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Macaque

The macaques (genus Macaca) comprise a diverse group of 23 species of Old World monkeys in the family Cercopithecidae and subfamily Cercopithecinae, characterized by their robust build, sexual dimorphism, and adaptability to varied environments.^[1]^[2] These medium-sized primates typically weigh between 3 and 18 kg, with males larger than females, and feature short to medium-length tails, pouch-like cheek pouches for food storage, and ischial callosities for sitting.^[1] They are quadrupedal, semi-terrestrial animals capable of both arboreal and ground-based locomotion, and are known for their opportunistic omnivorous diet consisting primarily of fruits, leaves, seeds, insects, and small vertebrates.^[2]^[1] Macaques exhibit the broadest geographic range of any non-human primate genus, inhabiting regions across southern, eastern, and southeastern Asia—from Japan and China to Indonesia and the Philippines—as well as northwestern Africa, where the Barbary macaque (Macaca sylvanus) is the only representative outside Asia.^[3]^[4] This distribution spans over 5 million square kilometers and includes diverse habitats such as tropical rainforests, temperate woodlands, grasslands, and even urban and agricultural areas near human settlements, demonstrating remarkable ecological plasticity.^[5]^[1] The genus originated in North Africa around 5.5 million years ago, dispersing to Eurasia, with rapid speciation occurring less than 5 million years ago, leading to four main phylogenetic groups: sylvanus, silenus, sinica, and fascicularis.^[4] Socially, macaques form large, multi-male/multi-female groups of 10 to over 100 individuals, with matrilineal kinship structures where females remain in their natal groups and males disperse at maturity to avoid inbreeding.^[1] These societies are organized around strict dominance hierarchies that influence access to food, mates, and grooming, with behaviors including alliance formation, reconciliation after conflicts, and vocalizations for communication.^[6] Species vary in traits such as pelage color (from golden to dark brown), facial markings, and tail length, which aid in species identification and adaptation.^[5] Notable species include the rhesus macaque (M. mulatta), widely used in biomedical research due to genetic similarities to humans, and the long-tailed macaque (M. fascicularis), valued for its role in ecological studies.^[2]^[3] Conservation efforts for macaques are critical, as habitat loss, hunting, and the pet trade threaten many populations; according to the IUCN Red List, two species are critically endangered, five are endangered, eight are vulnerable, and the rest are of least concern or near threatened.^[1] Despite their adaptability, species like the Sulawesi macaques face localized extinctions, underscoring the need for protected areas and international regulations to sustain this ecologically and scientifically significant genus.^[5]

Taxonomy and evolution

Classification

Macaques belong to the genus Macaca in the subfamily Cercopithecinae of the family Cercopithecidae, which encompasses the Old World monkeys distributed across Africa and Asia.^[4] This placement reflects their shared characteristics with other cercopithecines, such as baboons and guenons, while distinguishing them through specific morphological and ecological adaptations. The genus Macaca is one of the most speciose among primates, with 25 recognized extant species inhabiting diverse environments from tropical forests to temperate highlands.^[7] These species are systematically divided into four primary groups based on a combination of morphological features, such as cranial structure and pelage patterns, and genetic analyses including Alu element insertions: the fascicularis group, silenus group, sylvanus group, and sinica group.^[4] The fascicularis group includes species like the long-tailed macaque (Macaca fascicularis), noted for their adaptability to human-modified landscapes; the silenus group comprises Southeast Asian forms such as the lion-tailed macaque (M. silenus); the sylvanus group is represented solely by the Barbary macaque (M. sylvanus), the only macaque native to Africa; and the sinica group features East Asian species like the Tibetan macaque (M. thibetana) and rhesus macaque (M. mulatta). This grouping aids in understanding phylogenetic relationships and evolutionary divergence within the genus.^[8] Key diagnostic traits of the genus Macaca include bilateral cheek pouches that allow temporary food storage during foraging, colorful ischial callosities on the buttocks that facilitate prolonged sitting, and non-prehensile tails varying in length from long and slender in species like M. fascicularis to short or absent in others such as M. sylvanus.^[9] These features are typical of the Cercopithecinae subfamily but are particularly pronounced in macaques, supporting their omnivorous diet and terrestrial behaviors. Recent taxonomic revisions have refined this classification, including the description of the Arunachal macaque (Macaca munzala) as a new species in the sinica group from northeastern India in 2004 based on distinct pelage and cranial morphology, and the recognition of subspecies within M. fascicularis to account for regional variations, such as M. f. aurea in mainland Southeast Asia.^[10]^[11] Additional elevations, like Macaca leonina from a subspecies of M. nemestrina, highlight ongoing refinements driven by molecular data.^[8]

Phylogenetic history

The phylogenetic history of macaques traces back to early cercopithecines in Africa, with fossils like Victoriapithecus from the middle Miocene (approximately 15 million years ago) representing a basal ancestor to the subfamily Cercopithecinae, which includes the genus Macaca. This early lineage laid the groundwork for later divergences within Old World monkeys. The genus Macaca itself originated around 5.5 million years ago in northern Africa, diverging from other papionins (such as baboons in the genus Papio) during the late Miocene, with molecular clock estimates placing the initial split at approximately 7.0–6.7 million years ago.^[12]^[13] Fossil evidence supports this timeline, with early Macaca-like remains appearing in Eurasia by 5.9–5.3 million years ago, indicating rapid post-origin dispersal.^[13] Following their African origin, macaques underwent significant migrations facilitated by land bridges and favorable climatic conditions during the Pliocene and Pleistocene epochs. The basal sylvanus group, represented today by the Barbary macaque (Macaca sylvanus) in North Africa and a relict population in Gibraltar (Europe), remained largely in Africa but with fossil evidence of broader European distribution until historical times.^[12] Subsequent waves dispersed eastward into Asia, where the genus diversified extensively; molecular data suggest the sylvanus group diverged first, followed by migrations leading to the sinica group on the Asian mainland and the silenus and fascicularis groups in Southeast Asia around 5–4 million years ago.^[13] Recent genomic studies indicate that the fascicularis group originated from ancient hybridization between ancestors of the sinica and silenus groups.^[14] These movements were enabled by tectonic connections like the Gomphotherium Land Bridge, allowing colonization of diverse environments from temperate forests to tropical islands.^[13] Key evolutionary adaptations underpinned this expansion, particularly an omnivorous diet that included fruits, seeds, leaves, insects, and opportunistic scavenging, providing resilience in variable habitats compared to more specialized folivorous or frugivorous primates.^[15] Complementing this, macaques exhibited remarkable social flexibility, with multimale-multifemale group structures that could adjust in size and composition (from 10 to over 100 individuals) to match resource availability and predation risks, facilitating survival across ecological gradients.^[16] These traits, evident in both fossil dental morphology and modern behaviors, contributed to the genus's success, resulting in 25 extant species distributed over a vast range exceeding 5 million square kilometers.^[15] The major phylogenetic branches—sylvanus (North Africa/Europe), sinica (Asian mainland, e.g., rhesus macaque), fascicularis (Southeast Asia, e.g., long-tailed macaque), and silenus (insular Southeast Asia, e.g., lion-tailed macaque)—reflect this adaptive radiation, with mitogenomic analyses confirming their monophyly and sequential divergences.^[13]

Physical characteristics

Morphology and anatomy

Macaques exhibit a quadrupedal form adapted for versatile locomotion across terrestrial and arboreal environments, supported by robust limbs with strong musculature that enable efficient walking, running, and climbing. Their forelimbs and hindlimbs are of comparable length, facilitating a stable gait, while the skeletal structure includes a flexible spine and powerful shoulder and pelvic girdles for weight distribution during movement.^[17] The hands and feet of macaques are highly prehensile, each bearing five digits with flat nails rather than claws; the thumbs and big toes are opposable, allowing precise grasping of branches, food items, and substrates. This adaptation is enhanced by keratinized palms and soles featuring epidermal ridges for improved traction and sensory feedback. The overall limb configuration reflects an evolutionary balance between mobility and manipulation capabilities.^[17] Facial morphology in macaques includes a prognathic muzzle that houses the nasal and oral structures, forward-facing eyes that provide stereoscopic vision essential for depth perception in complex habitats, and a naked face with relatively hairless, pigmented skin capable of conveying expressive changes through color shifts and movements.^[17] The dentition follows a dental formula of 2.1.2.3 in both the upper and lower jaws, totaling 32 teeth in adults, with bilophodont molars featuring two transverse ridges that efficiently grind fibrous vegetation and other tough plant material. Internally, macaques possess enlarged salivary glands, including prominent parotid and submandibular glands, which produce secretions that moisten and aid in the temporary storage of food within expandable cheek pouches lining the buccal cavity. Macaques also feature ischial callosities, hardened skin pads on the buttocks that provide comfort during prolonged sitting on hard surfaces.^[18]^[17]^[19]^[1] Their vocal tract, comprising a descended larynx, flexible pharynx, and mobile tongue, supports the generation of a diverse array of calls ranging from coos to screams.^[18]^[17]^[19] Sexual dimorphism manifests primarily in body size, with males typically larger than females across macaque species.^[17]

Size, coloration, and variation

Macaques exhibit considerable variation in body size across species, with average head and body lengths ranging from 40 to 70 cm, excluding the tail, and weights typically between 3 and 18 kg.^[1] Sexual dimorphism is pronounced, with males generally 30-50% larger than females in both length and weight, a pattern more evident in terrestrial species than arboreal ones.^[20]^[21] Fur coloration in macaques is typically grayish-brown, providing camouflage in their varied environments, though it shows species-specific diversity such as the golden pelage of lion-tailed macaques (Macaca silenus). Tail length varies markedly, from absent in the Barbary macaque (Macaca sylvanus) to exceeding body length in species like the long-tailed macaque (Macaca fascicularis).^[22]^[23] Age and sex influence physical traits, with juveniles displaying lighter fur coloration compared to adults and less pronounced sexual dimorphism that develops post-maturity. In females, anogenital swelling occurs during estrus, serving as a visual signal of reproductive status and varying in size and intensity across species.^[24]^[25] Intraspecific variation in macaque size often follows clinal patterns related to latitude, consistent with Bergmann's rule, where individuals in higher latitudes tend to be larger, as observed in Japanese macaques (Macaca fuscata) with increased body weight and trunk length northward.^[26] Habitat conditions can subtly influence coloration for adaptive camouflage, though this is secondary to genetic factors.^[27]

Distribution and habitat

Geographic range

Macaques (genus Macaca) are native to a broad geographic area spanning Asia and North Africa. In Asia, their range extends from Afghanistan and Pakistan in the west through the Indian subcontinent, Southeast Asia, and southern China, reaching northward to Japan and southward to the Indonesian archipelago, including numerous islands. The only native African species is the Barbary macaque (Macaca sylvanus), which is restricted to fragmented cedar forests in the Atlas Mountains of Morocco and Algeria. This distribution makes macaques the most widespread nonhuman primate genus, occupying latitudes from about 40°N to 10°S.^[2]^[28]^[26] The historical range of macaques reflects an African origin for the genus around 7–9 million years ago, followed by dispersal into Asia approximately 5.5 million years ago during a period of diversification. Subsequent radiations, including westward and northward expansions, occurred around 3 million years ago, leading to the establishment of multiple clades and isolated island populations through natural migrations and vicariance events associated with tectonic changes and sea level fluctuations. Fossil evidence supports early presence in both regions, with macaques once more continuously distributed across Eurasia before Pleistocene isolations.^[14]^[29]^[30] Current populations across the approximately 23 macaque species number in the tens of millions, though precise global totals are challenging due to varying survey methods; for example, the long-tailed macaque alone is estimated at around 1 million individuals. Densities are highest in the tropical forests and human-modified landscapes of India and Indonesia, where species like the rhesus and long-tailed macaques thrive in large groups, often exceeding 50 individuals per square kilometer in optimal areas. These populations exhibit varying degrees of fragmentation due to habitat variability within their ranges.^[31]^[2] Introduced populations have established outside the native range since the 17th–20th centuries, primarily through human activities such as pet trade, research escapes, and deliberate releases. Notable examples include rhesus macaques in central Florida, USA, originating from imports in the 1930s for biomedical purposes and now numbering several hundred in forested areas; Barbary macaques in Gibraltar, Europe, descended from North African imports dating back centuries and maintained at around 230 individuals; and long-tailed macaques in Mauritius, introduced by Dutch settlers around 1602, where they have become invasive with populations in the thousands. Additional feral groups exist in places like Palau and Papua New Guinea in Oceania.^[32]^[33]^[34]^[35]

Habitat preferences

Macaques of the genus Macaca primarily inhabit tropical and subtropical forests across Asia, North Africa, and southern Europe, but the group exhibits exceptional ecological versatility, occupying a broad spectrum of niches including mangroves, coastal swamps, grasslands, semi-arid scrublands, and montane forests. This adaptability allows them to persist in both primary and secondary growth areas, often favoring disturbed habitats where human activity has altered the landscape. For example, long-tailed macaques (Macaca fascicularis) thrive in riverine zones, forest peripheries, and agricultural edges from sea level up to 1,800 meters.^[36]^[31] A core set of environmental requirements underpins macaque habitat selection: reliable access to freshwater sources, fruiting trees and diverse vegetation for foraging, and dense cover—such as understory shrubs or tall canopies—for predator avoidance and resting. These primates show high tolerance for edge habitats and anthropogenic fringes, frequently exploiting urban-adjacent areas like parks and plantations where food resources are supplemented by human waste. Their habitat choices are influenced by seasonal variations, including monsoons in Southeast Asia, which affect fruit availability and prompt shifts between arboreal and terrestrial foraging.^[37]^[21]^[38] Altitudinally, macaques range from coastal lowlands to high elevations, with rhesus macaques (Macaca mulatta) documented up to over 4,000 meters in the Himalayas, while species like the Tibetan macaque (Macaca thibetana) occupy subtropical to temperate mixed forests between 800 and 2,500 meters. Climatically, they span tropical rainforests to cool temperate zones, demonstrating physiological resilience to temperature extremes. In microhabitats, forested species tend to be semi-arboreal, climbing for fruits and escape, but become predominantly ground-dwelling in open grasslands; notably, Japanese macaques (Macaca fuscata) incorporate hot springs into their winter routines for thermoregulation in subalpine environments up to 2,900 meters. These preferences align with resource distribution, as fruit abundance drives occupancy in fruit-rich forests.^[37]^[39]^[40]

Behavior and ecology

Macaques typically live in matrilineal societies characterized by multi-male, multi-female troops ranging from 10 to over 200 individuals, depending on the species and habitat; for instance, rhesus macaques (Macaca mulatta) form groups of 20 to 100 members, while some populations of long-tailed macaques (Macaca fascicularis) can exceed 150.^[41] Females are philopatric, remaining in their natal groups and forming stable matrilines that often span multiple generations, whereas males disperse at sexual maturity to join other groups, reducing inbreeding.^[37] This structure fosters complex social networks where kinship plays a central role in alliances and resource access.^[42] Dominance hierarchies in macaques vary by species, ranging from despotic systems with steep, aggressive rank gradients to more egalitarian ones with tolerant interactions; rhesus and Japanese macaques (Macaca fuscata) exhibit despotic hierarchies, while Barbary macaques (Macaca sylvanus) show greater tolerance.^[43] Female hierarchies are generally linear and stable, inherited matrilineally with higher-ranking mothers conferring rank to daughters, promoting kin-biased support during conflicts.^[44] In contrast, male hierarchies are more fluid and contest-based, often involving coalitions, challenges, and rank reversals, particularly among immigrants seeking mating opportunities.^[42] Communication among macaques is multifaceted, relying on vocalizations such as coos for maintaining contact and screams during agonistic encounters, alongside facial expressions like grimaces to signal submission and lip-smacking for affiliation.^[45] Grooming serves as a primary bonding mechanism, reinforcing social ties and reducing tension, especially within matrilines, while olfactory signals, including urine marking, convey information about dominance, identity, and reproductive status.^[41]^[46] Group dynamics include fission-fusion patterns, where troops split into temporary foraging subgroups to optimize resource use before reuniting, and infanticide by incoming males, which accelerates female estrus by eliminating unrelated offspring and thereby enhances the killers' reproductive success.^[47]^[48]

Diet and foraging

Macaques are opportunistic omnivores, with their diet primarily consisting of plant matter such as fruits, leaves, seeds, flowers, and bark, which typically comprises 50-80% of their intake depending on species and habitat availability.^[49]^[50] This frugivorous foundation is supplemented by animal-derived foods, including insects, small vertebrates like lizards and birds, fungi, and occasionally eggs or crabs, allowing flexibility in resource-poor environments.^[50]^[51] In areas near human settlements, macaques readily incorporate anthropogenic food waste, such as grains, bread, and processed items, which can constitute a significant portion of their diet in urban or agricultural settings.^[52]^[53] Foraging behaviors in macaques combine ground-level searches with arboreal exploration, enabling them to exploit diverse microhabitats within their range. Species like the long-tailed macaque (Macaca fascicularis) demonstrate advanced tool use, employing stones to crack open nuts, shellfish, or other hard-shelled prey during extractive foraging along coastal or intertidal zones.^[54]^[55] These strategies are often solitary or small-group activities, with individuals scanning for opportunistic items while minimizing energy expenditure through efficient scanning and manipulation.^[56] Macaques exhibit seasonal adaptations to fluctuations in food availability, shifting to fallback resources such as bark, mature leaves, or lichens when preferred fruits become scarce during dry or winter periods.^[57]^[58] Prominent cheek pouches facilitate this by allowing individuals to collect and transport food items to safer locations for consumption, reducing exposure to predators or competitors during extended foraging bouts.^[59]^[60] This pouch usage is particularly vital in patchy environments, where rapid collection enhances survival during scarcity.^[61] Physiologically, macaques are hindgut fermenters with an enlarged cecum that supports microbial breakdown of fibrous plant materials, extracting nutrients from cellulose-rich fallback foods through symbiotic bacteria.^[62] Their digestive system features relatively rapid gut transit times, suited to a mixed omnivorous diet that includes easily digestible fruits alongside tougher vegetation, optimizing nutrient absorption without prolonged retention.^[63]^[64] This adaptation underscores their ecological versatility across tropical and temperate habitats.^[65]

Reproduction and development

Macaques exhibit a polygynandrous mating system, in which both males and females mate with multiple partners during the breeding season, leading to low paternity certainty and opportunities for post-copulatory sexual selection.^[66] In many species, particularly those in temperate regions like rhesus macaques (Macaca mulatta), females ovulate seasonally, with conception peaks typically occurring in winter to align births with periods of resource abundance in spring and summer.^[67] Gestation lasts 5-6 months, averaging 164 days in rhesus macaques and 167 days in cynomolgus macaques (Macaca fascicularis), and results in the birth of a single offspring, though twins occur rarely (less than 1% of cases).^[67]^[68] Newborn macaques are altricial, born with limited mobility and dependent on their mothers for survival; infants cling to the mother's ventral surface immediately after birth and begin suckling within the first hour.^[67] Maternal care is intensive during the first 6-12 months, involving nursing, grooming, and protection, with weaning typically occurring around 12 months, though nutritional independence begins earlier at 4-6 months as infants start solid foods.^[67] Allomothering, or care provided by non-maternal group members such as female kin or subadult siblings, is common and helps reduce maternal energetic costs while enhancing infant survival through additional vigilance and handling.^[69] Male involvement in parental care is generally minimal across macaque species, limited to occasional guarding against predators or infanticide in species like Barbary macaques (Macaca sylvanus), without direct provisioning or carrying. Infants achieve locomotor independence by 6-8 weeks and social integration into the group by 3-6 months, but remain vulnerable, with juvenile mortality rates ranging from 20-50% in the wild due primarily to predation, disease, and accidents.^[70] Sexual maturity is reached at 3-5 years for females and 4-7 years for males, varying by species and environmental conditions; for example, rhesus females mature at about 3 years, while males do so at 4 years.^[67] In the wild, the median lifespan of macaques is less than 15 years, with fewer than 5% surviving beyond 25 years, due to cumulative risks, whereas in captivity, lifespans extend to a median of over 25 years and a maximum of 40 years, reflecting reduced predation and better veterinary care.^[67]

Interactions with humans

As invasive species

Macaque species have established invasive populations outside their native ranges in several regions, including Florida in the United States, Gibraltar in Europe, and various Pacific islands such as Angaur in Palau. In Florida, rhesus macaques (Macaca mulatta) were intentionally introduced in the 1930s to an island in Silver Springs State Park by a tour boat operator to attract visitors, with initial releases of about six individuals followed by additional ones in the 1940s.^[32] These populations have since expanded, with estimates of nearly 200 to 300 individuals across five groups as of 2025, driven by the absence of natural predators and access to human-provided food sources like tourist scraps and nearby agriculture.^[71]^[72] In Gibraltar, Barbary macaques (Macaca sylvanus), introduced centuries ago likely by Moorish settlers, maintain a stable population of around 230 individuals that roam urban areas, benefiting from a lack of predators and supplemental feeding by tourists.^[33]^[73] On Pacific islands like Angaur in Palau, long-tailed macaques (Macaca fascicularis) were introduced in the early 20th century during German colonial rule and further spread via Japanese and U.S. military activities during World War II, leading to populations of about 5,000 that outnumber the island's 114 human residents by approximately 44 to 1 as of 2025 due to similar factors of no predators and reliance on human food waste.^[74]^[75] The spread of these invasive macaque populations often results from intentional releases for purposes such as biomedical research, tourism attractions, or as pets, as well as accidental escapes from facilities. In Florida, early releases were tourism-driven, but subsequent biomedical interests led to trapping and relocation of hundreds of individuals between 1998 and 2012, inadvertently aiding dispersal to form additional groups.^[76] In the Pacific, military releases during wartime contributed to establishment on islands like Angaur, where macaques have since dispersed across the 4-square-kilometer landmass.^[74] Dispersal rates can reach several kilometers per year, with documented group movements and home ranges averaging 1-2 km daily in human-modified habitats, facilitating expansion into new areas without natural barriers.^[2] Invasive macaques exert significant ecological and economic impacts, including crop raiding that causes substantial agricultural losses, competition with native wildlife, and potential hybridization risks in regions with related species. In areas like Florida and Palau, raiding of fruits, vegetables, and grains leads to estimated losses of up to 20% in affected farms, exacerbating food security issues on small islands where monkeys consume or destroy limited resources.^[77] These primates compete with native birds and small mammals for fruits and seeds, potentially disrupting local biodiversity, as seen with long-tailed macaques preying on eggs and displacing avian species in Pacific habitats.^[36] Hybridization poses additional threats where invasive macaques overlap with native primates, such as rhesus macaques interbreeding with Japanese macaques (Macaca fuscata) in introduced Asian contexts, leading to genetic dilution and reduced fitness in endemic populations.^[78] Management of invasive macaque populations involves challenges like implementing sterilization programs and culling, which are often controversial due to public sympathy for these charismatic animals and risks of disease transmission. In Florida's Silver Springs, ongoing proposals include sterilization of adult females or culling to manage growth, as the population has exceeded earlier predictions and continues to increase as of 2025, but face opposition amid concerns over herpes B virus, which is fatal to humans and prevalent in about 25% of the monkeys.^[79]^[80] Similarly, in Palau, trapping and contraception efforts have failed to curb growth, with culling debated due to ethical issues and potential zoonotic disease spread, highlighting the tension between ecological control and societal perceptions.^[75] These strategies underscore the difficulty in balancing invasive species management with public health and conservation ethics.^[81]

Uses in research and medicine

Macaques, particularly rhesus (Macaca mulatta) and cynomolgus (Macaca fascicularis) species, serve as key model organisms in biomedical research due to their physiological and genetic similarities to humans. Rhesus macaques have been extensively used in neuroscience since the 1960s, notably in studies mapping the visual cortex, where researchers like David Hubel and Torsten Wiesel demonstrated columnar organization in response to visual stimuli, laying foundational insights into sensory processing. These models continue to inform investigations into neural circuits, such as dendritic calcium signaling in motor cortex.^[82] Cynomolgus macaques, meanwhile, are prominent in vaccine development, including trials for HIV and COVID-19, where they replicate human-like immune responses to assess efficacy and safety; for instance, they have been used to evaluate SARS-CoV-2 vaccine candidates, showing comparable infection models to rhesus macaques.^[83]^[84] In genetics, macaques have marked significant milestones, including the first successful cloning of a primate via somatic cell nuclear transfer (SCNT) in 2018, when Chinese researchers produced two long-tailed macaque (Macaca fascicularis) clones named Zhong Zhong and Hua Hua, overcoming barriers to reprogramming that had previously limited primate cloning.^[85] This achievement built on earlier efforts and has advanced understanding of embryonic development and potential therapeutic cloning techniques, though it raised questions about efficiency and viability. Ethical considerations in macaque research emphasize the 3Rs principles—replacement, reduction, and refinement—introduced by Russell and Burch in 1959 to minimize animal use and suffering, which are now integral to protocols for non-human primate studies.^[86] Globally, approximately 100,000 macaques are used annually in laboratories, primarily for biomedical purposes, though alternatives like human-derived organoids are emerging to model brain development and reduce reliance on live animals.^[87]^[88] In the United States, the Animal Welfare Act (AWA) of 1966, amended in 1985, mandates standards for housing, veterinary care, and psychological well-being of non-human primates, including macaques, enforced by the USDA to ensure humane treatment.^[89] In the European Union, Directive 2010/63/EU similarly requires authorization for primate procedures, promotes the 3Rs, and sets minimum enclosure sizes for species like macaques to support social housing.^[90] Research involving macaques carries risks of zoonotic transmission, such as simian foamy virus (SFV), a retrovirus endemic to non-human primates that has infected up to 4% of occupationally exposed humans, including lab workers, through bites or mucosal contact, though it typically causes asymptomatic persistent infections without evident disease in humans.^[91]^[92] Regulations under the AWA and EU Directive 2010/63/EU include biosafety measures, such as personal protective equipment and medical surveillance, to mitigate these hazards.^[93]^[94]

Cultural and economic significance

Macaques hold profound religious significance in Hinduism, where species like the rhesus macaque (Macaca mulatta) are revered as embodiments of Hanuman, the monkey god from the epic Ramayana known for his strength, devotion, and loyalty to Lord Rama. Devotees across India maintain large populations of these monkeys at Hanuman temples, providing daily feedings of fruits, grains, and sweets as acts of worship, which sustains troops numbering in the hundreds at sites like the Galtaji Temple in Rajasthan or the Jagannath Temple in Puri, where over 130 rhesus macaques reside.^[95] This reverence fosters a cultural taboo against harming them, even as rhesus macaques cause substantial crop damage in agricultural areas, leading to conflicts where farmers report losses but hesitate to use lethal controls due to religious beliefs.^[96] In East Asian folklore, macaques inspire iconic figures such as Sun Wukong, the Monkey King from the 16th-century Chinese novel Journey to the West, depicted as a powerful, mischievous macaque-like deity with shape-shifting abilities and a staff weapon, symbolizing rebellion, immortality, and Buddhist enlightenment.^[97] This character, born from a stone egg in a macaque troop, has permeated literature, theater, and modern media, influencing global pop culture through adaptations like anime (e.g., Dragon Ball's Goku) and films that portray intelligent, anthropomorphic primates. While not direct models, macaques' social intelligence and adaptability have informed primate representations in Western cinema, such as the hierarchical ape societies in the Planet of the Apes franchise, which draws on real macaque behaviors observed in studies for dramatic tension.^[97] Economically, macaques drive tourism in several regions, boosting local economies through ecotourism. In Gibraltar, the only wild population of Barbary macaques (Macaca sylvanus) in Europe attracts approximately 700,000 visitors annually to the Upper Rock Nature Reserve, where guided tours and feeding sessions generate revenue for conservation and hospitality sectors, with the macaques serving as a flagship attraction since the 18th century.^[98]^[99] Similarly, in Bali, Indonesia, the Sacred Monkey Forest Sanctuary in Ubud, home to around 700 long-tailed macaques (Macaca fascicularis), draws approximately 120,000 visitors per year, with entry fees and surrounding businesses contributing significantly to the local economy, estimated at hundreds of thousands of dollars annually from direct tourism alone.^[100] However, the illegal pet trade undermines these benefits, as poaching for exotic pets persists despite international bans under CITES; for instance, 200–300 Barbary macaques are trafficked yearly from North Africa, fueling a black market worth millions globally and exacerbating population declines.^[101] Historically, macaques were traded across the Mediterranean for entertainment in ancient Rome, where Barbary macaques were imported as exotic pets and performers in circuses and private villas, often dressed in clothing or trained for tricks to amuse elites, as evidenced by mosaics and tomb inscriptions from sites like Ostia Antica.^[102] This trade, documented from the 1st century BCE, highlighted their status as symbols of luxury and exoticism, with some receiving elaborate burials alongside human owners, reflecting their integration into Roman society before stricter import controls emerged.^[103]

Conservation

Threats and status

Macaque species face significant conservation threats, primarily from habitat loss driven by deforestation across their native ranges in Asia and North Africa. In Southeast Asia, where most species occur, forest cover has declined at an average rate of 0.6% per year between 1990 and 2010, resulting in a net loss of 1.6 million hectares annually and severely fragmenting macaque habitats essential for their survival.^[104] This loss is largely attributed to agricultural expansion, logging, and infrastructure development, affecting over 76% of threatened primate species including macaques.^[105] Hunting for bushmeat, traditional medicine, and the pet trade further exacerbates population declines. In regions like Vietnam, intensive hunting targets macaques for consumption and medicinal uses, contributing to local extirpations and overall range reductions.^[106] The international pet trade, often involving poaching of infants after mothers are killed, has decimated populations of species such as the long-tailed macaque (Macaca fascicularis), with thousands seized annually in illegal shipments. In October 2025, the IUCN reaffirmed the long-tailed macaque's Endangered status following a review, citing an inferred 50–70% population decline over the past three generations due to habitat loss and exploitation.^[107] According to the IUCN Red List, of the 24 macaque species, two are classified as Critically Endangered (e.g., the Celebes crested macaque, Macaca nigra, and the lion-tailed macaque, Macaca silenus), nine as Endangered, eight as Vulnerable, and five as Near Threatened or Least Concern, with the majority showing declining population trends.^[108] Global wild macaque populations are estimated in the millions but remain fragmented, with many species persisting in small, isolated groups vulnerable to stochastic events. For instance, the lion-tailed macaque (Macaca silenus) numbers fewer than 4,000 individuals, confined to remnant forest patches in India's Western Ghats.^[109] In contrast, adaptable species like the long-tailed macaque maintain larger populations in urban and agricultural edges, though even these are declining by up to 50% in some areas over recent generations.^[110] Emerging threats include climate change, which is projected to alter macaque ranges by shifting suitable habitats and exacerbating resource scarcity, potentially leading to further contractions for highland species like the Tibetan macaque (Macaca thibetana).^[111] Disease outbreaks pose additional risks, with zoonotic pathogens such as Nipah virus capable of spilling over between macaques, bats, and humans in overlapping habitats, as demonstrated in experimental infections of cynomolgus macaques (Macaca fascicularis).^[112] While native populations decline, introduced macaque groups in non-native regions, such as parts of Asia and beyond, are expanding as notable exceptions.^[113]

Protection and management

Macaque species receive varying levels of international protection under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), with most listed in Appendix II, requiring export permits to regulate trade and prevent overexploitation.^[114] The lion-tailed macaque (Macaca silenus) is afforded stricter safeguards in Appendix I, prohibiting commercial international trade to protect its endangered status.^[115] Similarly, the Barbary macaque (Macaca sylvanus) was uplisted to Appendix I in 2016, implementing a global ban on commercial trade to curb poaching and trafficking from North African habitats.^[116] Nationally, protections include India's Wildlife (Protection) Act of 1972, which schedules lion-tailed macaques as a Schedule I species with the highest level of prohibition against hunting and trade, supported by reserves such as Bandipur National Park in the Western Ghats.^[115] In Gibraltar, the only European wild macaque population—Barbary macaques—is managed under local laws like the Animals Protection and Control Ordinance, which bans feeding to maintain natural behaviors and habitat use, though post-Brexit enforcement aligns with UK rather than EU directives.^[117] Conservation initiatives emphasize habitat restoration and conflict mitigation. Reintroduction efforts for the Barbary macaque in Morocco's Atlas Mountains, guided by population viability analyses, aim to bolster fragmented groups through captive-bred releases and habitat enhancement, with projects like the Barbary Macaque Awareness and Conservation initiative monitoring over 100 individuals since the early 2000s to assess long-term viability.^[118] In Indonesia, community-based management programs in areas like North Sulawesi's Tangkoko Nature Reserve engage local farmers in non-lethal deterrents, such as barrier fencing and alternative crop planting, reducing long-tailed macaque (Macaca fascicularis) crop raids by up to 40% while preserving forest connectivity.^[119] Successes highlight adaptive strategies. Japan's hunting ban on Japanese macaques (Macaca fuscata) since 1947 under national wildlife laws has stabilized populations in protected areas like Jigokudani, allowing recovery from historical declines through enforced no-hunt zones and supplemental feeding controls.^[59] Genetic monitoring via non-invasive fecal sampling has proven effective for species like the Formosan rock macaque (Macaca cyclopis) in Taiwan, enabling accurate population estimates and kinship analysis without disturbing wild groups, informing targeted habitat corridors.^[120] Ongoing challenges include transboundary illegal trade, such as the smuggling of long-tailed macaques from Cambodia into China for biomedical research, complicating enforcement across borders despite CITES quotas.^[121] Balancing ecotourism with habitat integrity remains critical, as provisioning at sites like China's Huangshan Mountain has habituated Tibetan macaques (Macaca thibetana), increasing aggression and disease transmission risks while fragmenting core foraging areas.^[122]

Species diversity

Living species

The genus Macaca includes 24 extant species of Old World monkeys, primarily native to Asia with one species extending to North Africa and Europe.^[123] These species are classified into seven phylogenetic groups based on molecular and morphological evidence: the M. sylvanus group (1 species), M. nemestrina group (often called silenus; 11 species), M. fascicularis group (1 species), M. arctoides group (1 species), M. mulatta group (3 species), and M. sinica group (7 species).^[124] The silenus group features species adapted to forested habitats in Southeast Asia and India, such as the lion-tailed macaque (M. silenus), which has distinctive black fur, a silver-white mane, and is endemic to the Western Ghats of southern India, where it faces habitat fragmentation and is classified as Endangered. Other silenus group members include the northern pig-tailed macaque (M. leonina), ranging across mainland Southeast Asia from India to Vietnam in tropical forests up to 1,800 m elevation, rated Vulnerable due to hunting and logging; and the southern pig-tailed macaque (M. nemestrina), found in similar habitats from Myanmar to Indonesia, also Vulnerable from agricultural expansion. The sinica group encompasses seven species largely confined to the Indian subcontinent and Himalayan regions, exhibiting adaptations to diverse elevations from lowlands to high-altitude forests. For instance, the Tibetan macaque (M. thibetana), the largest macaque, inhabits temperate forests in China, Bhutan, and Myanmar up to 4,500 m, and is listed as Near Threatened from poaching and habitat loss. The Assamese macaque (M. assamensis) occupies evergreen forests in Northeast India, southern China, and Southeast Asia, rated Endangered due to the pet trade and deforestation. Recent taxonomic revisions have added species like the Arunachal macaque (M. munzala), described in 2005 and restricted to high-altitude areas in Arunachal Pradesh, India, classified as Data Deficient but threatened by development; the white-cheeked macaque (M. leucogenys), identified in 2015 from southeastern Tibet and China, Vulnerable from illegal trade; and the Sela macaque (M. selai), elevated to full species status in 2022 based on genetic divergence, found in Arunachal Pradesh's mountainous forests and potentially at risk from isolation.^[125] Prominent species from other groups include the rhesus macaque (M. mulatta) of the mulatta group, widespread across South and Central Asia from Afghanistan to southern China in varied habitats including urban areas, with body length 47–65 cm and tail 20–30 cm; it is rated Least Concern due to its adaptability but faces local culling as a crop pest. The long-tailed macaque (M. fascicularis) of the fascicularis group inhabits Southeast Asia from the Nicobar Islands to the Philippines, including mangroves and coastal forests where it swims proficiently, but was uplisted to Endangered in 2022 owing to overexploitation for biomedical research and habitat conversion, with a suspected 50% population decline over three generations. As of October 2025, the IUCN reconfirmed this Endangered status following challenges from the biomedical industry.^[107] The stump-tailed macaque (M. arctoides) of the arctoides group ranges through southern China, Northeast India, and Southeast Asia in subtropical forests; it exhibits a short tail (5–10 cm) and brownish fur, is Vulnerable from hunting, and shows evidence of ancient hybridization with sinica and mulatta group species in contact zones, leading to genetic admixture.^[126] Sulawesi group species, part of the silenus clade, are endemic to the Indonesian island of Sulawesi and nearby islands, numbering eight taxa including the crested black macaque (M. nigra), with dark fur and a prominent crest, critically endangered from logging and hunting in northern Sulawesi's rainforests; and the Moor macaque (M. maura), south Sulawesi's largest primate, Vulnerable due to agricultural encroachment. The Barbary macaque (M. sylvanus), the sole sylvanus group member and only wild macaque outside Asia, lives in cedar forests of Morocco, Algeria, and Gibraltar at elevations up to 2,600 m, rated Endangered from habitat degradation and tourism pressures. Subspecies variation is notable, such as in the long-tailed macaque, where the Nicobar subspecies (M. f. umbrosa) is restricted to three Indian islands and classified as Vulnerable due to small population size and development threats like the Great Nicobar project. Hybridization occurs in overlap zones, as seen with stump-tailed macaques interbreeding with Assamese macaques, potentially complicating conservation genetics.^[127] Overall, most macaque species face extinction risks from habitat loss, hunting, and human-wildlife conflict, with 19 of 24 listed as Vulnerable or higher on the IUCN Red List.^[128]

Fossil species

The fossil record of macaques (genus Macaca) provides key insights into their evolutionary history, with the earliest known species indicating an African origin prior to dispersal into Eurasia. The oldest described macaque fossil is Macaca libyca, from the Late Miocene site of Wadi Natrun in Egypt, dated to approximately 6.2–5.0 million years ago (mya). This species co-occurred with the colobine Libypithecus markgrafi, suggesting early diversification of Old World monkeys in North Africa before the genus's radiation into Asia during the late Miocene. Several extinct macaque species highlight regional adaptations and dispersals. In Europe, Macaca majori from the Pliocene of Sardinia, Italy, represents an insular endemic form characterized by dwarfism, with dental and cranial features indicating a body size smaller than most continental macaques.^[129] This size reduction likely resulted from island dwarfing in response to limited resources on the isolated Mediterranean landmass.^[129] In Asia, Macaca anderssoni from the Early Pleistocene of Henan Province, northern China (approximately 2–1 mya), exhibits facial morphology adapted to colder climates, including a lower nasal profile that may have facilitated thermoregulation in glacial environments.^[130] Important fossil sites include the Siwalik Hills of northern India and Pakistan, where multiple macaque taxa are recorded from 5–2 mya, documenting the eastward migration and diversification of the genus during the late Miocene to early Pliocene. These remains, primarily dental fragments, belong to early Macaca lineages that overlapped with other cercopithecids in forested habitats. In Europe, sites such as the Upper Valdarno Basin in Italy have yielded Macaca florentina from around 1.5 mya, illustrating migratory pathways from Africa via the Mediterranean during the early Pleistocene.^[131] Evolutionary patterns inferred from the fossil record include body size reductions in insular populations, as seen in M. majori, contrasting with larger ancestral forms.^[129] Macaques became extinct in continental Europe around 1 mya, likely due to cooling climates during the early Pleistocene and increased competition from other primates and carnivores.^[132] This extinction event marked the retreat of the genus to refugia in North Africa and Asia, shaping its modern distribution.^[132]

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To date, direct evidence of zoonotic transmission of simian retroviruses from known source animals to humans has not been documented. Instead, proof for such ...
[89]
Protection of NIH Personnel Who Work with Nonhuman Primates
This policy provides requirements for training, supervision, compliance, personal protective equipment, medical surveillance, accident reporting, and wound care
[90]
Non-human primates in research and safety testing
The European Commission regularly publishes the statistical data on the number of animals used for experimental and other scientific purposes in the EU (Report ...
[91]
[PDF] A POPULATION SURVEY OF RHESUS MONKEYS AND HANUMAN ...
the survey of 2004 recorded 5 temple groups from Puri town. The number of monkeys of J agannath temple had increased to 134 in number. The J agannath temple.
[92]
Can India Solve Its Macaque Conundrum With Contraception?
Sep 7, 2021 · For the tens of thousands of wild rhesus monkeys that roam Indian cities, it makes little sense even to try.<|control11|><|separator|>
[93]
The real history behind the legend of Sun Wukong, China's Monkey ...
Aug 29, 2024 · He likely appears as a macaque, a kind of monkey that lives throughout Asia. He soon earns the title “Monkey King” through a daring act of ...
[94]
Monkey business: if macaques want your food, they're not going to ...
In Gibraltar, at least, the macaque population seems to be stable. This is why we must try to preserve the wild nature of the Rock's Barbary macaques, the only ...Missing: invasive impact
[95]
Explore the Sacred Monkey Forest Ubud in Bali, Indonesia
The Ubud Monkey Forest is frequented by over 10,000 tourists each month. The sanctuary is home to more hundreds (and possibly over a thousand) Balinese long- ...Introduction to the Sacred... · Location and How to Get to the...
[96]
Poaching and trafficking of Barbary macaques after the CITES ...
... macaque. In 2010 the illegal trade in Barbary macaques was estimated at 200–300 monkeys annually, with 20 confiscations and 74 requests for shelter (Van Uhm ...
[97]
Animal highlights from Ostia, Gateway to Rome - Monks and Monkeys
Jul 30, 2020 · Monkeys appear not to have been luxury pets, but were relatively common in ancient Rome. Another example from the same book (p. 470) is of a ...
[98]
Ancient Monkey Soldiers? Romans Buried Barbary Ape with Military ...
Oct 15, 2022 · This makes Barbary macaques the only known wild monkey species in Europe. War Elephants: The Military 'Tanks' of the Ancient World · Pet Monkeys ...
[99]
The future of Southeast Asia's forests | Nature Communications
Apr 23, 2019 · Between 1990 and 2010, Southeast Asia registered an average net loss of 1.6 million ha yr−1 (0.6% yr−1), reducing the region's forest cover from ...
[100]
Impending extinction crisis of the world's primates - PubMed Central
FACTORS THAT THREATEN PRIMATE POPULATIONS. The IUCN indicates that the main threats to primate species are loss of habitat due to agriculture (76% of species), ...
[101]
[PDF] Primates of the Greater Mekong: - WWF
The biggest threats to this species in. Viet Nam are habitat loss and hunting for meat. ... all apes and all Asian and African monkeys are at high risk of being ...
[102]
IUCN upholds long-tailed macaques' endangered status after ...
Oct 15, 2025 · The IUCN escalated the conservation status of the species, Macaca fascicularis, from vulnerable to endangered in 2022 after macaques poached ...
[103]
Mad about macaques - Born Free Foundation
May 2, 2024 · The global populations of the majority of macaque species (21 of 24) are decreasing. International Macaque Week is an opportunity to promote ...
[104]
Recent studies on Indian primates show declining population trends ...
Studies show 71% of Indian primate species have declining populations, with all but one study in protected areas showing declining trends.Missing: percentages | Show results with:percentages
[105]
[PDF] A Review on Conservation and Population Status of Lion Tailed ...
The current population status of the lion tailed macaque is estimated to be less than 4,000 individuals. However, population assessments and monitoring are ...
[106]
New Studies Show Staggering Drop in Macaque Populations - PETA
Jun 3, 2024 · In Cambodia, there has been a 97.5% decline in long-tailed macaque populations, with only an estimated 75,000 remaining. Less than 15 years ago, ...
[107]
Landscape genomics analysis provides insights into future climate ...
Nov 15, 2023 · This study explored how rhesus macaques adapt to climate change by integrating ecological and genetic methods and applying species distribution models (SDMs)
[108]
Resistance of Cynomolgus Monkeys to Nipah and Hendra Virus ...
Dec 5, 2019 · This surprising inability of all 3 henipaviruses to cause severe clinical disease in macaques similar to that seen in AGMs, with the exception ...<|control11|><|separator|>
[109]
Threatened Mammals With Alien Populations - Conservation Biology
Dec 4, 2024 · For example, four out of six threatened macaque species were introduced within Asia as pets. In certain countries (e.g., Indonesia) ...
[110]
[PDF] AC32 Inf. 10 - CITES
Jun 19, 2023 · Long-tailed macaque species is listed on CITES Appendix II, making it subject to permits/quotas for its trade and distribution. Indonesia.
[111]
Lion-Tailed Macaque, Macaca silenus
Lion-tailed macaques signal their affiliation with another monkey by silently baring their teeth. In many other macaque species, this same display is known as ...<|separator|>
[112]
Total trade ban for Gibraltar's monkeys agreed - BBC News
Sep 28, 2016 · Total trade ban for Gibraltar's monkeys agreed ... Europe's only non-human primate, the Barbary Macaque, has gained the highest level of species ...Missing: invasive | Show results with:invasive
[113]
Ape Management - HM Government of Gibraltar
It is illegal to feed the macaques and the penalty for such offence is £500.00. It is therefore strongly emphasised that the public do not feed the apes.The ...
[114]
https://cites.org/sites/default/files/documents/E-AC32-Inf-10.pdf
[115]
20 Years of Community Outreach Education at the Tangkoko Nature ...
... crop-raiding. We also addressed the unsustainable practice of hunting the monkeys as food/delicacy for special events, a long-standing cultural practice in ...
[116]
[PDF] Applicability of Non-Invasive Sampling in Population Genetic Study ...
Chu et al.: Non-invasive genetic sampling of Taiwanese macaques. 259 genetic studies of Taiwanese macaques (Macaca cyclopis). Fecal samples were collected as ...
[117]
[PDF] Illegal trade in Long-tailed Macaque (Macaca fascicularis) in ...
Cambodia is a global center of illegal wildlife trade, servicing as a transit point of illegal animal products, particularly ivory between Viet Nam and China 17 ...<|separator|>
[118]
Ecotourism Disturbance on an Endemic Endangered Primate in the ...
Jul 11, 2022 · Habitat suitability increased at low altitudes and allowed macaques to move farther away from areas of human disturbance, avoiding eco-tourism ...Missing: integrity | Show results with:integrity
[119]
https://wanprc.uw.edu/20-years-of-community-outreach-education-in-tangkoko-indonesia/
[120]
Genome-wide analysis reveals signatures of complex introgressive ...
At present, the genus Macaca is comprised of 23 extant species. Macaques are the most widely distributed non-human primates and occupy a wide range of habitats ...
[121]
The Sela macaque (Macaca selai) is a distinct phylogenetic species ...
We describe - Sela macaque (M. selai) as a new macaque species that interestingly exhibited high intra-specific genetic variation and also harbors at least two ...
[122]
Comparative genomics reveals the hybrid origin of a macaque group
Jun 1, 2023 · For example, our analyses confirm that the stump-tailed macaque is a member of the sinica group with a low level of introgression from mulatta/ ...
[123]
Anthropogenic Macaque Hybridization and Genetic Pollution of a ...
Aug 10, 2025 · Both suspected hybrids had a dark brown and anteriorly narrow crown patch and thinly haired tails as are common in pig-tailed macaques, and ...
[124]
The IUCN Red List of Threatened Species
No readable text found in the HTML.<|control11|><|separator|>
[125]
Investigating the dietary niches of fossil Plio-Pleistocene European ...
To further our understanding of fossil European macaque ecology, we investigated the dietary ecology of Macaca majori, an insular endemic species from Sardinia.
[126]
Phylogenetic relationship of a fossil macaque (Macaca cf. robusta ...
The first record of a fossil macaque from East Asia was Macaca anderssoni, which was described from a nearly complete face excavated from the Early Pleistocene ...
[127]
the biogeography and extinction of Macaca sylvanus in Europe - ADS
In this contribution, we provide an overview of the evolutionary history of Macaca in Europe, putting it into context with the wider late Miocene, Pliocene and ...Missing: reduction 1 mya competition
[128]
the biogeography and extinction of Macaca sylvanus in Europe
The genus Macaca originated in the late Miocene, probably in North Africa, diverging from other papionins around 7.6 ± 1.3 Ma (Tosi et al., 2005), with the ...