed. During the winter, the diet primarily consists of tree buds and bark. Nutritious food sources can be so scarce in the winter that Japanese macaques may need to rely on stores of fat to make it through the winter. In one troop that was studied, it was found that only 55% of the caloric and 38% of the protein requirement was met in the winter. For macaques living in the more southern regions of Japan where seasonal temperature changes are not as dramatic, at least some fruit is available throughout the year and this is their primary food source.

John (1996), Maruhashi (1980), Wada (1980), Wada (1981)

Predators are probably restricted to large raptors and carnivores, as well as humans.

To the extent that these animals serve as prey, they may impact predator populations. They may also have some affect on the populations of those animals upon which they prey. Because they are frugivorous, it is likely that these animals help to disperse seeds.

As more development takes place in Japan, encounters between Japanese macaques and humans are becoming more frequent. They are more freqently going into suburbs and causing a nuisance. Japanese macaques have also become agricultural pests for farmers.

Schrier (1990)

Japanese macaques, like many other primates, are capable of contracting many of the same diseases as humans, such as the Ebola virus and HIV. This makes them useful for medical studying and research purposes. Some populations of these monkeys bathe in hot springs during cold winter months. Others swim during hot summers. For these reasons, they are popular with tourists.

In 1990, numbers in the wild were estimated at 35,000 to 50,000 and declining. Today, Japanese macaques are listed as threatened by the U.S. ESA and the subspecies M. fuscata yakui, which is found in Yakushima, Japan, is listed as endangered by the IUCN. The main cause for the decline of Japanese macaque populations has been deforestation. Additionally, there are an estimated 5,000 Japanese macaques captured or shot every year, which happens even though the species is protected by the Japanese government. Japanese macaques have increasingly become agricultural pests and the rights of farmers have taken precedence over laws protecting the macaques that are eating their crops.

Although the numbers of Japanese macaque have been declining, it is interesting to note that they seem to be an extremely adaptable species. One example of this is a troop that was relocated from Japan to Texas in the 1970's. This troop adapted so successfully that macaques which have escaped from their sanctuary have become a serious nuisance.

Knight (1995), Parker (1990), Pavella (1993), Schrier (1990), Sprague and Marhushi (1993), Sprague and Maruhashi (1994)

Japanese macaques have been and continue to be a popular species for the study of primate behavior. Since the 1940's and 1950's, there has been much interest in the ecology and social behavior of these monkeys. One reason for this is that researchers have not only been able to study Japanese macaques in their natural habitat, but they have also been able to lure the macaques out into the open with food. Provisioning of Japanese macaques with food has led to special developments and fascinating observation of their "culture." One famous example of this is potato washing in a troop of Japanese macaques in Koshima, Japan. When researchers provisioned a troop of Japanese macaques by putting sweet potatos along the beach to bring them out into the open, one macaque began to wash the sand off of her sweet potatoes in the water instead of brushing it off with her hand as other macaques did. Over time, this behavior spread to other members of the troop and was passed on from generation to generation. Interestingly, this potato washing behavior became even more modified as Japanese macaques began washing their sweet potatos in salt water rather than fresh water, apparently to enhance flavor.

Many researchers in the Japanese forested mountains have also documented an unusual activity of the Japanese macaques. The animals know how to make tiny snowballs in their hands, using their opposable thumbs, and then roll them along the ground to create larger snowballs, much like human children do. While this behavior doesn't appear to have survival purpose, whole troops of Japanese macaques engage in the activity as a social process.

Kawai (1965)