Semnopithecus

Gray langurs, also called Hanuman langurs and Hanuman monkeys, are Old World monkeys native to the Indian subcontinent constituting the genus ''Semnopithecus''. Traditionally only one species ''Semnopithecus entellus'' was recognized, but since about 2001, additional species have been recognized. The taxonomy has been in flux, but currently eight species are recognized.

Gray langurs are fairly terrestrial, inhabiting forest, open lightly wooded habitats, and urban areas on the Indian subcontinent. Most species are found at low to moderate altitudes, but the Nepal gray langur and Kashmir gray langur occur up to in the Himalayas.

Characteristics

These langurs are largely gray (some more yellowish), with a black face and ears. Externally, the various species mainly differ in the darkness of the hands and feet, the overall color and the presence or absence of a crest. Typically all north Indian gray langurs have their tail tips looping towards their head during a casual walk whereas all south Indian and Sri Lankan gray langurs have an inverted "U" shape or a "S" tail carriage pattern. There are also significant variations in the size depending on the sex, with the male always larger than the female. The head-and-body length is from . Their tails, at are always longer than their bodies. Langurs from the southern part of their range are smaller than those from the north. At , the heaviest langur ever recorded was a male Nepal gray langur. The larger gray langurs are rivals for the largest species of monkey found in Asia. The average weight of gray langurs is in the males and in the females.

Langurs mostly walk quadrupedally and spend half of their time on the ground and the other half in trees. They will also make bipedal hops, climbing and descending supports with the body upright, and leaps. Langurs can leap horizontally and in descending.

Taxonomy

Traditionally, only ''Semnopithecus entellus'' was recognized as a species, the remainder all being treated as subspecies. In 2001, it was proposed that seven species should be recognized. This was followed in ''Mammal Species of the World'' in 2005, though several of the seven species intergrade, and alternative treatments exist where only two species (a northern and a southern) are recognized. Phylogenetic evidence supports at least three species: a north Indian, a south Indian and a Sri Lankan one.

It has been suggested that the '' Semnopithecus priam thersites'' is worthy of treatment as a species rather than a subspecies, but at present this is based on limited evidence. During a study based on external morphology and ecological niche modelling in Peninsular India six main types were found, but continued to label all as subspecies. Coat color is highly variable, possible due to phenotypic plasticity and therefore of questionable value in species delimitation.

It has been suggested that ''Trachypithecus'' should be considered only a subgenus of ''Semnopithecus''. If maintaining the two as separate monophyletic genera, the purple-faced langur and Nilgiri langur belong in ''Semnopithecus'' instead of their former genus ''Trachypithecus''. At present it is unclear where the ''T. pileatus'' species group (consisting of the capped langur, Shortridge's langur and Gee's golden langur) belongs, as available mtDNA data place it in ''Semnopithecus'', while Y chromosome data place it in ''Trachypithecus''. A possible explanation for this is that the ''T. pileatus'' species group is the result of fairly recent hybridization between ''Semnopithecus'' and ''Trachypithecus''.

As of 2005, the authors of ''Mammal Species of the World'' recognized the following seven ''Semnopithecus'' species
* Nepal gray langur ''Semnopithecus schistaceus''
* Kashmir gray langur ''Semnopithecus ajax''
* Tarai gray langur ''Semnopithecus hector''
* Northern plains gray langur ''Semnopithecus entellus''
* Black-footed gray langur ''Semnopithecus hypoleucos''
* Southern plains gray langur ''Semnopithecus dussumieri''
* Tufted gray langur ''Semnopithecus priam''

Results of analysis of mitochondrial cytochrome b gene and two nuclear DNA-encoded genes of several colobine species revealed that Nilgiri and purple-faced langurs cluster with gray langur, while ''Trachypithecus'' species form a distinct clade.
Since then, two other species have been moved from ''Trachypithecus'' to ''Semnopithecus'':
* Purple-faced langur ''Semnopithecus vetulus''
* Nilgiri langur ''Semnopithecus johnii''

In addition, ''Semnopithecus dussumieri'' has been determined to be invalid. Most of the range that had been considered ''S. dussumieri'' is now considered ''S. entellus''.

Thus the current generally accepted species within the genus ''Semnopithecus'' are:
* Northern plains gray langur (also known as the Hanuman langur or Bengal gray langur) ''Semnopithecus entellus''
* Kashmir gray langur ''Semnopithecus ajax''
* Tarai gray langur ''Semnopithecus hector''
* Black-footed gray langur ''Semnopithecus hypoleucos''
* Tufted gray langur ''Semnopithecus priam''
* Nepal gray langur ''Semnopithecus schistaceus''
* Purple-faced langur ''Semnopithecus vetulus''
* Nilgiri langur ''Semnopithecus johnii''

A 2013 genetic study indicated that while ''S. entellus'', ''S. hypoleucos'', ''S. priam'' and ''S. johnii'' are all valid taxa, there has been hybridization between ''S. priam'' and ''S. johnii''.
It also indicated that there has been some hybridization between ''S. entellus'' and ''S. hypoleucos'' where their ranges overlap, and a small amount of hybridization between ''S. hypoleucos'' and ''S. priam''. It also suggested that ''S. priam'' and ''S. johnii'' diverged from each other fairly recently.

Distribution and habitat

The entire distribution of all gray langur species stretches from the Himalayas in the north to Sri Lanka in the south, and from Bangladesh in the east to Pakistan in the west. They possibly occur in Afghanistan. The bulk of the gray langur distribution is within India, and all seven currently recognized species have at least a part of their range in this country.

Gray langurs can adapt to a variety of habitats. They inhabit arid habitats like deserts, tropical habitats like tropical rainforests and temperate habitats like coniferous forests, deciduous habitats and mountains habitats. They are found at sea level to altitudes up to . They can adapt well to human settlements, and are found in villages, towns and areas with housing or agriculture. They live in densely populated cities like Jodhpur, which has a population numbering up to a million.

Ecology and behavior

Gray langurs are diurnal. They sleep during the night in trees but also on man-made structures like towers and electric poles when in human settlements. When resting in trees, they generally prefer the highest branches.

Ungulates like bovine and deer will eat food dropped by foraging langurs. Langurs are preyed upon by leopards, dholes and tigers. Wolves, jackals, Asian black bears and pythons may also prey on langurs.

Diet

Gray langurs are primarily herbivores. However, unlike some other colobines they do not depend on leaves and leaf buds of herbs, but will also eat coniferous needles and cones, fruits and fruit buds, evergreen petioles, shoots and roots, seeds, grass, bamboo, fern rhizomes, mosses, and lichen

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