The Bengal slow loris (Nycticebus bengalensis), also known as the northern slow loris, is a strepsirrhine primate and a species of slow loris native to Bangladesh, Northeast India, Cambodia, Laos, Myanmar, Vietnam, southern China, and Thailand. It has the largest geographic range of any slow loris species.
Taxonomy and Phylogeny
Formerly considered a subspecies of the Sunda slow loris (Nycticebus coucang), it was recognized as a distinct species in 2001 by taxonomist Colin Groves. Phylogenetic analysis suggests it is most closely related to the Sunda slow loris, though introgressive hybridization has occurred between the two species in regions of sympatry in southern Thailand.
Anatomy and Physiology
The Bengal slow loris is the largest species of slow loris. It measures 26 to 38 cm (10–15 in) from head to tail and weighs between 1 and 2.1 kg (2.2–4.6 lb). It has dense, woolly, brown-gray fur on its back and white fur on its underside, with a dark dorsal stripe running up to the top of its head. It possesses a vestigial tail, a round head, flat face, large eyes adapted for nocturnal vision (enhanced by a tapetum lucidum), and a wet rhinarium. It secretes a toxin from a brachial gland on its elbow, which differs chemically from that of other slow loris species and may convey information about sex, age, health, and social status.
Behavior and Ecology
The Bengal slow loris is nocturnal and arboreal, inhabiting evergreen and deciduous rainforests with dense canopies. Its diet is primarily frugivorous but also includes insects, tree gum, snails, small birds, and reptiles. In winter, it relies heavily on plant exudates such as sap and gum, obtained by gouging bark. It lives in small family groups, marks territory with urine, and sleeps curled up in dense vegetation or tree holes during the day. It is not a seasonal breeder; females reproduce once every 12–18 months, typically giving birth to a single offspring after a six-month gestation. Offspring are carried for about three months and reach sexual maturity at approximately 20 months. The species can live up to 20 years.
Distribution
The species is found across Bangladesh, Northeast India (Assam, Mizoram, Nagaland, Meghalaya, Manipur, Tripura), Cambodia, Laos, Myanmar, Vietnam, Thailand, and southern China (Yunnan and Guangxi). It is sympatric with the pygmy slow loris in parts of China, Vietnam, and Laos, and with the Sunda slow loris on the southern Thai peninsula.
Conservation Status
The Bengal slow loris is listed as Endangered on the IUCN Red List (2020 assessment) and is included in CITES Appendix I, which prohibits international commercial trade. Major threats include the exotic pet trade, use in traditional medicine, habitat loss from deforestation and slash-and-burn agriculture, and hunting. Wild populations have declined severely, and the species is locally extinct in several regions. It is found within numerous protected areas across its range, but poaching and illegal logging remain rampant.
