Bonnet macaque

The bonnet macaque (Macaca radiata), also known as zati,^[2] is a species of macaque endemic to southern India. Its distribution is limited by the Indian Ocean on three sides and the Godavari and Tapti rivers, along with that of the rhesus macaque, its related competitor to the north.^[1][3][4] Land use changes in the last few decades have resulted in changes in its distribution boundaries with the rhesus macaque, raising concern for its conservation status in the wild.^[5][6]

Bonnet macaque
Bonnet macaque (Macaca radiata), Mangaon, Maharashtra, India
Conservation status
Vulnerable  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Primates
Suborder:	Haplorhini
Family:	Cercopithecidae
Genus:	Macaca
Species:	M. radiata
Binomial name
Macaca radiata (É. Geoffroy, 1812)
Bonnet macaque range
Synonyms
diluta Pocock, 1931

Juvenile

The bonnet macaque is diurnal, arboreal, and terrestrial. It can live up to 35 years in captivity.^[7]

The bonnet macaque feeds on fruits, nuts, seeds, flowers, invertebrates, and cereals. In southern India, this macaque has a commensal interaction with humans, feeding on food given by humans and raiding farms and houses.^[7]

Etymology

The bonnet macaque gained its name from the coil of hair located on its head, which has been noted to look similar to a hat.^[8]

Taxonomy

Two subspecies of bonnet macaques have been identified:^[9]

• Macaca radiata radiata, dark-bellied bonnet macaque,^[1] found in South and West India between the Tapti River, Palni Hills, and Timbale. In the 16th century it was introduced to the Mascarene Islands (Mauritius and Réunion).^[9]
• Macaca radiata diluta, pale-bellied bonnet macaque,^[1] found in Southeast India in the states of Kerala and Tamil Nadu. From the southern coast north to Kambam at the base of the Palni Hills and east to Puducherry.^[9] The radiata diluta macaques are known for their smaller size and paler coat color. They also have a seemingly longer and yellower head of hair.^[10]

Description

Males have a head-body length of 51.5–60 cm (20.3–23.6 in) with a 51–69 cm (20–27 in) tail while females are 34.5–52.5 cm (13.6–20.7 in) with a 48–63.5 cm (18.9–25.0 in) tail. Males weigh 5.4–11.6 kg (12–26 lb) and females 2.9–5.5 kg (6.4–12.1 lb).^[9]

Bonnet macaques have a cap-shaped whorl on the top of their heads that spreads outward from the center. The fur on their bodies can be either be dark brown or yellow. Despite these colors, the ears of the bonnet macaque are black. Females generally have redder faces when they are gestating or lactating.^[8][10]

Forest dwelling bonnets are generally smaller than the bonnets that thrive in forests.^[10]

Distribution and habitat

The bonnet macaques are a diurnal and arboreal species that resides in trees. They defend their own marked territory in the trees that they settle in, primarily fig trees near human civilizations or tall trees with enough leaves to feed off of.^[8]

Bonnets are native to and distributed throughout the Indian peninsula. It has been estimated that the population of bonnet macaques in India (where they are native to) is approximately 170,000. It is believed that 81,000 bonnets live in Karnataka, 64,000 in Andhra Pradesh, 16,000 in Tamil Nadu and finally 11,000 live in Kerala.^[10]

Behavior

The bonnet macaque has a very wide range of gestures and behaviors, which can be easily differentiated. Lip-smacking is one of the most common affiliative behaviors, where one individual may open and close its mouth in rapid succession, with its tongue between its teeth and its lips pressing against each other, giving an audible sound. A grimace is the most common gesture of fear or submission that a subordinate shows to a dominant individual during aggressive encounters. It consists of pulling back its upper lip, showing its upper teeth. It also has distinct alarm calls for predators such as pythons and leopards.^[11][12]

Social structure

Bonnet macaque with baby in Kerala

The bonnet macaque are very social animals and they communicate in a different range of facial expressions. The bonnet macaque, like other macaques, shares a linear dominance hierarchy; the alpha male is the most dominant male of the troop, followed by a beta male and a gamma male, and so on according to their dominance. Similarly, females also follow this linear hierarchy. The male and female hierarchies are different and of a non-overlapping or non-mixing types. Males are usually dominant over females.^[13] In their social groups females tend to stay in the same group they were born in, whereas males tend to disperse.^[9]

The females' dominance hierarchy is stable, whilst the males' dominance hierarchy is very dynamic. In the male hierarchy, males close in rank often fight to rise in rank. A male has the best chance of obtaining a high rank in his prime age, resulting in the greatest benefits to reproduction. High-ranking individuals have first access to breeding females. Females are receptive during only a few months in a year, resulting in competition between males. In this situation, the ranks established by aggressive encounters come into play. Most of these aggressive encounters are easily resolved, but competition between similarly built or similarly aggressive males results in brutal and sometimes fatal fights. Female bonnet macaques attempt kidnappings of lower-ranking females. These are done mostly by mother females and the majority of the time they are not successful in completing it.^[14] Different males may employ various means to rise in rank. Coalition formation between unrelated males to oust a more dominant male has been observed. Males often move from troop to troop to gain a higher rank with the resulting benefits. However, males remaining in a single troop have been observed to rise to become dominant male of that troop.

An important note is male bonnet macaques are generally far more laid back and carefree in their social lives than many other macaque species. Competition among male bonnet macaques is much more subdued and there is a much higher emphasis on pacifism. Male bonnet macaques groom each other, hug each other, sleep near each other, play together and engage in male-male mounting as a social defuser. While assertive males may take measures to monopolize matings, they cannot control females and these females will mate promiscuously, as macaques do. Some mysterious environmental pressures must have driven the bonnet macaque to form an unusually egalitarian social structure. Why this trend crops up convergently in separate macaque species rather than being an ancestral macaque trait is an enigma. A possible driving force may be these pacifist species inhabit more fertile habitats with more abundant food. Bonnet macaques are also strong swimmers.^[7]

In the case of females, the stable dominance hierarchy is a result of female philopatry, when individuals tend to remain with the troop into which they are born. This results in the formation of matrilinear groupings of closely related females.^[7]

Consumption

The bonnet macaques have been known to be omnivores. They have been regularly seen to be eating fruits, seeds, nuts, flowers, along with some invertebrates such as crickets, grasshoppers, termites, insect larva/eggs, and spiders. When eating food from the ground, the bonnets will rub the food between their palms before often stuffing their cheek pouches with food.^[8]

Reproduction

Bonnet macaques attain reproductive maturity when they are three to four years old.^[15] The majority of births take place from February to April, before the arrival of the monsoon.^[15] Bonnet monkeys are polygynandrous.^[16] The gestation period lasts 24 weeks and a single infant is the normal result of a pregnancy.^[15] The young will breast feed for six to seven months and begin assisted feedings of solid food from their mother thereafter.^[15] Other members of the troop, especially related females, will express interest in the infant in its first months of life.^[17]