proboscis monkey

The proboscis monkey belongs to the subfamily Colobinae of the Old World monkeys. The two subspecies are:

• N. l. larvatus (Wurmb, 1787), which occupies the whole range of the species excluding northeast Kalimantan{{Cite journal |last=Harding |first=Lee E. |date=2015-12-01 |title=Nasalis larvatus (Primates: Colobini) |url=https://academic.oup.com/mspecies/article-lookup/doi/10.1093/mspecies/sev009 |journal=Mammalian Species |language=en |volume=47 |issue=926 |pages=84–99 |doi=10.1093/mspecies/sev009 |issn=1545-1410}}
• N. l. orientalis (Chasen, 1940), restricted to north-east Kalimantan

However, the difference between the subspecies is small, and not all authorities recognise N. l. orientalis.

The genus name Nasalis comes from the Latin word nasus meaning "nose".{{cite encyclopedia |url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0059%3Aentry%3Dnasus1 |title= nāsus |last1= Lewis |first1= Charlton T. |last2= Short |first2= Charles |dictionary= A Latin Dictionary |edition= |publisher= Perseus Digital Library |date = 1879 }}{{Explain |reason=Who named & gave 1st description? |date=June 2024}}{{Additional citation needed|date=August 2023}}

This animal was made known to Westerners by Baron Friedrich von Wurmb in 1781, he later sent specimens of it to Stamford Raffles in Europe.{{cite book |editor-last1=Lydekker |editor-first1=Richard |date=1894 |title=The Royal Natural History |url=https://books.google.com/books?id=vUNKAAAAYAAJ&dq=1781+proboscis+monkey&pg=PA84 |location=New York, USA |publisher=Frederick Warne & Co. |pages=84–85 }}{{Additional citation needed|date=August 2023}}

File:Proboscis monkey (Nasalis larvatus) male head.jpg

File:Proboscis monkey (Nasalis larvatus) female Labuk Bay.jpg

The proboscis monkey is a large species, being one of the largest monkey species native to Asia. Only the Tibetan macaque and a few of the gray langurs can rival its size.

Sexual dimorphism is pronounced in the species. Males have a head-body length of {{convert|66|to|76.2|cm|in|abbr=on}} and typically weigh {{convert|16|to|22.5|kg|lb|abbr=on}}, with a maximum known weight of {{convert|30|kg|lb|abbr=on}}. Females measure {{convert|53.3|to|62|cm|in|abbr=on}} in head-and-body length and weigh {{convert|7|to|12|kg|lb|abbr=on}}, with a maximum known mass of {{convert|15|kg|lb|abbr=on}}.{{cite book|last1=Napier |first1=J. R. |last2=Napier |first2=P. H. |year=1985 |title='The Natural History of the Primates |location=Cambridge, Massachusetts, USA|publisher=MIT Press |isbn=0262640333}}{{Page needed|date=August 2023}}{{cite web |url=http://pin.primate.wisc.edu/factsheets/entry/proboscis_monkey/taxon |title=Primate Factsheets: Proboscis monkey (Nasalis larvatus) Taxonomy, Morphology, & Ecology |date=n.d. |website=Primate Info Net |publisher=University of Wisconsin–Madison |access-date=21 August 2012 |quote=}}{{cite web |url=http://www.brudirect.com/index.php/Special-Features/up-close-with-borneo-primates.html |title=Up Close With Borneo Primates |date=2 July 2012 |website=Special Features |publisher=Brudirect |access-date=21 August 2012}} The male has a red penis with a black scrotum.

The proboscis monkey has a long coat; the fur on the back is bright orange, reddish brown, yellowish brown or brick-red.{{cite book |last1=Payne |first1=J. |last2=Francis |first2=C. M. |last3=Phillips |first3=K. |year=1985 |title=A field guide to the mammals of Borneo |location=Kuala Lumpur, Malaysia |publisher=World Wildlife Fund Malaysia & The Sabah Society |isbn=9679994716}}{{Page needed|date=August 2023}} The underfur is light-grey, yellowish, or greyish to light-orange. Infants are born with a blue coloured face that at 2.5 months darkens to grey. By 8.5 months of age, the face has become cream coloured like the adults.{{Cite web|url=http://animaldiversity.org/accounts/Nasalis_larvatus/ |title=Nasalis larvatus (proboscis monkey) |last=Woltanski |first=Amy |date=2004 |website=Animal Diversity Web |publisher=University of Michigan Museum of Zoology |access-date=15 March 2017 }} Both sexes have bulging stomachs that give the monkeys what resembles a pot belly. Many of the monkeys' toes are webbed.

File:Nasalis larvatus Paris 150110.jpg

Further adding to the dimorphism is the large nose or proboscis of the male, which can exceed {{convert|10.2|cm|in|abbr=on}} in length,{{cite journal|last=Ellis |first=D. |date=1986 |title=Proboscis monkey and aquatic ape |journal=Sarawak Museum Journal |volume=36 |issue=57 |pages= 251–262}} and hangs lower than the mouth. Theories for the extensive length of their nose suggest it may be sexual selection by the females, who prefer louder vocalisations, with the size of the nose increasing the volume of the call.{{Cite web|url=http://www.worldlandtrust.org/education/species/proboscis-monkey|title=Proboscis Monkey |website=World Land Trust |access-date=2017-03-15}}Ankel-Simons F. (2007) [https://books.google.com/books?id=Mwl3M6c5KzoC Primate Anatomy: an introduction], 3rd Ed. San Diego: Academic Press {{ISBN|0080469116}}.

The nose is smaller in the female and is upturned in the young.{{cite web|url=https://www.britannica.com/animal/proboscis-monkey|title=proboscis monkey|author=|date=19 Feb 2020|website=www.britannica.com|publisher=Encyclopedia Britannica Inc.|access-date=11 Feb 2022}} Nevertheless, the nose of the female is still fairly large for a primate. The skull of the proboscis monkey has specialized nasal cartilages that support the large nose.

File:Proboscis monkey (Nasalis larvatus) juvenile Labuk Bay.jpg]]

The proboscis monkey is endemic to the island of Borneo and can be found in all three nations that divide the island: Brunei, Indonesia and Malaysia.{{cite journal|author1=Bradon-Jones D. |author2=Eudey A. A. |author3=Geissmann T. |author4=Groves C. P. |author5=Melnick D. J. |author6=Morales J. C. |author7=Shekelle M. |author8=Stewart C. B. |year=2004| title=Asian primate classification| journal= International Journal of Primatology| volume= 25 | issue=1|pages=97–164|doi=10.1023/B:IJOP.0000014647.18720.32|s2cid=29045930}} It is most common in coastal areas and along rivers.Bennett E. L., Gombek F. (1993) Proboscis monkeys of Borneo. Sabah (MY):Koktas Sabah Berhad Ranau. This species is restricted to lowland habitats that may experience tides.{{cite journal |author=Sebastian A. C. |year= 2000 |title=Proboscis monkeys in Danau Sentarum National Park| journal=Borneo Research Bulletin |volume=31 |pages=359–371}}{{cite journal|author1=Kawabe M. |author2=Mano T. |year=1972| title=Ecology and behavior of the wild proboscis monkey, Nasalis larvatus (Wurmb) in Sabah, Malaysia |journal=Primates |volume= 13| issue=2|pages=213–228 |doi=10.1007/BF01840882 |s2cid=20269823}} It favors dipterocarp, mangrove and riverine forests. It can also be found in swamp forests, stunted swamp forests, rubber forests, rubber plantations, limestone hill forests, nypa swamps, nibong swamps, tall swamp forests, tropical heath forests and steep cliffs. This species usually stays within at least a kilometer from a water source. It is perhaps the most aquatic of the primates and is a fairly good swimmer, capable of swimming up to {{convert|20|m|ft|abbr=on}} underwater. It is known to swim across rivers. Aside from this, the proboscis monkey is largely arboreal and moves quadrupedally and by leaps. It is known to jump off branches and descend into water.{{cite thesis |author=Boonratana R. |date=1993 |title=The ecology and behaviour of the proboscis monkey (Nasalis larvatus) in the lower Kinabatangan, Sabah |type=PhD |publisher=Mahidol University |url=https://www.researchgate.net/publication/35492838}}

File:Proboscis monkey (Nasalis larvatus) composite.jpg, from right to left), Labuk Bay, Sabah]]

File:011191 00001 Nasenaffen am Kinabatangan.jpg

Proboscis monkeys generally live in groups composed of one adult male, some adult females and their offspring. All-male groups may also exist.{{cite journal|author=Murai, T. |year=2004|title= Social behaviors of all-male proboscis monkeys when joined by females|journal=Ecological Research |volume= 19| issue=4|pages=451–454|doi=10.1111/j.1440-1703.2004.00656.x|bibcode=2004EcoR...19..451M |s2cid=46315032}} Some individuals are solitary, mostly males.{{cite journal|author=Boonratana R.|year=1999| title=Dispersal in proboscis monkeys (Nasalis larvatus) in the lower Kinabatangan, Northern Borneo| journal=Tropic Biodiversity |volume= 6| issue=3|pages=179–187 |url=https://www.researchgate.net/publication/225088971}} Monkey groups live in overlapping home ranges, with little territoriality, in a fission-fusion society, with groups gathering at sleeping sites as night falls. There exist bands which arise when groups come together and slip apart yet sometimes groups may join to mate and groom. Groups gather during the day and travel together, but individuals only groom and play with those in their own group.{{cite journal|author=Boonratana R. |year=2002 |title=Social organisation of proboscis monkeys (Nasalis larvatus) in the lower Kinabatangan, Sabah, Malaysia |journal= Malay Nat. Journal |volume=56| issue=1|pages=57–75}} One-male groups consist of 3 to 19 individuals, while bands can consist of as many as 60 individuals. Serious aggression is uncommon among the monkeys but minor aggression does occur.{{cite journal|author=Yeager C. P. |year=1992| title=Proboscis monkey (Nasalis larvatus) social organization: nature and possible functions of intergroup patterns of association| journal=American Journal of Primatology |volume= 26| issue=2|pages=133–137 |doi=10.1002/ajp.1350260207 |pmid=31948161 |s2cid=84905354}} Overall, members of the same bands are fairly tolerant of each other. A linear dominance hierarchy exists between females. Males of one-male groups can stay in their groups for six to eight years. Replacements in the resident males appear to occur without serious aggression. Upon reaching adulthood, males leave their natal groups and join all-male groups. Females also sometimes leave their natal groups, perhaps to avoid infanticide or inbreeding, reduce competition for food, or elevation of their social status.

In Sabah, Malaysia, proboscis monkeys have been observed in mixed-species groups with silvery lutungs, and interspecific mating and a possible hybrid has been observed. Researchers believe this may be a result of the two species being confined to a small patch of riverine forest due to deforestation in order to plant oil palm trees.{{cite journal|title=Is Malaysia's "mystery monkey" a hybrid between Nasalis larvatus and Trachypithecus cristatus? An assessment of photographs |journal=International Journal of Primatology |date=2022 |doi=10.1007/s10764-022-00293-z|pmid=35498121|author1=Lhota, S. |author2=Yap, J.L. |author3=Benedict, M.L. |author4=Ching, K. |volume=43 |issue=3 |pages=513–532 |pmc=9039274 |display-authors=3}}

Females become sexually mature at the age of five years. They experience sexual swelling, which involves the genitals becoming pink or reddened. At one site, matings largely take place between February and November, while births occur between March and May.{{cite journal|author1=Rajanathan R. |author2=Bennett E. L. |year=1990| title=Notes on the social behaviour of wild proboscis monkeys (Nasalis larvatus)| journal=Malay Nat. Journal |volume= 44| issue=1|pages=35–44}} Copulations tend to last for half a minute. The male will grab the female by the ankles or torso and mount her from behind. Both sexes will encourage mating, but they are not always successful.{{cite journal|author=Murai T.|year=2006| title=Mating behaviors of the proboscis monkey (Nasalis larvatus)| journal=American Journal of Primatology | volume= 68| issue=8|pages=832–837 |doi=10.1002/ajp.20266|pmid=16847976|s2cid=10625574}} When soliciting, both sexes will make pouted faces. In addition, males will sometimes vocalize and females will present their backsides and shake their head from side to side. Mating pairs are sometimes harassed by subadults. Proboscis monkeys may also engage in mounting with no reproductive purpose, such as playful and same-sex mounting, and females will attempt to initiate copulation even after they have conceived. Gestation usually last 166–200 days or slightly more. Females tend to give birth at night or in the early morning. The mothers then eat the placenta and lick their infants clean.{{cite journal|author=Gorzitze A. B.|year=1996| title=Birth-related behavior in wild proboscis monkeys (Nasalis larvatus)| journal=Primates| volume= 37| issue=1|pages=75–78 |doi=10.1007/BF02382922 |s2cid=39403318}} The young begin to eat solid foods at six weeks and are weaned at seven months old. The nose of a young male grows slowly until reaching adulthood. The mother will allow other members of her group to hold her infant. When a resident male in a one-male group is replaced, the infants are at risk of infanticide.{{cite journal|author1=Agoramoorthy G. |author2=Hsu M. J. |year=2004| title=Occurrence of infanticide among wild proboscis monkeys (Nasalis larvatus) in Sabah, Northern Borneo| journal=Folia Primatol.| volume= 76| issue=3|pages=177–179 |doi=10.1159/000084380 |pmid=15900105|s2cid=20111145}}

Proboscis monkeys are known to make various vocalizations. When communicating the status of group, males will emit honks. They have a special honk emitted towards infants, which is also used for reassurance. Males will also produce alarm calls to signal danger. Both sexes give threat calls, but each are different. In addition, females and immature individuals will emit so-called "female calls" when angry.{{cite journal|author1=Messeri P. |author2=Trombi M. |year=2000| title=Vocal repertoire of proboscis monkey (Nasalis larvatus, L.) in Sarawak| journal=Folia Primatol.| volume= 71| issue=4|pages=268–287}} Honks, roars and snarls are made during low-intensity agonistic encounters. Nonvocal displays include leaping-branch shaking, bare-teeth open mouth threats and erection in males, made in the same situations.

As a seasonal folivore and frugivore, the proboscis monkey eats primarily fruit and leaves. It also eats flowers, seeds and insects to a lesser extent. At least 55 different plant species are consumed, "with a marked preference for Eugenia sp., Ganua motleyana and Lophopetalum javanicum". Young leaves are preferred over mature leaves and unripe fruits are preferred over ripe fruit. Being a seasonal eater, the proboscis monkey eats mostly fruit from January to May and mostly leaves from June to December.{{cite journal|author=Yeager C. P.|year=1989 |journal= International Journal of Primatology |issue=6|pages=497–530 |doi=10.1007/BF02739363|title=Feeding ecology of the proboscis monkey (Nasalis larvatus) |volume=10 |s2cid=23442969}} Groups usually sleep in adjacent trees.{{cite journal |author=Yeager C. P.|year=1990| title=Proboscis monkey (Nasalis larvatus) social organization: group structure |journal=American Journal of Primatology |volume=20 |issue=2 |pages=95–106 |doi=10.1002/ajp.1350200204 |pmid=31963992 |s2cid=85675872}} Monkeys tend to sleep near rivers, if they are nearby. Proboscis monkeys will start the day foraging and then rest further inland. Their daily activities consist of resting, traveling, feeding and keeping vigilant. Occasionally, they chew their cud to allow more efficient digestion and food intake.{{Cite journal |last1=Matsuda |first1=I. |last2=Murai |first2=T. |last3=Clauss |first3=M. |last4=Yamada |first4=T. |last5=Tuuga |first5=A. |last6=Bernard |first6=H. |last7=Higashi |first7=S. |doi=10.1098/rsbl.2011.0197 |title=Regurgitation and remastication in the foregut-fermenting proboscis monkey (Nasalis larvatus) |journal=Biology Letters |volume=7 |issue=5 | pages=786–789 |year=2011 |pmid=21450728 |pmc=3169055}} As night approaches, the monkeys move back near the river and forage again. Predators (potential or confirmed) of the proboscis monkey include crocodilians like false gharials and saltwater crocodiles, the Sunda clouded leopard, sun bears and reticulated pythons as well as, for probably young or sickly monkeys, large eagles (such as the crested serpent eagle or black eagle), large owls, and monitor lizards.{{cite journal|author=Feilen, K. L. |author2=Marshall, A. J. |date=2014 |title=Sleeping site selection by proboscis monkeys (Nasalis larvatus) in West Kalimantan, Indonesia |journal=American Journal of Primatology|volume=76 |issue=12 |pages=1127–1139|doi=10.1002/ajp.22298 |pmid=24810395 |s2cid=26318484 }}{{cite journal|author=Stuebing, R. B. |author2=Bezuijen, M. R. |author3=Auliya, M. |author4=Voris, H. K. |year=2006 |title=The current and historic distribution of Tomistoma schlegelii (the False Gharial)(Müller, 1838)(Crocodylia, Reptilia) |journal=The Raffles Bulletin of Zoology |volume=54 |issue=1 |pages=181–197}} Monkeys will cross rivers at narrows or cross arboreally if possible. This may serve as predator avoidance.{{cite journal|author=Yeager C. P. |year=1991| title=Possible antipredator behavior associated with river crossings by proboscis monkeys (Nasalis larvatus)| journal=American Journal of Primatology |volume=24| issue=1|pages=61–66 |doi=10.1002/ajp.1350240107 |s2cid=84996963}}

The proboscis monkey is assessed as endangered in the IUCN Red List of Threatened Species and listed in Appendix I of CITES. Its total population has decreased by more than 50% in the past 36–40 years to 2008 due to ongoing habitat loss because of logging and oil palm plantations, and hunting in some areas due to the species being treated as a delicacy, as well as its use in traditional Chinese medicine. The population is fragmented: the largest remaining populations are found in Kalimantan; there are far fewer in Sarawak, Brunei and Sabah. The proboscis monkey is protected by law in all regions of Borneo. In Malaysia, it is protected by a number of laws including the Wildlife Protection Act (federal law), the Wildlife Protection Ordinance 1998 (Chapter 26) and Wildlife Conservation Enactment 1997 (Sabah state law).

The proboscis monkey can be found in 16 protected areas: Danau Sentarum National Park, Gunung Palung National Park, Kendawangan Nature Reserve, Kutai National Park, Lesan Protection Forest, Muara Kaman Nature Reserve, Mandor Reserve and Tanjung Puting National Park in Indonesia; Bako National Park, Gunung Pueh Forest Reserve, Kabili-Sepilok Forest Reserve, Klias National Park, Kulamba Wildlife Reserve, Lower Kinabatangan Wildlife Sanctuary, Sungei Samunsam Wildlife Sanctuary and Ulu Segama Reserve in Malaysia.

{{Reflist}}

• ARKive – [https://web.archive.org/web/20060507100133/http://www.arkive.org/species/GES/mammals/Nasalis_larvatus/ images and movies of the Proboscis monkey (Nasalis larvatus)]
• [http://pin.primate.wisc.edu/factsheets/links/nasalis Primate Info Net Nasalis Factsheets]
• [http://www.proboscismonkey.org/ Save the Proboscis Monkeys] Petition and weblog with info on the rare, endangered species.
• [https://web.archive.org/web/20201114001930/https://video.nationalgeographic.com/video/00000144-0a44-d3cb-a96c-7b4d86de0000 A Video about proboscis monkeys] by National Geographic
• John C. M. Sha, Ikki Matsuda & Henry Bernard (2011) [https://web.archive.org/web/20120318021743/http://www.nhpborneo.com/book/n025 The Natural History of the Proboscis Monkey]
• John C. M. Sha, Henry Bernard, and Senthival Nathan (2008) [http://www.primate-sg.org/storage/PDF/PC23.nasalis.sabah.V2.pdf Status and Conservation of Proboscis Monkeys in Sabah, East Malaysia]

{{C.Colobinae nav}}

{{Haplorhini|C.}}

{{Taxonbar|from1=Q3336165|from2=Q192029|from3=Q109647124}}

{{Authority control}}

Category:Colobinae

Category:Endemic fauna of Borneo

Category:Primates of Borneo

Category:Primates of Southeast Asia

Category:Mammals of Brunei

Category:Mammals of Indonesia

Category:Mammals of Malaysia

Category:Endangered fauna of Asia

Category:Mammals described in 1787

Category:Taxa named by Friedrich von Wurmb

Category:Sunda Shelf mangroves