The Taxonomy, Distribution, and Conservation Status of the Slender Loris (Primates, Lorisidae: Loris) in Sri Lanka

Abstract

External body dimensions and proportions, skull morphology, coat coloration, vocalizations, and genetics have contributed to an increase in the number of diagnosable species among nocturnal primates. Two species of slender loris are currently recognized for Sri Lanka: the red slender loris Loris tardigradus (Linnaeus, 1758), endemic to the wet zone and montane areas; and the grey slender loris Loris lydekkerianus Cabrera, 1908, which is widespread and also occurs in India. The red slender loris has two subspecies, namely the western red slender loris Loris tardigradus tardigradus (Linnaeus, 1758) and the Horton Plains slender loris Loris tardigradus nycticeboides Hill, 1942. Loris t. tardigradus is found in the lowland wet zone and L. t. nycticeboides is restricted to the montane region of south-central Sri Lanka. Two subspecies are also ascribed to Loris lydekkerianus in Sri Lanka, namely the northern Ceylon slender loris Loris lydekkerianus nordicus Hill, 1933, and the highland slender loris Loris lydekkerianus grandis Hill and Phillips, 1932. Loris l. nordicus is found in the dry zone, and L. l. grandis is restricted to the sub-montane region of Kandy and Matale. Another two subspecies are known from southern India. We examined specimens (live and museum) from all climate/vegetation zones in Sri Lanka, for facial and pelage features, external body morphology, and skull morphology, and concluded that there are at least two species and at least six subspecies, though we suspect that some, or all, of these subspecies may be distinct species. Names are available for four of these taxa, and here we describe two new subspecies.