Purple-faced langur  (Trachypithecus vetulus)

The purple-faced langur’s range has contracted greatly in the face of human encroachment. Deforestation as a result of agricultural, industrial and residential development has led to habitat loss and fragmentation, and the consequent isolation of subpopulations, which impedes out-breeding and genetic diversity. From 1956 to 1993 Sri Lanka lost more than 50 percent of its forests to human activities, followed by a similar rate of decline between 1994 and 2003. This species has also suffered from hunting and illegal trade of its meat and skin, with the skin used to make drums in some areas. The purple-faced langur is hunted mainly for subsistence living and trade at local village level. According to continuing trends, populations of this species are predicted to decline by more than 50 percent within the next 11 to 22 years (1).

The commercial exploitation of purple-faced langurs is regulated by their listing on Appendix II of the Convention on International Trade in Endangered Species (CITES) (3). All four subspecies are also protected under the Flora and Fauna Protection Ordinance 1993, and exist in a number of protected areas (1). However, the issue of habitat loss still places these subspecies, classified as Endangered and Critically Endangered, at serious risk of extinction (1). Indeed, the Critically Endangered western purple-faced langur (T. v. nestor) was officially recognised in 2004 as one of the world’s 25 most endangered primates. This subspecies requires good canopy cover, but possibly fewer than three forests currently exist within Sri Lanka that can support viable populations, and none of these are within protected areas. Furthermore, the human-modified areas that support much of the langur population, such as gardens and rubber plantations, are under private ownership and therefore unstable, changing rapidly due to human population expansion and development. Censuses are therefore urgently needed to identify forest areas suitable for conservation. Further studies are also essential to better understand the decline of sub-populations, in both space and time, in the extremely disturbed habitats where these langurs survive today (6).