Silvery Lutang, Trachypithecus cristatus

The silvery lutang (Trachypithecus cristatus), also known as the silvery langur or the silvered leaf monkey, is a species of Old World monkey that can be found Sumatra, Borneo, and Peninsular Malaysia. It prefers to reside in mangrove, riverine, and coastal forests. This species holds two recognized subspecies known as Trachypithecus cristatus selangorensis and Trachypithecus cristatus cristatus.

The silvery lutang varies in size depending upon the sex, with males reaching an average body length between twenty to twenty-three inches, with a weight of fifteen pounds, and females reaching a length of eighteen to twenty inches, with a weight of thirteen pounds. Its fur is black or dark brown in color with silver tips and females hold a white patch of fur on their groin. As is typical to langur species, it has a three-chambered stomach that allows it to digest its food in a similar manner to ruminants.

The silvery lutang is active during the daytime hours and rests in trees during the nighttime. It resides in groups that hold nine to forty individuals, with a social hierarchy that is led by a dominant male and then by a harem of females, which holds its own social hierarchy. These groups contain multiple females and juvenile individuals. Each group holds a home range between 49 and 110 acres and some home ranges overlap. Groups may separate while foraging for food, with females forming smaller groups that are separate from the male. When groups encounter each other, males will first try to ward off rival males and then fight if necessary. If strange groups only contain females, violence is much less likely to occur. This species is able to make a variety of calls including defense calls, alert calls, and communication calls.

The silvery lutang is able to breed throughout the year, but females can only give birth every eighteen to twenty-four months. After a pregnancy period between 181 and 200, females give birth to one young that has orange fur and white skin. Young will attach themselves to their mother for the early part of their life and will be taken care of by multiple females until they are weaned at eighteen months of age. Males will disperse from their natal colonies while females will remain. The average lifespan of this species is thought to be thirty-one years in captivity and wild females are thought to undergo menopause, living nearly nine years after their last birth.

The silver lutang primarily consumes leaves, but it will also consume small amounts of seeds, fruits, and flowers. This is not typical to monkeys within its subfamily, Colobinae, so it can reside in different areas of a forest than other monkeys. This species is hunted by large predators including tigers, leopards, and dholes, while infants can be hunted by civets and other small predators. This species is threatened by habitat loss caused by logging and by hunting for the pet trade and for food. The silver lutang appears on the IUCN Red List with a conservation status of “Near Threatened.”

Image Caption: Silvery Lutung. Credit: Stavenn/Wikipedia (CC BY-SA 3.0)