Simias concolor
simakobou
(Also: pig-tailed langur)

Simias 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. (Burton, 1995; Eudey and Members of the Primate Specialist Group 2000, 2004)

The habitat of S. concolor includes hillsides in primary forests. It is uncertain whether S. 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. (Burton, 1995; Nowak, 1999)

The body length of S. 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 S. concolor varies between 14 and 15 cm. Two color varieties exist for S. 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 S. 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. (Ankel-Simons, 2000; Burton, 1995; Noë and Bshary, 2001)

No information is available regarding the lifespan and longevity of S. concolor, but its relative N. larvatus lives at least 23 years in captivity. (Woltanski, 2004)

Little is known about the behavior of S. 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 S. 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. (Ankel-Simons, 2000; Nowak, 1999; Tilson, 1977; Vogel and Winkler, 1990)

Home Range

The size of the average S. 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. (Tilson, 1977; Vogel and Winkler, 1990)

Communication between individuals and groups of S. 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. (Burton, 1995; Tilson, 1977)

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 . (Burton, 1995; Tilson, 1977)

The only known enemy or predator of S. 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 S. concolor. (Vogel and Winkler, 1990; Whitten and Whitten, 1982)

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

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

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. (Burton, 1995)

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 S. 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 S. concolor has decreased by 50% during the last decade and will most likely continue to drop another 50% during the next decade. (Burton, 1995; Eudey and Members of the Primate Specialist Group 2000, 2004; Nowak, 1999)

This species was previously recognized under the name Nasalis concolor.