Macaca fuscata
Japanese macaque
Also known as: snow monkey

Japanese macaques, Macaca fuscata, inhabit subtropical or subalpine deciduous, broadleaf, and evergreen forests. They are found on three southern main islands of Japan: Honshu, Shikoku, and Kyushu, as well as a few smaller islands. Japanese macaques also survive well outside of their natural range, as with one introduced population in Laredo, Texas. (Gron, 2007; Smuts et al., 1986)

Japanese macaques inhabit subtropical and subalpine forests. In the northern part of their range, they inhabit cool temperate deciduous broadleaf forests. In this region, temperatures average 10.9 ˚C, and annual average rainfall totals 1500 mm. In the southern part of their native range, Japanese macaques live in evergreen broadleaf forests. In this region, temperature averages 20 ˚C, and annual average rainfall totals 3000 mm. Across their range, harsh winters are inevitable, and Japanese macaques tend to spend winter months at lower elevations. Although they have been spotted at elevations as high as 3180 m, during winter months they usually do not exceed elevations of 1800 m. (Fooden and Aimi, 2005; Gron, 2007)

Japanese macaques range in color from shades of brown and gray to yellowish brown. They have a colorful face and posterior end that are pinkish red in color. Their fur is very thick, which, because they do not hibernate, helps them stay warm during harsh winters. They have a short stumpy tail. Japanese macaques express sexual dimorphism; males are generally taller and more massive than females. Males average 11.3 kg in weight and 57 cm in height. Females average 8.4 kg in weight and 52.3 cm in height. There also seems to be a correlation between the body weight of Japanese macaques and climate. Japanese macaques in southern areas generally weigh less than those in northern areas of higher elevations, where more snow is present during winter months. Provisioned Japanese macaques have a larger skull than non-provisioned macaques. The skull of provisioned Japanese macaques averages 134.4 mm in length for males and 118.1 mm for females. The skull of non-provisioned individuals are slightly reduced, averaging 129.5 mm in males and 115.8 mm in females. (Fooden and Aimi, 2005; Gron, 2007)

In the wild, the oldest known male Japanese macaque was 28 years of age. The oldest known female was 32 years of age. (Fooden and Aimi, 2005)

Japanese macaques are both arboreal and terrestrial, and they are mostly quadrupedal when on the ground. Females spend more time in trees whereas males spend more time on the ground. They are also diurnal. Japanese macaques live in troops with a female-bonded social structure. Females do not leave their natal group, whereas males leave the troop as they mature. Troops usually have an alpha male, but social bonds between females exceed those between males. Hierarchal rankings are important to the social structure of Japanese macaques. High ranking individuals have access to food first, and thus low ranking females usually eat less nutritious food. Japanese macaques are nepotistic, meaning daughters inherit the rank of their mother. When a predator is spotted, individuals make a hollering vocalization to warm others in the group. (Belisle and Chapais, 2001; Fa and Lindburg, 1996; Fooden and Aimi, 2005; Gron, 2007; Hadhazy, 2010; Muroyama, 1991; Saito, 1996; Trivedi, 2009)

Japanese macaques exhibit some altruistic behaviors, and most are observed between mothers and daughters. These behaviors include protection, support, food-sharing, and alarm calling when a predator is observed. They may also practice co-feeding, in which a dominant individual gives access of food to subordinate individuals. (Belisle and Chapais, 2001; Fa and Lindburg, 1996; Hadhazy, 2010; Muroyama, 1991; Saito, 1996; Trivedi, 2009)

Social grooming is common among Japanese macaques. Grooming helps to remove parasites and also to create and maintain social bonds within the troop. Most grooming is performed between kin, usually mothers and daughters. Japanese solicit individuals to groom them by approaching an individual and presenting the neck, face, flank, or even rump. Adult females solicit individuals more often than immature offspring. Two different vocalizations are associated with grooming: one when they attempt to groom and one while soliciting grooming. (Belisle and Chapais, 2001; Fa and Lindburg, 1996; Hadhazy, 2010; Muroyama, 1991; Saito, 1996; Trivedi, 2009)

Japanese macaques live further north than any other nonhuman primates and have proven quite adaptable. In the Shiga Heights region on Honshu where humans altered temperature of volcanic hot springs for bathing, a troop of Japanese macaques surprisingly entered the hot springs, presumably to warm up. In 1988, a female Japanese macaque was observed washing sweet potatoes on the coast, and soon other members of the troop also washed food item such as cassava roots and grains of rice. They also peeled potatoes with their incisors and canine teeth. This washing of food may have some nutritional benefit such as adding salt to food. Because some Japanese macaques receive food from humans, they have more time that would otherwise have been allocated toward foraging. Surprisingly, one Japanese macaque was observed playing with rocks. Primatologists are not sure why this occurs, but it is thought to be a recreational event. When Japanese macaques did not have as much downtime, when they became less dependent on humans for daily food intake, they stopped playing with rocks. (Belisle and Chapais, 2001; Fa and Lindburg, 1996; Hadhazy, 2010; Muroyama, 1991; Saito, 1996; Trivedi, 2009)

Home Range

The home range of Japanese macaques is directly correlated with habitat type and averages 3.7 sq km. Day ranges vary with season. Southern Japanese macaques can travel up to 3.21 km a day during the month of August, whereas during winter months, they travel up to 5.02 km. The day range of northern Japanese macaques, which face colder weather, is restricted to 0.85 km for males and 0.93 km for females. When food availability is high, they tend to travel more often. (Gron, 2007)

Japanese macaques are social primates and often vocalize within their troop and with related species. There are six groups of vocalizations used by Japanese macaques, including peaceful, defensive, aggressive, and warning vocalizations, which signal their mood. Other vocalizations include those that occur during female estrus and during infancy. More than 50% of vocalizations are peaceful or soothing in nature. Japanese macaques also make body gestures and facial expressions. In captivity during certain threatening situations, they display different facial expressions, including ear-flattening, opening their mouth to display teeth, raising their eyebrows, and even erecting their ears. Subordinate individuals also grimace, lip-smack, display their hindquarters and practice gaze-avoidance. Display behaviors are also common in Japanese macaques, with several different postures such as kicking, shaking, and leaping. These expressions increase in frequency in males during mating season, but they do not increase in females. (Gron, 2007)

Japanese macaques are generalist omnivores, and their diets change seasonally. During the summer, especially June and between September and November, they mostly eat fruits. They also eat seeds, although seeds account for less than 20% of their food intake during these months. During April and May and from December to March, Japanese macaques eat mostly flowers and some nectar. During the winter months, a large part of their diet consists of fibrous mature leafs. They also consume young leafs, which are easier to digest, from April to June. Japanese macaques also opportunistically eat fungi. (Hanya, 2004; Tsuji and Takatsuki, 2004)

On the small island of Kinkazan, off of the eastern coast of Japan’s biggest Island Honshu, Japanese macaques compete for fibrous plant foods with sika deer. Of the six staple food plants on the island, the abundant Japanese barberry (Berberis thunbergii) and Japanese zelkova (Zelkova serrata) are unpalatable to the deer. A large part of the diet of Japanese macaques on the island is thus composed of these plants. (Hanya, 2004; Tsuji and Takatsuki, 2004)

Japanese macaques have a variety of predators, including avian birds such as mountain hawk-eagles. Feral dogs frequently attacked and killed Japanese macaques, though they are now rare as populations of dogs are now regulated by the Japanese government. Japanese wolves also preyed on this species, although this subspecies of wolves went extinct in the early 1900s. Raccoon dogs may also prey on Japanese macaques. The most lethal predator of Japanese macaques is humans. Because they are considered agricultural pests, more than 10,000 Japanese macaques have been killed since 1998. When a predator is spotted, Japanese macaques make a hollering vocalization to warm others in the group. Japanese macaques have also been observed hollering when Japanese giant flying squirrels glide above them. This may be out of fear, as they may look like other avian predators. (Fooden and Aimi, 2005; Hadhazy, 2010; Smuts et al., 1986)

Japanese macaques eat a variety of plants and insects and, because they eat fruit and seeds, act as seed dispersers. They have been observed crushing and eating seeds and are also considered seed predators. About 36% of seeds on average were recovered after passing through the gastrointestinal process in captive Japanese macaques. Although Japanese macaques compete with Sika deer for some plants on Kinkazan Island, they are also commensalists. When Japanese macaques climb to the tops of trees to forage for the most energy sufficient foods, they inadvertently knock down leaves, which Sika deer eat. (Majolo, 2004; Tsuji, Morimoto, and Matsubayashi, 2009)

Japanese macaques are considered to be a nuisance, and they are the third worst crop pest behind wild boar and deer. They are also easily habituated to humans and may not be easily scared away. Increased predation on crops and presence near humans may be due to the reduction of natural habitat because of logging. Japanese macaques also carry similiar diseases to humans.

Japanese macaques are highly studied for their unusual behavioral patterns. They also carry similar diseases to humans. They may also attract tourists, although they are easily habituated to humans. Some individuals have become habituated to humans in as little as week, while others took several years or more. (Fooden and Aimi, 2005; Smuts et al., 1986)

Japanese macaques are considered a species of least concern by the ICUN and threatened by the US Federal List. Although populations are stable, they do face threats from deforestation and hunting because they are agricultural pests. Yakushima Island in Japan was designated a Natural World Heritage Site in 1993. Although established to protect native species, tourism to the island has increased to mixed effect. There are approximately 100,000 Japanese macaques in the wild. ("Japanese macaques (Snow Monkey)", 2010; Gron, 2007)

Originally Japanese macaques may have reached the islands of Japan by crossing a land bridge from Korea during the Middle Pleistocene, as long as 500,000 years ago. In 1972, 150 Japanese macaques were transported from Honshu to Laredo, Texas, where they were placed in an arid brush land habitat. This troop has survived quite well, growing to 470 individuals by 1989. (Fooden and Aimi, 2005; Gron, 2007; Lindburg, 1980)