Douc Langurs
(Pygathrix nemaeus)
The place of the douc langur in the general phylogeny of the Asian colobines has been the subject of an ongoing debate. The standard description of the red shanked douc langur is as follows. The legs are maroon from the knees to the ankle with the thighs, fingers and toes black. The body is gray with agouti hairs of black, white & gray. The arms are white from the elbows to the wrists & the upper arms are gray like the body.
A prominent white triangular rump patch surrounds the long (589- 770 millimeter) tail of the same color. Adult and juvenile males can be distinguished from females by the circular white spot found on either side and superior to the corners of the rump patch. This dimorphic characteristic is found in both the red and black shanked douc langur. Both sexes of each species exhibit a white perineum.
The white hairs on the cheeks of the red shanked douc are long (in comparison to the black shanked douc) and red predominates over black in the two colored frontal band over the eyes. The face around the eyes is reddish yellow. In the black shanked douc, the cheek hairs are characteristically short and black predominates over red on the two color frontal band. The region around the eyes is black, imparting a black coloring to the entire face.
In the black shanked douc langur, the hindlimbs are entirely black and the forelimbs (except for the fingers) and the body are gray (agouti hairs) with the chest being a lighter gray than the rest of the body.
Douc langur diets are dominated by tree leaves, petoles and buds with secondary use of fruits and seeds.
Douc langurs inhabit tropical rainforests from sea level to 2,000 meters. Douc langurs are found most frequently in primary evergreen forests of Vietnam and Laos. Once thought to be rare with limited distributions, recent fieldwork has demonstrated that douc langur populations are quite widespread and found in a variety of habitats and that they display ecological and social flexibility.
The red shanked douc langur (Pygathrix nemaeus nemaeus) has been located in north, central and southern provinces of Vietnam. The black shanked douc langur (Pygathrix nemaeus nigripes) distribution appears to be confined to various provinces of southern Vietnam.
While douc langur monkeys are restricted to wooded habitats, they occur in a variety of forest types. Populations of doucs have been located from both monsoon forests as well as rainforests and include: semi-evergreen, lowland lower montane and upper montane forest types.
The species is diurnal and arboreal. It eats a wide variety of leaves and also certain abundant fruits. Early reports suggested a group size of 30-50 individuals, but recent observations indicate a usual range of 4-15. Groups contain 1 or more adult males and generally about twice as many adult females. Each sex apparently has its own dominance hierarchy, and males are dominant over females. In the wild, a peak in births probably occurs between February and June, being correlated with maximum seasonal availability of fruit. The estrous cycle is 28-30 days long, and estimates of gestation have ranged from 165 to 190 days.
Douc Langurs are considered as endangered species.They are thought to have declined because of environmental disruption brought on by military activity during the Viet Nam War and because of excessive hunting by people for food.
