Dusky langurs are Old World monkeys, a term describing monkeys from Africa and Asia. The main colour can vary through shades of grey and brown, but the front and tail are lighter. They have white patches around the eyes and mouth. Baby dusky leaf monkeys are born with bright yellow or orange fur and pink faces, they develop their adult colours at six months old.
These monkeys have defined territories that the male(s) will guard. Calls tell other dusky leaf monkeys where the boundaries are. Groups will have a least one male, two females and their offspring with typically 5-20 individuals in a group. In addition to maintaining the territory boundary, males keep the group together and watch for predators. Females look after the offspring.
Females often have a genital swelling to show that they are fertile. Breeding occurs throughout the year, with most babies born in January, February or March.
The diet of dusky langurs is mainly leaves. They also eat other plant material such as seeds, fruit and flowers.
The number of these monkeys has declined at a rate of 30% over the last 30 years. This means that they almost meet the criteria of Vulnerable. However, they are currently classed as Near Threatened. The main threats include habitat loss as farming and human settlements expand and hunting for food. In Malaysia there are also significant deaths on roads.