Raffles' banded langur[1]
Presbytis femoralis in Singapore
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Infraorder: Simiiformes
Family: Cercopithecidae
Genus: Presbytis
Species:
P. femoralis
Binomial name
Presbytis femoralis
(Martin, 1838)
Raffles' banded langur range in Singapore and Johor, Malaysia

The Raffles' banded langur (Presbytis femoralis), also known as the banded leaf monkey or banded surili, is a species of primate in the family Cercopithecidae. It is endemic to Singapore and southern Peninsular Malaysia.[2] The species underwent taxonomic revisions in 2019 and 2020, in which two former subspecies were elevated to separate species. As a result, the Raffles' banded langur meets the criteria for being listed as critically endangered by the IUCN. It is mainly threatened by habitat loss.[2]

Taxonomy

The taxonomy of Presbytis femoralis underwent several changes. Up until 2019, three subspecies of P. femoralis were recognized: P. f. femoralis (nominate), P. f. percura (the East Sumatran banded langur), and P. f. robinsoni (Robinson's banded langur).[1] Presbytis f. femoralis lives in Singapore, and in the states of Johor and Pahang of southern Peninsular Malaysia, P. f. robinsoni lives in the northern Malay Peninsula, including southern Myanmar and Thailand, and P. f. percura lives in east-central Sumatra.[2][3]

Genetic data suggested that at least P. f. femoralis and P. f. robinsoni were different species[4] which was also in agreement with their morphological characters. However, resolving all subspecies-level boundaries within banded langurs required data for P. f. percura, which was the least studied among them.[5] Most recently, mitochondrial genomes were obtained for P. f. percura, and based on multiple species delimitation algorithms (PTP, ABGD, Objective Clustering) applied to a dataset covering 39 species and 43 subspecies of Asian colobines, all three subspecies of banded langurs were resurrected to species.[6][7][8]

William Charles Linnaeus Martin formally described P. femoralis based on material that had been collected by Sir Stamford Raffles in Singapore.[9] Martin had given the distribution as "Sumatra etc.", not mentioning Singapore explicitly, resulting in some confusion over the actual type locality.[9][10] Gerrit Smith Miller Jr. resolved the issue in 1934, determining that Singapore was the actual type locality.[9][10]

Description

The Raffles' banded langur is 43.2 to 61.0 centimetres (17.0 to 24.0 in) long, excluding the tail, with a tail length of 61.0 to 83.8 centimetres (24.0 to 33.0 in).[11] It weighs 5.9 to 8.2 kilograms (13 to 18 lb).[11] It has dark fur on the back and sides with white-colored fur forming a band on the chest and along the inner thighs.[4][10][12]

Habits

The Raffles' banded langur is diurnal and arboreal, preferring rainforest with trees of the family Dipterocarpaceae.[12][11] It comes to the ground less frequently than most other leaf monkeys.[13] It lives in both primary and secondary forest, and also in swamp forests and mangrove forests, and even in rubber plantations.[11] It moves primarily by walking on all fours and by leaping.[11]

According to wildlife researcher Charles Francis, it typically lives in groups of 3 to 6.[12] However, a study in Perawang, Sumatra found an average group size of 11 monkeys in mixed-sex groups.[14] The latter study also found an average ratio of 1 adult male to 4.8 adult females in mixed-sex groups and a ratio of 1.25 adult monkeys for every immature monkey in mixed-sex groups.[14] It also found an average range size for a group of 22 hectares, and an average population density of 42 monkeys per square kilometer.[14] Other studies found somewhat smaller home ranges, of between 9 and 21 hectares.[11]

The Raffles' banded langur appears to have two birth seasons, once between June and July and another between December and January.[15] In this study, at least six infants were born between 2008 and 2010, and the authors found low infant mortality, with several infants surviving at least to seven months old.[15] The study also found that the infant coloration of the Singapore population is indistinguishable from that of the Johor, Malaysia population, with infants having white fur with a black stripe down the back from the head to the tail, crossed by another black stripe across the shoulders and to the forearms.[15] Males leave their natal group before reaching maturity, at about 4 years old.[13]

The call of mature males sounds like "ke-ke-ke."[12] Mammalogist Ronald M. Nowak described the species' alarm call as "a harsh rattle followed by a loud chak-chak-chak-chak."

Raffles' banded langurs have occasionally been observed being groomed by long-tailed macaques.[16]

Diet

The Raffles' banded langur has a primarily vegetarian diet. Specialized bacteria in its gut allow it to digest leaves and unripe fruit.[13] The Perawang study found that nearly 60% of the diet consisted of fruits and seeds.[14] Another 30% consisted of leaves, primarily young leaves.[14] A different study found that fruit made up 49% of the diet.[11] Unlike some other monkeys, such as the long-tailed macaque, the banded langur destroys the seeds it eats, and so it is not a significant factor in dispersing seeds.[17]

Conservation status

The IUCN assessed Presbytis femoralis as being critically endangered in 2021. At the time they assessed the (then) subspecies P. f. femoralis as vulnerable.[2] After the taxonomic reassessment, there are only about 300–400 Raffles' banded langurs remaining—about 250 to 300 and possibly fewer in Malaysia and about 60 in Singapore.[6][18] As a result of the small, fragmented population and continuing risk of further deforestation, the species meets the criteria to be listed as critically endangered by IUCN.[6]

Singapore population

The Raffles' banded langur was once common throughout the island of Singapore but that population is now critically endangered with approximately 60 individuals left in the Central Catchment Nature Reserve.[6][19][20][21] The species was formerly found in the Bukit Timah Nature Reserve, but that population died out in 1987.[22] The last individual to live in Bukit Timah is now displayed at the Raffles Museum of Biodiversity Research.[22][23] The Central Catchment population had declined to as few as 10–15 monkeys before recovering to about 40 by 2012,[20] 60 by 2019.[6] and about 70 by 2022.[24]

The Singapore population feeds from at least 27 plant species, including Hevea brasiliensis leaves, Adinandra dumosa flowers and Nephelium lappaceum fruits.[3][4] They appear to prefer specific fruits and will travel long distances to reach their preferred fruit, rather than settle for more accessible foods.[21] The National Biodiversity Centre, in partnership with the Evolution Lab of the National University of Singapore, launched an ecological study to determine suitable conservation strategies. A 2012 study found extremely low genetic diversity within the remaining Singapore population and suggested that translocation of Raffles' banded langurs from Malaysia may be necessary to provide the Singapore population with enough genetic diversity to survive in the long run.[20] In 2016, a cross-border partnership between Singapore and Malaysia was formed with the establishment of a Raffles' Banded Langur Working Group funded by the Wildlife Reserves Singapore Conservation Fund.[4][25]

The main threat to the Singapore population appears to be habitat loss.[26] 99.8% of Singapore's original primary forest, including much of its dipterocarp flora, has been eliminated, with less than 200 ha remaining, primarily in Bukit Timah and the MacRitchie Reservoir and Nee Soon Swamp Forest portions of Central Catchment.[27] The Nee Soon Swamp Forest is the primary area of Central Catchment where the Raffles' banded langur is found.[28][29] The monkey groups inhabit forest fragments that have limited arboreal connections to other fragments.[4] Other contributors to the species' decline in Singapore have been hunting for food and the pet trade.[21] The species has been legally protected in Singapore since 1947.[27] The Singapore government hopes that the development of Thomson Nature Park near Central Catchment will help maintain the Raffles' banded langur population, since it is located near a traditional feeding area for the monkeys and will increase the forested area they can use.[30][31][32] Rope bridges are being used to facilitate movements between Central Catchment and nearby forest patches.[33] The government also hopes that eventually when the vegetation matures the Eco-Link@BKE will allow banded leaf monkeys to repopulate Bukit Timah.[34] A group of bachelor males once tried to make its way to Bukit Timah without using the EcoLink but one was killed crossing the highway and the group now lives in Windsor Nature Park.[35] In April 2021 a single Raffles' banded langur was observed in Bukit Timah but it is unclear whether it used the Eco-Link@BKE to get there.[36][37] The National Parks Board staff wrote of the sighting at the website of the Lee Kong Chian Natural History Museum.[37] Concerns have been raised as to whether construction of the Cross Island MRT line through Central Catchment may adversely impact the Raffles' banded langur population in the area.[38]

In 2020 a group of two dusky leaf monkeys was observed in Singapore, possibly having swum from Johor, and they were able to chase away a group of eleven Raffles' banded langurs that had been feeding on Adenanthera pavonina seeds. If more individuals arrive in Singapore, they may be able to outcompete the banded langurs.[39][40]

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. 171. ISBN 0-801-88221-4. OCLC 62265494.
  2. 1 2 3 4 5 Ang, A., Boonratana, R. & Nijman, V. (2021). "Presbytis femoralis". IUCN Red List of Threatened Species. 2021: e.T39801A205832720. Retrieved 14 November 2021.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. 1 2 "Andie Ang Primatologist". Andie Ang. Retrieved 2015-08-02.
  4. 1 2 3 4 5 Ang, A.; D'Rozario, V.; Jayasri, S.L.; Lees, C.M.; Li, T.J.; Luz, S. (2016z). "Species Action Plan for the Conservation of Raffles' Banded Langur (Presbytis femoralis femoralis) in Malaysia and Singapore" (PDF). IUCN SSC Conservation Breeding Specialist Group. Retrieved 2017-07-25.
  5. ↑ Rizaldi; Ilham, K.; Prasetio, I.; Lee, Z.; Jabbar, S. & Ang, A. (2019). "Preliminary study on the distribution and conservation status of the East Sumatran banded langur Presbytis femoralis percura in Riau Province, Sumatra, Indonesia" (PDF). Asian Primates Journal. 8 (1): 25–36.
  6. 1 2 3 4 5 Ang, A.; Roesma, D.I.; Nijman, V.; Meier, R.; Srivathsan, A. & Rizaldi (2020). "Faecal DNA to the rescue: Shotgun sequencing of non-invasive samples reveals two subspecies of Southeast Asian primates to be Critically Endangered Species". Scientific Reports. 10 (1): 9396. Bibcode:2020NatSR..10.9396A. doi:10.1038/s41598-020-66007-8. PMC 7287133. PMID 32523128.
  7. ↑ Nuwer, Rachel (22 June 2020). "New monkey species found hiding in plain sight". National Geographic. Retrieved 2020-06-24.
  8. ↑ "Presbytis". ITIS. Retrieved 2021-11-12.
  9. 1 2 3 Low, M.E.Y. & Lim K.K.P. (30 October 2015). "The Authorship and Type Locality of the Banded Leaf Monkey, Presbytis Femoralis" (PDF). Nature in Singapore. 8: 69–71. Retrieved 2018-01-09.
  10. 1 2 3 Miller, Gerrit S. (May 1934). "The Langurs of the Presbytis Femoralis Group". Journal of Mammalogy. 15 (2): 124–137. doi:10.2307/1373983. JSTOR 1373983.
  11. 1 2 3 4 5 6 7 Rowe, N. (1996). A Pictorial Guide to the Living Primates. Pogonias Press. p. 179. ISBN 978-0964882508.
  12. 1 2 3 4 Francis, C.M. (2008). A Guide to the Mammals of Southeast Asia. Princeton University Press. pp. 78, 263–265. ISBN 9780691135519.
  13. 1 2 3 Attenborough, David (2019). Wild City:Forest Life. Channel NewsAsia.
  14. 1 2 3 4 5 Kirkpatrick, R.C. (2007). "The Asian Colobines". In Campbell, C.J.; Fuentes, A.; MacKinnon, K.C.; Panger, M.; Bearder, S.K. (eds.). Primates in Perspective. Oxford University Press. pp. 201–223. ISBN 9780195171334.
  15. 1 2 3 Ang, A.; Ismail, M. & Meier, R. (2010). "Reproduction and infant pelage coloration of the banded leaf monkey, Presbytis femoralis (Mammalia: Primates: Cercopithecidae) in Singapore" (PDF). Raffles Bulletin of Zoology. 58 (2): 411–415. Archived from the original (PDF) on 2016-10-03. Retrieved 2015-08-02.
  16. ↑ Lee, Z.H., Ang, A. & Ruppert, N. (26 August 2021). "First record of interspecies grooming between Raffles' Banded Langur and Long-tailed Macaque". Journal of Threatened Taxa. 13 (9): 19246–19253. doi:10.11609/jott.7510.13.9.19246-19253. Retrieved 2021-09-05.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  17. ↑ Corlett, R.T. & Lucas, P.W. "Mammals of Bukit Timah" (PDF). The Gardens' Bulletin Singapore Supplement No. 3. Singapore Botanic Gardens: National Parks Board. p. 98. ISSN 0374-7859. Retrieved 2015-08-14. {{cite book}}: |journal= ignored (help)
  18. ↑ Ming, Toh Ee (January 14, 2020). "Singapore's rarest monkeys need love and space to live, says local scientist devoted to saving primates". South China Morning Post. Retrieved 2020-04-08.
  19. ↑ "Ang Hui Fang's Banded Leaf Monkey work in The Straits Times – The Biodiversity Crew @ NUS". The Biodiversity Crew @ NUS. 2010-04-12. Retrieved 4 November 2014.
  20. 1 2 3 Ang A.; Srivasthan A.; Md.-Zain B.; Ismail M.; Meier R. (2012). "Low genetic variability in the recovering urban banded leaf monkey population of Singapore". Raffles Bulletin of Zoology. 60 (2): 589–594. Retrieved 2015-08-02.
  21. 1 2 3 Ang, A. (July–September 2010). "Living Treasures in the Tree Tops: A Fresh Look at Singapore's Banded Leaf Monkeys". BeMuse Magazine. Splash Publishing. pp. 46–50. Retrieved 2018-08-17.
  22. 1 2 "Hope remains for last monkeys". Singapore Press Holdings. April 8, 2002. Archived from the original on October 29, 2013. Retrieved 2013-10-23.
  23. ↑ "Raffles' banded langur (Banded leaf monkey)". National Library Board Singapore. Retrieved 2019-01-28.
  24. ↑ Wei, Chong Xin (22 June 2022). "Increase in population of critically endangered monkey in S'pore, but more needs to be done". Straits Times. Retrieved 2022-06-22.
  25. ↑ "Conservation of Singapore's own Raffles' banded langur". Wildlife Reserves Singapore Group. Retrieved 2020-04-07.
  26. ↑ "Singapore Red Data Book 2008:Banded Leaf Monkey" (PDF). National Parks Board. Retrieved 2013-10-23.
  27. 1 2 Corlett, Richard T. (July 1992). "The Ecological Transformation of Singapore, 1819–1990". Journal of Biogeography. 19 (4): 411–420. doi:10.2307/2845569. JSTOR 2845569.
  28. ↑ Min, Chew Hui & Pazos, Rebecca (December 11, 2015). "Animals Crossing". Straits Times. Retrieved 2019-01-30.{{cite web}}: CS1 maint: multiple names: authors list (link)
  29. ↑ Ng, Peter & Lim, Kelvin (September 1992). "The conservation status of the Nee Soon freshwater swamp forest of Singapore". Aquatic Conservation: Marine and Freshwater Ecosystems. 2 (3): 255–266. doi:10.1002/aqc.3270020305.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  30. ↑ Tan, Audrey (April 11, 2016). "More parks to save shy monkey from extinction". Straits Times. Retrieved 2019-01-28.
  31. ↑ "NParks announces plans for Upcoming Thomson Nature Park". National Parks Board. October 8, 2016. Retrieved 2019-01-28.
  32. ↑ "Media Fact Sheet A: Thomson Nature Park" (PDF). National Parks Board. Retrieved 2019-01-28.
  33. ↑ Ow, Sebastian; Chan, Sharon; Toh, Yuet Hsin; Chan, Soo Hooi; Lakshminarayanan, Jayasri; Jabbar, Sabrina; Ang, Andie; Loo, Adrian (21 April 2022). "Bridging the gap: assessing the effectiveness of rope bridges for wildlife in Singapore" (PDF). Folia Primatologica. -1 (aop): 287–298. doi:10.1163/14219980-20211110. S2CID 248337612. Retrieved 2022-04-22.
  34. ↑ "Eco-Link@BKE". National Parks Board. Retrieved 2019-01-28.
  35. ↑ Min, Chew Hui (22 August 2020). "IN FOCUS: How urbanised Singapore is learning to live with its wildlife". Channel News Asia. Retrieved 2020-08-22.
  36. ↑ Seah, Kimberley (2 July 2021). "Bukit Timah Monkey Makes Rare Appearance After Last Of Its Kind Passed In 1987". Must Share News. Retrieved 2021-07-04.
  37. 1 2 Tan, Audrey (1 July 2021). "Rare monkey sighted in Bukit Timah area after more than 30 years". The Straits Times. Retrieved 2021-07-04.
  38. ↑ Youjin, Low (5 December 2019). "Explainer: What are Raffles' banded langurs, and how will the Cross Island Line affect them?". Today Online. Mediacorp Pte. Retrieved 2021-03-02.
  39. ↑ Ang, Andie; Jabbar, Sabrina; Khoo, Max (26 June 2020). "Dusky Langurs Trachypithecus obscurus (Reid, 1837) (Primates: Cercopithecidae) in Singapore: potential origin and conflicts with native primate species". Journal of Threatened Taxa. 12 (9): 15967–15974. doi:10.11609/jott.5818.12.9.15967-15974.
  40. ↑ Tan, Audrey (4 July 2020). "Monkey species native to Malaysia spotted in Singapore". Straits Times. Retrieved 2020-07-04.

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