Rhesus Macaque

## Description

The rhesus macaque (Macaca mulatta ), colloquially rhesus monkey, is a species of Old World monkey. There are between six and nine recognised subspecies that are split between two groups, the Chinese-derived and the Indian-derived. Generally brown or grey in colour, it is 47–53 cm (19–21 in) in length with a 20.7–22.9 cm (8.1–9.0 in) tail and weighs 5.3–7.7 kg (12–17 lb). 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 a great variety of habitats, from grasslands to arid and forested areas, but also close to human settlements. Feral colonies are found in the United States, thought to be either released by humans or escapees after hurricanes destroyed zoo and wildlife park facilities.

The rhesus macaque is diurnal, arboreal, and terrestrial. It is mostly herbivorous, mainly eating fruit, but will also consume seeds, roots, buds, bark, and cereals. Studies show almost 100 different plant species in its diet. It will also eat invertebrates, drink water from streams and rivers, and has specialised cheek pouches where it can temporarily store food.

Like other macaques, the rhesus macaque is gregarious with troops comprising 20-200 individuals. The social groups are matrilineal, whereby a female's rank is decided by the rank of her mother. There has been extensive research into female philopatry, common in social animals, as females tend not to leave social group. It communicates with a variety of facial expressions, vocalisations, body postures, and gestures. Facial expressions are used to appease or redirect aggression, assert dominance, and threaten other individuals and vocalisations may be made to elicit grooming, while moving, or in threatening situations. It spends most of its day feeding and resting, the rest is occupied with travelling, grooming, and playing.

Due to its relatively easy upkeep, wide availability, and closeness to humans anatomically and physiologically, it has been used extensively in medical and biological research on human and animal health-related topics. It has facilitated many scientific breakthroughs including vaccines for rabies, smallpox, and polio and antiretroviral medication to treat HIV/AIDS. The rhesus macaque became the first primate astronaut in 1948, but died during the flight. It is listed as Least Concern in the IUCN Red List of Threatened Species in view of its wide distribution, presumed large population, and its tolerance of a broad range of habitats.

## Appearance

The Rhesus macaque is a monkey of the Old World. They are either pale brown or gray, usually with pink faces. Their tails are quite long, they have a rib cage that is wider than average, with dorsal scapulae, and they have thirty-two teeth. They are charismatic monkeys and like to have fun and can be cheeky. Their coats have faded undertones on the underside. Their faces are furless and in adults - bright red, and adults also have bright red rumps. They have large cheek pouches for storing food while out foraging.

## Distribution

Rhesus macaques are native to India, Bangladesh, Pakistan, Nepal, Myanmar, Thailand, Afghanistan, Vietnam, southern China, and some neighboring areas. They have the widest geographic ranges of any non-human primate, occupying a great diversity of altitudes throughout Central, South, and Southeast Asia. Rhesus macaques may be found in forests, mangroves, scrub, grasslands, and mountainous regions. They also adapt well to human presence and form larger troops in human-dominated landscapes than in forests.

## Behavior

Rhesus macaques are social, diurnal, and both terrestrial and arboreal animals. They walk using four limbs, walking on the ground on both their toes and on the soles of their feet. They are very active and loud. They like being in the water and can swim well. They form groups of as many as 200 individuals, and when the size of a group reaches 80 to 100, a subgroup of females can split off to create a new group. Generally, groups are made up of several unrelated males, with many closely related females. Males and females within a group demonstrate a preference for high-ranking individuals of the opposite sex. Rhesus monkeys are not territorial. Every group of individuals generally has its own sleeping area. Confrontations between different groups are rare. When groups meet, usually the weaker group avoids the stronger one.

## Diet

Rhesus macaques are omnivorous animals, eating seeds, roots, bark, fruits and cereals. They have also been observed eating termites, grasshoppers, ants, and beetles. When the monsoon approaches, ripe fruits provide them with a much-needed source of water. When rhesus macaques live far from a water source, which is not common, they get water from dewdrops off tree leaves.

## Reproduction

Rhesus macaques are polygynandrous when males and females have multiple mating partners during a breeding season. Breeding seasons vary widely amongst populations. Those monkeys living in areas with cold winters mate in the autumn and those living where there are less pronounced seasonal changes have less well-defined seasons for mating. The gestation period lasts about 165 days, and usually a single young is born. Newborns nurse for about a year. Females become reproductively mature at 2.5 to 3 years old and males at 4.5 to 7 years old.

## Population

### Threats

The Rhesus macaque living in the wild is threatened, but a large population is captive across the world for biological, medicinal, and psychological research, especially for studies about perception, learning, and behavior. They raid crops in India but there the Hindu religion considers them to be sacred animals, so they avoid human persecution.

### Number

The IUCN Red List and other sources don’t provide the number of the Rhesus macaque total population size. Currently, this species is classified as Least Concern (LC) on the IUCN Red List.

### Ecological niche

Rhesus monkeys may help with the dispersal of seeds. Being a species that is preyed upon, they may affect populations of predators.

## Fun Facts

The name "rhesus" is from the Greek “Rhesos,” who was the King of Thrace who gave assistance to Priam at Troy. Audebert, who used the name for the species, declared that the word had no meaning.

Rhesus macaques are very mischievous. They have been known to overrun villages in India - stealing food by breaking into homes and jumping off buildings to swim in the water.

Rhesus macaques have specialized pouch-like cheeks, where they can temporarily hoard their food.

Rhesus macaques interact using a variety of facial expressions, vocalizations, body postures, and gestures. Perhaps the most common facial expression the macaque makes is the "silent bared teeth" face. During movements, macaques make coos and grunts. When they find rare food of high quality, macaques emit warbles, harmonic arches, or chirps. When in threatening situations, macaques emit a single loud, high-pitched sound called a shrill bark. Screeches, screams, squeaks, pant-threats, growls, and barks are used during aggressive interactions. Infants "gecker" to attract their mother's attention.

These monkeys are used a lot for research and are especially useful in the areas of biology, medicine, and psychology.