Presbytis siamensis 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Primates Cercopithecidae

Scientific Name: Presbytis siamensis (Müller & Schlegel, 1841)
Infra-specific Taxa Assessed:
Common Name(s):
English White-thighed Surili, Pale-thighed Langur
Presbytis amsiri Kawamura, 1984
Presbytis catemana Lyon, 1908
Presbytis dilecta Elliot, 1909
Presbytis nigrimanus (I. Geoffroy, 1843)
Presbytis nubigena Elliot, 1909
Taxonomic Notes: Taxonomy is disputed and in need of review. This taxon was formerly considered a subspecies of P. femoralis. Separated from P. femoralis by Brandon-Jones (1984).

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Nijman, V., Geissman, T. & Meijaard, E.
Reviewer(s): Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)
Considering the extensive habitat loss that has taken place within the range of the species, there is reason to believe that this species is in decline, probably at a rate of less than 30% over three generations (approximately 30 years), thus qualifying if for listing as Near Threatened (almost meets criterion A2c). It will be necessary to reassess this species once its taxonomy has become clearer.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species occurs in Indonesia (eastern Sumatra and the Riau Archipelago in the Strait of Malacca), Peninsular Malaysia, and extreme southern peninsular Thailand. It is found throughout the Malay Peninsula except for the south and northwest. In Sumatra, it occurs in a few small sections of the eastern forests (between the Siak and Inderagiri Rivers, between the Rokan and Barimun Rivers, the Lake Toba region, and perhaps the Jambi district); in the Riau Archipelago it is found on Kundar, Bintang, and probably Batam and Galang Islands. Population isolates are known within the range of P. femoralis in Thailand and P. melalophos in Sumatra (Groves 2001).

Presbytis siamensis siamensis
Occurs in Malaysia and Thailand. Found in most of Peninsular Malaysia except for the south and northwest (Perak north to the Piah Valley; Selangor; Negri Sembilan; Pahang; Melaka), with a population isolate reported in Thailand at 6°22'N, 101°08'E within the range of P. femoralis robinsoni (Groves 2001).

Presbytis siamensis rhionis
Known for certain only from Pulau Bintang, in the Riau Archipelago, Indonesia; might occur on Pulau Batam and Pulau Galang as well (Groves 2001).

Presbytis siamensis cana
Occurs in Indonesia. Found in eastern Sumatra between the Siak and Inderagiri Rivers, and on Palau Kundur in the Riau Archipelago (Groves 2001).

Presbytis siamensis paenulata
Occurs in Indonesia. Found in east-central Sumatra, where it is confined to a small wedge of coastal forest and with a population isolate reported from near Lake Toba (Groves 2001).
Countries occurrence:
Indonesia (Sumatera); Malaysia; Thailand
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:There is very little information available on this species relating to abundance.
Current Population Trend:Decreasing
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:There is very little information available on this species relating to habitat and ecology other than what can be inferred from closely related forms. The subspecies P. s. rhionis is known to occur in lowland wet forest, swamp forests, and secondary re-growth mixed rubber gardens (Yanuar 1993/1994).

Threats [top]

Major Threat(s): It seems likely that deforestation and conversion of habitat are the major threats to this species, and hunting to a lesser extent. Oil palm plantations are expanding greatly within its range at the expense of lowland forest habitat.

Conservation Actions [top]

Conservation Actions: This species is listed on CITES Appendix II. It presumably occurs in a number of protected areas. There is an urgent need to clarify the taxonomy and distribution of this species, as there is very little information at this time. Since siamensis has been separated from femoralis, there has been confusion about what is known of femoralis, and what of that actually pertains to siamensis.

Citation: Nijman, V., Geissman, T. & Meijaard, E. 2008. Presbytis siamensis. The IUCN Red List of Threatened Species 2008: e.T18134A7668889. . Downloaded on 22 January 2018.
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