Vanishing Troops of Nilgiri Langurs
from the Western Ghats of India
-Dr. Arvind Singh
The Nilgiri langur is a species of primate found in Nilgiri Hills of the Western Ghats in South India. This species of monkey has various common names like; ‘Black leaf monkey’, ‘Indian hooded leaf monkey’ ‘Hooded leaf monkey’, ‘John’s langur’, Nilgiri leaf monkey’ and ‘Nilgiri black langur’. Unlike Common langurs the Nilgiri langurs are shy, retiring and occupy a dense forest habitat.
The scientific name of Nilgiri langur is Trachypithecus johnii and it belongs to the Cercopithecidae family of Primates. Nilgiri langur was earlier placed under genus Presbytis, and subsequently placed under genus Semnopithecus. However, currently, it is included in the genus Trachypithecus. Its position is debatable as recent studies indicate that Nilgiri langur and Purple-faced langur are more closely related to Hanuman langur rather than Leaf monkeys of South-east Asia and therefore should be placed under the genus Semnopithecus.
Nilgiri langur is a threatened species because of the declining trend in their population size. It is placed on the International Union for Conservation of Nature and Natural Resources (IUCN) Red List as ‘Vulnerable’. Those species which are likely to move into the endangered category in the mid-term future if the causal factors continue to operate are known as vulnerable. However, the species which are facing the threat of extinction in the near future are known as endangered.
Distribution Range:
Nilgiri langur is endemic to the southern portions of the Western Ghats, a mountain range in the South of India. The species ranges from Kanyakumari to Coorg Hills, Srimangla range of Brahmagiri ˗ Makut protected area forming its northernmost limit in the Western Ghats. Thus its range includes the South Indian states Kerala, Karnataka, and Western Tamil Nadu.
Physical Characteristics:
Nilgiri langur is a Colobine monkey. They share many of the Colobine features, such as a complex stomach, a reduced thumb, and a long tail. Nilgiri langurs have glossy black fur on their body and golden brown fur on their head. They have dark faces and white side-burns. Females have a white patch on the inside of the thighs which is also present in young females. The young’s have pink skin and are covered with reddish-brown hairs.
Nilgiri langurs are sexually dimorphic with males slightly larger than females. The males have a total body length that ranges between 70 to 80 cm weighing between 9.1 and 14.8 kg. The length of females ranges from 58 to 60 cm weighing between 10.9 and 12 kg. The tails of both males and females vary in length between 68.5 and 96.5 cm.
Nilgiri langurs have complex foregut with microbial fermentation and enlarged salivary glands for assisting the breakdown of indigestible plant material especially cellulose.
Habitat and Ecology:
Nilgiri langurs inhabit a wide range of forest habitats in the Western Ghats. They are found primarily in secondary moist deciduous forests and wet evergreen to semi-evergreen forests. Nilgiri langurs prefer locations that are close to the water and far away from human beings.
Nilgiri langurs are arboreal and diurnal species, sleeping in the middle or lower canopy in trees of medium height. They are rarely seen on the grounds. They live at elevations between around 300 and 2,500 m. and are most commonly found at about 1,400 m. Nilgiri langurs live in the Sholas of Western Ghats. Sholas are dense evergreen forests occupying the watercourses or folds in high elevation grasslands. In the lower elevations, they reside the wet evergreen forests where the canopy is about 60 cm in height and also utilizes the mixed deciduous forests in such areas.
Nilgiri langurs are primarily folivorous with young leaves comprising as high as 44.06 % of their diet, but they also feed upon fruits, nuts, buds, flowers, seeds, bark, stem, insects, and earth. They play an important role in seed dispersion in their ecosystem. Preferring new leaves, they feed on a variety of plants depending on the season.
Nilgiri langurs prefer the leaves of teak trees and consume the larger leaves more frequently than others that occasionally make up their diet. While eating the leaves they first eat the tips, then they rip off the sides to expose the midrib, which is also consumed by them.
Nilgiri langurs are reported to choose foods based on digestibility. Generally, they have a diet that is low in both fiber and vegetable tannin. They consume over 115 different species including, at least 58 tree species, 6 shrub species, 13 non-woody plants, 32 vines and 6 parasitic plants.
On average the Nilgiri langur spends about 7- 8 hours in feeding. Feeding is a primarily morning and late afternoon activity and the middle of the day is reserved for activities like grooming, play amongst youngsters and sleeping. Nilgiri langurs generally live in animal troops (one male and several females) of 6-8 individuals in deciduous forest and 18-20 individuals in an evergreen forest.
Nilgiri langurs exhibit territorial behaviors when confronted by other troops of their species. This defense of territory directly involves only one adult male of each group. Males defend their home areas through physical displays, vocalization, and chases.
Nilgiri langurs have an average home range of around 10,000-meter square. The size of the home range fluctuates with the quality of habitat during the seasons. The home range is smaller on the availability of preferred food while the home range increases on the scarcity of preferred food.
Nilgiri langurs breed year-round but only conceive when resources are available in plenty. Young ones have been reported in June and in September however, the number of births is greater in June. The length of the gestation period of Nilgiri langurs in the wild is not known. However, in captivity, the gestation period for Nilgiri langur is between 140 and 220 days. Nilgiri langurs typically have only one offspring at a time. At birth, the infant weighs around 0.5 kg.
Threats to Survival:
Poaching and habitat loss are the two main threats to the survival of Nilgiri langurs.
Poaching is a key threat to the survival of Nilgiri langurs, where their pelt organs, blood, and flesh are used to produce crude medicines and aphrodisiacs. Prior to the Wildlife Protection Act, 1972, these crude medicines were widely available and even advertised. Karinkorangu Rasayanam was one of the leading products at that time. Besides this, they are also poached for their skins which are used as drum heads.
Habitat destruction, primarily due to developmental projects like dams and hydroelectric projects have led to decline in their population size.
Nilgiri langurs are also captured and sold as pets.
Conservation:
The population of Nilgiri langur is estimated to be between 5,000 and 15,000 individuals with less than 10,000 mature individuals.
Nilgiri langurs have been protected under Schedule I, Part I of Indian Wildlife Protection Act, 1972. It is also listed on Appendix II of the Convention on International Trade in Endangered Species (CITES). The following actions are needed for the conservation of the Nilgiri langurs.
1. To strictly enforce the Wildlife Protection Act and CITES.
2. To regularly monitor the population of Nilgiri langurs in their natural habitats.
3. To check the habitat loss of the animal.
4. To restore the degraded habitats of the animal.
5. To promote captive breeding of Nilgiri langur and subsequent release in their natural habitats.
6. To educate people about the biological/ecological significance of Nilgiri langurs.
2. To regularly monitor the population of Nilgiri langurs in their natural habitats.
3. To check the habitat loss of the animal.
4. To restore the degraded habitats of the animal.
5. To promote captive breeding of Nilgiri langur and subsequent release in their natural habitats.
6. To educate people about the biological/ecological significance of Nilgiri langurs.
Conclusion:
Conclusively it can be said that Nilgiri langur is a threatened species of primate endemic to the Western Ghats of India. Its population is declining mainly due to poaching and habitat loss. The shrinking population of this primate species is a matter of serious concern and needs attention to conserve the species for the maintenance of biodiversity and ecological balance.
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Dr. Arvind Singh is M. Sc. and Ph. D. in Botany with an area of specialization in Ecology. He is a dedicated Researcher having more than four dozen published Research Papers in the Journals of National and International repute. His main area of Research is Restoration of Mined Lands. However, he has also conducted Research on the Vascular Flora of Banaras Hindu University-Main Campus, India.keywords: nilgiri, langur, nilgiri langur, gray langur, langur monkey, indian langur, nilgiri langur iucn, nilgiri langur information, nilgiri langur habitat, nilgiri langur images, nilgiri langur facts