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Phayre's leaf monkey (''Trachypithecus phayrei''), also known as Phayre's langur, is a species of Old World monkey native to
South Asia South Asia is the southern Subregion#Asia, subregion of Asia that is defined in both geographical and Ethnicity, ethnic-Culture, cultural terms. South Asia, with a population of 2.04 billion, contains a quarter (25%) of the world's populatio ...
and
Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...
, namely
India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
,
Bangladesh Bangladesh, officially the People's Republic of Bangladesh, is a country in South Asia. It is the List of countries and dependencies by population, eighth-most populous country in the world and among the List of countries and dependencies by ...
, and
Myanmar Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...
. Populations from further east are now thought to belong to other species. It is listed as
Endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...
on the
IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological ...
and is threatened by hunting and loss of habitat. The species epithet commemorates Arthur Purves Phayre.


Taxonomy

The
scientific name In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...
''Presbytis phayrei'' was used by
Edward Blyth Edward Blyth (23 December 1810 – 27 December 1873) was an English zoologist who worked for most of his life in India as a curator of zoology at the Asiatic Society, Royal Asiatic Society of Bengal in Calcutta. He set about updating the museum ...
in 1847 for two young individuals captured alive in the Arakan Mountains in Myanmar. Phayre's langur is one of the most widespread members of the genus, but its actual distribution and intraspecific taxonomy remain controversial. Previously, three subspecies were recognized, namely ''T. p. crepusculus'', ''T. p. phayrei'' and ''T. p. shanicus''. Three separate species ''T. phayrei'', ''T. melamera'' (formerly ''T. p. shanicus''), and '' T. popa sp. nov.'' have been proposed based on mitochondrial genomes. Currently, the name Phayre's leaf monkey refers to ''T. phayrei,'' residing in forests of East Bengal, Northeast India and western Myanmar, specifically, areas to the west of the Chindwin and
Irrawaddy River The Irrawaddy River (, , Ayeyarwady) is the principal river of Myanmar, running through the centre of the country. Myanmar’s most important commercial waterway, it is about 1,350 miles (2,170 km) long. Originating from the confluence of the ...
s.


Characteristics

Phayre's langur is characterized by white coloration around the ventral, mouth, and eye area. The broad ring-shaped patches around the eyes resemble spectacles, contributing to the local name of “''Chasma bandor''” in Bengali, or spectacled monkey. The white fur is especially contrasting with the overall deep bluish-brown fur all over its body with darker shades at the head, below the elbows, and at the end of the tail. There is a presence of a sagittal crest on the heads of both adult males and females, giving it a triangular shape. The infants have a straw-colored natal coat, making it easily distinguishable in a group. The average head-body length ranges from in males and in females. The tail is usually longer than its body, with an average of for males and , for females. In comparison to ''T. melamera'' and ''T. popa'', it has a shorter tail length. The average mass of Phayre's langur is observed to be around for males and for females. In field studies males and females are differentiated through the shape of the patches around the eyes. Female have cone-shaped white patches bending in towards the nose while males have a rounder shape. This shape difference causes a slightly wider gap in males than in females. Like most Old World monkeys, it has the dental formula of Distinctive to other colobines Phayre's langur show craniodental adaptations such as medially positioned rows of teeth and stronger masseter pterygoid muscles for seed-eating.


Distribution and habitat

Pharye's langur is found in
tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...
,
deciduous In the fields of horticulture and botany, the term deciduous () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed Leaf, leaves, usually in the autumn; to the shedding of petals, aft ...
, and
evergreen In botany, an evergreen is a plant which has Leaf, foliage that remains green and functional throughout the year. This contrasts with deciduous plants, which lose their foliage completely during the winter or dry season. Consisting of many diffe ...
forests of North-East India, Eastern Bangladesh, and Western Myanmar. It can also be seen residing in secondary forests such as bamboo clusters and rubber plantations. Tree species with large canopies like '' Artocarpus chama'', '' Artocarpus lacucha'', '' Ficus racemosa'', ''Trophis aspera'', '' Mangifera indica'', and ''Grewia nervosa'', in Bangladesh, are used for resting in their shade. In India, the most common roosting trees range from heights of and have an extensive canopy, e.g., '' Ficus hispida'' and '' Triadica sebifera'' in Mizoram. Currently, a total of 1200 individual langurs have been recorded in India and 376 individuals in Bangladesh, 288 of which resided in the northeastern forests of Bangladesh.


Behavior and ecology


Group structure

The Phayre's langur usually forms multi-male and multi-female with a presence of a dominant male alpha in the group. All-male groups, one-male groups, and one-female groups have also been observed, though less common. A high level of territoriality is seen within the species and between groups. The groups tend to maintain occupancy in their
home range A home range is the area in which an animal lives and moves on a periodic basis. It is related to the concept of an animal's territory which is the area that is actively defended. The concept of a home range was introduced by W. H. Burt in 1943. ...
, showing
philopatry Philopatry is the tendency of an organism to stay in or habitually return to a particular area. The causes of philopatry are numerous, but natal philopatry, where animals return to their birthplace to breed, may be the most common. The term derives ...
. Foraging is done by maintaining groups throughout different ranges. While foraging, groups tend to avoid ranging areas of neighboring groups suggesting the formation of borders between them, agonistic interactions are observed in places of overlapping borders. Female dispersal is also observed between the groups, females that leave the group tend to obtain alpha rank in the new group. Linear dominance is seen in females, where rank has a linear relationship with age. Males on reaching maturation show some dispersal, they either form new multi-male groups or return to their natal group. For males, age and rank dominance also show a linear relationship though, the ranks can change depending on the resource-holding potential, which is shown to decrease in aging monkeys.


Reproduction

Female Phayre's langurs are pregnant by an average age of 5.3 years with an average gestation period of 205 days. The females show promiscuous behavior, studies do show a preference for more experienced males, usually of higher dominance. Polygynous relationships are common, where males offer protection to copulated females. Females usually nurse their infants on average 22 months with weaning at around 19–21 months. The natal coat starts to become darker 26 weeks after birth.


Communication

Vocalization is observed in both males and females. Based on observations in the wild, a loud “kah-kah-kah” is used to sound alarm in the troop, while in the presence of a predator a softer “whoo” call is used. The dominant male alpha uses the “cheng-kong” sound to assemble the group. Additionally, vocalization essential is for maintaining contact with troop members while foraging. In agonistic interactions, barking sounds such as “ngre-go, ngre-go” are used to maintain their group's territory.


Activity budget

The Phayre's Leaf Monkey is diurnal and arboreal. The average life span of it being 20–30 years, in the wild, and an average of 28.3 in captivity. A study conducted in the Satchari National Park, Bangladesh, found on average the Phayre's leaf Monkey spends, most of its time foraging and feeding (40.7%), the rest is spent traveling (31.8%), resting (18.3%), grooming (7.8%) and playing (1.4%). It is seen that males and juveniles tend to spend more time moving than adult females, who also have the highest percentage of resting among them. It is noticed that the activity patterns have variations based on habitats, seasons, and food availability, for example, food shortages lead to increased travel time. The variation in caloric content of different foods have shown to affect the energy budgets, i.e., poor quality food leads to higher feeding distribution to maintain the caloric requirements.


Diet

The Phayre's leaf monkey is a folivore. It feeds on leaves, shoots, seeds, flowers, gum, and fleshy parts of fruits. The diet varies between seasons and different regions, showing adaptation to the local flora. In Dampa Tiger Reserve, the Phayre's langurs feeds on '' Citrus grandis'', '' Gmelina arborea'', '' Ficus maclellendii'', ''Buetneria pilosa'', with a preference towards bamboos such as ''
Musa ornata ''Musa ornata'', the flowering banana, is one of more than 50 species of banana in the genus ''Musa (genus), Musa'' of the family (biology), family Musaceae. Most of these species are large tropical evergreen perennial plant, perennials, mainly f ...
'', '' Melocanna baccifera'' and '' Dendrocalamus longispathus'' during summer. Plant parts with less fiber and high proteins and sugars such as young leaves are usually preferred while foraging. In Satchari National Park in Bangladesh, they feed primarily on '' Ficus hispida'', '' Albizia chinensis'', and ''
Vachellia nilotica ''Vachellia nilotica'', more commonly known as ''Acacia nilotica'', and by the vernacular names of gum arabic tree, babul, thorn mimosa, Egyptian acacia or thorny acacia, is a flowering plant, flowering tree in the family Fabaceae. It is native t ...
''. The high bamboo consumption in their diets is attributed to the abundance of this plant in North-East India because of its invasive nature. Phayre's langurs living in local rubber plantations in Mizoram majorly consume leaves of '' Hevea brasiliensis'' showing that diet is affected by the plant diversity in its home range. In Tripura, India, it mainly feeds on leaves of '' Albizia procera'', '' Albizzia lebbek'' and ''A. stipulata'', '' Melocanna bambusoides'', '' Macaranga denticulata'', '' Callicarpa arborea'', '' Dillenia pentagyna'', '' Litsea'' sp., ''
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 ...
'', '' Gmelina arborea'', '' Artocarpus chaplasha'', '' Syzygium fruticosum'', '' Ficus racemosa'', '' Ficus hispida'', '' Ficus indica'' and ''F. fistulosa''.


Conservation

The
IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological ...
has deemed the population of Phayre's langur to be decreasing. The recent reclassification of Phayre's langur has led to the underestimation of the status of the decline in the species' population. It is also listed in the CITES Appendix II, to protect its illegal
poaching Poaching is the illegal hunting or capturing of wild animals, usually associated with land use rights. Poaching was once performed by impoverished peasants for subsistence purposes and to supplement meager diets. It was set against the huntin ...
and trading locally. The major threats to Phayre's langur are
habitat destruction Habitat destruction (also termed habitat loss or habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved elsewhere, or are dead, leading to a decrease ...
, fragmentation, logging, roadkill,
ecotourism Ecotourism is a form of nature-oriented tourism intended to contribute to the Ecological conservation, conservation of the natural environment, generally defined as being minimally impactful, and including providing both contributions to conserv ...
, electrocution and hunting. In India, organizations like the Wildlife Trust of India have employed wildlife staff trained in anti-poaching tactics to work in forests, and locals have also been involved. In both India and Bangladesh, Pharye's langur is protected through national and local legislation and through implementation of international conservation laws and policies, i.e., the Wild Life (Protection) Act, 1972, in India and Wildlife (Conservation and Security) Act, 2012, in Bangladesh . The ‘'' jhooming''‘, a form of shifting cultivation practiced by tribes in India, led to concerns over reducing forestland for the Phayre's langur population, but a study showed that they adapted to the local practice. The regenerating secondary forests through ‘''jhooming''‘ provide a habitat for the langurs when primary forests are unsuitable to stay in due to anthropogenic factors.


References


External links


Image at ADW
{{Taxonbar, from=Q692268 Phayre's leaf monkey Primates of Southeast Asia Mammals of Bangladesh Mammals of Myanmar Mammals of India Endangered fauna of Asia Phayre's leaf monkey Phayre's leaf monkey Symbols of Tripura Endangered Fauna of China