Bengal Slow Loris: the venomous primate Nycticebus bengalensis

Estimated reading time: 27 minutes

Bengal Slow Loris Nycticebus bengalensis

Red List Status: Endangered

Locations: Bangladesh, Bhutan, Cambodia (west of the Mekong River), China (southern and western Yunnan, possibly southwestern Guangxi), north-eastern India (Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, Tripura), Laos Myanmar (including the Mergui Archipelago), Thailand (north of the Isthmus of Kra), and Vietnam.

The major threats that this species’ habitat faces include farming, timber removal, human settlement, road building, dams, power lines, fragmentations, soil loss and erosion, and deliberately set fires.

IUCN Red List

Appearance and behaviour

Nycticebus bengalensis is the largest of all slow loris species, a nocturnal primate whose soulful eyes, moon-like face and deliberate movements have made them both iconic and vulnerable. Once widespread across the lush forests of Asia, their numbers have been slashed by more than half in just over two decades, driven by relentless hunting, the illegal pet trade, and the clearing of forests for palm oil and timber. Every destroyed tree and every loris taken for trade deepens the silence in these forests. Stand up for the Bengal Slow Loris—use your wallet as a weapon and BoycottPalmOil Boycott4Wildlife.

They use a ‘toilet claw’ for grooming

The Bengal Slow Loris is cloaked in dense, woolly brown-grey fur, with a lighter, creamy underside. A striking dark stripe runs from the crown of their head, sometimes forking towards the eyes, which are set in triangular patches of dark fur. Their hands and feet are pale, and they possess a distinctive “toilet-claw” on the second toe for grooming.

They squirt venom from their elbow when threatened

Nycticebus bengalensis has a round head and short ears lend them a gentle, almost spectral appearance, while their enormous, forward-facing eyes glow with a vivid orange under torchlight. They move with slow, deliberate grace, gripping branches with powerful, opposable toes, and sleep curled in dense foliage or tree hollows by day. At night, Bengal Slow Lorises emerge to forage, marking their territory with scent and communicating through soft whistles and scent cues. Uniquely, they are venomous, secreting a pungent oil from a gland near the elbow, which they spread on their toothcomb for defence.

Threats

Palm oil and timber deforestation

The Bengal Slow Loris is Endangered, with forests disappearing beneath the advance of palm oil plantations, logging, and agriculture. Bulldozers flatten ancient trees, leaving behind barren earth and fragmented canopies. Roads, power lines, and dams dissect once-continuous habitats, isolating populations and exposing them to new dangers. In many regions, slash-and-burn agriculture turns vibrant green into ash, and selective logging removes the old trees that lorises depend on for food and shelter.

Hunting, the illegal pet trade, and traditional medicine

Hunters pursue the Bengal Slow Loris for bushmeat, Chinese medicine, and the illegal pet trade. In border markets like Mong La, Myanmar, hundreds are killed and sold annually—limbs traded as key rings, bodies dried for medicine, and infants taken for pets. The demand as tourist photo props is especially severe in Thailand, where almost all lorises in the trade are Bengal Slow Lorises. Captured individuals endure stress, loneliness, and early death in captivity, with wild populations pushed ever closer to extinction.

Infrastructure projects, roads, forest destruction

As forests are fragmented, Bengal Slow Lorises are forced to the edges, crossing roads where many are killed by vehicles. Human settlements encroach deeper, bringing fire, pollution, and the constant threat of capture. Even protected areas offer little safety, as poaching and illegal logging persist.

Climate change and river pollution

Changing rainfall, altered fruiting patterns, and polluted rivers further erode the delicate balance of the forests these primates call home. As the climate shifts, the resources Bengal Slow Lorises rely on become scarce, compounding the effects of habitat loss and hunting.

Diet of Nycticebus bengalensis

Under the cover of darkness, Bengal Slow Lorises forage for nectar, plant sap, tree gum, fruits, and small invertebrates. Their diet is dominated by plant exudates—sticky gums and saps from wounded trees, which they lap up with specialised tongues. These exudates are a vital, year-round staple, especially when fruit is scarce. They also hunt insects, snails, or small vertebrates, their slow movements belying a patient, methodical approach. By feeding, they become pollinators and seed dispersers, quietly sustaining the health and diversity of their forest home.

Reproduction and mating

Bengal Slow Lorises are not seasonal breeders—females can attract mates with a loud whistle at any time of year. Gestation lasts around six months, and usually only one infant is born at a time, though twins are rare. Newborns arrive with eyes open, covered in soft fur, and are carried by their mothers for the first three months. During this period, mothers may leave their young on branches while foraging, returning frequently to nurse and groom them. Weaning occurs at around six months, and young lorises reach sexual maturity by about 20 months. In the wild, Bengal Slow Lorises can live up to 20 years.

Bengal slow loris habitat

Bengal Slow Lorises live in tropical evergreen rainforest, semi-evergreen forest, and mixed deciduous forest across South and Southeast Asia. 

They depend on old-growth trees for sap, gum, and shelter, and requires a continuous forest canopy to move safely between feeding sites. However, palm oil and timber corporations are rapidly destroying their home. Infrastructure projects like major roads also pose a threat.

FAQs: Bengal slow loris facts

What are some key Bengal Slow Loris facts?

The Bengal Slow Loris is the largest of all slow loris species and one of the world’s only venomous primates. Nycticebus bengalensis can live up to 20 years in the wild and plays a vital ecological role as a pollinator and seed disperser within their rainforest home. Furthermore, females can attract mates with a loud whistle at any time of year and give birth to a single infant after a six-month gestation. Their enormous orange-glowing eyes give them exceptional night vision, and their powerful, opposable toes allow them to grip branches with extraordinary strength. Consequently, every Bengal Slow Loris lost to the pet trade or palm oil rainforest destruction represents a unique and irreplaceable loss to their entire ecosystem.

What is the Bengal Slow Loris range?

The Bengal Slow Loris has the widest geographic range of any slow loris species. Nycticebus bengalensis is found across Bangladesh, Bhutan, Cambodia, China, northeast India, Laos, Myanmar, Thailand, and Vietnam. However, this wide range is deeply misleading. Palm oil corporations and logging companies have destroyed vast areas of their rainforest home, eliminating Bengal Slow Lorises from large portions of their former territories entirely.

Are Bengal lorises endangered?

Yes they are! Bengal Slow Loris population has declined by more than 50% over the past three generations. Further declines of 50% are expected over the next three generations due to ongoing hunting and habitat loss. Furthermore, over much of Asia their populations have disappeared entirely.

What is the Bengal Slow Loris venom?

The Bengal Slow Loris is one of the world’s only venomous primates. Nycticebus bengalensis secretes a pungent toxin from a brachial gland located near their elbow. They lick this secretion onto their toothcomb, transforming their bite into a venomous weapon capable of causing severe anaphylactic shock in humans and other animals. Furthermore, this venom is thought to serve as a defence against predators, and possibly as a deterrent against ectoparasites. Therefore, the viral videos of Bengal Slow Lorises raising their arms cutely are actually a deeply stressed animal preparing a defensive venom transfer, not a display of affection.

Why do Nycticebus bengalensis spit toxic venom?

Bengal slow loris venom can cause severe allergic reactions in humans and other animals. This is an evolutionary defence mechanism to ward of predators. Bengal Slow Lorises along with other lorises and are the world’s only venomous primates. They secrete a toxin from a gland near the elbow, which they spread on their teeth and use for defence.

What is the current Bengal Slow Loris population?

No precise Bengal Slow Loris population count exists. Populations across much of their former range in Cambodia, China, and parts of Southeast Asia have already vanished entirely. Consequently, the remaining populations are fragmented and increasingly isolated from one another, raising serious concerns about long-term genetic viability.

How long do Bengal Slow Lorises live?

In the wild, Bengal Slow Lorises can live up to 20 years, though many perish far earlier due to hunting, capture, and habitat destruction. In captivity, their lifespan may be shorter due to stress and poor conditions.

Is the Bengal Slow Loris nocturnal?

Yes, the Bengal Slow Loris is strictly nocturnal. Nycticebus bengalensis emerges after dark to forage for nectar, plant sap, tree gum, fruits, and small invertebrates, using their enormous forward-facing eyes to navigate in very low light. During the day they sleep curled into tree hollows to avoid being visible to predators.

What is the Bengali name for the Bengal Slow Loris?

In Bengali, the Bengal slow loris Nycticebus bengalensis is commonly known as Lajjabati Bandar (লজ্জাবতী বানর), which translates to “shy monkey” or “bashful monkey”.

Do Bengal Slow Lorises make good pets?

No. Bengal Slow Lorises suffer extreme stress, loneliness, and early death in captivity. The pet trade rips families apart, inflicts cruelty, and fuels their extinction in the wild. Keeping them as pets is illegal and unethical.

How does the illegal pet trade endangered the Bengal Slow Loris?

The illegal pet trade is a primary driver of the Bengal Slow Loris’s decline. Infants are torn from their mothers, adults are mutilated or killed. Lorises sold as pets often die from stress, malnutrition, and loneliness. The trade also fuels demand for tourist photo props and traditional medicine.

Why are Bengal Slow Lorises used in Chinese medicine?

Bengal loris body parts are used in Chinese and other traditional medicine across Asia. Despite no scientific evidence, these folk medicines continue to be used. Demand for these false and scientifically baseless remedies is driving the hunting and trade that threatens their survival.

What is the Bengal Slow Loris price in the illegal trade?

There is no legitimate price for a Bengal Slow Loris because buying, selling, or owning one is illegal under CITES Appendix I and national wildlife laws across their entire range. However, in illegal wildlife markets, particularly border markets like Mong La in Myanmar, Nycticebus bengalensis individuals are sold for significant sums. Furthermore, infants seized from their mothers fetch higher prices as supposed pets, while adults are killed and sold for body parts used in traditional medicine. Any search for a Bengal Slow Loris price is actively contributing to the demand that drives their poaching and extinction in the wild.

How do Bengal Slow Lorises contribute to their ecosystem?

Sadly, Bengal loris habitat continues to be threatened by palm oil deforestation. However, these resilient primates are important pollinators and seed dispersers and they play a vital role in maintaining forest health. Without the bengal loris, trees and forests have little chance regenerate and recover from mass deforestation. So it is essential that we protect them.

Do Bengal Lorises live in protected areas where they are safe?

Bengal loris habitat is under threat from palm oil and timber deforestation despite environmental protection. Enhanced enforcement and indigenous-led stewardship are urgently needed to safeguard their future.

How does climate change affect Bengal Lorises?

Climate change disrupts the fruiting patterns of trees, alters rainfall, and increases the frequency of fires, all of which threaten the Bengal Slow Loris habitat and food sources.

What can be done to help Bengal Slow Lorises?

Support indigenous-led conservation and agroecology, refuse to buy products containing palm oil, and never participate in the illegal pet trade or tourist photo prop industry. Stronger law enforcement and habitat protection are also critical.

Take Action!

Fight for the survival of the Bengal Slow Loris every time you shop. Boycott palm oil. Boycott products that drive deforestation. Reject the illegal pet trade and tourist photo prop industry. Support indigenous-led conservation and agroecology. Use your wallet as a weapon and demand a future where the forests still whisper with the movement of Bengal Slow Lorises. #BoycottPalmOil #Boycott4Wildlife

Support the conservation of this species

Endangered Primate Rescue Centre (EPRC)

Further Information

Nekaris, K.A.I., Al-Razi, H., Blair, M., Das, N., Ni, Q., Samun, E., Streicher, U., Xue-long, J. & Yongcheng, L. 2020. Nycticebus bengalensis (errata version published in 2020). The IUCN Red List of Threatened Species 2020: e.T39758A179045340. https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T39758A179045340.en. Downloaded on 08 February 2021.

Nijman, V., Shepherd, C. R., & Nekaris, K. A. I. (2014). Trade in Bengal slow lorises in Mong La, Myanmar on the China border. Primate Conservation, 28, 139-144.

Pliosungnoen, M., Gale, G., & Savini, T. (2010). Density and microhabitat use of Bengal slow loris in primary forest and non-native plantation forest. American Journal of Primatology, 72(12), 1108–1117. https://doi.org/10.1002/ajp.20875

Wikipedia contributors. (n.d). Bengal slow loris. In Wikipedia, The Free Encyclopedia. Retrieved June 13, 2025, from https://en.wikipedia.org/wiki/Bengal_slow_loris

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