Presbytis thomasi 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Primates Cercopithecidae

Scientific Name: Presbytis thomasi (Collett, 1892)
Common Name(s):
English Thomas’s Langur, North Sumatran Leaf Monkey, Sumatran Grizzled Langur, Thomas's Langur, Thomas's Leaf Monkey
French Semnopithèque De Thomas
Spanish Langur De Thomas
Presbytis nubilus Miller, 1942

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2c ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Supriatna, J. & Mittermeier, R.A.
Reviewer(s): Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)
The species is considered Vulnerable due to past and continued population declines, estimated at more that 30% over the past 40 years (3 generations) due to loss of habitat, especially to logging and oil palm plantations.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species is found in northern Sumatra (Indonesia) in Aceh Province north of the rivers Simpangkiri and Wampu (Wilson and Wilson 1976), where the range has recently been discovered to extend to the south bank of the Simpangkiri River (Aimi and Bakar 1996). A study on the behaviour of this species was performed at Ketambe Research Station, Leuser Ecosystem, Sumatra, Indonesia (3°41 N, 97°39 E) (Sterck et al. 2005). Another study on its behaviour was performed at two sites in Leuser Ecosystem, northern Sumatra, one of which was also Ketambe, and the other was Bukit Lawang (3°30 N, 98°6 E) (Wich and de Vries 2006).
Countries occurrence:
Indonesia (Sumatera)
Additional data:
Upper elevation limit (metres):1500
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:During a study of this species' behaviour by Sterck et al. (2005) 163 different individuals were recorded, in a study area of 200 ha.
Current Population Trend:Decreasing
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:This species has been recorded from undisturbed primary rainforest near Ketambe Research Station in Sumatra (Sterck et al. 2005). It has also been recorded from a mosaic of primary and secondary forest with rubber plantations on its fringes (Wich and de Vries 2006), and in rubber tree plantations (Gurmaya 1986). It ranges in elevation from 0 to approximately 1,500 m, and the home range has been observed to be 12.3-15.7 ha.

These animals are primarily folivorous (Ungar 1995) but also feed on fruits and flowers, and occasionally on toadstools and the stalks of coconuts (Gurmaya 1986), as well as gastropods such as ground snails (Steenbeek 1999). Females are considered adult at an age of 60 months, roughly one year before the average age at which infants were born (74 months), and the youngest age at which a female in a study population gave birth (Sterck et al. 2005).

Threats [top]

Major Threat(s): Hunting does not seem to be a significant threat, but loss of primary habitat due to logging and conversion to oil palm plantations is probably displacing some populations.

Conservation Actions [top]

Conservation Actions: This species is listed on CITES Appendix II and is protected by Indonesian law. It is known to occur in at least one large national park, Gunung Leuser.

Classifications [top]

1. Forest -> 1.6. Forest - Subtropical/Tropical Moist Lowland
suitability:Suitable  major importance:Yes
1. Forest -> 1.9. Forest - Subtropical/Tropical Moist Montane
suitability:Suitable  major importance:Yes
14. Artificial/Terrestrial -> 14.3. Artificial/Terrestrial - Plantations
1. Land/water protection -> 1.1. Site/area protection
2. Land/water management -> 2.1. Site/area management

In-Place Research, Monitoring and Planning
In-Place Land/Water Protection and Management
  Occur in at least one PA:Yes
In-Place Species Management
In-Place Education
  Included in international legislation:Yes
  Subject to any international management/trade controls:Yes
2. Agriculture & aquaculture -> 2.1. Annual & perennial non-timber crops -> 2.1.2. Small-holder farming
♦ timing:Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

2. Agriculture & aquaculture -> 2.1. Annual & perennial non-timber crops -> 2.1.3. Agro-industry farming
♦ timing:Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

5. Biological resource use -> 5.3. Logging & wood harvesting -> 5.3.5. Motivation Unknown/Unrecorded
♦ timing:Ongoing    
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

3. Monitoring -> 3.1. Population trends

Bibliography [top]

Aimi, M. and Bakar, A. 1996. Distribution and deployment of Presbytis melalophos group in Sumatera, Indonesia. Primates 37(4): 399-409.

Groves C.P. 2001. Primate Taxonomy. Smithsonian Institution Press, Washington, DC, USA.

Gurmaya, K. 1986. Ecology and behavior of Presbytis thomasi in northern Sumatra. Primates 27(2): 151–172.

Steenbeek, R. 1999. Tenure related changes in wild Thomas's langurs I: between-group interactions. Behaviour 136: 595v625.

Steenbeek, R. and Van Schaik, C. 2001. Competition and group size in Thomas's langurs (Presbytis thomasi): the folivore paradox revisited. Behavioral Ecology and Sociobiology 49(2-3): 100–110.

Sterck, E. H. M., Willems, E. P., Van Hooff, J. A. and Wich, S. A. 2005. Female dispersal, inbreeding avoidance and mate choice in Thomas langurs (Presbytis thomasi). Behaviour 142: 845-868.

Ungar, P. S. 1995. Fruit preferences of four sympatric Primate species at Ketambe, northern Sumatra, Indonesia. International Journal of Primatology 16(2): 221-245.

Wich, S. A. and de Vries, H. 2006. Male monkeys remember which group members have given alarm calls Royal Society of London. Proceedings Biological Sciences 273(1587): 735-740.

Wilson, C. C. and Wilson, W. L. 1976. Behavioral and morphological variation among primate populations in Sumatra. Yearbook of Physical Anthropology 20: 207-233.

Citation: Supriatna, J. & Mittermeier, R.A. 2008. Presbytis thomasi. The IUCN Red List of Threatened Species 2008: e.T18132A7667839. . Downloaded on 26 September 2018.
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