Indonesian Primate Profile

Jurnal Primatologi Indonesia, Vol. 13, No. 2, Juli 2016, hlm. 1-2 ISSN 1410-5373 Indonesian Primate Profile Presbytis thomasi Common names: Kedih (Indonesia); Thomas’s Langur, North Sumatran Leaf Monkey, Thomas’s Langur, Sumatran Grizzled Langur, Thomas’s Leaf Monkey (British); Semnopithèque De Thomas (French); Langur De Thomas (Spanish) Picture 1 Left, Presbytis thomasi (kedih) at Bukit Lawang, North Sumatra (source: Richard Gonzalez); right, white kedih at Taman Margasatwa Ragunan, Jakarta (source: Walberto Sinaga) Presbytis thomasi is one of the several pinkish skin which also covers their muzzle. langurs found in the oriental Islands; however, The average weight of a Thomas's langur its geographic range is fairly limited. They is 6,69 kg for adult females, and 6,67 kg for are native to North Sumatera, Indonesia; adult males. The tail length is 500 to 850 mm, more specifically, north of Wampu River and and body length is 420 to 620 mm (Colijn and Simpang Kiri River (Colijn and Muchtar 1996, Muchtar 1996, Flannery 2004, Nowak 1999). Nowak 1999). The mating system of P. thomasi is When searching through tropical still being disputed. In the Encyclopedia of rainforests, rubber plantations, and both primary Mammals, it is noted that the species is a and secondary forests, one is able to encounter monogamous primate. The female initiates the Thomas’s langurs. Since they are arboreal, mating by performing various acts to persuade we can find this unique species high in trees. her male counterpart, such as releasing certain However, they position in trees depends on the smells and displaying genitalia (Colobus and time of day. During the day, they select trees that Leaf Monkeys 2001). have lots of twigs and leaves to protect them However, others dispute the monogamy from the harsh sunlight. At night, they sleep in of the species. Steenbeck et al. (1999) stated that the top of tall trees in open areas (Colijn and within groups, there are often several females Muchtar 1996, Flannery 2004, Gurmaya 1986). and one breeding male. A possible resolution This species have very distinctive between the two observations is that only one appearance. Due to their unique facial coloration, of the females in the group breeds with the male it is easy to distinguish the North Sumatran leaf while the other females help raise the young monkeys from other primates. (Steenbeek et al. 1999). The white fur on the underside and arms There is no specified breeding interval for (which contrasts the black fur surrounding the Thomas’s langurs. However, even though the rest of the body) continues up around the neck. breeding season is not restricted, there tends Two white stripes, starting from the top of the to be an increase in mating when the following head, running down the sides, coming together weaning period is expected to correspond with in a V-shape and encircling the eyes. A purple- an abundance of food. The gestation period silver inner layer forms rings around their lasts 5 to 6 months. At the end of gestation, P. orange-brown eyes. Under their dark skin is a thomasi female produce one young at a time. 2 Jurnal Primatologi Indonesia, Volume 13, Nomor 2, Juli 2016, hlm. 1-2 Females rarely produce more than one offspring Colijn E, Muchtar M. 1996. Primates of at a time, and never more than two. Weaning Indonesia-Presbytis Thomasi (Collet occurs at 12 to 15 months, after which an 1893) (On-line). The Indonesian Nature offspring is supposed to become independent. Conservation Database. Accessed February Although they are fully independent, juveniles 08, 2004 at http://www.nature-conservation. do not reach sexual maturity until 4 or 5 years of or.id/primates/presbytis_thomasi.html. age (Colobus and Leaf Monkeys 2001, Eimerl Eimerl S, DeVore I. 1965. Life Nature Library: and DeVore 1965). The Primates. New York: Time-Life Books. The average lifespan of P. thomasi is 20 Flannery S. 2004. Thomas Leaf-monkey years. In captivity, the average lifespan is 29 (Presbytis thomasi) (On-line). The Primata. years. The nine-year difference may be due Accessed April 10, 2004 at http://members. to numerous factors such as the destruction tripod.com/uakari/presbytis_thomasi.html. of habitat, hunting by humans, the presence Gurmaya K. 1986. Ecology and Behavior of of natural predators, and attacks between Presbytis thomasi in Northern Sumatra. neighboring groups (Colobus and Leaf Monkeys Primates, 27(2): 151-172. 2001). Nowak R. 1999. Primates; Family These langurs spend most of the day in CERCOPITHECIDAE: Old World groups either resting, feeding, or moving. These Monkeys. Pp. 599-600 in Walker›s groups usually consist of five females and one Mammals of the World, Vol. I, 6th Edition. male, but there can also be small groups of Baltimore and London: The Johns Hopkins males or individual males living alone. University Press. Within these groups, there is a dominance Steenbeck R, van Schaik C. 2001. hierarchy that everyone, both male and female, Competition and group sive in Thomas’s are subject to a dominance in hierarchy. It has langurs (Presbytis thomasi): the folivore been suggested that an individual’s rank within paradox revisited. Behavioral Ecology and the hierarchy may depend on its age or its ability Sociobiology, 49(2-3): 100-110. Accessed to defend itself against others in the group March 07, 2004. (Colobus and Leaf Monkeys 2001, Eimerl and Steenbeek R, Piek R, van Buul M, van DeVore 1965, Gurmaya 1986, Steenbeek et al. Hooff J. 1999. Vigilance in wild Thomas’s 1999). langurs (Presbytis thomasi): the importance Even though this langur is known for of infanticide risk. Behavioral Ecology having a calmer demeanor in gestures and and Sociobiology, 45: 137-150. Accessed responses to conspecifics than other primates, February 11, 2004. competition has been observed within groups. Sterck E. 1997. Determinants of female Competition increases with the size of the group, dispersal in Thomas Langurs. Am J of and the femlaes show a preference for smaller Primatol, 42(3): 179-198. groups due to the decrease in risk of infanticide. Sterck E. 2002. Predator sensitive foraging Group sizes are often dependent upon female in Thomas langurs. Pp. 74-91 in L Miller, dispersal (Colobus and Leaf Monkeys 2001, ed. Eat or be eaten: Predator sensitive Steenbeck and van Schaik 2001). foraging among primates. Cambridge, UK: Many factors influence a female’s Cambridge University Press. decision to leave her group and join another. Swindler D. 1998. Introduction to the These include competition for food, the risk of Primates. Seattle and London: University of predation, and avoidance of inbreeding. Washington Press. More important is the avoidance of infanticide. Often a female leaves her group to protect her young from infanticide (Sterck 1997). References Andromeda Oxford Ltd. 2001. Colobus and Leaf Monkeys. Pp. 380-393 in D Macdonald, ed. The Encyclopedia of Mammals, Vol. II: Primates and Large Herbivores, 2nd Edition. 132 West 31st Street, New York NY 10001: Facts on File, Inc..

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