Rhesus macaque

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Subspecies:M. m. brevicauda,M. m. lasiota,M. m. mulatta,M. m. sanctijohannis,M. m. vestita,M. m. villosa

Other names:rhesus monkey; macaque rhsus (French); mono resus (Spanish); rehesusapa or rhesusmakak (Swedish);M. m. lasiota: west Chinese rhesus macaque;M. m. sanctijohannis: insular Chinese rhesus macaque or south Chinese rhesus macaque;M. m. vestita: Tibetan rhesus macaque

Regions:China, India, Bhutan, Laos, Burma, Nepal, Bangladesh, Thailand, Vietnam, Pakistan, Afghanistan

Weight:7.7 kg (M), 5.34 kg (F)SwitchMetric English

Divided according to country of origin, rhesus macaques are referred to as Chinese-and Indian- derived. Chinese-derived rhesus macaques include subspeciesM. m. vestita,M. m. lasiota,M. m. sanctijohannis, andM. m. brevicauda. Indian-derived rhesus macaques are found in other countries besides India, but are still informally referred to as Indian-derived and includeM. m. mulattaandM. m. villosa(Smith & McDonough 2005). In breeding colonies at research centers in the United States, rhesus macaques have sometimes been bred separately according to their country of derivation but in other cases, crossbreeding has occurred, leading to some confusion about thetaxonomicseparation of individuals used in research (Smith & McDonough 2005).

Rhesus macaques, both Chinese- and Indian-derived, range in color from dusty brown to auburn with little to no fur found on their reddish-pink faces. Their rumps are the same color as their faces and they have medium-length tails that average between 207.6 and 228.9 mm (8.17 and 9.01 in) (Fooden 2000). Males and females aresexually dimorphic, like other species of macaques, and males measure, on average, 531.8 mm (1.74 ft) and weigh, on average, 7.70 kg (17.0 lb) while females have an average height of 468.8 mm (1.54 ft) and an average weight of 5.34 kg (11.8 lb) (Fooden 2000; Singh & Sinha 2004). They arequadrupedaland, depending on the type of habitat in which they are found, can be predominantlyarborealor predominantlyterrestrial(Seth et al. 2001). Rhesus macaques are also skilled swimmers and have been observed crossing bodies of water up to one kilometer (.621 mi) wide. When they are seen in the water they are usually searching for food, escaping from danger, regulating their body temperature, or playing. Swimming is a skill seen in infants as young as two days old (Fooden 2000).

The only primates with a broader geographic distribution than rhesus macaques are humans (Southwick et al. 1996). Rhesus macaques are found ubiquitously throughout mainland Asia; from Afghanistan to India and Thailand to southern China (Rowe 1996; Smith & McDonough 2005).M. m. vestita,M. m. lasiota, andM. m. sanctijohannisare found in western, central, and eastern China, respectively (Groves 2001; Smith & McDonough 2005). Another Chinese species of rhesus macaque,M. m. brevicauda, is found on Hainan Island, off the southwest coast of China. The Indian-derived rhesus macaques are separated by region withM. m. villosafound in the Kashmir and Punjab region of India (the northern part of the country), Pakistan, and Afghanistan andM. m. mulattafound in India, Bhutan, Burma, Nepal, Bangladesh, Thailand, Laos, and Vietnam (Groves 2001; Smith & McDonough 2005). It is likely that there will be additional subspecies added andM. m. mulattawill be reclassified into several more distinct subspecies based on genetic and morphological differences (Groves 2001).

A free-ranging colony of rhesus macaques was established in 1938 on an island in the Caribbean. Introduced to Cayo Santiago, Puerto Rico, rhesus macaques have been studied under semi-natural conditions for almost 70 years and have provided an unprecedented resource for information about behavior, population demography, and long-term histories of individuals social and physical development (Rawlins & Kessler 1986a). Furthermore, with the establishment of this colony of free-ranging macaques came the birth of a new field of study, sociobiology, pioneered by Stuart Altmann who observed rhesus monkeys on Cayo Santiago and worked with notable sociobiologist E.O. Wilson (Bercovitch pers. comm.).

Rhesus macaques are the most studied nonhuman primate, both in the field and in laboratory settings, though most of the field research comes from rhesus macaques in India (Richard et al. 1989). One of the notable early field researchers of rhesus monkeys is Charles Southwick, who began surveying them in 1959 (Seth 2000). Donald Lindburg has been another force in rhesus macaque studies, assessing the abundance of rhesus in India as well as reporting declines in the population which was important at the time of their export (Seth 2000; Smith & McDonough 2005).

Because they are found in such a broad geographic area, it is difficult to concisely summarize the types of habitats rhesus macaques populate. In the most general terms, they are found in both tropical and temperate habitats including semidesert, drydeciduous, mixed deciduous and bamboo, and temperate forests as well as in tropical forests andmangroveswamps, usually at elevations from sea level to 2000 m (6561 ft), but they have been seen at elevations up to 4000 m (13,123 ft) in China and northeastern India (Seth & Seth 1986; Fooden 2000; Srivastava & Mohnot 2001). Rhesus macaques are also found in areas close to humans in urban settings or near cultivated fields (Southwick et al. 1996).

In the northernmost part of their range, the rhesus of the Taihang Mountains in China live in asecondarydeciduous forest at elevations between 300 and 1200 m (984 and 3937 ft) with a temperate climate and cold, snowy winters similar to the climate of the central, Midwestern United States (Qu et al. 1993). In this region, there are hot, rainy, and humid summers with severely cold and dry winters, and temperatures ranging between -20 C (-4 F) and 40 C (104 F) during the year. Annual rainfall averages 641 mm (2.10 ft), with the rainiest period lasting from June to August (Qu et al. 1993). This is similar to the climate of the region of Pakistan where they are found, but the habitat in Pakistan is dominated by mixed evergreen and deciduous forests that are highly disturbed (Goldstein & Richard 1989). In their tropical range in China, and similarly in Burma, Laos and Thailand, the rainy season lasts from May to October with annual rainfall averaging 1575 mm (5.17 ft). Temperature is more stable in India and northern China throughout the year, ranging between 22 C (72 F) and 28 C (82 F). The habitat includes primary and secondary tropical and dry evergreen forests and bamboo forests (Jiang et al. 1991; Southwick et al. 1996; Borries et al. 2002).

In India, rhesus macaques are found in flat, cultivated areas, where agricultural fields dominate the landscape and in the plains, foothills and mountainous regions where habitat includes cultivated fields, tropical forests and dry, deciduous forests. Average annual rainfall ranges between 420 and 2150 mm (1.38 and 7.05 ft), depending on elevation, and annual range in temperature is between -4 C (25 F) and 48 C (118 F) (Seth & Seth 1986). During the hottest parts of the year, groups in the Himalayan region of India migrate to higher elevations where cooler temperatures persist throughout the summer months (Seth et al. 2001). In urban areas of India, they are found on roadsides, canal banks, in railway stations, villages, towns, and temples (Richard et al. 1989). It is estimated that 48.5% of rhesus macaques in northern India live in villages, towns, cities, temples and railway stations where they are in close and frequent contact with people at all times. About 37.1% of the population lives with some human contact on roadsides and canal banks and only 14.4% of the rhesus macaques in the northern part of the country live in isolation from humans and do not rely on them at all for food (Southwick & Siddiqi 1994).

Rhesus macaques are exceptionally adapted to coexisting with humans and thrive near human settlement, in both urban and agricultural areas. It is impossible to characterize their natural diet without considering the impact of humans. Because they are found in higher densities in areas of human disturbance compared to forests, in some areas rhesus macaques derive, both directly and indirectly, a substantial part of their diet from human activities (Richard et al. 1989). In fact, up to 93% of their diet can be from human sources, either from direct handouts or from agricultural sources (Southwick & Siddiqi 1994). Rhesus macaques areomnivoresand feed on a wide array of plant and invertebrate products. Byraiding crops, they have access to a huge variety of cultivated fruits and vegetables, and in highly urban areas, theyforageby picking through garbage (Goldstein & Richard 1989; Richard et al. 1989). Throughout their range and especially in India, they inhabit temples and are fed as a form of worship by local people (Wolfe 2002). Some of the most common foods given to rhesus macaques in temples include bread, bananas, peanuts, seeds, other fruits and vegetables, and assorted miscellaneous foods like ice cream and fried bread (Wolfe 1992). In less human-influenced areas, they focus on fruits, flowers, leaves, seeds, gums, buds, grass, clover, roots, bark, and they supplement their diet with termites, grasshoppers, ants, beetles, and mushrooms. Rhesus macaques also eat bird eggs, shellfish, and fish (Fooden 2000). During the driest parts of the year, they may even eat the dirt from termite mounds (Lindburg 1971). On Cayo Santiago, the rhesus macaques also consume dirt possibly because the mineral composition of the soil on the island is similar to pharmaceuticals used in humans to treat upset stomach. The Cayo rhesus may be eating dirt to relieve the discomfort associated with intestinalparasites(Knezevich 1998). At higher elevations, where seasonal snowfall restricts food sources, rhesus macaques are restricted to eating the leaves of evergreen trees and bark as well as a few berries that grow in winter. During the winter months at high elevations, rhesus macaques suffer from food and climate stress and have higher levels of mortality if the cold weather lasts too long (Qu et al. 1993).

Home range size and day range length are dependent on habitat in rhesus macaques. Temple, village, and urban rhesus macaques have small home ranges between .01 and 3.0 km² (.004 and 1.16 mi²) in size because they derive almost all of their food from human visitors leaving offerings, crop raiding, oropportunisticforaging on human byproducts (Seth & Seth 1986). The day ranges for these urbanized areas are variable but the average is about 1.15 km (.715 mi) (Fooden 2000). In more forested areas of India, home range size can be up to 15 km² (5.79 mi²), but rhesus monkeys only move, on average, 1428 m (.887 mi) per day (Lindburg 1971). In China, home ranges vary in size from .1 to .72 km² (.039 to .278 mi²) near villages, while in mountainous areas, home ranges are much larger and span between 11 and 22 km² (4.25 and 8.49 mi²) but average 16 km² (6.18 mi²) (Southwick et al. 1996). Daily path lengths in this environment range from 1050 to 3500 m (.652 to 2.17 mi) (Makwana 1978).

Both climate and season affect the timing of the onset of daily activities as well as the type of activities undertaken. In the warmest times of the year, rhesus macaques spend more time resting than during more temperate months (Seth & Seth 1986; Seth 2000). Home ranges of rhesus macaques overlap and groups have high frequencies of intergroup contact, which is characterized by generally mild social interactions (Melnick et al. 1984). Across all habitat types, feeding and resting are the major activities of the rhesus macaques day and they spend the rest of their time traveling, grooming, playing, and other activities (Seth & Seth 1986).

Potential predators of rhesus macaques includeraptors, dogs, weasels, leopards, tigers, sharks, crocodiles, and snakes (Fooden 2000).

Because of their anatomical andphysiologicalcloseness to humans, the relative ease at which they can be maintained and bred in captivity, and the available supply from India, rhesus macaques have long been the nonhuman primate of choice on which to conduct research on human and animal health-related topics (Mitruka 1976). Some of the direct benefits to human health that would not have been possible without the use of rhesus macaques include: development of the rabies, smallpox, and polio vaccines, discovery of rhesus factor in blood, creation of drugs to manage HIV/AIDS, understanding of the female reproductive cycle and development of the embryo, propagation of embryonic stem cells, and a number of behavioral discoveries (Mitruka 1976; Anonymous 2005).

Content last modified: July 20, 2005

Written byKristina Cawthon Lang. Reviewed byFred Bercovitch.

Cawthon Lang KA. 2005 July 20. Primate Factsheets: Rhesus macaque (Macaca mulatta) Taxonomy, Morphology, & Ecology . . Accessed 2020 July 13.

Rhesus macaques live in large,multi-male/multi-femalegroups that have an average of 10 to 80 individuals, regardless of habitat type. Groups may number in the hundreds in mountainous areas and areas of high human food subsidization or agricultural habitats (Lindburg 1971; Seth & Seth 1986; Qu et al. 1993; Southwick et al. 1996). Rhesus groups are characterized byfemale philopatryand male dispersal; females remain in theirnatal groupsand formdominance hierarchiesaccording to theirwhile males emigrate from their natal groups at the beginning of the breeding season shortly before puberty, and may transfer groups throughout their lives in search of mating opportunities (Melnick et al. 1984). Female rhesus macaques very rarely leave their natal groups (Fooden 2000).

Among females, rank remains relatively stable over a lifetime and is passed on to female offspring. Each female rises in rank above her older sister, and therefore when old, high-ranking females disappear or die, they are usually replaced by their youngest daughters (Seth 2000). One of the benefits of dominance for a rhesus macaque is priority access to food and space. High-ranking females have greater access to feeding sites because they displace lower-ranking females and they are less likely to be disturbed during feeding compared to subordinates (Deutsch & Lee 1991). Because they have cheek pouches, though, low-ranking females do not consume less food than high-ranking females, they simply store as much as they can into their cheek pouches and then move away from the group to eat (Deutsch & Lee 1991). This method of feeding is more energetically expensive than remaining in the same area while feeding, so low-ranking females may be consuming the same amount but using more energy to consume it (Deutsch & Lee 1991).

Dominance status and rank among males is not stable over a lifetime, compared to female rhesus macaques. Immature males inherit the rank of their mothers, but as they mature, their status changes based upon a combination of social and aggressive skills (Lindburg 1971; Berard 1999; Bercovitch pers. comm.). Aggression is sometimes used to establish and reinforce social position, though, and aggressive behavior seen in macaques includes slapping, pushing, pulling fur, tail yanking, and biting as well as other non-contact behaviors such as displays and threats (Lindburg 1971). Once males attain dominant status, they enjoy this rank for an average of two years before being displaced by another male (Bercovitch 1997).

Females reach puberty around age three while males are sexually mature by age four (Rawlins & Kessler 1986b). Theovarian cyclelasts for 28 days and is characterized by the darkening of the skin surrounding theanogenitalregion accompanied by menstruation (Catchpole & van Wagenen 1975).Estruslasts for eight to 12 days, with the day ofovulationoccurring at the midpoint of the estrus period. Females have increased sexual activity during ovulation, exhibiting the highest number of copulations seen during the ovarian cycle (Fooden 2000). Females reproduce from three until about 20 years of age (Rawlins & Kessler 1986b). Males reach puberty between three and 3.5 years of age but do not reach adult body size until about eight years old (Dixson & Nevison 1997; Bercovitch et al. 2003). Though males are capable of reproducing by age four, they are not reproductively successful until after age eight, or when they reach adult size. During this time between becoming sexually mature and when they begin to mate, young rhesus macaques are learning the social skills, including fighting ability, that will influence their success throughout their lives (Bercovitch et al. 2003). Both males and females reach sexual maturity sooner in captivity (Catchpole & van Wagenen 1975).

There is marked birth seasonality in rhesus macaques, with the majority of mating occurring in October through December and births coinciding with the end of the rainy season, or during the period of highest food abundance (Lindburg 1971; Qu et al. 1993). At Cayo Santiago, the mating season is much longer and begins in July and lasts until December (Chapais 1986). High-ranking males have more opportunities to mate with females than low-ranking males, but do not always sire a disproportionate number of infants. Lower-ranking males may have similar reproductive success compared to high-ranking males because they are new immigrants and are more attractive to females because of this (Berard 1999). From one breeding season to the next, females will drastically reduce the amount of mating they do with familiar males and over a period of three years, they try not to mate with any familiar males given the opportunity to mate with unfamiliar males (Bercovitch 1997; Berard 1999).

During the breeding season, females enter into consortships with one or more males. An individual female will spend longer amounts of time in contact with, grooming, and mating with these males. Males and female rhesus macaques are promiscuous breeders, mating multiple times with multiple mates (Lindburg 1971). Both males and females initiate these consort relationships and competition for access to mates is related to the high levels of aggression seen in rhesus macaque groups during this time of year.Gestationlasts 164 days in rhesus macaques and theinterbirth intervalis between 12 and 24 months (Fooden 2000). If a female does not have a successful pregnancy or her infant dies in the first year of life, she is more likely to give birth the following season than a female who successfully rears an infant (Seth 2000).

While the majority of parental care is the responsibility of the mother, rhesus infants are also handled by close female relatives and protected by adult males. In the first few days, the infant is carriedventrallyand protected from other group members by the mother. Ventral clinging is the position most frequently adopted during travel for the first four months of life, but rhesus infants begin to ridedorsallyfor short periods during the second week (Lindburg 1971). By six weeks of age, locomotor skills are developed enough for the infant to move independently, but they do not move very quickly at this age, and if the mother is traveling too quickly, she will pick up the infant and carry it (Lindburg 1971). Some young rhesus are carried until they reach one year of age, though it is rare. During early infancy, rhesus macaques nurse exclusively for the first two weeks of life, after which they begin to experiment with solid food. At about four months of age, rhesus mothers begin to resist the attempts of their offspring to nurse, and young rhesus macaques are fullyweanedby the birth of their next sibling (Fooden 2000).

Exploration off of the mother begins as early as five days old and continues to increase so that by the third week, the infant breaks physical contact with the mother as frequently as possible (Lindburg 1971). During this time, juvenile and adolescent females are intensely interested in the infant and will approach the mother and groom her in an attempt to get near the infant. When an infant is off the mother, a young rhesus female will touch the infant and try to carry it, but the mother is watchful of this interaction and any sign of distress from the infant may elicit an aggressive response from the mother towards the younger female (Lindburg 1971; Berman 1986). This practice of aunting behavior seen in young female rhesus macaques will influence their ability to successfully raise infants (Seth 2000).

Mother rhesus macaques show differential investment in their offspring depending on the sex of the infant. Maestripieri (2001) argued that rhesus mothers invest more energy into rearing daughters than sons as is evidenced by a female-biased birth ratio and longer interbirth intervals following the successful rearing of daughters compared to sons. He hypothesized that because mortality rates are higher among infant males, then in order for a mother rhesus to maximize her reproductive output, she should invest the most amount of energy into the infant that is more likely to survive. Females have higher survival rates than males, possibly due to lower disease or stress levels than males, an adult female should not invest as heavily in a male that is more likely to die (Maestripieri 2001). On the other hand, Bercovitch and Berman (1993) found that on Cayo Santiago, mothers who had sons had a delay in the next reproduction, and therefore there is a higher cost in producing males, not females.

Vocal and gestural communication is important in rhesus macaques. Facial expression, body postures, and gestures are all forms of non-vocal communication among rhesus macaques and are important in interactions between individuals at short distances (Partan 2002). One facial expression that is seen throughout macaque species and is one of the most common expressions in rhesus macaques is the silent bared teeth face (Maestripieri 1999). Among rhesus macaques this is seen between individuals of differing rank with the lower-ranking or submissive animal performing the silent bared teeth face to the dominant animal (Flack et al. 2000). Another common facial expression used in dominance interactions include a fear grimace accompanied by a scream, heard in frightened animals and used to appease or redirect aggression (Rowe 1996). Dominant animals use a silent open mouth stare as a threat to other animals; this is accompanied by the tail sticking straight out behind the body with the monkey standingquadrupedally(Partan 2002). Another common visual communication signal is the present rump, where the tail is raised and the genitals are exposed to the more dominant individual (Maestripieri 1999).

Vocalizations of rhesus macaques include coos and grunts, which are commonly heard expressions during group movement, duringaffiliativeinteractions, and when one animal approaches another to groom (Hauser 1998). Warbles, harmonic arches, and chirps, are heard in the context of finding high-quality, rare food items. The most common alarm call heard among rhesus macaques, the shrill bark, is emitted in threatening situations and is consists of a single, loud, high-pitched sound (Lindburg 1971). Vocalizations made during aggressive interactions include screeches, screams, squeaks, pant-threats, growls, and barks (Lindburg 1971). Infants have their own repertoire of vocalizations which include geckers, which are harsh staccato sounds heard during weaning conflict. It is usually heard along with convulsive jerks of the body, and looks and sounds much like a human childs temper tantrum (Lindburg 1971; Partan 2002).

Content last modified: July 20, 2005

Written byKristina Cawthon Lang. Reviewed byFred Bercovitch.

Cawthon Lang KA. 2005 July 20. Primate Factsheets: Rhesus macaque (Macaca mulatta) Behavior . . Accessed 2020 July 13.

IUCN Red ListM. mulatta: LC (What is Red List?)

(Click on species name to see IUCN Red List entry, including detailed status assessment information.)

The Indian population of rhesus macaques was massively impacted by the widespread export for use in biomedical research in the mid-20 th century. By the time their international export began to be regulated in 1977, the Indian population was reduced by 90% (Malik 1992). Countries that had demanded these monkeys for use in research, including the United States, established self-sustaining breeding colonies and curbed the demand for wild-born animals resulting in a rebound in the Indian population (Southwick & Siddiqi 2001). In China, rhesus macaques are widespread and thriving (Zhang 1998).

Problems of habitat destruction do not seem to affect rhesus macaques like other primates; they are well adapted to life near humans and can thrive in highly disturbed environments. Because of the cessation of export and the rhesus macaques adaptability to human-disturbed environments, the Indian population is increasing (Rao 2003). This increase may not necessarily be positive because in areas where rhesus macaques are in contact with humans they are menaces: threatening or biting children and the elderly, stealing food from people, raiding crops and damaging property leading to decreased tolerance and persecution of rhesus macaques in some areas (Imam et al. 2002; Wolfe 2002; Rao 2003). This is one rare case where the destruction of habitat and replacement with agricultural land has led to an increase in the number of primates, but at a serious social cost. These problems will only be exacerbated if habitat destruction does not stop and will likely force government control measures, like trapping and relocation, to decrease the population for the health and safety of humans in India (Imam et al. 2002; Rao 2003). In Bangladesh, forest dwelling rhesus macaques are threatened because of cattle grazing, illicit timber and fuelwood harvesting, and settlement pressure. The forests in which they are found are not continuous or undisturbed (Sazedul Islam & Zahirul Islam 2001).

The root cause of this conflict between humans and rhesus macaques is the eradication of natural habitat, forcing monkeys into proximity with humans. Though they excel in human-disturbed environments, rhesus macaques living in forested areas are usually healthier, eating a better diet, and in overall better condition than urban macaques (Lindburg 1971). Restoration of their natural habitat in densely populated areas may decrease conflict, but given that they will likely move into areas where humans make food readily available, this may not be a permanent solution. In the long term, management will be necessary to conserve healthy populations of rhesus macaques and prevent persecution by humans from being a threat to their survival (Muroyama & Eudey 2004). Translocation of large numbers of monkeys may be one management option to remove rhesus macaques dependent on human sources of food. In one area of significant human-rhesus macaque conflict, about 600 macaques were captured and successfully relocated to forested areas nearby (Imam et al. 2002).

In countries like Bangladesh, where forest loss is occurring at a rapid rate, some measures that may influence the survival of rhesus macaques in forest settings include replanting deforested areas, involving local people in conservation activities such as tree planting and providing income through these activities, and establishing plantations specifically for fuelwood and timber needs that can be sustainably harvested (Sazedul Islam & Zahirul Islam 2001).

Rhesus macaques were once seriously threatened by the rate of capture and export for use in biomedical research. In the 1960s, often 50,000 juvenile rhesus macaques were trapped and shipped from India per year, crippling the population growth of rhesus in India (Southwick & Siddiqi 2001). In 1978, a total ban on rhesus export was the first step in reestablishing the population, and the numbers in India have more than doubled since the 1970s (Southwick & Siddiqi 2001). There are still some rhesus macaques trapped and used for reasearch within India, but the effect of the population is negligible compared to previous levels of usage (Southwick & Siddiqi 1994). Chinese rhesus macaques are not frequently subject to harvesting for biomedical research within China because of the 23 established primate captive breeding facilities in that country (Fan & Song 2003).

In orthodox Hindu tradition, monkeys are sacred animals to be revered and protected, but as humans and animals begin to compete for similar resources or monkeys become nuisances, causing not only property damage, but also injury to humans, the traditional bond is degraded (Imam et al. 2002; Wolfe 2002). In some areas of India, rhesus macaques are subjected to stoning, trapping, and shooting because they are such pervasive, destructive pests. Over 95% of the local people in one region of India felt harassed by the rhesus macaques either because of bites, stealing of household items, or other reasons (Imam et al. 2002). Though their populations continue to expand, the deterioration of traditional beliefs that leads to their persecution could have an effect on rhesus macaque conservation in the future. If the conservation ethic connected to deifying rhesus macaques is lost, it will be difficult to rekindle in the future if the population stops growing or decreases (Imam et al. 2002).

Mitigating human-rhesus conflict