The primates of Sri Lanka are endemic and considered to be Critically Endangered or Endangered. The western purple-faced langur (Trachypithecus vetulus nestor) and the Horton Plains slender loris (Loris tardigradus nycticeboides) are Critically Endangered (IUCN 2007) and have been listed amongst the World’s 25 Most Endangered Primates (Dela and Rowe 2006; Nekaris 2006).
The Toque Macaques (three subspecies), the gray-handed crested langur (Semnopithecus priam thersites), the remaining three subspecies of the purple-faced langur, and the Sri Lankan subspecies of the lorises, L. tardigradus and L. lydekkerianus, are all Endangered (IUCN 2007).
The forest cover of Sri Lanka has been declining at a steady rate over the past few decades due to agricultural and irrigational developmental projects and to human settlements (Erdelen 1988; Wickramagamage 1998). Recent developments in the industrial and agricultural sectors and the growing human population have been particularly damaging to the country’s remaining forests, and a greater awareness of their plight and measures for their protection are paramount for the survival of these primates.
The total closed-canopy forest cover decreased from about 84% of the total land area in 1881 to about 30% in 2005. Rudran (2007) estimated that 81% of the habitat of the Critically Endangered western purple-faced langur is in deforested areas with dense human populations, and only two natural forest patches of about 21 km2 remaining around two reservoirs. Owing to the expansion of the plantation industry, forest cover in the hill country has been reduced to isolated patches on hill tops and a handful of reserves above the 1,524 m contour (Wickramagamage 1998), posing a serious threat for the survival of the Endangered slender loris, L. t. nycticeboides (Mittermeier et al. 2007) and this species was rediscovered after 72 years by researchers from Nuwaraeliya.
Most of the forests in wet zone and dry zone areas have been fragmented. As a result, primates tend to frequent farms and agricultural plots in search of food. This inevitably creates conflict, as has been reported in many parts of Sri Lanka.