Simias concolor

Geographic Range

Nasalis concolor (the pig-tailed langur) is presently found only on the Mentawai Islands off the west coast of Sumatra in Indonesia. This species has been eliminated entirely from some islands due to logging and hunting by humans.

• Biogeographic Regions
• oriental oriental
  • native native

• Other Geographic Terms
• island endemic island endemic

Habitat

The habitat of N. concolor includes hillsides in primary forests. It is uncertain whether N. concolor also resides in swamps and mangrove forests with different sources stating different information regarding its presence in these environments. This species is entirely arboreal and only comes down from the trees when it is disturbed.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• rainforest rainforest

Physical Description

The body length of N. concolor ranges from 490 to 550 mm in males and from 460 to 550 mm in females. The average weight is around 8.7 kg for males and 7.1 kg for females. The tail length of N. concolor varies between 14 and 15 cm. Two color varieties exist for N. concolor , a dark grey phase and a creamy buff phase, with the dark grey phase being more common. The creamy buff phase is found in roughly one in four individuals. The limbs are of equal length and the tail is rather short compared to other primate species in the subfamily Colobinae . Adult pig-tailed langurs have black faces and small snub-noses. The coat of the dark phase of N. concolor is blackish-brown with light speckled hair on the nape, shoulder, and upper back. The tail of this species is not only short, but also hairless, except for a small amount of hair at the tail tip.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Reproduction

Males have been observed participating in displays of strength that consist of leaping through the trees to attract mates. The social group of N. concolor includes one male and up to four females with which the male mates.

• Mating System
• polygynous polygynous

Few data exist regarding the reproductive cycle of N. concolor , but it is believed that a single birth occurs sometime during June and July. This species also exhibits sexual swelling, a trait that is rare in other Asian colobines.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

Little is known about the parental investment of N. concolor , but there is information about their close relatives, proboscis monkeys, Nasalis larvatus . Female N. larvatus carry, nurse, and stay close to their young for about a year. While the males do not provide as much care as the females, they do protect their young from males from other groups.

• Parental Investment
• altricial altricial
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

No information is available regarding the lifespan and longevity of N. concolor , but its relative N. larvatus lives at least 23 years in captivity.

Behavior

Little is known about the behavior of N. concolor because there are so few in such a limited geographical range as well as the difficulty in spotting them in their dense forest habitat. There are two distinct group types exhibited in N. concolor , family groups and groups of all males; each exhibit unique behaviors. The most common type of grouping is the family group of one male and up to 4 females. These groups can be formed with a single adult couple and their young or with more than one adult female with a single male. Family group members maintain very close proximity, rarely traveling more than 5 m (16 ft.) away from one another. They also restrict vocal communication, only using it at designating group boundaries and as a warning to predators. The all male groups exhibit behaviors that produce excessive noise as they travel through the forest, communicate with others, and leap in displays of strength.

• Key Behaviors
• arboreal arboreal
• diurnal diurnal
• motile motile
• sedentary sedentary
• territorial territorial
• social social

Home Range

The size of the average N. concolor territory is between 16.3 and 50 acres (6.5 to 20 ha). Individuals are not observed deep inside other territories, but are seen on the margin of adjacent territories. During encounters with other groups, the males approach, make loud vocalizations and return to their home territory with the other group members following behind. Chasing and fighting are generally not observed during these encounters.

Communication and Perception

Communication between individuals and groups of N. concolor is achieved by producing loud calls in a series of vocalizations ranging from 2 to 25 nasal barks. These barks can travel at least 500 m through the rainforest. The purpose of these calls is believed to be to maintain group structure and boundaries. Males call out with loud nasal barks and females reply with sharp squeals. It is also likely that chemical cues are used widely in communicating reproductive state and that vision and touch are important.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

This species eats leaves, fruits, and berries. Feeding occurs after sunrise near the trees used for sleeping and again in the afternoon. Adult males lead the foraging and the females and young follow behind .

• Primary Diet
• herbivore herbivore
  • folivore folivore
  • frugivore frugivore

• Plant Foods
• leaves
• fruit
• flowers

Predation

The only known enemy or predator of N. concolor is man. Other large predators on the Mentawai Islands include crested serpent eagles ( Spilornis cheela ) and pythons ( Python reticulatus ), both may also prey on N. concolor .

Ecosystem Roles

There is little available information on the ecosystem role of the pig-tailed langur. They may aid in seed dispersal of tropical fruiting trees.

Economic Importance for Humans: Positive

Pig-tailed langur meat is considered a delicacy. These are important members of the ecosystems in which they live, they could contribute to the development of the ecotourism industry in the Mentawai islands.

• Positive Impacts
• food food
• ecotourism ecotourism

Economic Importance for Humans: Negative

There are no known adverse affects of N. concolor on humans.

Conservation Status

Pig-tailed langurs are listed as an endangered species under the IUCN. The population consists of fewer than 10,000 individuals. Habitat loss due to logging is the main cause of population decline. Hunting is also a major problem, especially in the Pagai Islands because N. concolor meat is considered a delicacy. This species receives protection at the Teiteibatti Wildlife Reserve, located on the only island that provides such security. It is believed that the population size of N. concolor has decreased by 50% during the last decade and will most likely continue to drop another 50% during the next decade.

Other Comments

This species was previously recognized under the name Nasalis concolor .

Additional Links

Encyclopedia of Life

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Lyndsay Rankin (author), Michigan State University, Barbara Lundrigan (editor, instructor), Michigan State University.

References

Ankel-Simons, F. 2000. Primate Anatomy: An Intrduction . San Diego, California: Academic Press.

Burton, F. 1995. The Multimedia Guide to the Non-human Primates . Scarborough, Ontario: Prentice Hall Canada.

Eudey, A., Members of the Primate Specialist Group 2000. 2004. "IUCN Red List of Threatened Species: Simias concolor" (On-line). Accessed March 16, 2006 at http://www.iucnredlist.org/search/details.php?species=20229 .

Nowak, R. 1999. Pig-tailed Langur. Pp. 596-597 in Walker's Mammals of the World , Vol. 1, 6th Edition. Baltimore: The Johns Hopkins University Press.

Noë, R., R. Bshary. 2001. Colobus and Leaf Monkeys. Pp. 380-395 in The Encyclopedia of Mammals , Vol. 2, Revised Edition. New York: Facts on File.

Tilson, R. 1977. Social organization of simakobu monkeys (Nasalis concolor) in Siberut Island, Indonesia. Journal of Mammalogy , 58(2): 202-212.

Vogel, C., P. Winkler. 1990. Langurs and Colobi. Pp. 296-324 in Grzimek's Encyclopedia of Mammals , Vol. 2, 1 Edition. New York: McGraw-Hill Publishing Company.

Whitten, A., J. Whitten. 1982. Preliminary observations of the Mentawai macaque on Siberut Island, Indonesia. International Journal of Primatology , 3(4): 445-459.

Woltanski, A. 2004. "Nasalis larvatus" (On-line). Animal Diversity Web. Accessed April 18, 2006 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Nasalis_larvatus.html .