Silvery lutung

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Silvery lutung [1]
Silvered Leaf Monkey (Trachypithecus cristatus) (8125672881).jpg
At Bako National Park, Sarawak, Malaysia
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Infraorder: Simiiformes
Family: Cercopithecidae
Genus: Trachypithecus
Species group: Trachypithecus cristatus group
Species:
T. cristatus
Binomial name
Trachypithecus cristatus
Raffles, 1821
Silvery Lutung area.png
Silvery lutung range
Synonyms

Presbytis cristata

The silvery lutung (Trachypithecus cristatus), also known as the silvered leaf monkey or the silvery langur, is an Old World monkey. It is arboreal, living in coastal, mangrove, and riverine forests in Peninsular Malaysia, Sumatra, Borneo, Java, and other nearby islands. It is the type species of its species group.

Contents

Description

The silvery lutung is a medium-sized monkey with a long, non-prehensile tail. It has grey-tipped, dark brown or black fur, giving it a uniform silvery appearance. Unlike some related species, there are no paler markings on the face or body, except for a patch of whitish hair on the groin of females. A crest of fur runs along the top of the head, and the hair on the cheeks is long, often obscuring the ears. The hands and feet are hairless, with dark-coloured skin, and have opposable thumbs and toes. [3]

Females range from 46 to 51 centimetres (18 to 20 in) in head-body length, with an average weight of 5.7 kilograms (13 lb) and a tail length of 67 to 75 centimetres (26 to 30 in). Males are slightly larger, from 50 to 58 centimetres (20 to 23 in) in length, with an average weight of 6.6 kilograms (15 lb) and a tail length of 67 to 75 centimetres (26 to 30 in). [4]

Like other langurs, the silvery lutung has a large three-chambered stomach to digest the cellulose found in its herbivorous diet. This allows for fermentation of food, and has some similarities with the stomach of ruminants. The intestine is unusually long, even compared to those of other langurs, and has several pouches along its length, which carry out further fermentation of plant matter. The teeth have grinding ridges and other modifications to allow the more efficient processing of tough leaves. [3]

Distribution and habitat

The silvery lutung is found across Borneo, Sumatra, and Java, as well as in parts of the southwestern Malay Peninsula, the Natuna Islands, and other nearby islands. It inhabits mangrove swamps and nearby forest regions and generally avoids travelling far from coasts or rivers. [2]

Taxonomy

The number and identity of subspecies of the silvery lutung is currently debated. A 2008 analysis confirms the presence of only two subspecies: [5]

The Malay Peninsula form has been subsequently elevated to a separate species, the Selangor silvered langur T. selangorensis [6]

However, some sources distinguish the silvery lutungs of the Natuna Islands as a separate subspecies, T. c. vigilans. [1] [2]

Evolution

Genetic analysis has shown that the silvery lutung probably first evolved during a rapid speciation event that occurred between 0.95 and 1.25 million years ago, during which all the living species of the T. cristatus species group evolved. Because of the relative speed and diversity of this event, the species of the group are difficult to distinguish genetically, and there is some uncertainty as to which represents genuinely distinct species. [5] However, the closest living relative of the silvery lutung may be the Javan lutung, [7] although silvery lutungs have also been reported to produce hybrids with Phayre's leaf monkey, generally considered to belong to a different species group. [3]

Fossils of the species are known from the late Pleistocene onwards and occupy the same geographic range as today. Some of these fossils had significantly larger cheek teeth than living animals, although they have not been assigned to a distinct subspecies. [3]

Hybridization

In Sabah, Malaysia, silvery lutungs have been observed in mixed-species groups with proboscis monkeys, and interspecific mating and a possible hybrid has been observed. [8] The suspected hybrid was first sighted when it was a juvenile near the Kinabatangan River in Malaysian Borneo. [9] Researchers began monitoring the animal and analyzing photos of it as it matured which led to the conclusion it was an extremely rare phenomenon. [9] Researchers say hybridization between closely related species is not unheard of, however, the offspring of two distantly related species is rarely observed in the wild, going on to say this particular hybrid is only the second time intergeneric hybridization (offspring resulting from the matings between different genera) has been recorded in wild primates. [9] Hybrid animals are often infertile, particularly with distantly related species, because it causes malfunctions in the chromosomes. [9]  However, a photo of the animal as an adult showed her holding an infant that she appeared to be nursing. [9] Researchers believe this may be a result of the two species being confined to a small patch of riverine forest due to deforestation to plant oil palm trees, [8] a form of habitat fragmentation, that created a segregated population of both species.

Behaviour and ecology

Silvery lutungs grooming Trachypithecus cristatus at the Bronx Zoo 005.jpg
Silvery lutungs grooming

Silvery lutungs are diurnal, and travel in groups of around 9-40 individuals with one adult male and many adult females communally caring for infants. They rarely leave the trees, which provide them protection from ground-dwelling predators, and rapidly flee if threatened. Each group occupies a home range of 20 to 43 ha (49 to 106 acres), although these may overlap with those of neighbouring groups. During the day, individuals may travel up to 500 m (1,600 ft) through the forest, with some forming all-female subgroups that separate from the group containing the male. The entire group shelters in a single tree at night. [3]

The social structure of silvery lutungs is matrilineal and harem based. Females remain in the group for life, while males leave shortly after reaching adulthood, living in small groups of their own until they can take over an established harem. Within the group, males dominate the females, and females with young dominate those without. However, there is relatively little aggression within the group compared with some related species.

Because group ranges often overlap, different groups frequently come into contact with one another. The adult male protects his group and territory from competing males, communicating his dominance to other males via vocalizations and fighting. In the absence of males, however, females from different groups are more likely to interact peacefully. The most serious conflicts occur when a male intrudes directly on the territory of another male, which may result in the intruder displacing the resident and taking control of the group. In many other primates, such a displacement would normally be followed by the male-killing any infants sired by his predecessor; although this may occur in silvery lutungs, it has not been directly observed and may be less common than in some other species. [3]

Although less vocal than other closely related species, silvery lutungs make at least thirteen different vocalisations, with the most common being used by adult males defending their territory. Other vocalisations express fear, anger, excitement, and satisfaction, in addition to various calls made by infants. [3]

Diet

The silvery lutung is a specialist folivore, including a higher proportion of leaves in its diet than any other colobine monkey. Although it does also eat fruit, and some seeds and flowers, these comprise only 9% of the diet, and it is also able to feed on tougher and more mature leaves than any of its close relatives. [10] Because of these differences, silvery lutungs do not normally live in the same parts of the forest as other monkeys. Where other species are found in the same area, silvery lutungs are more commonly found in the middle canopy of the forest, leaving the higher branches to monkeys with a more frugivorous diet. [3]

Reproduction

Infant silvery lutung, showing orange fur and pale skin Mutslangoer.JPG
Infant silvery lutung, showing orange fur and pale skin

Silvery lutungs breed year round, with no clear breeding season, although each female typically gives birth no more than once every 18 to 24 months. [11] The female attracts the male by making side-to-side motions with her head, and copulation may occur several times during an encounter. Unusually, females have been reported to reach menopause in the wild and may survive up to nine years after giving birth. [3]

The female gives birth to a single young after a gestation period of 181 to 200 days. The young weigh about 400 g (14 oz), measure about 20 cm (7.9 in) and are well developed, with a strong grip for holding onto the mother. Silvery lutungs are born with orange fur and with white hairless skin on the face, hands, and feet. The skin rapidly changes to the dark adult colour, but the fur does not reach the adult pattern for three to five months after birth. The young are cared for by females communally and are not weaned for 18 months, even though the biological mother stops lactating after just 12 months. [12] The young are sexually mature almost as soon as they finish weaning, and, on average, females first give birth at 35 months of age. [13]

Silvery lutungs have lived up to 31 years in captivity. [3]

Predators

Local predators able to feed on silvery lutungs include leopards, tigers, dholes, and some large snakes. Binturongs, and various other small carnivores are probably able to feed on infants. [3]

Diseases

Silvery lutungs are unusually susceptible to human diseases, including AIDS, and have therefore been widely used in medical research. [14]

Conservation

The silvery lutung is classified as Vulnerable on the IUCN Red List and is listed in Appendix II of CITES. [2] Its habitat is heavily threatened throughout its range by logging and the development of oil palm plantations. It is also threatened by hunting for meat and by capture for the pet trade. [15]

Related Research Articles

<span class="mw-page-title-main">Old World monkey</span> Family of mammals

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, red colobus, and macaques. Common names for other Old World monkeys include the talapoin, guenon, colobus, douc, vervet, gelada, mangabey, langur, mandrill, drill, surili (Presbytis), patas, and proboscis monkey.

<span class="mw-page-title-main">Proboscis monkey</span> Primate species

The proboscis monkey or long-nosed monkey is an arboreal Old World monkey with an unusually large nose, a reddish-brown skin color and a long tail. It is endemic to the southeast Asian island of Borneo and is found mostly in mangrove forests and on the coastal areas of the island.

<i>Semnopithecus</i> Genus of Old World monkeys

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 since about 2001 additional species have been recognized. The taxonomy has been in flux, but currently eight species are recognized.

<span class="mw-page-title-main">Red-shanked douc</span> Species of Old World monkey

The red-shanked douc is an arboreal and diurnal Old World monkey belonging to the Colobinae subfamily. They are endemic to Laos, Vietnam, and Cambodia. They are known for their bright colors and exhibit sexual dimorphism through their body size. The species has been declared critically endangered by the International Union for Conservation of Nature, with the main threats being: hunting, habitat loss and pet trade. They are one of three species in the genus Pygathrix, the other two being the black-shanked and gray-shanked doucs.

<span class="mw-page-title-main">Purple-faced langur</span> Species of Old World monkey

The purple-faced langur, also known as the purple-faced leaf monkey, is a species of Old World monkey that is endemic to Sri Lanka. The animal is a long-tailed arboreal species, identified by a mostly brown appearance, dark face and a very shy nature. The species was once highly prevalent, found in suburban Colombo and the "wet zone" villages, but rapid urbanization 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 based on DNA evidence indicating that is it more closely related to the gray langurs.

<span class="mw-page-title-main">Colobinae</span> Subfamily of Old World monkeys

The Colobinae or leaf-eating monkeys are a subfamily of the Old World monkey family that includes 61 species in 11 genera, including the black-and-white colobus, the large-nosed proboscis monkey, and the gray langurs. Some classifications split the colobine monkeys into two tribes, while others split them into three groups. Both classifications put the three African genera Colobus, Piliocolobus, and Procolobus in one group; these genera are distinct in that they have stub thumbs. The various Asian genera are placed into another one or two groups. Analysis of mtDNA confirms the Asian species form two distinct groups, one of langurs and the other of the "odd-nosed" species, but are inconsistent as to the relationships of the gray langurs; some studies suggest that the gray langurs are not closely related to either of these groups, while others place them firmly within the langur group.

<i>Trachypithecus</i> Genus of Old World monkeys

Trachypithecus is a genus of Old World monkeys containing species known as lutungs, langurs, or leaf monkeys. Their range is much of Southeast Asia.

<span class="mw-page-title-main">Gee's golden langur</span> Species of Old World monkey

Gee's golden langur, also known as simply the golden langur, is an Old World monkey found in a small region of Western Assam, India and the neighboring foothills of the Black Mountains of Bhutan. Long considered sacred by many Himalayan people, the golden langur was first brought to the attention of the Western world by the naturalist Edward Pritchard Gee in the 1950s. Adult males have a cream to golden coat with darker flanks while the females and juveniles are lighter. The golden langur has a black face and a long tail up to 100 cm (39 in) in length. It lives in high trees and has a herbivorous diet of fruits, leaves, seeds, buds, and flowers. The average group size is eight individuals, with a ratio of several females to each adult male. It is one of the most endangered primate species of India and Bhutan.

<span class="mw-page-title-main">Nilgiri langur</span> Species of Old World monkey

The Nilgiri langur is an Asian langur of the Old World monkey. It has glossy, black fur and an orangey-golden brown, hair-like mane on its head. Females have a white patch of fur on the inner thigh. It typically lives in troops of nine to ten individuals, with or without offspring, depending on seasonality. Its diet consists of fruits, shoots and leaves. It is listed as vulnerable on the IUCN Red List and is threatened by habitat destruction and poaching for its body parts, thought to supposedly contain aphrodisiac properties.

<span class="mw-page-title-main">East Javan langur</span> Species of Old World monkey

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<span class="mw-page-title-main">Delacour's langur</span> Species of Old World monkey

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<span class="mw-page-title-main">François' langur</span> Species of Old World monkey

François' langur, also known as Francois' leaf monkey, the Tonkin leaf monkey, or the white side-burned black langur is a species of Old World monkey and the type species of its species group. It is one of the least studied of the species belonging to the Colobinae subfamily.

<span class="mw-page-title-main">Phayre's leaf monkey</span> Species of Old World monkey

Phayre's leaf monkey, also known as Phayre's langur, is a species of Old World monkey native to South Asia and Southeast Asia, namely India, Bangladesh, and Myanmar. Populations from further east are now thought to belong to other species. It is listed as Endangered on the IUCN Red List and is threatened by hunting and loss of habitat. The species epithet commemorates Arthur Purves Phayre.

<span class="mw-page-title-main">Raffles' banded langur</span> Species of primate

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<span class="mw-page-title-main">White-thighed surili</span> Species of Old World monkey

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<span class="mw-page-title-main">Dusky leaf monkey</span> Species of Old World monkey

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<span class="mw-page-title-main">Selangor silvered langur</span> Species of Old World monkey

The Selangor silvered langur is a species of leaf monkey found on the west coast of Peninsular Malaysia. It had been previously considered a form of silvery lutung. Roos and colleagues elevated this population to a subspecies level, Trachypithecus cristatus selangorensis, in 2008. It has since come to be regarded by primatologists as a separate species, Trachypithecus selangorensis.

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References

  1. 1 2 Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Baltimore: Johns Hopkins University Press. p. 176. ISBN   0-801-88221-4. OCLC   62265494.
  2. 1 2 3 4 Meijaard, E. & Nijman, V. (2020). "Trachypithecus cristatus". IUCN Red List of Threatened Species . 2020: e.T22035A17959977. doi: 10.2305/IUCN.UK.2020-2.RLTS.T22035A17959977.en . Retrieved 19 November 2021.
  3. 1 2 3 4 5 6 7 8 9 10 11 Harding, L.E. (2010). "Trachypithecus cristatus (Primates: Cercopithecidae)". Mammalian Species. 42 (1): 149–165. doi: 10.1644/862.1 .
  4. ↑ Napier, P.H. (1985). Catalogue of Primates in the British Museum (Natural History) and elsewhere in the British Isles. Part III: family Cercopithecidae, subfamily Colobinae. London: British Museum (Natural History).
  5. 1 2 Roos, C.; Nadler, T.; Walter, L. (2008). "Mitochondrial phylogeny, taxonomy and biogeography of the silvered langur species group (Trachypithecus cristatus)". Molecular Phylogenetics and Evolution. 47 (2): 629–636. Bibcode:2008MolPE..47..629R. doi:10.1016/j.ympev.2008.03.006. PMID   18406631.
  6. ↑ Roos, C.; Boonratana, R.; Supriatna, J.; Fellowes, J.R.; Groves, C.P.; Nash, S.D.; Rylands, A.B.; Mittermeier, R.A. (2014). "An updated taxonomy and conservation status review of Asian primates" (PDF). Asian Primates Journal. 4 (1): 2−38.
  7. ↑ Rosenblum, L.L.; et al. (1997). "High mitochondrial DNA diversity with little structure within and among leaf monkey populations (Trachypithecus cristatus and Trachypithecus auratus)". International Journal of Primatology. 18 (6): 1005–1028. doi:10.1023/A:1026304415648. S2CID   19214458.
  8. 1 2 Lhota, S.; Yap, J.L.; Benedict, M.L.; Ching, K. (2022). "Is Malaysia's "mystery monkey" a hybrid between Nasalis larvatus and Trachypithecus cristatus? An assessment of photographs". International Journal of Primatology. 43 (3): 513–532. doi:10.1007/s10764-022-00293-z. PMC   9039274 . PMID   35498121.
  9. 1 2 3 4 5 Reporter, Robyn White Nature (2022-05-05). "Hybrid 'Mystery Monkey' Discovered in Borneo". Newsweek. Retrieved 2024-01-27.
  10. ↑ Caton, J.M. (1999). "Digestive strategy of the Asian colobine genus Trachypithecus". Primates. 40 (2): 311–325. doi:10.1007/bf02557555. S2CID   19986844.
  11. ↑ Medway, L. (1970). "Breeding of the silvered leaf monkey, Presbytis cristata, in Malaya". Journal of Mammalogy. 51 (3): 630–632. doi:10.2307/1378413. JSTOR   1378413.
  12. ↑ Shelmidine, N.; et al. (2009). "Patterns of reproduction in Malayan silvered leaf monkeys at the Bronx Zoo". American Journal of Primatology. 71 (10): 852–859. doi:10.1002/ajp.20712. PMID   19472173. S2CID   7671570.
  13. ↑ Shelmidine, N.; et al. (2007). "Genital swellings in silvered langurs: what do they indicate?". American Journal of Primatology. 69 (5): 519–532. doi:10.1002/ajp.20359. PMID   17154387. S2CID   34267698.
  14. ↑ Lo, S-C.; et al. (1989). "Fatal infection of silvered leaf monkeys with a virus-like infectious agent (VLIA) derived from a patient with AIDS". American Journal of Tropical Medicine and Hygiene. 40 (4): 399–409. doi:10.4269/ajtmh.1989.40.399. PMID   2712198.
  15. ↑ Corlett, R.T. (2007). "The impact of hunting on the mammalian fauna of tropical Asian forests". Biotropica. 39 (3): 292–303. Bibcode:2007Biotr..39..292C. doi:10.1111/j.1744-7429.2007.00271.x. S2CID   85988264.
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