Rhesus Monkey

All of us have a unique blood group. It is a set of alphabets with the ‘+’ or ‘-’ sign at the end. Have you ever wondered what these + and – sign signifies? To understand the value of these signs, you need to know their origin. These signs are called rhesus positive and rhesus negative. The rhesus word refers to the Rhesus monkey. So one kind is Rh positive and another is Rh negative monkey. Let us know more about these monkeys in detail.

Geographical Distribution of Rhesus Macaque

If you have ever been to any temples in India, you will encounter a large herd of Rhesus monkeys. Rhesus macaques are mostly found in India, Pakistan, Bangladesh, Nepal, Thailand, Myanmar, Afghanistan, and their neighboring areas. They are found in several altitudes and ecosystems, showing their great adaptability to a wide range of climatic conditions. 

Rhesus monkeys are found in open areas, arid regions, grasslands, forests, woodlands, and even mountains. They have the widest habitat amongst non-human primates. They also have the ability to swim, with many adults found to swim around half a mile between islands. They also have a close relationship with humans and rely on the refuse and handouts from them. In fact, they are found to form larger groups near human habitats than in forests.

Different Subspecies of Rhesus Monkeys

Different countries have different subspecies of Rhesus macaque. Types of monkeys differ mainly due to their geographical habitats. The Rhesus subspecies found in India is called M.m.mulatta. They are closely related to M. rhesus villosus from Kashmir and M.m. mcmahoni from Pakistan. China also has a series of Rhesus subpopulations. However, the molecular differences found amongst these Rhesus subpopulations are not consistent in defining any subspecies conclusively. Moreover, Rhesus macaque types of monkeys are another known kind. 

General Habits of Rhesus Monkeys

Rhesus monkeys are predominantly diurnal. They show both terrestrial and arboreal behavior. They are the most famous amongst macaque species. They generally measure around 19-25 inches (47-64 cm) long, with a long tail. Male Rhesus monkeys weigh around 11 kg, while female Rhesus monkeys weigh around 8.5 kg. The legs and rump are orange in both sexes. They are mainly quadrupedal but can also balance on two legs.

• Food Habits of Rhesus Macaca

Rhesus monkeys are chiefly herbivores. They feed mainly on the fruits of plants, although they can also consume seeds, roots, leaves, buds, and even cereals. They can consume above 90 different plant species belonging to 46 families. The Indian rhesus macaques are often used to tell whether the fruit is poisonous or not. 

Rhesus monkeys prefer to have water from succulent fruits. They also use dewdrops from leaves as water sources if they live in arid regions. They also feed on small insects like ants, grasshoppers, and termites. If sources of food are abundant, they live in patches. They also prefer to forage near their home ranges. They also form groups around rivers and streams. Their cheeks are specialized like pouches, allowing them to hoard the food while eating.

• Cognitive Abilities of Rhesus Monkeys

Rhesus monkeys show excellent group-based behavior. Their cognitive abilities have been a major topic in psychological research. They have shown positive responses to understanding simple rules, making similar or different judgments, and understanding each other’s mental states. They can also demonstrate self-agency, a specialized form of self-awareness. Due to their high intelligence and extremely docile nature, they are often kept as pets. However, some monkeys can turn out to be bad-tempered as well.

There has been a curious case of the cognitive ability of the Indian Macaque monkey in 2014. The power lines overhead knocked one Rhesus monkey out unconscious. That individual was revived by another Rhesus monkey who performed a series of resuscitations systematically.

• Group Behavior of Rhesus Macacas

Rhesus monkeys live in groups. This behavior is shown by other macaque monkeys as well. The groups are generally large, comprising around 20-200 individuals. The females mostly outnumber the males in the group, and also show the tendency of philopatry, where the individual returns to a particular place due to some reasons. Although males prefer to show a tendency to leave the group, females prefer to stay longer. 

The Rhesus groups also show matrilineal hierarchies. This means that the rank of a female monkey depends on that of her mother. There can be multiple matrilineal lines inside a group, although the younger ones tend to supersede the older sisters. The major reason behind such a phenomenon may be that the younger ones are more fertile and fit. 

However, the rank criteria are opposite for males. Adult males obtain dominance over other members of the group by their experience and age. The dominant males generally drive out the juvenile ones after they have attained an age of 5 years. However, the central male dominance is maintained by two to three oldest males who show codominance. 

Other individuals are restricted to the periphery. They are communicated with the central dominant group through a group of subordinates. There is a special group of subordinates at the edge of the groups responsible for making alarm calls whenever danger comes. The higher-ranked individuals also show despotic behaviors towards non-kins. The top-ranked females are also sexually coercive towards unreceptive males. They injure them by biting off digits and even damaging their genitals.

• How Do Rhesus Macaques Communicate With Each Other?

Communication is an important aspect of any group behavior. Rhesus macaques also use different patterns of communication amongst each other. They use different facial expressions, body postures, vocalizations, and even gestures. The ‘silent bared teeth’ is the most common form of expression amongst Rhesus monkeys. That is a way of expression used by juniors to their superiors. 

When the monkey gets afraid, they make a fear grimace with a scream to appease the higher dominant ones. They also use such expressions to redirect aggressions. The present rump is another submissive expression by the recessive ones. In this expression, the individual raises its tail and shows its genitals to the dominant individuals. 

Rhesus monkeys show dominant expressions as well. For example, they perform an open mouth stare by placing them on their quadrupedal and the tail sticking straight outwards. By doing so, the dominant threatens other individuals. 

When Rhesus monkeys move around, they make occasional grunts and coos. They also use these expressions during grooming and other affiliative interactions. When they come across high-quality food, they attract other members of the group by making harmonic arches, chirps, and even warbles. However, they make shrill barks when they encounter threatening conditions. During aggressive interactions, Rhesus monkeys make screams, squeaks, screeches, growls, and even barks. The infants make gecker expressions to catch the attention of their mothers. 

• Reproduction and Infant Care Amongst Rhesus Macacas

Sexual activities are common both in and outside the breeding period. Adult males prefer to increase their reproductive ability and success by doing so. Females show preference to males outside their group. The breeding period can last for around eleven days where the females mate multiple times with several males in the group and even outside the group. Sexual dominance is often expressed by males, where they fight for sexually receptive females.

Female macaques can breed when they are four years old. They attain menopause when they are twenty-five years old. The females mainly take care of the offspring. If the mother is a higher-ranked dominant, they pass on the parenting responsibility to their daughters. Although males do not take care of their offspring, they prefer to have peaceful relations with the offspring coming from their consort pairs.

[Image will be Uploaded Soon]

Contribution of Rhesus Monkeys to Human Blood Group Nomenclature 

There are different ways of classifying human blood groups. The most commonly used one is the ABO blood group system and the Rhesus system. The Rhesus system is based on the presence of the Rhesus antigen in human blood. This antigen is also known as the D antigen, present on the red blood cells. The Rhesus antigen is first identified from Rhesus monkeys and is named accordingly. 

Some humans show the presence of this antigen on their red blood cells and are considered Rh-positive. Those who do not have the antigen are considered to be Rh-negative. Monkeys belonging to the Rhesus group mostly show this D antigen. Rh-positive recipients can receive blood from both Rh-positive and Rh-negative donors. However, Rh-negative recipients cannot receive blood from Rh-positive donors. Several other factors are considered during the blood transfusion process.