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.
Biogeographic Regions: nearctic (Introduced ); oriental (Native )
- Gron, K. 2007. "Japanese Macaque Macaca Fuscata" (On-line). Accessed September 29, 2010 at http://pin.primate.wisc.edu/factsheets/entry/japanese_macaque.
- Smuts, B., D. Cheney, R. Seyfarth, R. Wrangham, T. Struhsaker. 1986. Primate Societies. Chicago: University of Chicago Press.
Japan (Shikoku, Kyushu and Honshu Islands)
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.
Average mass: male 11.3 kg; female 8.4 kg.
Average length: male 57 cm; female 52.3 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger
Average mass: 8882.5 g.
Habitat and Ecology
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.
Range elevation: 3180 (high) m.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: forest ; mountains
Aquatic Biomes: coastal
- Fooden, J., M. Aimi. 2005. Systematic Review of Japanese Macauqes, Macaca Fuscata. Zoology, 104: 1-105.
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.
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.
Animal Foods: eggs; insects
Plant Foods: leaves; roots and tubers; wood, bark, or stems; seeds, grains, and nuts; fruit; nectar; flowers
Other Foods: fungus
Primary Diet: herbivore (Folivore , Frugivore , Nectarivore ); omnivore
- Hanya, G. 2004. Diet of a Japanese Macaque Troop in the Coniferous Forest of Yakushima. International Journal of Primatology, Vol. 25 No. 1: 55-71.
- Tsuji, Y., S. Takatsuki. 2004. Food Habits and Home Range use of Japanese Macaques on an Island Inhabited by Deer. Ecological Research, 19: 381-388.
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.
Ecosystem Impact: disperses seeds
- Majolo, B. 2004. Apparent feeding association between Japanese macaques (Macaca fuscata yakui) and sika deer (Cervus nippon) living on Yakushima Island, Japan B.. Ethology Ecology & Evolution, 16: 33-40.
- Tsuji, Y., M. Morimoto, K. Matsubayashi. 2009. Effects of the Physical Characteristics of Seeds on Gastrointestinal Passage Time in Captive Japanese Macaques. Journal of Zoology, 280: 171-176.
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.
- Mountian Hawk-Eagles Nisaetus nipalensis
- Feral Dogs Canis lupus familiaris
- Raccoon Dogs Nyctereutes procyonoides
- Japanese Wolf Canis lupus hattai
- Humans Homo sapiens
Life History and Behavior
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.
Communication Channels: visual ; tactile ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
In the wild, the oldest known male Japanese macaque was 28 years of age. The oldest known female was 32 years of age.
Status: wild: male 28 years; female 32 years.
Status: captivity: 22.7 years.
Status: captivity: 27.0 years.
Status: captivity: 33.0 years.
Status: captivity: 32.0 years.
Status: wild: 30.0 years.
Lifespan, longevity, and ageing
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.
Mating System: polygynandrous (promiscuous)
Female Japanese macaques reach sexual maturity around 3.5 years of age, while males reach sexual maturity 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. Breeding usually occurs between March and September. Gestation lasts an average of 171.7 days, although this is misleading; adding one standard deviation in either direction produces a range of 157 to 188.5 days with a 95% confidence level. When females are ready to give birth, they usually leave the troop and find a safe and private place. Japanese macaques generally have 1 offspring during a breeding season. Twins are rare and occur once in every 488 births. At birth, males weigh on average 539.7 g and females 548.8 g. Weaning may occur as early as 6 to 8 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.
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.
Breeding interval: Japanese macaques can breed once a year.
Breeding season: Japanese macaques breed from September to April
Average number of offspring: 1.
Range gestation period: 5 to 6 minutes.
Range weaning age: 6 to 24 + months.
Average age at sexual or reproductive maturity (female): 3.5 years.
Average age at sexual or reproductive maturity (male): 4.5 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous
Average birth mass: 496 g.
Average number of offspring: 1.5.
Average age at sexual or reproductive maturity (male)
Sex: male: 1369 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 1483 days.
Parental care is an important aspect of the growth of Japanese macaques, and infant mortality is high in this species. Mortality before 1 year of age is 28.4%. During the first 4 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 1 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.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Male, Female); pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female); post-independence association with parents; extended period of juvenile learning; inherits maternal/paternal territory; maternal position in the dominance hierarchy affects status of young
- Fooden, J., M. Aimi. 2005. Systematic Review of Japanese Macauqes, Macaca Fuscata. Zoology, 104: 1-105.
- Gron, K. 2007. "Japanese Macaque Macaca Fuscata" (On-line). Accessed September 29, 2010 at http://pin.primate.wisc.edu/factsheets/entry/japanese_macaque.
- Wolfe, L., M. Noyes. 1981. Reproductive Senescence Among Female Japanese Macaques (Macaca Fuscata Fuscata). Journal of Mammalogy, 62/4: 698-705. Accessed October 04, 2010 at http://www.jstor.org/stable/1380591.
Molecular Biology and Genetics
Statistics of barcoding coverage: Macaca fuscata
Public Records: 0
Specimens with Barcodes: 3
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2000Data Deficient (DD)
- 1996Endangered (EN)
- 1994Vulnerable (V)
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.
US Federal List: threatened
CITES: no special status
IUCN Red List of Threatened Species: least concern
- 2010. "Japanese macaques (Snow Monkey)" (On-line). Accessed October 15, 2010 at http://www.conservation.org/learn/biodiversity/species/profiles/more_primates/tree/Pages/japanese_macaque.aspx.
Date Listed: 10/19/1976
Lead Region: Foreign (Region 10)
Where Listed: Entire
Population location: Entire
Listing status: T
For most current information and documents related to the conservation status and management of Macaca fuscata , see its USFWS Species Profile
Relevance to Humans and Ecosystems
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.
Negative Impacts: injures humans (carries human disease); crop pest
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.
Positive Impacts: ecotourism ; research and education
The Japanese macaque (//; Macaca fuscata), is a terrestrial Old World monkey species native to Japan. They are also sometimes known as the snow monkey because they live in areas where snow covers the ground for months each year – no other non-human primate is more northern-living, nor lives in a colder climate. Individuals have brown-grey fur, red faces, and short tails. There are two subspecies.
In Japan, the species is known as Nihonzaru (Nihon ニホン "Japan" + saru サル "monkey") to distinguish it from other primates, but the Japanese macaque is very familiar in Japan, so when Japanese people simply say saru, they usually have in mind the Japanese macaque.
The Japanese macaque is sexually dimorphic. Males weigh on average 11.3 kg (25 lb), while females average 8.4 kg (19 lb). Macaques from colder areas tend to weigh more than ones from warmer areas. Male average height is 570.1 mm (22.44 in) and female average height is 522.8 mm (20.58 in). Their brain size is approximately 95 g (3.4 oz). Japanese macaques have short stumps for tails that average 92.51 mm (3.642 in) in males and 79.08 mm (3.113 in) in females. The macaque has a pinkish face and posterior. The rest of its body is covered in brown, greyish, or yellowish hair. The coat of the macaque is well-adapted to the cold and its thickness increases as temperatures decrease. The macaque can cope with temperatures as low as -20 °C (-4 °F).
Macaques mostly move on all fours. They are semi-terrestrial, with females spending more time in the trees and males spending more time on the ground. Macaques are known to leap. They are also great swimmers and have been reported to swim over half a kilometer. The longevity for the macaque averages 6.3 years (at least for females). However, they have been known to live much longer; males have lived up to 28 years and females up to 32 years.
Japanese macaques live in matrilineal societies, and females stay in their natal groups for life, while males move out before they are sexually mature. Macaque groups tend to contain a number of adults of both sexes. In addition, a macaque troop contains several matrilines. These matrilines may exist in a dominance hierarchy with all members of a specific group ranking over members of a lower-ranking group. Temporary all-male groups also exist, composed of those that have recently left their natal groups and are about to transfer to another group. However, many males spend ample time away from any group and may leave and join several groups.
Males within a group have a dominance hierarchy, with one male having alpha status. The dominance status of male macaques usually changes when a former alpha male leaves or dies. Other ways in which status changes is when an alpha male loses his rank or when a troop splits, leaving a new alpha position open. The longer a male is in a troop, the higher his status is likely to be. Females also exist in a stable dominance hierarchy, and a female's rank depends on her mother. Younger females tend to rank higher than their older siblings. Higher-ranking matrilines have greater social cohesion. Strong relationships with dominant females can allow dominant males to retain their rank when they otherwise would not.
Females maintain both social relationships and hygiene through grooming. Grooming occurs regardless of climate or season. Females which are matrilineally related groom each other more often than unrelated individuals. Females will also groom unrelated females to maintain group cohesion and social relationships between different kinships in a troop. Nevertheless, a female will only groom a limited number of other females, even if the group expands. Females will also groom males, usually for hygienic purposes, but it can serve to attract dominant males to the group. Mothers pass their grooming techniques to their offspring most probably through social rather than genetic means.
Mating and parenting
A male and female macaque will form a pair bond and mate, feed, rest and travel together, and this typically lasts 1.6 days on average during the mating season. Females enter into consortships with an average of four males a season. Higher-ranking males have longer consortships than their subordinates. In addition, higher-ranking males will try to disrupt consortships of lower-ranking males. Females will attempt to mate with males of any rank. However, dominant males mate more as they are more successful in mate guarding. The female decides whether mating will take place. In addition, dominance does not mean a male will successfully mate with a female. Males may also temporarily join another troop during the mating season and mate with the females. Females will also engage in same-sex mounting. Such behavior is likely because of hormones and females are mounted more often by other females than males.
During the mating season, the face and genitalia of males redden and the tail will stand erect. In addition, females' faces and anogenital regions turn scarlet. Macaques will copulate both on the ground and in the trees, and roughly one in three copulations leads to ejaculation. Macaques signal when they are ready to mate by looking backward over a shoulder, staying still, or walking backwards towards their potential partner. A female will emit a "smooth-late-high coo", or "squawk", "squeak", or produce an atonal "cackle" during copulation. Males have no copulatory vocalizations.
A macaque mother moves to the periphery of her troop to give birth in a secluded spot, unless the group is moving, when the female will have to stay with it. Macaques usually give birth on the ground. Infants are born with dark-brown hair. They will consume their first solid food at five to six weeks old, and can forage independently from their mothers by seven weeks. A mother carries her infant on her belly for its first four weeks. After this time, the mother will carry her infant on her back, as well. Infants continue to be carried up to and past a year. A mother and her infant tend to avoid other troop members, and the mother may socialize again very slowly. However, alloparenting has been observed, usually by females which have not had infants of their own. Male care of infants occurs in some groups, but not in others; usually, older males protect, groom, and carry an infant as a female would.
Infants have fully developed their locomotive abilities within three to four months. When an infant is seven months old, its mother discourages suckling; full weaning happens by its 18th month. In some populations, male infants tend to play in larger groups more often than females. However, female infants have more social interaction than their male counterparts. Males prefer to associate with other males around the same age, when they are two years old. Female infants will associate with individuals of all ages and sexes.
During feeding or moving, Japanese macaques will often emit "coos". These most likely serve to keep the troop together and strengthen social relations between females. Macaques usually respond to coos with coos of their own. Coos are also uttered before grooming along with "girney" calls. Variants of the "girney" call are made in different contexts. This call also serves as appeasement between individuals in aggressive encounters. Macaques have alarm calls for alerting to danger, and other calls to signal estrus that sound similar to danger alerts. Threat calls are heard during aggressive encounters and are often uttered by supporters of those involved in antagonistic interactions. The individual being supported will support the caller in the future.
Intelligence and culture
The Japanese macaque is a very intelligent species. Researchers studying this species at Koshima Island in Japan left sweet potatoes out on the beach for them to eat, then witnessed one female, named Imo (Japanese for yam or potato), washing the food off with river water rather than brushing it off as the others were doing, and later even dipping her clean food into salty sea water. After a while, others started to copy her behavior. This trait was then passed on from generation to generation, until eventually all except the oldest members of the troop were washing their food and even seasoning it in the sea. She was similarly the first observed balling up wheat with air pockets, throwing it into the water, and waiting for it to float back up before picking it up and eating it free from dirt. An altered misaccount of this incident is the basis for the "hundredth monkey" effect.
The macaque has other unusual behaviours, including bathing together in hot springs and rolling snowballs for fun. Also, in recent studies the Japanese macaque has been found to develop different accents, like humans. Macaques in areas separated by only a few hundred miles can have very different pitches in their calls, their form of communication. The Japanese macaque has been involved in many studies concerning neuroscience and also is used in drug testing.
The Japanese macaque is diurnal. In colder areas, from autumn to early winter, macaques feed in between different activities. In the winter, macaques have two to four feeding bouts each day with fewer daily activities. In the spring and summer, they have two or three bouts of feeding daily. In warmer areas such as Yakushima, daily activities are more varied. The typical day for a macaque is 20.9% inactive, 22.8% traveling, 23.5% feeding, 27.9% social grooming, 1.2% self-grooming, and 3.7% other activities. Macaques usually sleep in trees, but will also sleep on the ground, as well as on or near rocks and fallen trees. During the winter, macaques huddle together for warmth in sleeping grounds. Macaques at Jigokudani Monkey Park are notable for visiting the hot springs in the winter to warm up.
The Japanese macaque is omnivorous and will eat a variety of foods. Over 213 species of plant are included on the macaque's diet. It also eats insects, bark and soil. On Yakushima Island, fruit, mature leaves and fallen seeds are primarily eaten. The macaque also eats fungi, ferns, invertebrates, soil and other parts of plants. In addition, on Yakushima, their diets vary seasonally with fruits being eaten in the summer and herbs being eaten in the winter. Further north, macaques mostly eat foods such as fruit and nuts to store fat for the winter, when food is scarce. On the northern island of Kinkazan, macaques mostly eat fallen seeds, herbs, young leaves and fruits. When preferred food items are not available, macaques will dig up underground plant parts (roots or rhizomes) or eat soil and fish.
Distribution and habitat
The Japanese macaque is the northernmost-living nonhuman primate. It is found on three of the four main Japanese islands: Honshu, Shikoku, and Kyushu. The northernmost populations live on the Shimokita Peninsula, the northernmost point of Honshu. Several of Japan’s smaller islands are also inhabited by macaques. The southernmost population living on Yakushima Island is a subspecies of the mainland macaques. The total population of Japanese macaques has been estimated to be 114,431 monkeys.
The Japanese macaque lives in a variety of habitats. It inhabits subtropical forests in the southern part of its range and subarctic forests in mountainous areas in the northern part of its range. It can be found in both warm and cool forests, such as the deciduous forests of central and northern Japan and the broadleaf evergreen forests in the southwest of the islands. Warm temperate evergreen and broadleaf forests and the cool temperate deciduous broadleaf forests are the most important habitats for macaques.
In 1972, a troop of about 150 Japanese macaques were relocated from Kyoto to a primate observatory in southwest Texas, USA. The observatory is an enclosed ranch-style environment and the macaques have been allowed to roam with minimal human interference. At first, many perished in the unfamiliar habitat, which consists of arid brushland. The macaques eventually adapted to the environment, and learned to forage for mesquite beans, cactus fruits, and other foods. The macaques flourished, and by 1995, the troop consisted of 500 to 600 individuals. In 1996, hunters maimed or killed four escaped macaques; as a result, legal restrictions were publicly clarified and funds were raised to establish a new 186-acre (75-ha) sanctuary near Dilley, Texas.
Relationship with humans
Traditional manmade threats to macaques have been slash-and-burn agriculture, use of forest woods for construction and fuel, and hunting. These threats have declined due to social and economic changes in Japan since World War II, but other threats have emerged. The replacement of natural forest with lumber plantations is the most serious threat. As human prosperity has grown, macaques have lost their fear of humans and have increased their presence in both rural and urban areas, with one macaque recorded living in central Tokyo for several months.
The Japanese macaque has featured prominently in the religion, folklore, and art of Japan, as well as in proverbs and idiomatic expressions in the Japanese language. In Shinto belief, mythical beasts known as raijū sometimes appeared as monkeys and kept Raijin, the god of lightning, company. The "three wise monkeys", which warn people to "see no evil, hear no evil, and speak no evil", are carved in relief over the door of the famous Tōshō-gū shrine in Nikkō. The Japanese macaque is a feature of several fairy tales, such as the tale of Momotaro and the fable about the The Crab and the Monkey. As the monkey is part of the Chinese zodiac, which has been used for centuries in Japan, the creature was sometimes portrayed in paintings of the Edo Period as a tangible metaphor for a particular year. The 19th-century artist and samurai Watanabe Kazan created a painting of a macaque. During the Edo Period, numerous clasps for kimono or tobacco pouches (collectively called netsuke) were carved in the shape of macaques.
Spoken references to macaques abound in the history of Japan. Before his rise to power, the famed samurai Toyotomi Hideyoshi was compared to a monkey in appearance and nicknamed Kozaru ("Little Monkey") by his lord and master, Oda Nobunaga.[not in citation given] This was a humorous jibe at first, but was later used pejoratively by Hideyoshi's rivals. In modern Japanese culture, because monkeys are considered to indulge their libido openly and frequently (much the same way as rabbits are thought to in some Western cultures), a man who is preoccupied with sex might be compared to or metaphorically referred to as a monkey, as might a romantically involved couple who are exceptionally amorous.
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