Purple-faced Langur
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The purple-faced langur (''Semnopithecus vetulus''), also known as the purple-faced leaf monkey, is a
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of
Old World monkey Old World monkeys are primates in the family Cercopithecidae (). Twenty-four genera and 138 species are recognized, making it the largest primate family. Old World monkey genera include baboons (genus '' Papio''), red colobus (genus '' Piliocolob ...
that is
endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
to
Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...
. The animal is a long-tailed
arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally (scansorial), but others are exclusively arboreal. The hab ...
species, identified by a mostly brown appearance, dark face (with paler lower face) and a very shy nature. The species was once highly prevalent, found in suburban
Colombo Colombo, ( ; , ; , ), is the executive and judicial capital and largest city of Sri Lanka by population. The Colombo metropolitan area is estimated to have a population of 5.6 million, and 752,993 within the municipal limits. It is the ...
and the "wet zone" villages (areas with high temperatures and high humidity throughout the year, whilst rain deluges occur during the monsoon seasons), but rapid
urbanization Urbanization (or urbanisation in British English) is the population shift from Rural area, rural to urban areas, the corresponding decrease in the proportion of people living in rural areas, and the ways in which societies adapt to this change. ...
has led to a significant decrease in the population level of the monkeys. It had traditionally been classified within the genus '' Trachypithecus'' but was moved to the genus ''
Semnopithecus ''Semnopithecus'' is a genus of Old World monkeys native to the Indian subcontinent, with all species with the exception of two being commonly known as gray langurs. Traditionally only the species ''Semnopithecus entellus'' was recognized, but si ...
'' based on DNA evidence indicating that is it more closely related to the
gray langur ''Semnopithecus'' is a genus of Old World monkeys native to the Indian subcontinent, with all species with the exception of two being commonly known as gray langurs. Traditionally only the species ''Semnopithecus entellus'' was recognized, but si ...
s. In Sinhala, it is known as ශ්‍රී ලංකා කළු වඳුරා ʌlu vʌⁿðura(Sri Lanka black monkey).


Description

In the purple-faced langur, males are usually larger than females. Males measure in head-body length with a tail of . Females possess a head-body length and tail length of . The pelage may generally vary from blackish to grayish. The species tends to have whitish to gray short 'trousers' rounded off by purplish-black faces with white sideburns. Part of the back is covered with whitish fur, and tail is also furred with black and white mixed colors. The feet and hands are also purplish-black in color. Size varies among the subspecies. Typically adults will weigh somewhere between , averaging about .Vandercone, R. (2011). ''Dietary Shifts, Niche Relationships and Interspecific Competition in Sympatric Grey Langur (Semnopithecus entellus) and Purple-faced Langur (Trachypithecus vetulus) in Sri Lanka''. PhD Thesis, Department of Anthropology; University of Washington. The smallest subspecies (''S. v. nestor'') commonly weighs between . Average weight from other subspecies has been recorded up to in females and in males with some exceptionally big langurs weighing up to perhaps . Among the primates that live in Sri Lanka, it is somewhat smaller than the
tufted gray langur The tufted gray langur (''Semnopithecus priam''), also known as Madras gray langur, and Coromandel sacred langur, is an Old World monkey, one of the species of langurs. This, like other gray langurs, is mainly a leaf-eating monkey. It is found i ...
despite leading males of the group of purple-faced langurs often being larger than the tufted gray langur that lived together in the habitats. In the subspecies known as the "bear monkey" (''S. v. monitcola'') usually has a darker coat and usually sports a heavy mustache. In this species, the hair of crown directed backwards throughout, not radiating. it lacks the crest of tufted gray langurs and has hair on the crown no longer than on temples and nape. Purple-faced langurs have a rump that is pure white or whitish gray. Purple-faced langur (Semnopithecus vetulus vetulus) head.jpg, ''S.v.vetulus'' Purple faced langur.jpg, ''S.v.nestor'' Weissbartlangur.jpg, ''S.v.monticola'' Semnopithèque blanchâtre mâle.JPG, ''S. v. philbricki''


Subspecies

According to the Mammals of Sri Lanka, the 4 subspecies are recognized as follows. * Southern lowland wetzone purple-faced langur, ''Semnopithecus vetulus vetulus'' – "Color varies greatly. Black upper torso, light brown cap, well defined silvery rump patch that extends to legs. Prominent white whiskers. Tail is also white colored. Many white morphs are observed in this subspecies. They can be all-white to partly white leucistic." * Western purple-faced langur or north lowland wetzone purple-faced langur, ''Semnopithecus vetulus nestor'' – "It is the smallest of all subspecies. Upper torso dark grayish brown with light grayish brown rump patch, darker grayish brown legs and white cap." * Dryzone purple-faced langur, ''Semnopithecus vetulus philbricki'' – "Largest subspecies. Grayish brown torso, ill-defined grayish rump patch, dark cap. Prominent white cheeks with tufts. Exceptionally long slimy tail." * Montane purple-faced langur or Bear Monkey, ''Semnopithecus vetulus monticola'' – "Dark gray brown coat. Large but ill-defined grayish rump patch. Prominent white cheek tufts, light brownish gray cap. Fur long and shaggy due to habitat they live is cold." All four recognizable subspecies exhibit different cranial and pelage characteristics, as well as body size. The western purple-faced langur is one of the 25 most endangered primates in the world. Most groups of langurs contain only one adult male. A possible subspecies called ''Semnopithecus vetulus harti'' is recognized, but not yet given validity. This subspecies is known from some skins found from
Jaffna Jaffna (, ; , ) is the capital city of the Northern Province, Sri Lanka, Northern Province of Sri Lanka. It is the administrative headquarters of the Jaffna District located on a Jaffna Peninsula, peninsula of the same name. With a population o ...
peninsula and north of the Vavuniya. Uniquely, this subspecies has yellowish golden hair on its scalp and a golden sheen to its fur. Other than these differences, anatomy and all the other aspects are similar to the ''Semnopithecus vetulus philbricki''. Although traditionally classified within the genus '' Trachypithecus'' based on morphological similarities,
DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
and vocal evidence suggests that the purple-faced langur actually is more closely related to the
gray langur ''Semnopithecus'' is a genus of Old World monkeys native to the Indian subcontinent, with all species with the exception of two being commonly known as gray langurs. Traditionally only the species ''Semnopithecus entellus'' was recognized, but si ...
s of the genus ''Semnopithecus''.


Habitat and status

The purple-faced langur is found in closed canopy forests in Sri Lanka's mountains and the southwestern part of the country, known as the "wet zone". Only 19% of Sri Lanka consists of forested areas. This habitat has decreased from 80% in 1980 to ~25% in 2001. Currently, this range has decreased to below 3%. The range consists of the most densely populated lowland rainforest areas of Sri Lanka. Deforestation has resulted in the langurs home ranges to be exposed to direct sunlight. Purple-faced langurs are most often found in small and widely scattered groups. Ninety percent of the langurs range, now consists of human populated areas. Populations are critically low within and between sites. Threats to this species include infringement on range by croplands, grazing, changing agriculture, road production, soil loss/erosion and deforestation, poisoning from prevention of crop raiding, and hunting for medicine and food. Its range has constricted greatly in the face of human encroachment, although it can still be seen in Sinharaja, Kitulgala, Kandalama,
Mihintale Mihintale is a mountain peak near Anuradhapura in Sri Lanka. It is believed by Sri Lankans to be the site of a meeting between the Buddhist monk Mahinda (buddhist monk), Mahinda and King Devanampiyatissa which inaugurated the presence of Buddhis ...
, in the mountains at Horton Plains National Park or in the rainforest near the city of
Galle Galle (, ; , ) (formerly ) is a major city on the southwestern tip of Sri Lanka, south of Colombo. Galle is the provincial capital and largest city of Southern Province, Sri Lanka and is the capital of Galle District. Galle was known as ''Gi ...
.


Behaviour and ecology


Diet

The purple-faced langur is mostly folivorous, but will also feed on fruits, flowers, and seeds. While they normally avoid human habitations, fruit such as jak ('' Artocarpus heterophyllus''), rambutan ('' Nephelium lappaceum''), banana (''
Musa balbisiana ''Musa balbisiana'', also known simply as plantain, is a wild-type species of banana. It is one of the ancestors of modern cultivated bananas, along with '' Musa acuminata''. Description It grows lush leaves in clumps with a more upright habit ...
''), and mango (''
Mangifera indica ''Mangifera indica'', commonly known as mango, is an evergreen species of flowering plant in the family Anacardiaceae. It is a large fruit tree, capable of growing to a height and width of . There are two distinct genetic populations in modern m ...
'') may contribute up to 50% to their diet in cultivated areas. In the wild, food such as the fruits of '' Dimocarpus longan'' and '' Drypetes sepiaria'' are taken. Purple-faced langur digestion is adapted to derive the majority of required nutrients and energy from complex carbohydrates found in leaves, with the help of specialized stomach bacteria. Where the species' diet is currently heavily dependent cultivated fruits, the ability to derive sufficient nutrition may become impaired. Seasonal availability of fruit may serve to increase this effect. ''Semnopithecus vetulus'' feed on a less diverse diet than ''S. priam'', with a greater proportion of leaves. Food plants that have been identified include '' Holoptelea integrifolia'', '' Hydnocarpus venenata'', ''
Macaranga peltata ''Macaranga peltata'' is a plant found in northern Thailand, Sri Lanka and India. It is one of the most widely occurring early successional woody species in Sri Lanka, specially in low country wet zone. Some of the many common names include kenda ...
'', '' Manilkara hexandra'', ''
Mikania scandens ''Mikania scandens'' is a species of flowering plant in the family Asteraceae. Its common names include climbing hempvine, climbing hempweed, and louse-plaster. It is native to the eastern and central United States, with its distribution extendin ...
'', ''
Mischodon ''Mischodon'' is a genus in the family (biology), family Picrodendraceae, described in 1854. The only known species is ''Mischodon zeylanicus'', a tree native to southern India, Sri Lanka, and the Andaman Islands.Balakrishnan, N.P. & Chakrabarty, ...
zeylanica'', '' Pterospermum suberifolium'', ''
Tetrameles nudiflora ''Tetrameles'' is a genus of flowering plants in the family Tetramelaceae with one species, ''Tetrameles nudiflora''. It grows as a large deciduous tree and is found across southern Asia from India through southeast Asia, Malesia, and into northe ...
'', '' Vitex altissima'', and '' Wrightia angustifolia''. The purple-faced langur was found to be dominated by tufted gray langurs in mixed feeding groups.


Communication

Loud calls are often used to distinguish between individual purple-faced langurs. The elements of a call fall into three categories: harsh barks, whoops, and residuals. Individuals can be differentiated by the number of phrases and residuals within a call. Calls occur more often in the morning mostly stimulated by neighboring groups and territorial battles. More calls occur during sunny periods than cloudy. The fewest calls occur in the evening. Daytime calls usually aid in the defense of home ranges. The loud barking call, particularly of the highland form, can be mistaken for the roar of a predator such as a
leopard The leopard (''Panthera pardus'') is one of the five extant cat species in the genus ''Panthera''. It has a pale yellowish to dark golden fur with dark spots grouped in rosettes. Its body is slender and muscular reaching a length of with a ...
. Calls of the purple-faced langur differ from those of any of the subspecies. Environmental characters impact call times as well as anthropogenic disturbance. Vocalization can be used to alert members of predators, attract mates, defend territory, and locate group members. Vocalization is extremely important for the use in conservation especially because they are very difficult to observe directly. Adult males are the most vocal among the entire group. Defensive whooping calls are also accompanied by intense visual and locomotive displays. Vocalizations are also helpful in determining taxonomic identification. Based on alarm calls issued in response to these and known predators of the similar tufted gray langur, the main potential predators of this species are likely to be
leopard The leopard (''Panthera pardus'') is one of the five extant cat species in the genus ''Panthera''. It has a pale yellowish to dark golden fur with dark spots grouped in rosettes. Its body is slender and muscular reaching a length of with a ...
s followed infrequently perhaps by Indian pythons and mugger crocodile. For young or infirm langurs, black eagles, spot-bellied eagle-owls and possibly other larger birds of prey are perhaps not infrequently a threat.
Monitor lizard Monitor lizards are lizards in the genus ''Varanus,'' the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and West African Nile monitor, one species is also found in south America as an invasive species. A ...
s may also feed on purple-faced langurs (possibly through
scavenging Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding be ...
or picking off the young or sickly).Hart, D. L. (2000). ''Primates as prey: Ecological, morphological and behavioral relationships between primate species and their predators''. Washington University in St. Louis.


Conservation

Some conservation strategies consist of improving management of the already protected areas as well as locate and protect new areas and corridors within ranges. Efforts to help increase populations may help survival. It would be beneficial to lower human-langur conflicts. Rope bridges could be established for langurs to move between ranges safely, which may decrease the crossing of power lines and roads. Replanting
pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as cu ...
plantations with native species exploited by these langurs, could possibly increase its preferred habitat as well. Public education of conservation to the local people emphasizing compassion and kindness as well as explaining the importance and necessity of these mammals to the ecosystems overall biodiversity.


References


External links

* * *ARKive
images and movies of the purple-faced langur ''(Trachypithecus vetulus)''

Video of Purple-faced leaf langur Monkey roaming in Buddhist Hermitage
{{Taxonbar, from1=Q518364, from2=Q101500289 Semnopithecus Endemic fauna of Sri Lanka Mammals of Sri Lanka Endangered fauna of Asia Mammals described in 1777 Taxa named by Johann Christian Polycarp Erxleben