Together with the red slender loris (Loris tardigradus), the grey slender loris (Loris lydekkerianus) is a type of slender loris (genus Loris) in the strepsirrhine primate family Lorisidae.[1] In 1908 Spanish zoologist Ángel Cabrera first described the Mysore slender loris (Loris tardigradus lydekkerianus) in Chennai, India, which he named for the English naturalist Richard Lydekker. This subspecies was further described by William Charles Osman Hill in his seminal primate book Primates: Comparative Anatomy and Taxonomy (1953). Hill believed there was one species of slender loris which was further split into six subspecies, two in India and four in Sri Lanka. In 1998 biological anthropologist Colin Groves recognised two species, L. tardigradus and L. lydekkerianus, which have been widely accepted by the scientific community. Loris lydekkerianus now includes four geographically separated subspecies, L. l. lydekkerianus (previously L. t. lydekkerianus) and L. l. malabaricus in India and L. l. nordicus and L. l. grandis in Sri Lanka.

• Genus Loris

  • Red slender loris, Loris tardigradus

  • Gray slender loris, Loris lydekkerianus

    • Malabar slender loris, Loris lydekkerianus malabaricus

    • Mysore slender loris, Loris lydekkerianus lydekkerianus

    • Northern Ceylonese slender loris, Loris lydekkerianus nordicus

    • Highland slender loris, Loris lydekkerianus grandis

A slender loris group known as the montane slender loris (taxon nycticeboides) has had uncertain classification and variously placed as a subspecies of L. lydekkerianus, L. tardigradus, and as a distinct species. A 2019 study based on partial CO1 sequences showed the taxon can be classified in a single haplogroup with L. t. tardigradus.

Found in southern India and Sri Lanka, the gray slender loris inhabits primary and secondary rainforest, dry semi-deciduous forest, and montane cloud forest up to 2,000 metres (6,600 ft) above sea level. It is found in south-western India roughly between the Tapti and Godavari Rivers down to the south coast of the subcontinent. The subspecies are separated geographically. In south-western India, the Malabar gray slender loris occurs in the wet forests of the Western Ghats in the states of Karnataka, Kerala and Tamil Nadu up to an altitude of 1,200 metres (3,900 ft). The Mysore gray slender loris inhabits the tropical dry forests of the Eastern Ghats in the states of Andhra Pradesh, Karnataka and Tamil Nadu, frequenting open Euphorbia scrub forests and Acacia trees at an altitude of 300–500 metres (980–1,640 ft). It can also be found on the dry eastern slopes of the Western Ghats.

Although considered near threatened on the IUCN Red List and classified under Schedule I (Part 1) of the Indian Wildlife Act, 1972, the threat to these primates is increasing. Loris is used to make love potions, treat leprosy and eye ailments. Some villagers keep lorises as pets, but because they are difficult to maintain there is high mortality. Some cities have them captive in zoos, and astrologers use them to pick out tarot cards. Insects form the main source of food for lorises. Farmlands, which are high in cattle waste, produce large amounts of insects. Thus lorises do not compete with humans for resources and therefore tend to be tolerated by them. Habitat fragmentation is also a threat to the loris population, as well as loss of acacia trees, which is a preferred tree species for the loris. Conservation efforts are developing and more research on conservation efforts are ongoing.

Gray Slender Loris (Loris lydekkerianus lydekkerianus) - Thattekad Bird Sanctuary, Kerala India

Sri Lanka Gray Slender Loris (Loris lydekkerianus nordicus) - Sigiriya Forest area

Red Slender Loris (Loris tardigradus) - Kitulgala Forest, Sri Lanka