JAPANESE MACAQUES (SNOW MONKEYS): CHARACTERISTICS, FEEDING, REPRODUCTION

SNOW MONKEYS (JAPANESE MACAQUE)

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Japanese macaques (Macaca fuscata), commonly known as snow monkeys, are found in the wild only in Japan. They live farther north than any other non-human primate. The average lifespan for females in captivity is 22.7 years; for males it is 27.0 years. In the wild, the oldest known male Japanese macaque was 28 years of age. The oldest known female was 32 years of age.

There are an estimated 150,000 Japanese macaque living in Japan, a tenfold increase from the World War II era. It is believed that Japanese macaques reached the islands of Japan by crossing a land bridge from the Korean peninsula 500,000 to 300,000 years ago, long before the first humans arrived. They arrived mostly from the south and west and adapted to the climate and spread over time.

The Japanese macaques living in Shimokita Peninsula in Aomori Prefecture in far northern Honshu are the northernmost population of monkeys in the world. Their numbers have increased 10-fold in the last 40 years. They are protected but widely regarded as pests. Monkeys that endure very cold weather are also found in the mountains of China and Tibet. 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. [Source: Brandon Hardman, Animal Diversity Web (ADW) /=]

Humans have been fascinated with Japanese macaques for some time. Like tanukis they are central characters in many Japanese folk tales and stories. Representations of macaques have been found on prehistoric pottery. In folklore, such as the famous story about the monkey and the crab, monkeys are portrayed as clever thieves.

Japanese macaques are listed by some sources as threatened even though there seems to be plenty of them around. On the International Union for Conservation of Nature (IUCN) Red List Japanese macaques are listed as a species of Least Concern; The US Federal List: classifies them as Threatened. In CITES (Convention on International Trade in Endangered Species of Wild) they have no special status.

Good Websites and Sources: Primate Info on the Japanese Macaque primate.wisc.edu/factsheets ;Japanese Macaque blueplanetbiomes.org ; Study: Sperm Competition and the Function of Masturbation in Japanese Macaques Photos Snow Monkey Gallery acapixus.dk/galleri ; Yudanaka is the home of Jigokudani (Hell Valley), where snow monkeys take a hot spring bath. Websites: Jigokudani snow monkey site jigokudani-yaenkoen.co ; Kojima Island (near Nichinan in Miyazaki in southern Kyushu) is famous for it troops of wild macaques who wash their food in both saltwater and freshwater and separating grains of rice from sand by cleverly throwing them into the water and collecting the rice grains, which float. Animal Info animalinfo.org/country/japan ;Japan Animals Blog /japan-animals.blogspot.com ;

Macaques

Macaques are medium-size monkeys with stout bodies and strong limbs. There are 23 species in five families and 40 different subspecies. They range across from the Old World from the Atlantic to the Pacific, including Spain, Morocco, Afghanistan Sri Lanka, Tibet, and Japan, but are found mostly in Southeast Asia, Indonesia and India. Forests and mountains have been their traditional habitat but many now live in cities.

Aside from humans, macaques are the most widespread primate genus. By some estimates, in evolutionary terms, the primate line that produced humans separated from macaque line about 25 million years ago. "The macaque is one of the most successful and versatile of all primates,”David Attenborough wrote. “If you wanted to pick a monkey that was bright, adaptable, versatile, resilient, enterprising, tough and capable of surviving in extreme conditions and taking on all comers, the macaque would win hands down.” They do equally well in mountains. marshes, rain forests and cities.

Macaques constitute the genus (Macaca) of gregarious Old World monkeys of the subfamily Cercopithecinae. Relatives of guenons, they are primarily frugivorous (preferring fruit), although their diet also includes seeds, leaves, flowers, and tree bark. Some species such as the long-tailed macaque, also called the crab-eating macaque, supplement their diets with small amounts of meat from shellfish, insects, and small mammals. On average, a southern pig-tailed macaque in Malaysia eats about 70 large rats each year. All macaque social groups are arranged around dominant matriarchs. [Source: Wikipedia]

Japanese Macaque Habitat and Where They Are Found

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Japanese macaques range from semi-tropical regions of islands south of Kyushu to the forests and mountains of northern Honshu. Hokkaido is too cold for them. They inhabit subtropical, subalpine, deciduous, broadleaf, and evergreen forests. They are found on the main Japanese islands Honshu, Shikoku, and Kyushu, as well as a few smaller islands. [Source: Brandon Hardman, Animal Diversity Web (ADW) /=]

Japanese macaques live in temperate areas with a climate similar to the U.S. or Europe in forests and mountains. They can also be found in coastal areas and marshes and live at elevations up of 3180 meters (10433feet).

In the northern part of their range, they inhabit cool temperate deciduous broadleaf forests, where temperatures average 11˚C, and annual average rainfall is around 150 centimeters. In the southern part of their native range, they live in evergreen broadleaf forests, where the temperature averages 20˚C, and annual average rainfall is around 300 centimeters. In many places where they live they endure harsh winters. Those that live in the mountains descend at lower elevations in the winter. Although they have been spotted at elevations as high as 3180 meters, during winter months they usually do not exceed elevations of 1800 meters. /=\

Japanese Macaque Characteristics

Sexual Dimorphism (differences between males and females) is present among Japanese macaques: Males are larger than females. Adult males are 88 to 95 centimeters (34.6 to 37.6 inches) tall. Females are 79 to 84 centimeters (31 to 33 inches) from head to foot. The average body and head length for male is 57 centimeters (22 inches); for female it is 52.3 centimeters (20.6inches). The average weight of a male 11.3 kilograms (24.9 pounds); for a female it is 8.4 kilograms (18.5 pounds). Males have a different shaped face and bright red testicles.

Japanese macaque have pink faces and rumps and grey, burnt amber, brown and yellowish brown fur. They have strong teeth and short, stumpy tails that are only about 10 centimeters (four inches) long. Adult males are as strong as a man. Their fur is very thick. They do not hibernate and, helps them stay warm during harsh winters. Japanese macaques can survive in temperatures that drop to as low -14̊C in the winter. They are cloaked in thick, soft fur which consists of an outer layer of course hairs and shorter denser tufts underneath. This thick coat of hair allows them to live so far north. Japanese macaques normally survive the cold months by feeding on thin shoots and winter buds of deciduous trees. They also strip away the outer bark of trees and eat the inner bark.

There appears to be a correlation between the body weight of Japanese macaques and the climate they live in. Those in southern areas generally weigh less than those in northern areas or areas of higher elevations, where snow is present during winter months. Provisioned Japanese macaques (ones that has been fed beyond what is naturally available their natural environment) have larger skulls than non-provisioned macaques. The skull of provisioned Japanese macaques averages centimeters in length for males and 11.8 centimeters for females. The skull of non-provisioned individuals average 12.95 centimeters in males and 11.6 centimeters in females. [Source: Brandon Hardman, Animal Diversity Web (ADW) /=]

The Japanese macaques found in Yakushima in southern Japan are not as well adapted for cold weather and are identified as a subspecies. They are generally smaller and have less fur than the Japanese macaques found further north. For thpse further north, a large body gives them a higher ratio of body weight to skin surface area and this helps prevent heat loss through perspiration.

Japanese Macaque Food and Eating Behavior

Japanese macaques are primarily herbivores (eat plants or plants parts), folivores (eat leaves), frugivores (eat fruits), mainectarivores (eat nectar from flowers), omnivores (eats a variety of things, including plants and animals). Japanese macaques have traditionally subsisted on fruits, seeds, beechnuts, acorns, chestnuts, insects and shellfish but will eat most anything: roots, tubers, bulbs, shoots, buds, spiders, snails, centipedes, moles, shrews, crayfish, shoots, leaves, mussels. grubs, insects, worms, crabs, fallen nuts and even frogs and poisonous snakes. They favor shoots and spring plants in the spring and fruits and seeds in the autumn. When desperate in severe winter months they eat bark. They also eat a wide variety of crops and human food.

Japanese macaque diets change seasonally. Brandon Hardman wrote in Animal Diversity Web: 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 percent 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 and raid farms and gardens and eat crops. [Source: Brandon Hardman, Animal Diversity Web (ADW) /=]

On the small island of Kinkazan, off of the eastern coast of 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. /=\

Japanese Macaque Mating and Reproduction

Japanese macaques are polygynandrous (promiscuous), with both males and females having multiple partners. There are few monogamous relationships in the troop but when they do appear they are very strong. Adults seem to be more tolerant of some youngsters than others, but it is not clear whether they are the fathers of these young monkeys. The rear end of females turned red during the breeding season.

Japanese macaques engage in seasonal breeding. The breeding season is from September to October with births usually taking place in April and May. Typically one offspring is born. The gestation period ranges from five to six minutes. The weaning age ranges from six months to two years. On average females reach sexual or reproductive maturity at age 3.5 years while males do so at around 4.5 years. Although males as young as 1.5 years of age have been observed mounting females, they do not successfully copulate until they are older.

According to Animal Diversity Web: Courtship is a very important part of reproduction in Japanese macaques. Japanese macaques spend on average 1.6 days with their potential mate during courtship. During this time, they feed, nest, and travel together. Females stay with higher ranking males longer than with lower ranking males. When high ranking males observe a low ranking male with a potential mate, they may try to disrupt their courtship. Copulation can occur arboreally or terrestrially. Females have two types of mating calls. The first is a squawk or squeak that is vocalized just before copulation. The second sounds like an atonal cackle and is vocalized after copulation. Japanese macaques are polygynandrous; males and females copulate with available individuals and have multiple partners during a breeding season. [Source: Brandon Hardman, Animal Diversity Web (ADW) /=]

Japanese Macaque Offspring and Parental Care

According to Animal Diversity Web: When Japanese macaque females are ready to give birth, they usually leave the troop and find a safe and private place. At birth, males weigh on average 539.7 grams and females 548.8 grams. Weaning may occur as early as six to eight months in some Japanese macaques. In some special cases, however, mothers may continue to nurse their offspring for up to 2.5 years if they have no other intervening births. Female Japanese macaques can produce a perfectly viable infant up to 25 years of age, although this is usual. Fertility does not appear to be correlated with menopause. /=\

Parental care is an important aspect of the growth of Japanese macaques, and infant mortality is high in this species. Mortality before one year of age is 28.4 percent. During the first four weeks of life, infants are carried near the abdomen of adults. Young are carried near the abdomen or on the dorsal side of adults until they are one year old. Female Japanese macaques groom their adult offspring more often than their juvenile offspring. This may occur during the time frame when offspring observe behavioral patterns of their mothers, learning multiple successful traits needed later in life. In some troops of Japanese macaques, male paternal parental care is also present. Occasionally males, even high-ranking males, have been observed grooming and protecting infants. Males also carry infants from time to time. /=\

Some female Japanese macaques have been observed carrying the body of their infant that was stillborn or otherwise killed, such as in an attack by raccoons or dogs. This behavior sometimes lasts for several days. Males have also been observed committing infanticide. This may reduce time before a female is able to reproduce again, giving the male an opportunity to reproduce. /=\

Japanese Macaques on Yakushima

Yakushima is an island south of Kyushu, the southernmost of Japan’s main islands. Ben Crair wrote in Smithsonian magazine: “About 10,000 Japanese macaques live on the island — about the same as the human population of around 13,000. The monkeys lived in groups of fewer than 50, and none are provisioned. They foraged for fruit, leaves, acorns and shoots as well as insects and spiders. “On Yakushima, monkeys love mushrooms,” said Akiko Sawada, a research fellow from Chubu University Academy of Emerging Sciences. The Yakushima monkeys ate more than 60 different varieties, and Sawada was studying if they could smell whether a mushroom was poisonous. She also thought it possible that this was social knowledge, with a young monkey learning which mushrooms to eat and which to avoid by watching its mother and other adults. It was difficult to say if a behavior at Yakushima was cultural or had been learned some other way, like instinct or simple trial and error. All of these processes worked together to shape a monkey’s life, and in a completely natural setting could not easily be unraveled. [Source: Ben Crair, Smithsonian magazine, January-February 2021]

Sawada took me to the quiet western coast of Yakushima, where scientists had habituated several monkey groups. The monkeys were easy to find, as they liked to groom and sunbathe on the road. They hurried out of the way for cars that sped along but barely budged for cars that slowed down. It was also mating season, and males and females paired off to consort at a distance from jealous peers. Sawada pointed out how one of the older monkeys leaned back and looked down her arms when she groomed a partner: Her vision was getting worse.

“We followed a large group from the road into the forest. Professor Sugiyama was right: There was less conflict as the monkeys spread out over a wide area to forage. Some cracked acorns with their teeth; others climbed trees for fruit. A young female unrolled curled dead leaves from the forest floor. “I think she’s looking for cocoons,” Sawada said.

“Four deer joined us on the hike. They were as small as dogs and nearly as unafraid of people. The monkeys were messy eaters, and deer followed them to pick up their scraps. A relationship developed, and monkeys sometimes groomed and rode the deer. At another research site near Osaka, monkeys sometimes even mounted deer in a rare example of interspecies sex. It’s possible that the deer were gentle partners for small-bodied adolescents who were routinely rejected by the opposite sex or risked physical harm from aggresive adults. “Future observations at this site will indicate whether this group-specific sexual oddity was a short-lived fad or the beginning of a culturally maintained phenomenon,” the researchers there wrote.

“That afternoon, Sawada showed me videos of different monkey behaviors she and her colleagues had recorded in the forest. In one, a monkey devoured a giant centipede; in another, a monkey rubbed a caterpillar between her hands to remove its stinging quills before she ate it; in a third, a monkey plucked plump white hornet larvae from a nest. Sawada giggled as she played a video of the monkeys who lived at high altitudes and ate bamboo: They were, for reasons no one really understood, extremely fat.

Alien Monkeys and Primate Research in Japan

In the early 1960s, a group of ten Taiwanese macaques escaped from a small zoo in Wakayama Prefecture. Eating bayberries and other local foods and thriving in the mild climate, the group expanded to 200 members by the 2000. Some Taiwanese macaques have tails shorter than their parents, which has led some people to believe they crossbred with Japanese macaques, which have shorter tails. Some worry that if this trend continues the purity of Japanese macaques could be threatened. A troop of about 100 rhesus monkeys live on the Boso peninsula in Chiba prefecture. No one is exactly sure how they got there.

The pioneer of Japanese macaque studies in Japan are Kinji Imanishi (1902-1992), Junichito Itani (1926-2001) and Masao Kawai (1923- ), ecologists at Kyoto University, who came to Koshima to study wild horses after World War II but began studying the monkeys on Kojima after becoming fascinated by their unusual behavior. Their first major discovery came in 1953 when a Satsue Mirto, a former primary school teacher in Miyazaki, wrote the scientists, describing a 1½-year-old female she saw washing a potato.

The Kyoto University primate study group discovered an auditory communication system among the monkeys and described the hierarchy of monkey groups, creating the basis for primatology. The theory that the monkeys possessed culture and passed it on from one generation to the next was published in 1954 and stirred up controversy around the world by giving examples in the animal kingdom of behaviors once though to be the exclusively human, blazing a trail for primatologists like Jane Goodall and Dian Fossey

Toshisada Nishida of Kyoto University is one of the world’s leading chimpanzee researchers. The recipient of the 2008 Louis Leakey anthropological award, he has spent much of life studying chimpanzees in Tanzania. Among his discoveries are that low ranking males sometimes play a kingmaking role, deciding who the dominate male will be.

Researcher can distinguish individual monkeys based on the shape of the eyes and nose, color the face, wrinkles between the eyebrows. Nelson Broche Jr. at the Koshima Field Station collects and measures stress hormones in the saliva of Japanese macaques.

Image Sources: Japan-Animals blog, Wolfgang Kaehler, JNTO, Japan Zone, British Museum

Text Sources: Animal Diversity Web animaldiversity.org ; National Geographic, Live Science, Yomiuri Shimbun, Japan National Tourist Organization (JNTO), Natural History magazine, David Attenborough books, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Discover magazine, The New Yorker, Time, Reuters, Associated Press, AFP, Lonely Planet Guides, Wikipedia, The Guardian, Top Secret Animal Attack Files website and various books and other publications.

Last updated December 2024