Purple Faced Langur, Trachypithecus vetulus

The purple-faced langur or purple-faced leaf monkey (Trachypithecus vetulus) is a species of Old World monkey that can be found in Sri Lanka. It prefers to reside in mountainous areas in southwestern regions of this range, in habitats known as wet zones. It can be found in the canopies of dense forests at low elevations. This species holds four subspecies including the western purple-faced langur, which is one of the most endangered primates in the world, and the dryzone purple-faced langur. These subspecies and the main species vary in color and skull shape.

The purple-faced langur is thought to reside in groups of up to twenty-five individuals, like other langurs, and it is known to make a variety of sounds. These sounds are loud calls that are used to identify individuals, alert others to danger, and find mates. The calls are separated into the three categories of whoops, harsh barks, and residuals. It has been found to emit more calls on sunny days than on cloudy days, and most calls subside during the evening hours. The calls of the main species are distinct from those of all four subspecies and can even resemble the roar of a leopard. This species is primarily consumes leaves, but it will seeds, flowers, and fruits, especially within areas that have a high rate of human encroachment.

The main threat to the purple-faced langur is habitat loss, which has caused a loss of sixty-five percent of its wet-zone habitat between the years of 1980 and 2001. It now holds only three percent of its original range and humans now populate ninety percent of this range. This species is also threatened by hunting and secondary threats caused by human encroachment including roads, pesticides, and a decrease in food supply. Conservation efforts are focused on habitat management, creating new protected areas as refuges for the species, and increasing population numbers. The purple-faced langur currently appears on the IUCN Red List with a conservation status of “Endangered.”

Image Caption: Purple-faced langur spotted in Horton Plains national park, Sri Lanka. Credit: Damithf/Wikipedia (CC BY-SA 3.0)