Bengal slow loris (Nycticebus bengalensis)

GenusNycticebus (1)
SizeHead-body length: 26 – 38 cm (2)
Weightup to 2 kg (2)

Classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix I of CITES (3).

The largest of the slow loris species, the Bengal slow loris was only recently recognised as a distinct species, having previously been classed as a variation of Nycticebus coucang (2) (4). The Bengal slow loris has a round head with short ears and large, forward-facing eyes (2), which reflect light, giving off a brilliant orange-red “eyeshine” (5). The coat is thick and woolly, with brown-grey upperparts and white underparts, and a distinct dark stripe running up the midline of the back (2). Having a barely noticeable, vestigial tail, this tree-dwelling species relies on its specially adapted hands and feet for climbing, which each bear an opposable thumb widely separated from the other four digits, giving it a pincer-like grip (6). The Bengal slow loris produces a variety of vocalisations such as high-pitched whistles, chitters and clicks (7).

The Bengal slow loris occurs in north-eastern India, Bangladesh, Cambodia, Lao PDR, Myanmar, Vietnam, southern China and Thailand (2).

Generally found in tropical and sub-tropical evergreen and semi-evergreen rainforests, the Bengal slow loris prefers areas with dense canopy cover, as well as forest edges, where insect prey appear to be more abundant (2) (8).

Active during the night, the Bengal slow loris can be found stalking through the trees with slow, deliberate movements as it searches for food (6). Its diet is varied, consisting mainly of plant exudates such as gums and resins, but also nectar, fruits, insects, bark and bird eggs (9).

One of the more curious aspects of slow loris biology is the production of a toxic substance from glands on the insides of the elbows. This toxin, secreted in sweat, is licked off the gland and mixed with saliva (activating the toxin) where it appears to be channelled up the fine comb-like teeth at the front of the mouth. When defending itself, the loris’s bite may transmit this poison, and people who have been bitten have reported it to be particularly painful, with anaphylactic shock occurring in some cases (7).

Little is currently known about the social behaviour or reproductive biology of the Bengal slow loris in the wild (2).

There is currently severe degradation and loss of suitable Bengal slow loris habitat occurring throughout its range. The extent of this destruction in certain regions is decimating local populations or eradicating them entirely (2). In north-eastern India, one of the key causes of habitat loss is a practice known as jhum, whereby hillside forest is burnt in order to create fertile agricultural land. In addition, and as a result of development in and around Bengal slow loris habitat, it has been recorded that numerous individuals are killed by vehicles while crossing roads (10).

Aside from habitat destruction, the Bengal slow loris has been extensively hunted for its meat (10) and for use in traditional medicine. Many have also been trapped for sale in the international pet trade, and while this is now illegal, a black market trade persists (2).

In response to the high levels of trade in loris species, the Bengal slow loris was transferred in 2007 from the Convention on International Trade in Endangered Species (CITES) Appendix II, where commercial trade is permitted, to Appendix I, making all international trade in this species illegal. In addition to this international protection, the Bengal slow loris is protected by national law in the countries in which it occurs, although enforcement is lacking in many regions. The same is true of Bengal slow loris habitat, which, despite having national reserve or conservation area status throughout much of this species’ range, is still being degraded by illegal logging activities (2)

Insufficient data and a belief that there was only a single species of slow loris has meant that, in the past, population assessments may have significantly overestimated the Bengal slow loris population (11). Now classed as a separate species, and with recent surveys indicating that in some regions it is severely threatened, it has been classified as Vulnerable by the IUCN (1). This should hopefully promote increased efforts to monitor and understand the Bengal slow loris in the wild and, in turn, encourage efforts to protect and conserve it (11).

To learn more about loris protection and conservation see:

Authenticated (07/05/2009) by Dr. Sindhu Radhakrishna, National Institute of Advanced Studies. Indian Institute of Science Campus.

  1. IUCN Red List (October, 2010)