The black-shanked douc is an endangered species of douc found mostly in the forests of eastern Cambodia, with some smaller populations in Vietnam. This species is unique among the doucs in having a largely greyish-blue face. No global population estimate exists, although the Wildlife Conservation Society report an estimated 23,000 individuals present in Cambodia's Keo Seima Wildlife Sanctuary. Prior to the discovery of the significance of this population, the largest populations were believed to be in adjacent Vietnam, where the largest known population is around 500-600 individuals. They are primarily arboreal and their diet consists on leaves, of which they obtain most of their water.
Black-shanked doucs preferentially utiliseevergreen forest, where they maintain the largest group sizes and highest relative densities compared to those in other habitat types. They are also commonly found in semi-evergreen and mixed deciduous forest, although occurrence in this latter type may be sub-optimal due to limited food resources, and can be found in dry deciduous dipterocarp forest but likely only where there are patches of the preferred forest types.
Sociality
Group sizes depend on habitat suitability, and are smaller in sub-optimal habitats. Four major social units occur in the species: one-male units, bands comprising several one-male units, bachelor groups and lone males. In a study in Keo Seima Wildlife Sanctuary, one-male units averaged 7.5 individuals, and were composed of a single male, several females and offspring. Black-shanked doucs have a fission-fusion social system, with fusion of one-male units into bands occurring more commonly in the wet season. The maximum band size recorded in this study was 26 individuals.
Diet
In a study of the largest known population, black-shanked douc were observed to mostly consume seeds, with 40% of feeding records being dedicated to seeds. Leaves, especially young leaves, also were a significant part of the diet. Black-shanked douc were highly selective in their diet, feeding from only 35 positively-identified plant species and with 44% of all feeding records coming from only five plant species.
