Species Diversity of Monkeys in Western Ghats

Atindra Karar
Atindra Karar
The lion-tailed macaque ranges through three southern Indian states: Karnataka, Tamil Nadu, and Kerala.
The lion-tailed macaque ranges through three southern Indian states: Karnataka, Tamil Nadu, and Kerala.


India has been identified as one of the 12 mega-diversity countries with about 126,000 species. India has 8% of the global biodiversity it covers only 2.4% of the land area of the world. The Western Ghats is among the 18 biodiversity hotspots in the world. The Western Ghats covers only 5% of the land area of India but has 30% of India’s species. The Western Ghats mountains of southern India are separated into northern and south spans by the Palghat Gap in the land of Kerala. The rainforest in Karnataka, though narrow in breadth from West to East, is generally conterminous from North to South. The climax rainforest in Karnataka extends from about sea position up to about 950 meters a.s.l. The rainforest in areas south of Palghat Gap occurs from about 600 meters a.s.l. to almost 1800 meters a.s.l. Due to these altitudinal as well as latitudinal differences, the forest types in these regions differ. In Karnataka, the low-elevation rainforest is primarily Dipterocarpus-Humboldtia-Poeciloneuron type, whereas, in the more southern region, the medium-elevation rainforest is of Cullenia-Mesua-Palaquium type.

Lion-Tailed Macaque

Lion-tailed macaques (Macaca silenus) are endemic to the rainforests of the Western Ghats and are endangered as a result of the fragmentation of their habitats and low population growth. The home range and core areas were 130.48 ha (95 % kernel) and 26.68 ha (50 % kernel) respectively. The lion-tailed macaques had a longer day range, had a higher number of sleeping spots, and used core areas in the summer as compared to the precipitation and the post-monsoon seasons. The major food resources used in a particular season influenced the ranging patterns and sleeping site use. The range was mainly influenced by Artocarpus heterophyllus in monsoon, Cullenia exarillata and Toona ciliata in post-monsoon, and Artocarpus heterophyllus and Ficus amplissima in summer. The distribution of these four plant species is, therefore, critical to the range, and thus to the conservation of the lion-tailed macaque. The lion-tailed macaque (Macaca silenus), endemic to the rainforests of the Western Ghats in India, is listed as Endangered on the IUCN Red List of Threatened Species, is in Appendix I of CITES, and is protected under Schedule I of India Wildlife Protection Act. The status of the endemic and endangered lion-tailed macaque (Macaca silenus) has not been properly assessed in several regions of the Western Ghats of southern India. A minimum of 17 groups of macaques were observed in these hills. Low detection and occupancy probabilities indicated a low density of lion-tailed macaques in the area. The height of the tallest trees correlated positively whereas human disturbance and the proportion of evergreen forests correlated negatively with occupancy in grid cells. The landscape harbours an estimated population of 1108 individuals of lion-tailed macaques, which is about one-third of the entire estimated wild population of this species. The sympatric arboreal mammals found included common langurs, bonnet macaques, and Malabar giant squirrels. The lion-tailed macaques are sympatric with other primates and giant squirrels in the undisturbed core areas.

The lion-tailed macaque ranges through three southern Indian states: Karnataka, Tamil Nadu, and Kerala. Due to its largely particular feeding habits, limited range of habitation (about 2500 km2), delayed sexual maturity, long interbirth intervals, low population development, and a small remaining wild population, this species has been classified as endangered. Kumar (1995) estimated 3500-4000 lion-tailed macaques for the entire Western Ghats, a number afterward put at 3500. These entities were believed to correspond to 49 subpopulations separated in rainforest fractions scattered over eight sites. Karanth (1992), while outlining the conservation prospects for the Western Ghats, emphasized the importance of the lion-tailed macaque as a flagship species of the rapidly declining rainforests of this biodiversity hotspot. Large Conterminous populations of the lion-tailed macaque are anticipated to happen only in veritably some regions over the entire Western Ghats and the conservation status of the species is likely to differ across these scanty populations. The Kalakad- Mundanthurai Tiger Reserve in southern Tamil Nadu, for instance, has large tracts of rainforest, amounting to about 400 km, and is believed to have a good population of the species although a status inspection has not been conducted there. The Indira Gandhi Wildlife Sanctuary in the Anamalai hills in the state of Tamil Nadu has about 32 groups of lion-tailed macaques, all of which are restricted to severely fragmented forests and, hence, the future of this population is unpredictable. The Silent Valley National Park in the state of Kerala has received the attention of the entire country because of its 14 groups of lion-tailed macaques. Drastic declines sometimes lead to the loss of even 65% of the existing groups.

Feeding ecology

Lion-tailed macaques feed largely on fruits > 60%, mainly Ficus spp. which is seasonal, patchy in distribution, and rare fruit and flowers of Cullenia exarillata which are in abundance and very important resources in Anamalai Hills. There were two annual peaks for feeding during the months of December to February and May to July and the months which had the least feeding and most foraging activities from September to April. A significant difference was also established in terms of more fruit consumption and less insect feeding in the wet season as compared to drier months in the Andiparai shola of Anamalai hills. The propriety food species are Cullinea exarillata, Palaquium ellipticum, Ficus beddomi and Dryptes elata respectively and Cullenia exarillata is one of the high-priority food species for lion-tailed macaque. This clearly shows that the Cullenia exarillata is one of the major food species for lion-tailed macaques in the southern Western Ghats, which is absent north of Brahmagiri Wildlife Sanctuary in Karnataka.

Most macaques have an omnivorous diet with varying proportions of fruits, leaves, flowers, arthropods, and, to some extent, small vertebrates. The lion-tailed macaque’s (Macaca silenus) diet mainly consists of fruits, arthropods, flowers, and other minor items such as moss, mushroom, and grass. It is widely distributed in peninsular India and occurs in the Western Ghats, Eastern Ghats, and Central India. The squirrel inhabits mainly moist deciduous, riverine, and evergreen forests. The average body weight of an adult squirrel is about 2 kg with a body length of 35–41 cm and a tail length of about 60 cm. A sub-adult Indian giant squirrel (Ratufa indica) is predated by an adult, male, lion-tailed macaque. Although feeding on vertebrates is not frequent, there have been sporadic reports of lion-tailed macaques foraging on frogs, lizards, bats, small birds, three striped squirrels, nestlings of the Indian giant squirrel, and the large, brown, flying squirrel. While feeding on arthropods and smaller prey is common among most age-sex classes in the lion-tailed macaque, foraging on larger prey is mainly reported among adult males. The prey was detected at a close range and captured. This tactic of capturing prey – scavenge hunting – requires the least specialized predatory skills and energy and is characteristic of omnivorous primates. 

Fission event

Macaca silenus has a modal group size of about 18 in large forestland complexes, though the group size varies significantly in forestland fractions. Most groups have only one adult male with several adult females and immature individuals. They are primarily frugivorous, but faunal components account for about 19% of their total diet. Macaca silenus groups increase their home range and daily path length during the dry season when compared with the wet season. Since meeting their nutritional needs appears to be more challenging in the dry season, M. silenus would fission more frequently during the dry season than in the wet season. As many as 11 instances of temporary fissions in a group of Lion-tailed Macaques Macaca silenus have been reported in the Western Ghats of India. More group splits occurred in the dry season than in the wet season. The frequency of fissions was higher in the mornings than in the afternoons. The subgroup that initiated the fission group was always smaller than the main subgroup, defined as the subgroup with the alpha male. The average duration of the splits was 133.6 minutes. The second subgroup travelled greater distances during fission events than the main subgroup. M. silenus, especially larger groups, form fission-fusion social groups, especially when resources are scarce.

The Bonnet Macaque

The bonnet macaque (M. radiata) is a niche generalist indigenous to southern India but is losing its range to the quite larger-bodied and more aggressive rhesus macaque (M. mulatta).  It is not a typically forest-dwelling species, and its populations are declining drastically in its traditional habitats which include Hindu temples, tourist spots, and roadsides with fruit-bearing trees and crops. The population has remained stable only where the habitat allows the macaques to forage in the scrub jungle and includes a temple where the monkeys can obtain food from visitors. India is dotted with small hillocks with natural scrub or deciduous forestland greenery with one or two Hindu temples, and it appears that alike territories are the most suitable places for the long-term conservation of this species. Bonnet macaques show more advanced variability than lion-tailed macaques. This indicated evolved within-group competition in bonnet macaques than in lion-tailed macaques.

Species diversity of langurs

Folivorous Nilgiri langurs and black-footed grey langurs didn't show variability in any actions, indicating weak or negligible within-group competition. The interindividual differences in activities in the other species were potentially due to the differences between lactating and non-lactating females. Langurs were less variable than macaques, indicating evolved within-group competition in macaques than in langurs. A higher frequency of aggressive interactions was observed during feeding among macaques than among langurs, substantiating higher within-group competition in macaques than in langurs.

The status of the South Indian black leaf-monkey or Nilgiri langur, Presbytis (Trachypithecus) johnii, is particularly difficult to assess because of the complexity of the terrain within its range and because of confusion in the naming of parts of this terrain.  The Western Ghats from Goorg southward, the Nilgiri, Anamalai, Brahmagiri, Tinnevelly, and Palni Hills are usually not below 3000 ft.  This term is preferred to the more often used "Nilgiri langur" since "langur" is a Hindi name for Presbytis entellüs, which is an animal distinctly different from  P. johnii, the Nilgiri Hills are only one of many hill ranges in which the species occurs and in the vernacular languages of S.  India, this species is usually called “black monkey". The common langur (Semnopithecus entellus), a colobine monkey is widespread across India and Sri Lanka (15).

Nilgiri langurs are indigenous and listed in Schedule I of the Indian Wildlife Protection Act (1972), primate species pioneer in the Western Ghats between 8 ̊ and 12 ̊ N from Agasthyamalai in Kerala in the south to Kodagu in Karnataka in the north. These folivores are known to live in groups with infrequent social interactions and form metapopulation by dispersing between forest fragments. Nilgiri Langurs (Trachypithecus johnii) is indigenous to the rain forestlands of the Western Ghats. The group size of langur ranged from 2 to 20 while that of chital was 2 to 80. Nilgiri langurs are arboreal primates endemic to the Western Ghats and are distributed across the states of Kerala, Karnataka, and Tamil Nadu. They are characterized by thick black fur, long hairs on the crown and sides of the head with a flaxen mane around their black hairless faces. The young ones are red-brown in colour and this colour turns black.  The animals attain full adult colouration in about  4-5 months. The species has been listed under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (Appendix II). They are protected and covered under the Indian Wildlife Protection Act, of 1972. Under the IUCN Red data list, these langurs are listed as vulnerable.

Langur - chital association

The fallen fruits and leaves on the forest floor, a result of arboreal foraging by the common langur, attract a large congregation of chital (Axis axis) very often to forage on the fallen food items.  Primate-ungulate associations play a crucial role in the dispersal of heavy-seeded fruits.  Such mutual associations minimize the chances of predation risk upon both species as they recognize and respond to anti-predator alarm calls produced by either of the species.  Predation risk from large predators tends to increase the size of primate groups so that they can benefit from increased vigilance. Participation in the association does not inflict any cost in terms of inter-specific food competition since they have nonoverlapping niches. The estimated mean group size of langur and chital was 7.6 ± 0.44 SE and 18.0 ± 2.6 SE respectively.  On 48 occasions, chital fed on food materials dropped by langur during its arboreal forage; such as leaves (73.1%), fruits (17.3%), and flowers (9.6%). Anogeissus latifolia and Tectona grandis are the most frequently utilized trees during the association.  Leaves (64.2%) represented the main food item for langur followed by fruits (24.5%), and flowers (11.3%). Mixed species association between langur and other ungulates/ primates such as gaur Bos gaurus, sambar Rusa unicolor sambar Rusa unicolor sambar and bonnet macaque Macaca radiata are also noticed. In Mudumalai, chital fed on food items of 14 tree species dropped by langur.

Mixed species association

Phylogenetic conservatism or rapid anthropogenic habitat modifications could increase the incidences of interspecific associations of Hanuman and Nilgiri langurs (Semnopithecus johnii) (Family: Cercopithecidae, subfamily: Colobinae) in the southern Western Ghats. A troop of Nilgiri Langurs around O Valley tea estate at Devimalai Ghat, Gudalur, Tamil Nadu with some hybrid looking individuals and a Tufted female Grey Langur (S. priam) amongst them were reported. A total of six and two uni-male troops of Nilgiri Langurs and grey langurs respectively with Tufted female Grey Langurs, and aberrant coat-coloured infants were observed at the Neelikkal section of Silent Valley National Park. 

Molecular analysis of species

Earlier, the Nilgiri langurs were classified as a separate genus Kasi, which was replaced by Trachypithecus because of their morphological similarities with other rainforest langurs of Asia. Molecular genetics studies grounded on mtCYTB have grouped Nilgiri langurs under the Semnopithecus sp. along with other common langurs of India. Phylogenetic analysis showed that the Nilgiri langur sequence (MW717575) has clustering as a subtree with the rest of the Trachypithecus sequence from GenBank. In general, all the Semnopithecus and Trachypithecus sequences were found to cluster as a single clade. The sequences of Trachypithecus vetulus, which are endemic to Sri Lanka were found to form a separate clade. Karanth et al. (2008) based on mtCYTB, protamine P1, and lysozyme genes, the phylogeny among the different colobine species is resolved. Hanuman Langurs (S. entellus) are inter-related with Nilgiri Langur and Purple-faced-Langur. They observed paraphyly in T. vetulus and polyphyly of the Semnopithecus genus which was split into three groups (S. entellus of North India, S. entellus of South India along with T. johnii, and S. entellus of Sri Lanka along with T. vetulus).

Adaptation in the human colony

Each troop of the ranging patterns of five lion-tailed macaque Macaca silenus troops, forming the Puthuthottam sub-population, visited the road or human habitation at varying rates, with the largest troop visiting most frequently. Home ranges sizes were observed to be highly reduced when compared to wild populations, and also greatly varied across troops, with relatively low overlap given the macaque density in the available area. All five macaque troops showed a preference for human-modified habitats such as roads and human settlements where anthropogenic food was easily available. Bonnet macaques are usually commensal with humans in most of their habitat all over southern India. In the disturbed but still, core areas, common langur and bonnet macaque are sympatric. In the more disturbed areas towards the forest fringes on the eastern side, only bonnet macaque is found.


An increasing dependence amongst members of the lion-tailed macaque Macaca silenus troops on anthropogenic foods, has led to many threats faced by individuals including fatal collisions with vehicular traffic and electrocutions. The fragmentation of the rainforests of India’s Western Ghats mountains has left the endemic lion-tailed macaque surviving in numerous forest patches in a mosaic of commercial tea and coffee plantations on the Valparai Plateau, Anamalai Hills, some macaque groups have putatively altered their geste, getting frequented to people, suffering from frequent roadkill, and facing problems related to people feeding them and their use of open waste dumps. Habitat fragmentation is a major threat to the species that has a population of only around 4,000 individuals in the wild. While lion-tailed macaques are largely confined to forestland innards, in recent times, groups in rainforest fractions close to developed areas and entered by roads have shown behavioural changes, getting frequented to people. As a result, roadkill has increased, as have incidents of conflict due to people feeding them or because they enter houses or visit open waste dumps. Poor garbage disposal (tourists throwing food away by the side of the road, residents throwing out food close to human habitations) attracted macaques and brought them into greater contact with human foods and habitations. Retaliatory measures by residents, such as chasing them using firecrackers and throwing sticks or stones indicate a decreased tolerance towards macaques.

Further, towards the human habitations and disturbed areas, the lion-tailed macaques are absent and the forest is engrossed by commensal species. The niche features and the population structure indicates that this region is an implicit area for maintaining a biologically feasible population of lion-tailed macaques. Still, several factors similar to extraction of energy wood, collection of minor forestland yield, grazing by domestic animals, and a colony of marketable tree species are causing serious trouble to the niche. The number has also been reduced by the continued loss of rainforest habitat in the Western Ghats and hunting.

Kyasanur forestland disorder (KFD) is a major tick-borne viral haemorrhagic fever caused by the KFD virus (KFDV) (Flaviviridae). The disorder was reported to be confined to five sections of Karnataka until 2011. During 2012–2016, the emergence of KFD has been reported in newer areas of Karnataka and adjoining states. Therefore, the survey of tick vectors was carried out in these new areas of Karnataka and adjoining states reported monkey deaths of KFD. An aggregate of 4772 ticks, comprising eight species of genus Haemaphysalis and one species each of genus Amblyomma, Ixodes, and Rhipicephalus was collected. Haemaphysalis spinigera, the lead vector of KFDV was the predominant tick species (59.5%) collected followed by H. turturis (8.6%). The plenty of H. spinigera ranged from 9.2 to 33.9 per man-hour in the six sections surveyed. A high plentitude of Haemaphysalis vectors in the six sections indicated that the sections are open for KFD outbreaks.

More than 3,314 monkey deaths attributed to KFD were reported in KFD-endemic states in India during 1957–2020. An aggregate of 13 gastrointestinal parasite taxa was recovered, which are known to infect humans and animals. Parasite species richness was more advanced in agitated forestland fractions than in untroubled ones. A negative association between Schistosoma sp. and Trichuris trichiura was also observed. Erection size, closeness to human settlements, and other niche variables similar as tree consistency, canopy cover, and tree height didn't show any significant relationship with parasitism in Nilgiri langur, which might be attributed to their capability to survive in an agitated terrain. Nilgiri langurs move between forest patches using the surrounding matrix and form a metapopulation. Dispersing individuals may act as parasite transmitters among individuals of different forest fragments. 

Larvae and nymphs of these ticks feed on monkeys; when they are base browsing, supplying routes of infection and spread. Macaca radiata and Semnopithecus entellus are 2 monkey species in the KFD-endemic region frequently associated with KFD; these monkeys can succumb to the virus quickly. Reporting of monkey deaths from KFD during the past 60 years has been unsystematic and inconsistent.

Nine gastrointestinal parasite taxa consisting of 5 nematodes (Ancylostoma, Bunostomum, Haemonchus, Strongyloides and Trichuris), 2 cestodes (Diphyllobothrium and Moniezia), one each of trematode (Cotylophoron) and protozoan (Balantidium) are being detected in lion-tailed macaque groups. Strongyloides were the most prevailing parasite constituted in 8 forestland fractions followed by Trichuris and Ancylostoma constitute in 7 forestland fractions. Both the cestodes constituted only one forestland fraction. Out of 9 taxa related, 6 happened near human settlements and 3 happened in both. Of the 3 occurring in both, 2 have a higher prevalence near settlements. All the rare ones were constituted only in fractions near settlements. The groups near human settlements have greater prevalence and number of taxa, and these variables also have significant positive correlations with group size. The population of lion-tailed macaque itself is heavily fragmented, with nearly 40% of the population occurring as small isolated populations. It occurs in advanced consistency as well as group size in forestland fractions than in conterminous forestlands. There is a negative correlation between fragment area and habitat degradation as indicated by tree densities, basal area, and canopy height and the smaller fragments are more likely to have human settlements nearby. Lion-tailed macaques in forestland fractions also spend further time on the ground compared to those in conterminous forestlands and feed on far lesser plant species. Thus, by all criteria, it is expected that an increased parasitic infection in the lion-tailed macaques is caused by increased host densities and higher cross-species infestation.


Data on tick distribution will be useful in creating a KFD threat chart for strengthening the ongoing prophylactic measures similar to vaccination and supply of insect repellents to the high-threat groups and profound health education.

Identification of contiguous forest habitats for viable lion-tailed macaque populations, improving the quality of their degraded habitats, and the linking of forest fragments with native vegetation as management measures are required for their conservation. To reduce negative interactions with people and promote harmonious human-macaque co-existence, a combination of measures that would involve plantation management, conservation organizations, and the state forest and municipal authorities include cost-effective monkey-proofing of houses, regular garbage collection, preventing open waste disposal and the feeding of macaques, mitigating the effects of roads, and promoting people’s awareness, rainforest restoration, and the use of native shade trees in plantations. Cover bridges have been put up and maintained by conservation groups since 2011 to enable the movement of arboreal mammals across roadways and thereby reduce the threat of roadkill. Monkey-proof housing roofs are likely to reduce conflict incidents and enhance positive perception towards the macaques. The lion-tailed macaques, along with common langurs and bonnet macaques, are restricted only to the relatively undisturbed core areas.

The entire Kudremukh region with the adjoining ranges must immediately be declared a National Park. The region must be preserved as a high-priority biodiversity region. The villagers who have settled inside the forest must be gradually relocated outside the forest by providing attractive alternatives. The removal of minor forest produce (MFP) must be totally stopped, for the benefit of lion-tailed macaques that consume MFP.  A limit must be assessed on the number of domestic cattle possessed by villagers, and non-milk cows should not be allowed at all. The rolling grassland on the hilltops is a natural feature of the Western Ghats. The planting of exotic trees for commercial purposes must be stopped. The existence of more than 30 groups with an estimated population size of about 638 monkeys is confirmed and the boundaries are fixed to notify the region as a protected area.


Species conservation depends on the needs of the species concerned. Species distribution models are a key component for understanding a species’ potential occurrence, specifically in vastly undersampled landscapes. Such studies are important for understanding within-group feeding competition in primates as interindividual difference in the frequency of the behaviour is a good indicator of feeding competition. An assessment of the overall status of an animal species requires a thorough knowledge of the geography of its presumed range. Without this knowledge, it is difficult to judge the significance of reports covering particular limited areas within the range or to appreciate where further investigations are required.

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