Survey of the slender loris (Primates, Lorisidae Gray, 1821: Loris tardigradus Linnaeus, 1758 and Loris lydekkerianus Cabrera, 1908) in Sri Lanka

Abstract

In 2001 and 2002, surveys of slender lorises were carried out in Sri Lanka, providing the first recent information on four taxa (Loris lydekkerianus nordicus, L. l. grandis, L. tardigradus tardigradus, and L. t. nycticeboides) endemic to the island. Thirty-one sites across five ecological zones were surveyed. Approximately 766 km were covered in 17 areas where no lorises were found; 192 km were walked or motored in 14 sites yielding 185 sightings of Loris: L. l. nordicus (n=111), L. t. tardigradus (n=69), L. l. grandis (n=4), and L. t. nycticeboides (n=1). Density estimates, based on sightings of animals/km, were: L. t. tardigradus (0.86–13 animals/km) and L. l. nordicus (0.33–50 animals/km). Significantly fewer sightings occurred within protected areas than were made outside of them. Animal densities varied across habitat type with the highest density of lorises occurring in the dry zone in monsoon forests. Presence of Loris is positively associated with insect presence, and negatively associated with primary forest with little undergrowth; taxa differ in their ability to thrive on the edge of human habitations. Human-induced threats include habitat loss, electrocution on live wires, road accidents, the pet trade, and use in traditional medicine. Further behavioural and ecological studies are needed to estimate the habitat requirements for the different taxa of slender loris.