Proboscis monkey

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Proboscis monkey
CITES Appendix I (CITES)[2]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Infraorder: Simiiformes
Family: Cercopithecidae
Subfamily: Colobinae
Tribe: Presbytini
Genus: Nasalis
É. Geoffroy, 1812
Species:
N. larvatus[1]
Binomial name
Nasalis larvatus[1]
Wurmb, 1787

The proboscis monkey or long-nosed monkey (Nasalis larvatus) 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.[3]

This species co-exists with the

monotypic genus Nasalis.[5][6]

Taxonomy

The proboscis monkey belongs to the subfamily Colobinae of the Old World monkeys. The two subspecies are:[2]

  • N. l. larvatus (Wurmb, 1787), which occupies the whole range of the species from Cambodia to the Philippines
  • 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.[2]

The genus name Nasalis comes from the Latin word nasus meaning "nose".[7][additional citation(s) needed]

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.[8][additional citation(s) needed]

Description

Male
Female

The proboscis monkey is a large species, being one of the largest monkey species native to

gray langurs
can rival its size.

Sexual dimorphism is pronounced in the species. Males have a head-body length of 66 to 76.2 cm (26.0 to 30.0 in) and typically weigh 16 to 22.5 kg (35 to 50 lb), with a maximum known weight of 30 kg (66 lb). Females measure 53.3 to 62 cm (21.0 to 24.4 in) in head-and-body length and weigh 7 to 12 kg (15 to 26 lb), with a maximum known mass of 15 kg (33 lb).[9][10][11] The male has a red penis with a black scrotum.[12]

The proboscis monkey has a long coat; the fur on the back is bright orange, reddish brown, yellowish brown or brick-red.[12][13] The underfur is light-grey, yellowish, or greyish to light-orange.[12][13] 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.[14] Both sexes have bulging stomachs that give the monkeys what resembles a pot belly. Many of the monkeys' toes are webbed.[12]

Nose

Nasal cartilages that were left intact in a specimen skull in order to show the structures that support the nose

Further adding to the dimorphism is the large nose or proboscis of the male, which can exceed 10.2 cm (4.0 in) in length,[15] 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.[16][12][13]

The nose is smaller in the female and is upturned in the young.[17] 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.[3]

Distribution and habitat

Juvenile in Labuk Bay, Sabah

The proboscis monkey is

riverine forests.[19] It can also be found in swamp forests, stunted swamp forests, rubber forests, rubber plantations, limestone hill forests, nypa swamps, nibong swamps, and tall swamp forests, tropical heath forests and steep cliffs.[20] 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 20 m (66 ft) underwater. It is known to swim across rivers.[20] Aside from this, the proboscis monkey is largely arboreal and moves quadrupedally and by leaps.[9] It is known to jump off branches and descend into water.[22]

Behavior and ecology

Social behavior

composite image, from right to left), Labuk Bay, Sabah
A group of proboscis monkeys by the river Kinabatangan

Proboscis monkeys generally live in groups composed of one adult male, some adult females and their offspring.

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.[19][22][23] Groups gather during the day and travel together, but individuals only groom and play with those in their own group.[23] One-male groups consist of 3 to 19 individuals,[24][19] while bands can consist of as many as 60 individuals.[19][25] Serious aggression is uncommon among the monkeys but minor aggression does occur.[26] Overall, members of the same bands are fairly tolerant of each other. A linear dominance hierarchy exists between females.[22] 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.[24] Upon reaching adulthood, males leave their natal groups and join all-male groups.[19][25] Females also sometimes leave their natal groups, perhaps to avoid infanticide or inbreeding, reduce competition for food, or elevation of their social status.[24][25]

In

oil palm trees.[6]

Reproduction

Females become sexually mature at the age of five years. They experience sexual swelling, which involves the genitals becoming pink or reddened.[24][27] At one site, matings largely take place between February and November, while births occur between March and May.[28] Copulations tend to last for half a minute.[22][24] The male will grab the female by the ankles or torso and mount her from behind.[22] Both sexes will encourage mating, but they are not always successful.[27] 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.[19][27][28][14] Mating pairs are sometimes harassed by subadults.[27] 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.[14] Gestation usually last 166–200 days or slightly more.[28] Females tend to give birth at night or in the early morning. The mothers then eat the placenta and lick their infants clean.[29] 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.[22][28][29] When a resident male in a one-male group is replaced, the infants are at risk of infanticide.[30]

Communication

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.[31] 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.[22]

Feeding and activities

As a seasonal folivore and frugivore, the proboscis monkey eats primarily fruit and leaves.

monitor lizards.[35][36] Monkeys will cross rivers at narrows or cross arboreally if possible. This may serve as predator avoidance.[37]

Conservation status

The proboscis monkey is assessed as

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.[14] The population is fragmented: the largest remaining populations are found in Kalimantan; there are far fewer in Sarawak, Brunei and Sabah.[2]
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:

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.[2]

References

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  2. ^
    doi:10.2305/IUCN.UK.2021-1.RLTS.T14352A195372486.en
    . Retrieved 17 January 2022.
  3. ^ a b "Proboscis monkey". Animal Diversity Web. December 2019. Retrieved 11 December 2019.
  4. ^ "Conservation of the Proboscis Monkey and the Orangutan in Borneo: Comparative Issues and Economic Considerations" (PDF). Working Papers on Economics, Ecology and the Environment. March 2007.
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  7. ^ Lewis, Charlton T.; Short, Charles (1879). "nāsus". A Latin Dictionary. Perseus Digital Library.
  8. ^ Lydekker, Richard, ed. (1894). The Royal Natural History. New York, USA: Frederick Warne & Co. pp. 84–85.
  9. ^
    ISBN 0262640333.[page needed
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  10. ^ "Primate Factsheets: Proboscis monkey (Nasalis larvatus) Taxonomy, Morphology, & Ecology". Primate Info Net. University of Wisconsin–Madison. n.d. Retrieved 21 August 2012.
  11. ^ "Up Close With Borneo Primates". Special Features. Brudirect. 2 July 2012. Retrieved 21 August 2012.
  12. ^
    ISBN 0080469116
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  13. ^
    ISBN 9679994716.[page needed
    ]
  14. ^ a b c d Woltanski, Amy (2004). "Nasalis larvatus (proboscis monkey)". Animal Diversity Web. University of Michigan Museum of Zoology. Retrieved 15 March 2017.
  15. ^ Ellis, D. (1986). "Proboscis monkey and aquatic ape". Sarawak Museum Journal. 36 (57): 251–262.
  16. ^ "Proboscis Monkey". World Land Trust. Retrieved 2017-03-15.
  17. ^ "proboscis monkey". www.britannica.com. Encyclopedia Britannica Inc. 19 Feb 2020. Retrieved 11 Feb 2022.
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  19. ^ a b c d e f g h i Bennett E. L., Gombek F. (1993) Proboscis monkeys of Borneo. Sabah (MY):Koktas Sabah Berhad Ranau.
  20. ^ a b c Sebastian A. C. (2000). "Proboscis monkeys in Danau Sentarum National Park". Borneo Research Bulletin. 31: 359–371.
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  22. ^ a b c d e f g h i j k l Boonratana R. (1993). The ecology and behaviour of the proboscis monkey (Nasalis larvatus) in the lower Kinabatangan, Sabah (PhD). Mahidol University.
  23. ^ a b c Boonratana R. (2002). "Social organisation of proboscis monkeys (Nasalis larvatus) in the lower Kinabatangan, Sabah, Malaysia". Malay Nat. Journal. 56 (1): 57–75.
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  25. ^ a b c d Boonratana R. (1999). "Dispersal in proboscis monkeys (Nasalis larvatus) in the lower Kinabatangan, Northern Borneo". Tropic Biodiversity. 6 (3): 179–187.
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  28. ^ a b c d Rajanathan R.; Bennett E. L. (1990). "Notes on the social behaviour of wild proboscis monkeys (Nasalis larvatus)". Malay Nat. Journal. 44 (1): 35–44.
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  31. ^ Messeri P.; Trombi M. (2000). "Vocal repertoire of proboscis monkey (Nasalis larvatus, L.) in Sarawak". Folia Primatol. 71 (4): 268–287.
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  36. ^ Stuebing, R. B.; Bezuijen, M. R.; Auliya, M.; Voris, H. K. (2006). "The current and historic distribution of Tomistoma schlegelii (the False Gharial)(Müller, 1838)(Crocodylia, Reptilia)". The Raffles Bulletin of Zoology. 54 (1): 181–197.
  37. S2CID 84996963
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External links

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