|Scientific Name:||Nasalis larvatus|
|Species Authority:||(Wurmb, 1787)|
|Infra-specific Taxa Assessed:|
Nasalis capistratus (Kerr, 1792)
Nasalis nasica (Lacépède, 1799)
Nasalis recurvus Vigors & Horsfield, 1828
|Taxonomic Notes:||There is very little difference between the two subspecies, and indeed N. l. orientalis is not recognized by all authorities (M. Richardson pers. comm.)|
|Red List Category & Criteria:||Endangered A2cd ver 3.1|
|Assessor(s):||Meijaard, E., Nijman, V. & Supriatna, J.|
|Reviewer(s):||Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)|
The species is listed as Endangered as it has undergone extensive population reductions across its range, and ongoing hunting and habitat destruction continue to threaten most populations. Numbers have declined by more than 50% (but probably less that 80%) over the past 3 generations (approximately 36-40 years).
|Range Description:||This species is endemic to Borneo, occurring in Brunei, Indonesia (Kalimantan) and Malaysia (Sabah and Sarawak). It was orignally found over the whole of coastal Borneo, as well as on the satellite islands of Berhala, Sebatik and Pulau Laut (Groves 2001).
N. l. larvatus
It has the same range as the species as a whole, with the exception of northeastern Kalimantan.
N. l. orientalis
It is restricted to northeastern Kalimantan, Indonesia.
Native:Brunei Darussalam; Indonesia (Kalimantan); Malaysia (Sabah, Sarawak)
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||In Sarawak, less than 1,000 animals are thought to remain in patchily distributed populations. In Sabah, the only remaining large populations are in the Kinabatangan flood plain, and around Dewurst Bay in the Eastern Deltas. Brunei estuaries support one population. The species is in greater abundance in Kalimantan (Indonesian Borneo), where Meijaard surveyed the population. The Indonesian populations range in size from over 1,000 to less than 100, depending on past and current threats (Meijaard and Nijman 2000). The Pulau Kaget Nature Reserve population in South Kalimantan has reportedly been extinct since 1997 (Meijaard and Nijman 2000). Also, the population in the Mahakam Delta, East Kalimantan which would have numbered in the thousands up until the early 1990s, has now been decimated due to conversion of the coastal swamps to shrimp farms (E. Meijaard pers. comm.).|
|Habitat and Ecology:||
This species is associated with riparian-riverine forests, coastal lowland forest, including mangroves, peat swamp, and freshwater swamp forest (Boonratana 2000). It rarely ranges far from its local habitat's waterway (Meijaard and Nijman 2000). It has been suggested that it is restricted to the coastal areas and areas near rivers because the interior has soils that are low in minerals and salts, which are a necessary part of its diet (Bennett and Sebastian 1988). It is found at low elevations, up to no more than about 350 m asl (Meijaard and Nijman 2000).
The species is mostly folivorous (about 52% of all feedings) and frugivorous (about 40% of all feedings), and prefers young leaves and unripened non-fleshy fruits. Monthly diet of this species changes with availability throughout the year (Yeager 1989). Boonratana (2000) observed this species swimming across the Kinabatangan River in northern Borneo, and frequently across its tributaries. The home range size of a focal one-male group was 220.5 ha (Boonratana 2000). Boonratana (2000) reports that this species never entered agricultural lands, nor areas used intermittently as log dumps for logging operations carried out in the area before and during the study. This species returned to the river every night at the study site of Sukau, moving inland during the day (Boonratana 2000). It avoids areas with heavy deforestation, such as agricultural land (Salter and MacKenzie 1985). Where there is no hunting the species can persist in disturbed forests and secondary habitats.
|Use and Trade:||As well as being hunted for food, the species is also hunted for bezoar stones, an intestinal secretion used in traditional Chinese medicine.|
Because of this species' association with riverine and coastal habitat, the major cause for its recent decline is thought to be habitat destruction. People favour these animals' habitats for logging, cultivation, and settlement. The planned land use for Central Kalimantan cited by E. Meijaard illustrates this tendency, with much of the riverine forest being marked for conversion. Clearing riverbanks and mangroves has a significant impact. Forest fires, especially those along the rivers, have a major impact on distribution. The 1997-1998 Bornean forest fires were thought to have destroyed the greatest proportion of remaining habitat of any primate in Kalimantan.
The species is relatively lethargic and easily hunted; with little effort entire populations can be hunted to extirpation. Opportunistic hunting of Nasalis larvatus for food occurs; the species is also hunted for bezoar stones, an intestinal secretion used in traditional Chinese medicine. Hunting has been felt most significantly in the Bornean interior, but is increasing in coastal areas (Meijaard and Nijman 2000).
This species is listed on CITES Appendix I, and is protected by law throughout its range (Meijaard and Nijman 2000). In some portions of its range its legal protection suffers from governmental and institutional deficiencies, including lack of conservation funds and knowledge, and poor and inappropriate management (Meijaard and Nijman 2000). It is known to occur in 16 protected areas: Danau Sentarum Wildlife Reserve, Gunung Palung Nature Reserve, Kendawangan Nature Reserve, Kutai National Park, Lesan Protection Forest, Muara Kaman Nature Reserve, Mandor Reserve, Tanjung Putting National Park (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, Ulu Segama Reserve (Malaysia). It formerly occurred in Pulau Kaget Nature Reserve (Indonesia), but is now extirpated there.
This species is almost never seen in captivity outside of Asia, as, owing to their dietary specialization on particular leaves and other vegetable material, they are hard to keep alive (E. Meijaard pers. comm.).
Bennett, E. 1988. Proboscis monkeys and their swamp forests in Sarawak. Oryx 22(1): 69-74.
Bennett, E. and Sebastian, A. 1988. Social organization and ecology of proboscis monkeys (Nasalis larvatus) in mixed coastal forest of Sarawak. International Journal of Primatology 9(3): 233–255.
Boonratana, R. 1993. The ecology and behaviour of the proboscis monkey (Nasalis larvatus) in the lower Kinabatangan, Sabah. Asian Primates 4(1): 13-14.
Boonratana, R. 1999. Dispersal in proboscis monkeys (Nasalis larvatus) in the Lower Kinabatangan, northern Borneo. Tropical Biodiversity 6: 179-187.
Boonratana, R. 2000. Ranging behavior of proboscis monkeys (Nasalis larvatus) in the Lower Kinabatangan, northern Borneo. International Journal of Primatology 21: 497–518.
Boonratana, R. 2002. Social organisation of proboscis monkeys (Nasalis larvatus) in the Lower Kinabatangan, Sabah, Malaysia. Malayan Nature Journal 56: 57-75.
Groves, C. P. 2001. Primate taxonomy. Smithsonian Institution Press, Washington, DC, USA.
Jeffrey, S. 1982. Threats to the proboscis monkey. Oryx 16: 337–339.
Meijaard, E. and Nijman, V. 1999. The local extinction of the proboscis monkey Nasalis larvatus in Pulau Kaget Nature Reserve, Indonesia. Oryx 34: 66-70.
Meijaard, E. and Nijman, V. 2000. Distribution and conservation of the proboscis monkey (Nasalis larvatus) in Kalimantan, Indonesia. Biological Conservation 92: 15-24.
Payne, J., Francis, C.M. and Phillipps, K. 1985. A field guide to the mammals of Borneo. The Sabah Society and WWF Malaysia, Kota Kinabalu and Kuala Lumpur, Malaysia.
Salter, R. and MacKenzie, N. 1985. Conservation status of proboscis monkey in Sarawak. Biological Conservation 33: 119 - 132.
Yeager, C. 1989. Feeding ecology of the proboscis monkey (Nasalis larvatus). International Journal of Primatology 10(6): 497-529.
Yeager, C. 1990. Notes on the sexual behavior of the proboscis monkey (Nasalis larvatus). American Journal of Primatology 21(3): 223-227.
Yeager, C. 1990. Proboscis monkey (Nasalis larvatus) social organization: group structure. American Journal of Primatology 20(2): 95-106.
Yeager, C. 1996. Conservation status of proboscis monkey groups and the effects of habitat degradation. Asian Primates Newsletter 5: 3-5.
Yeager, C. P. 1991. Proboscis monkey (Nasalis larvatus) social organization: intergroup patterns of association. American Journal of Primatology 23: 73-86.
Yeager, C. P. 1992. Proboscis monkey (Nasalis larvatus) social organization: nature and possible functions of intergroup patterns of association. American Journal of Primatology 26: 133-137.
|Citation:||Meijaard, E., Nijman, V. & Supriatna, J. 2008. Nasalis larvatus. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 07 July 2015.|
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