Trachypithecus obscurus (Reid, 1837)

Russell A. Mittermeier, Anthony B. Rylands & Don E. Wilson, 2013, Cercopithecidae, Handbook of the Mammals of the World – Volume 3 Primates, Barcelona: Lynx Edicions, pp. 550-755 : 747

150.

Dusky Langur

Trachypithecus obscurus

French: Langur obscur / German: Brillenlangur / Spanish: Langur de anteojos

Other common names: Dusky/Spectacled Leaf Monkey, Dusky Leaf-monkey, Spectacled Langur; Blond-tailed Langur/ Creamy-tailed Dusky Langur (flavicauda), Cantor's Dusky Langur/Cantor’s Langur (halonifer), Koh Pennan Dusky Langur/ Phangan Langur (seimund)), Perhentian Island Dusky Langur/Perhentian Langur (styx), Reid's Dusky Langur (obscurus), St. Matthew Island Dusky Langur/Zadetkyi Kyun Langur (sanctorum), Tarutao Langur / Terutau Island Dusky Langur (carbo)

Taxonomy. Semnopithecus obscurus Reid, 1837 ,

Malaysia. Restricted by F. N. Chasen in 1940 to Malacca.

With T. phayrei , T. barbei , and T. crepusculus , I. obscurus forms the obscurus species group. The island subspecies, in particular, are quite similar to one another. Seven subspecies: recognized2.

Subspecies and Distribution.

T.o.obscurusReid,1837—PeninsularMalaysia(SfromaboutPerlis).

1:o.carboThomas&Wroughton,1909—Langkawi,Terutau,andDayangBuntingIs,offtheWcoastoftheThai-MalayPeninsula.

T: o. flavicauda Elliot, 1910 — S Myanmar (S of ¢.15° 10’ N, and including James, Kisseraing, and King Is in the Mergui Archipelago), SW Thailand (including Khao Lak I), and N Peninsular Malaysia (S to Perlis).

1: o. halonifer Cantor, 1845 — Penang I, off W Peninsular Malaysia.

1: o. sanctorum Elliot, 1910 — Mergui Archipelago (Saint Matthew I), off W Myanmar.

1 o. sesemundi Chasen, 1940 — Ko Phangan I; it also may occur on the adjacent E coast of the Thai—-Malay Peninsula.

I: o. styx Kloss, 1911 — East Perhentian I; it also may occur on the adjacent E coast of the Thai-Malay Peninsula.

Descriptive notes. Head-body 42-68 cm (males) and 43-60 cm (females), tail 64—81 cm (males) and 57-79 cm (females); weight 6.1-9.1 kg (males) and 5.8-6 kg (females). Coloration of the Dusky Langur varies considerably, but it is generally grayishblue or black above, with a lighter underside and contrasting whitish or gray on legs and tail, which may also be yellow. Some subspecies can have a prominent light or white crown. Face is dark gray, with characteristic “spectacles” of white skin surrounding eyes, and muzzle is whitish or pink. Sexes are generally similar in appearance, although males are somewhat heavier. “Reid’s Dusky Langur” (7. o. obscurus ) is bronze to medium drab-brown above, with limbs and tail contrastingly pale. There is a distinct dorsalstripe. Its posterior crown patch is creamy or yellow-brown. In the “Blond-tailed Langur” (1. o. flavicauda), there is considerable variation, with some individuals much less contrastingly patterned than others, although all are basically black with creamyyellow or brownish-gray on legs and tail. Adult females tend to be paler and browner than adult males, and subadult males are more blackish. “Cantor’s Langur” (1. o. halonifer) is generally brownish, with a distinct dorsal stripe. Its limbs and tail do not contrast greatly with its body. Its crown is a drab creamy-buff. The “Perhentian Langur” (7: o. styx) is uniformly deep brown, with no trace of a dorsal stripe. Its limbs and tail are only slightly lighter and grayer than its upper body. Crown is buffy. The “Tarutao Langur” (7. o. carbo) is similar to Cantor’s Langur but slightly darker, with its dorsal stripe less clearly marked. The “Phangan Langur” (7. o. seimundi) is a dark insular form similar to the Tarutao Langur but with a browner frontal band and slightly paler limbs. The “Zadetkyi Kyun Langur” (7. o. sanctorum) is black above, with a creamy colored posterior chest. Its arms are black, legs are dark smoky-gray, and feet are black. Its tail is yellow-gray.

Habitat. Primary, secondary, lowland, submontane, and montane forest, up to elevations of 1800 m. The Dusky Langur seems to prefer old growth forests. It can also be found in scrub areas, rubber tree plantations, and gardens. Depending on the region, it is sympatric with the Selangor Silvery Langur (7. selangorensis ), the Banded Langur ( Presbytis femoralis ), and the Pale-thighed Langur ( P. siamensis ).

Food and Feeding. The Dusky Langur is largely folivorous. Its diet contains leaves (58%), fruits (mainly figs) and seeds (35%), and flowers (7%). Insects are occasionally eaten. Groups of Dusky Langurs frequently raid rubber plantations, where they are capable of causing significant damage in a short period of time. Individuals can eat upwards of two kilograms of vegetation daily. Groups split up into subgroups to feed.

Breeding. The Dusky Langur most likely is not a seasonal breeder. Females do not show a sexual swelling during the periovulatory period of their ovarian cycle. A single young is born after a gestation of c¢.150 days. Infants are covered by a bright apricot natal coat that contrasts sharply with adult coloration. All adults participate in raising offspring, and allomothering has been observed.

Activity patterns. The Dusky Langur lives and feeds in the high canopy (25-50 m). It spends ¢.46% of its day resting, 34% feeding, and 20% traveling.

Movements, Home range and Social organization. The Dusky Langur lives in unimale— multifemale or multimale-multifemale groups of 10-17 individuals, with an average of 2-5 males/group. It moves ¢.950 m/day and has a home range of c.33 ha. All-male groups and solitary males also have been observed. Population densities on the mainland are estimated at 1-8-7-3 groups/km?. Locomotion consists of 50% quadrupedal walking and running, 40% leaping, and 9% climbing.

Status and Conservation. CITES Appendix II. Classified as Near Threatened on The IUCN Red List. The subspecies styx, seimundi, and sanctorum are classified as Vulnerable, and obscurus , flavicauda, halonifer, and carbo as Least Concern on The [UCN Red Lust. Major threats to Dusky Langurs are hunting for food and habitat loss and degradation, mainly because of expanding oil palm plantations, agriculture, urbanization, and touristic development. They are sometimes also killed in road accidents. For the insular forms, their restricted distributions make them more vulnerable. The Dusky Langur occurs in at least nine protected areas: Cantor’s Langur in Penang National Park in Malaysia; Reid’s Dusky Langur in Krau Wildlife Reserve and Taman Negara National Park in Malaysia; the Blond-tailed Langur in Khao Sok, Kaeng Krachan, Khao Sam Roi Yot, and Thale Ban national parks in Thailand; the Tarutao Langur in Taratau National Park in Thailand; and the Phangan Langur in Phangan National Park in Thailand. Population estimates are not available, but populations are believed to be stable or only slowly declining. Mainland subspecies are widespread and still common, while insular forms have restricted distributions. Survey work to determine the population and conservation status is needed, particularly for the insular forms.

Bibliography. Badham (1967a), Bennett & Davies (1994), Boonratana et al. (2008), Chasen (1940), Curtin (1976), Curtin & Chivers (1978), Fleagle (1978), Geissmann et al. (2004), Groves (2001), Johns (1986b), MacKinnon & MacKinnon (1980b), Napier (1985), Osterholz et al. (2008), Raemaekers & Chivers (1980), Roos et al. (2007).

Figures

149. Tenasserim Langur (Trachypithecus barber), 150. Dusky Langur (Trachypithecus obscurus), 151. Phayre’s Langur (Trachypithecus phayrei), 152. Indochinese Gray Langur (Trachypithecus crepusculus), 153. Cat Ba Langur (Trachypithecus poliocephalus), 154. White-headed Langur (Trachypithecus leucocephalus), 155. Delacour’s Langur (Trachypithecus delacouri), 156. Francois’s Langur (Trachypithecus francoisi), 157. Black Langur (Trachypithecus ebenus), 158. Laos Langur (Trachypithecus laotum), 159. Hatunh Langur (Trachypithecus hatinhensis)

Subspecies and Distribution. T.o.obscurusReid,1837—PeninsularMalaysia(SfromaboutPerlis). 1:o.carboThomas&Wroughton,1909—Langkawi,Terutau,andDayangBuntingIs,offtheWcoastoftheThai-MalayPeninsula. T: o. flavicauda Elliot, 1910 — S Myanmar (S of ¢.15° 10’ N, and including James, Kisseraing, and King Is in the Mergui Archipelago), SW Thailand (including Khao Lak I), and N Peninsular Malaysia (S to Perlis). 1: o. halonifer Cantor, 1845 — Penang I, off W Peninsular Malaysia. 1: o. sanctorum Elliot, 1910 — Mergui Archipelago (Saint Matthew I), off W Myanmar. 1 o. sesemundi Chasen, 1940 — Ko Phangan I; it also may occur on the adjacent E coast of the Thai—-Malay Peninsula. I: o. styx Kloss, 1911 — East Perhentian I; it also may occur on the adjacent E coast of the Thai-Malay Peninsula.