Rhesus macaque
The rhesus macaque, colloquially rhesus monkey, is a species of Old World monkey in the Macaca genus. There are between six and nine recognised subspecies split between two groups, the Chinese-derived and the Indian-derived. Generally brown or grey in colour, it is in length with a tail and weighs. It is native to South, Central, and Southeast Asia and has the widest geographic range of all non-human primates, occupying a great diversity of altitudes and habitats.
The rhesus macaque is diurnal, arboreal, and terrestrial. It is mostly herbivorous, feeding mainly on fruit, but also eating seeds, roots, buds, bark, and cereals. Rhesus macaques living in cities also eat human food and trash. They are gregarious, with troops comprising 20–200 individuals. The social groups are matrilineal. Individuals communicate with a variety of facial expressions, vocalisations, body postures, and gestures.
As a result of the rhesus macaque's relatively easy upkeep, wide availability, and closeness to humans anatomically and physiologically, it has been used extensively in medical and biological research. It has facilitated many scientific breakthroughs including vaccines for rabies, smallpox, polio, and antiretroviral medication to treat HIV/AIDS. A rhesus macaque became the first primate astronaut in 1948.
The rhesus is listed as Least Concern in the IUCN Red List.
Etymology
The name "rhesus" is reminiscent of the mythological king Rhesus of Thrace, a minor character in the Iliad. However, the French naturalist Jean-Baptiste Audebert who named the species, stated: "it has no meaning". The rhesus macaque is also known colloquially as the "rhesus monkey".Taxonomy
According to Zimmermann's first description of 1780, the rhesus macaque is distributed in eastern Afghanistan, Bangladesh, Bhutan, as far east as the Brahmaputra Valley, Barak valley and in peninsular India, Nepal, and northern Pakistan. Today, this is known as the Indian rhesus macaque Macaca mulatta mulatta, which includes the morphologically similar M. rhesus villosus, described by True in 1894, from Kashmir, and M. m. mcmahoni, described by Pocock in 1932 from Kootai, Pakistan. Several Chinese subspecies of rhesus macaques were described between 1867 and 1917. The molecular differences identified among populations, however, are alone not consistent enough to conclusively define any subspecies.The Chinese subspecies can be divided as follows:
- M. m. mulatta is found in western and central China, in the south of Yunnan, and southwest of Guangxi;
- M. m. lasiota, the west Chinese rhesus macaque, is distributed in the west of Sichuan, northwest of Yunnan, and southeast of Qinghai; it is possibly synonymous with M. m. sanctijohannis, if not with M. m. mulatta.
- M. m. tcheliensis, the north Chinese rhesus macaque, lives in the north of Henan, south of Shanxi, and near Beijing. Some consider it as the most endangered subspecies. Others consider it possibly synonymous with M. m. sanctijohannis, if not with M. m. mulatta.
- M. m. vestita, the Tibetan rhesus macaque, lives in the southeast of Tibet, northwest of Yunnan, and perhaps including Yushu; it is possibly synonymous with M. m. sanctijohannis, if not with M. m. mulatta.
- M. m. littoralis, the south Chinese rhesus macaque, lives in Fujian, Zhejiang, Anhui, Jiangxi, Hunan, Hubei, Guizhou, northwest of Guangdong, north of Guangxi, northeast of Yunnan, east of Sichuan, and south of Shaanxi; it is possibly synonymous with M. m. sanctijohannis, if not with M. m. mulatta.
- M. m. brevicaudus, also referred to as Pithecus brevicaudus, lives on the Hainan Island and Wanshan Islands in Guangdong, and the islands near Hong Kong; it may be synonymous with M. m. mulatta.
- M. m. siamica, the Indochinese rhesus macaque, is distributed in Myanmar, in the north of Thailand and Vietnam, in Laos, and in the Chinese provinces of Anhui, northwest Guangxi, Guizhou, Hubei, Hunan, central and eastern Sichuan, and western and south-central Yunnan; possibly synonymous with M. m. sanctijohannis, if not with M. m. mulatta.
Description
The rhesus macaque has a dental formula of and bilophodont molar teeth.
Distribution and habitat
Rhesus macaques are native to India, Bangladesh, Pakistan, Nepal, Myanmar, Thailand, Afghanistan, Vietnam, southern China, and some neighbouring areas. They have the widest geographic ranges of any non-human primate, occupying a great diversity of altitudes throughout Central, South, and Southeast Asia. Inhabiting arid, open areas, rhesus macaques may be found in grasslands, woodlands, and in mountainous regions up to in elevation. They are strong swimmers, and can swim across rivers. Rhesus macaques are noted for their tendency to move from rural to urban areas, coming to rely on handouts or refuse from humans. They adapt well to human presence, and form larger troops in human-dominated landscapes than in forests. Rhesus monkeys live in patches of forest within agricultural areas, which gives them access to agroecosystem habitats and makes them at ease in navigating through them.The southern and the northern distributional limits for rhesus and bonnet macaques, respectively, currently run parallel to each other in the western part of India, are separated by a large gap in the center, and converge on the eastern coast of the peninsula to form a distribution overlap zone. This overlap region is characterized by the presence of mixed-species troops, with pure troops of both species sometimes occurring even in close proximity to one another. The range extension of rhesus macaque – a natural process in some areas, and a direct consequence of introduction by humans in other regions – poses grave implications for the endemic and declining populations of bonnet macaques in southern India.
Kumar et al provides a summary of population distribution and habitat in India. It states that there were sightings of rhesus macaques in all surveyed habitats except semi-evergreen forests.
Fossil record
Fossilized isolated teeth and mandible fragments from Tianyuan Cave and a juvenile maxilla from Wanglaopu Cave near Zhoukoudian represent the first recognized occurrence of rhesus macaque fossils in the far north of China, and thus the population of rhesus macaques which lived around Beijing decades ago is believed to have originated from Pleistocene ancestors rather than being human-introduced. Fossil mandible fragments from the Taedong River Basin around Pyongyang, North Korea, have also been assigned to this species.Exogenous">Exogeny">Exogenous colonies
Rhesus macaques have also been introduced and acclimated to other areas, such as the United States, where they are considered an invasive species.Around the spring of 1938, a colony of rhesus macaques was released in and around Silver Springs in Florida by a tour boat operator known locally as "Colonel Tooey" to enhance his "Jungle Cruise". Tooey had been hoping to profit from the boom in jungle adventure stories in film and print media, buying the monkeys to be attractions at his river boat tour. Tooey apparently hadn't been aware of rhesus macaques being proficient swimmers, meaning his original plan to keep the monkeys isolated to an island inside the river didn't work. The macaques nevertheless remained in the region thanks to daily feedings by Tooey and the boat tours. Tooey subsequently released additional monkeys to add to the gene pool and avoid inbreeding. The traditional story that the monkeys were released for scenery enhancement in the Tarzan movies that were filmed at that location is false, as the only Tarzan movie filmed in the area, 1939's Tarzan Finds a Son!, does not contain rhesus macaques. Whilst this was the first colony established and the longest lasting, other colonies have since been established intentionally or accidentally. A population in Titusville, Florida, was featured at the now defunct Tropical Wonderland theme park, which coincidentally was at one time endorsed by Johnny Weissmuller, who had portrayed Tarzan in the aforementioned films. This association might have contributed to the misconception the monkeys were associated directly with the Tarzan films. This colony either escaped or was intentionally released, roaming the woods of the area for a decade. In the 1980s a trapper captured several monkeys from the Titusville population and released them in the Silver Springs area to join that population. The last printed records of monkeys in the Titusville area occurred in early 1990s, but sightings continue to this day.
Various colonies of rhesus macaque are speculated to be the result of zoos and wildlife parks destroyed in hurricanes, most notably Hurricane Andrew. A 2020 estimate put the number at 550–600 rhesus macaques living in the state; officials have caught more than 1,000 of the monkeys in the past decade. Most of the captured monkeys tested positive for herpes B virus, which leads wildlife officials to consider the animals a public health hazard.
Despite the risks, the macaques have continued to enjoy long-standing support from residents in Florida, strongly disagreeing with their removal. The Silver Springs colony has continued to grow in size and range, being commonly sighted in both the park grounds, the nearby city of Ocala, Florida, and the neighboring Ocala National Forest. Individuals likely originating from this colony have been seen hundreds of kilometers away, in St. Augustine, Florida and St. Petersburg, Florida. One infamous individual, named the "Mystery Monkey of Tampa Bay", evaded capture for years, inspiring social media posts and a song.
Exogenous colonies have also resulted from research activities. There is a colony of rhesus macaques on Morgan Island, one of the Sea Islands in the South Carolina Lowcountry. They were imported in the 1970s for use in the local labs. Another research colony was established by the Caribbean Primate Research Center of the University of Puerto Rico on the island of Cayo Santiago, off of Puerto Rico. There are no predators on the island, and humans are not permitted to land, except as part of the research program. Another Puerto Rico research colony was released into the Desecheo National Wildlife Refuge in 1966. they are continuing to do ecological harm, damage crops amounting to $300,000/year and cost $1,000,000/year to manage.