Nycticebus coucang

Geographic Distribution and Habitat

The Sunda slow loris (Nycticebus coucang), also known as the greater slow loris, is named for the Sunda Islands in Malaysia, where the species lives; they are also native to parts of Indonesia, Thailand, and Singapore.

Locals in these regions know the Sunda slow loris by other names. Its scientific name, coucang, derives from its common name in Indonesian, kukang. But it is also known there as malu-malu (meaning “shy”). In Thailand, slow lorises are called ling lom, which means “wind monkey”—an allusion to how quietly they move through the trees.

Sunda slow lorises thrive in primary and secondary tropical lowland evergreen forests. But they are considerably adaptable for primates and can survive in a variety of different habitats. The species has even been known to mete out an existence in logged and degraded forests, on plantations, and in people’s gardens. Researchers have noticed that lorises seem to prefer sticking around the edge of forests, possibly because there are more insects to be found there. That is only a hypothesis, however. The reason could just as likely be that their data is skewed due to the fact that lorises at the forest edge are simply easier to spot than those deeper in the jungle where foliage is thicker.

Sunda slow loris range. Map: IUCN, 2020

Size, Weight, and Lifespan

Unlike other species of loris, male and female Sunda slow lorises are basically indistinguishable. They do not vary by weight, size, color or shape.

Individuals are roughly 10–15 inches (27–38 cm) in length. They weigh approximately 21–24 oz (599–685 g) and live to be about 20 years old when left in the wild.

What Does It Mean?

In ecology, the ability of an animal to avoid observation or detection by other animals through methods such as camouflage, nocturnality, subterranean lifestyle, and mimicry.

Visit the Glossary for more definitions


Sunda slow lorises have a signature white stripe of fur that runs between their large eyes, which are encircled by dark black rings. Their fur is otherwise a light—sometimes reddish-brown—except for a darker streak of brown along the back. The fur is thick and hides their ears and vestigial tail. The face is flat, head round, and limbs angled so that they look like they could stand upright if they wanted. They never do, though. Instead, they “crawl” through the foliage. While their movements may appear haphazard and random, they hardly ever slows down or missteps.

Sunda slow lorises are strepsirrhine primates. At first glance, they might look like something between a sloth and a monkey, but lorises are distinct from monkeys, apes, and tarsiers (all haplorhine primates), and have no relation to sloths (arboreal mammals of the order pilosa dwelling in South America—oceans away from loris country). Lorises do share their side of the primate family tree with lemurs (found in Madagascar only) and bush babies (African continent) and are closely related to the African potto. It is important to make these distinctions clear since people frequently confuse or conflate lorises with other animals, including a species of Australasian possum known as a cuscus, which is not a primate but a marsupial. Each of these species inhabits its own environment, meaning different efforts are necessary for their conservation.

Slow lorises, including the Sunda, are distinguished by their huge, captivating eyes. These are both a blessing and a curse for lorises. While this adaptation gives them the ability to see at night when they are active and foraging for food, it also taps into the evolutionary wiring of human primates who feel the urge to nurture small beings with eyes so big in proportion to their heads. People see them and assume that lorises must be cute and helpless creatures. In reality, slow lorises are more than capable of looking out for themselves in the wild and almost always die when held in captivity. Unfortunately, the demand for slow lorises as pets continues to thrive and is the greatest threat to their survival.


Slow lorises have long been thought to be frugivorous (fruit-eating) creatures, but their diet is more varied and eclectic than researchers originally realized. Only about a quarter of what they eat consists of fruit with another two-thirds consisting of nectar, certain parts of nectar-producing plants, saps, and gums. Spiders and other arthropods, insects, bird eggs, and even occasionally small vertebrates such as geckos make up the rest of what they eat and are important sources of protein.

Behavior and Lifestyle

Sunda slow lorises are nocturnal and arboreal. During the day they find hidden places in the canopy where they can sleep. Other species of loris will happily make themselves comfortable in hiding spots they find on the ground, but Sunda slow lorises hardly ever venture down there. At night, Sunda slow lorises climb out of their nooks and crannies to forage and hunt for food, “crawling” quietly and at a steady pace through the jungle foliage.

Sunda slow lorises are especially solitary and self-reliant primates. Rarely does an individual come into contact with another unless it is to mate. They are in no way anti-social creatures, however. They simply go about socializing in less physical ways than many other types of primates. Though they will indeed groom or vocalize with a mate, the majority of their interactions tend to be olfactory. In many other species of primate, evolution has diminished the olfactory sense considerably. Lorises, however—with their semi-elongated snouts and wet noses—happen to rely on it heavily. Scent marking is a form of social cuing for lorises who deposit their scent marks using either their urine, a toxic oil that they secrete from special glands located on their elbows and anus, or a combination of both. They deposit these oils by licking or rubbing it onto the desired substrate as they make their journey through the jungle.

Sunda slow lorises also use their toxic oil for protection, purposefully spreading the oils through their fur. When they encounter a predator, they roll up into tight little balls, leaving only their toxic coats exposed. Most of the time, slow lorises rely on crypsis to remain out of harm’s way. Crypsis refers to any form of behavior that might help a creature avoid detection. In the case of slow lorises, such behaviors are their nocturnality, their slow and steady movements, their solitary lifestyles, and their keen senses of smell.

Fun Facts

Sunda slow lorises are solitary, self-reliant, and yet peculiarly social primates.

They rely on their olfactory senses more than many other types of primates.

Slow lorises may use ultrasound to communicate cryptically with each other.

Their biggest conservation threat is their high demand on the illegal pet trade.

They avoid predation by drawing as little attention to themselves as possible.

Daily Life and Group Dynamics 

During the day, the Sunda slow loris finds a comfortable and dark place to curl up and avoid predators. When darkness falls, she becomes active. She puts her large eyes to good use as she “crawls” through the canopy, ever on the lookout for nectar-filled flowers from which to forage or small critters to hunt. Though her gait may appear awkward to an outsider, her pace is steady. She moves more quietly than the gentlest breeze. Her ability to never trip, misstep, nor make any kind of sudden movement ensures that she draw no unwanted attention to herself.

Though she is radically self-reliant for a primate, her solitude is somewhat of a ruse. A few other lorises’ ranges overlap her own, and she is kept privy to their comings and goings by means of their scent marks.

Researchers call these loris social units “spatial groups.” They are relatively small, typically consisting of one male, one female, and one to three younger individuals.

Very rarely, and only ever one at a time, does she encounter the other members of her spatial group. Their meetings are never antagonistic. Two might call to each other, making pant-growls or click-calls. If they are especially amiable, the two might take turns grooming the other. If she encounters a male, he might track her as a potential mate. Other times, two lorises from the same spatial group just happily ignore each other and go on their merry ways.

Sunda slow lorises—male or female—do not actively defend their home ranges to any degree. If an outsider loris happens to encroach on their range, both typically just pretend the other doesn’t exist. Seldom do their meetings become aggressive.


Slow lorises use both vocal and olfactory methods to communicate with each other.

They make eight distinct calls. They use whistles and short keckers in amiable situations, such as playing or mating. Females, in particular, will use whistling to alert and attract nearby potential mates. Snarls, grunts, long keckers, and screams are used to signal aggression between lorises. Being solitary primates who rely on crypsis to keep out of harm’s way, lorises do not use alarm calls to warn each other about approaching predators.

Infants make clicking sounds, or click-calls, when separated from their mother or when in distress. Researchers have also detected young lorises making ultrasonic vocalizations, beyond the range of human hearing, when exploring new environments. This could be a way to communicate their nervousness or a strategy to self-soothe. Another species of loris, the Javan slow loris, was recently found to use ultrasonic communication almost constantly. It seems likely that this behavior would extend to all species of slow lorises, but that has yet to be confirmed.

Lorises regularly use their own urine and the toxic oil they secrete from special glands on their elbows to leave scent marks wherever they pass. Lorises habitually pee during locomotion—a behavior researchers refer to as “rhythmic urination.” The composition of their toxic oils are particular to each species. These they deposit using their tongues, licking their glands and spreading it in the desired location. Sunda slow lorises have another of these special glands near their anus that allows them to deposit a mixture of urine and toxic oil by rubbing their behinds against a substrate.

Lorises have been observed using some forms of body language and facial communication. For instance, lorises bare their teeth when antagonized or fearful. But this expression is also common during moments of social play. Infant lorises who find themselves in stressful situations seem to express their anxieties by grinning.

Reproduction and Family

Unlike other loris species, the female Sunda slow loris does not show sexual swellings. They also experience estrus at several times throughout the year.

A male tracks a female in estrus, following her scent marks through the jungle. When he finds her, the female begins the mating ritual, presenting herself to the male by hanging from a branch and making whistle calls at him. At the end of their intercourse, the male leaves a copulatory plug, making it near-impossible for other males to mate with her for the foreseeable future.

Gestation takes an average of 191 days. At the end of this period, the female gives birth to a single infant. Twins do occur, but are rare for lorises—especially Sunda slow lorises.

Her infant is born with open eyes and all of his fur. He is cared for exclusively by his mother and is able to cling to her within an hour of being born. Good thing, too, since he is incapable of navigating the jungle canopy on his own! Instead, he clings to the fur on his mother’s belly. In this manner, she carries him around the jungle, hiding him away in different spots where she can suckle and groom him in relative safety. Eventually, after a week or so, she is comfortable leaving him in order to forage on her own at night. Before she departs, though, she makes sure to lick her toxic oils into his fur in the off-chance a predator should come upon him.

By watching and attempting to mimic his mother’s movements, he gradually learns how to traverse the canopy on his own in the signature loris way. He is weaned sometime around 4–6 months and reaches sexual maturity by approximately 20 months. Female Sunda slow lorises usually take more time to reach adulthood—anywhere from 18 to 24 months.

Research on the reproductive behaviors of wild slow lorises is scarce. It is not yet known whether they are a polyandrous or monogamous species. And the case might be different for each loris species. Given that lorises so rarely encounter one another in the wild, it seems unlikely to some researchers that they would have more than one mate. However, some evidence for polyandry has been recorded, including instances where a female was tracked by up to six males who each attempted to mate with her.

It is also important to note that the difficulty of studying lorises in the wild (being the nocturnal, chiefly solitary and unassuming creatures that they are) means that most of what humans do know about their reproductive behaviors is gathered from captive studies. While such research may provide some insight into the nature of the Sunda slow loris, it is not necessarily consistent with their behaviors in the wild.

Ecological Role

The diet of the Sunda slow loris is varied enough so that the species does not play a major ecological role in any of the places where it lives. That being said, its absence–were it to become extinct–would more than subtly disturb the ecology of those ecosystems.

Sunda slow lorises are preyed upon by reticulated pythons, hawk-eagles, and—in areas where their ranges overlap—Bornean orangutans.

Conservation Status and Threats

The Sunda slow loris is classified as Endangered by the International Union for Conservation of Nature (IUCN, 2015), appearing on the IUCN Red List of Threatened Species.

Like other primates, Sunda slow lorises are negatively affected by the encroachment of humans into their habitats. In some places the rates of forest conversion are so extreme that even highly adaptable and resilient creatures like slow lorises are direly impacted. The development of timber and palm oil plantations depletes regular sources of food and results in the fragmentation of slow loris habitats. As their ranges shrink so does their access to potential mates. This has the affect of slowing, if not altogether halting, gene flow between spatial groups.

Sunda slow lorises are hunted by humans for meat and are often shot by farmers who consider them crop pests. In China, the bones of slow lorises are used in folk medicine, and their pelts are used to make a traditional hunting bag. They are also used for pseudo-medicinal purposes in Vietnam, where local peoples sometimes dry or pickle their bodies in rice wine.

Human civilization also affects lorises in less direct ways. Though it is somewhat rare, roads and highways that intersect lorises’ ranges put them at risk of being hit and killed by automobiles. There is also some evidence that their activities are negatively affected by the constant and bright lights that accompany urban development and infrastructure.

The greatest threat to slow lorises is their value to humans as adorable and exotic pets. As tremendously self-reliant creatures in the wild, slow lorises do anything but thrive as pets. Of the thousands of slow lorises that end up in captivity, few survive the ordeal.

After she is poached, and before she is put on the market, a loris’ captors clip out her teeth. This is an extremely painful procedure that is done without anesthetic. Without teeth she is more valuable, since the bite of a slow loris (the only venomous primate in the world) is toxic to humans and can be deadly if not treated. The majority of lorises who have their teeth removed die shortly thereafter from grizzly and painful infections. Even when a slow loris manages to avoid infection, without her teeth she can never be reintroduced to the wild. If she is rescued, she will likely spend the rest of her life in a rescue facility.

A captive loris that somehow avoids death by infection is still likely to die from a combination of malnutrition and aggravated stress. Loris owners typically know nothing in regards to caring for their captives properly. Many assume that the task will be similar to raising a dog or a cat and are unaware of slow lorises’ complex biologies and complicated lifestyles. There is the simple fact that slow lorises in captivity no longer have access to the high quantities of nectar, saps, and gums that they would normally eat in the wild. Additionally, many of the fruits slow lorises eat in the wild are endemic to the areas where they live. By simplifying their loris’ natural diet and relying on fruits like bananas and apples, owners ensure that their captives develop a number of serious health issues such as diabetes, obesity, and renal failure until they eventually perish. Slow lorises cannot live on fruit alone.

In order to understand how stressful life in captivity is for a slow loris, it is helpful to imagine the situation from the creature’s perspective. A small, self-reliant creature is removed from her natural habitat and confined to a small cage where she is forced to depend on a being who knows very little about how she had lived her life in the wild. Having had her teeth removed, she is suffering from an infection that makes it difficult and painful for her to eat anything. Her big and sensitive eyes, once perfect for her nocturnal lifestyle, are a source of constant pain now that she lives in an environment specifically designed for (human) diurnal creatures. Over time, her regular exposure to light may even make her blind. Fully aware that the being who she depends on has none of her own interests in mind, she is constantly on-edge and anxious. Whenever this being insists on handling her, her lack of teeth—with which she would normally have defended herself—forces her to feel utterly helpless. With all these factors in mind it is not surprising that lorises who are kept in such conditions quickly and consistently die. Unfortunately, the death of a loris does not often discourage their captor from acquiring a replacement.

A slow loris that manages to survives in these horrific conditions long enough to be rescued is unlikely to ever lead a normal loris life again. Rescued lorises are typically in bad shape and suffer from a number of health issues. Without teeth, these lorises can no longer groom each other or forage for gum and saps. For some, the stress of being rescued is the final straw and kills them.

The trend of keeping slow lorises as pets is often fueled by social media. Owners who want to show off their captive lorises post pictures and videos of them on the internet. A popular video that went viral a number of years ago depicted a slow loris in a brightly lit room as he was being “tickled” by his captor. To a human audience that knows little about lorises, the creature may have appeared happy as it raised its arms above its head. But this behavior is actually how a slow loris begins to apply its venom and, therefore, was actually a desperate effort to ward off what he obviously perceived as a most cruel and sadistic predator. This and other videos that go viral not only inspire those that watch them to want their own lorises, they also teach the message that keeping a loris in captivity is a perfectly acceptable behavior.

Unfortunately, the centers where rescued slow lorises wind up seldom follow ideal protocols for their rehabilitation and release into the wild. For instance, some rescue centers have been known to release too many slow lorises into the same area at once. It is possible that these individuals have not undergone thorough health evaluations, nor is it certain they have been properly identified. The first monitored study that tracked rescued slow lorises after their release showed a 93% death rate!

Conservation Efforts

While Sunda slow lorises and other loris species are generally threatened by forest degradation, their self-reliant personalities make them somewhat resilient to these trends. They also happen to benefit from the conservation efforts made in the name of less-resilient primate species with whom they share their habitats. Regardless, as humans continue to convert forests into farms and plantations, slow loris habitats inevitably grow more and more fragmented. In some places where Sunda slow lorises live, such as Singapore, efforts have been made to reconnect forests that have been divided in the ceaseless wake of urban and residential development. Specifically, the Eco-Link@BKE, an ecological bridge that spans the Bukit-Timah Expressway and reconnects the Bukit Timah and Central Catchment Nature Reserves, was designed to help creatures like the Sunda regain access to their former ranges. It takes a fair amount of time before an ecological bridge develops a canopy that is useful to arboreal creatures like the Sunda since they depend on continuous canopy coverage to get around.

Efforts specific to slow loris conservation focus primarily on combatting their biggest threat, which is the exotic pet trade. Slow lorises are protected by both international and local laws that make their capture illegal. These laws are often difficult to enforce, however. When and where local governments fail, organizations like International Animal Rescue (IAR) work to implement these laws and hold poachers and owners of illegal pets accountable for their crimes. IAR takes part in the rescue of captive slow lorises and oversees their rehabilitations. Its facilities include a veterinary clinic, spacious enclosures, a public education center, and quarantine enclosures where new and sick lorises are temporarily housed. The organization is committed to releasing as many of the slow lorises that wind up in its care as possible, but also permanently house individuals who it deems not fit for release. IAR’s “Tickling is Torture” campaign, launched in June 2015, targets videos and pictures of pet slow lorises and asks people to oppose the illegal pet trade by pledging to never like or share such images and videos on social media. By March 2016, they had accumulated over 450,000 pledges!

Another organization doing important slow loris conservation work is the Little Fireface Project (LFP). The project began in 1994 as a subsidiary of the Nocturnal Primate Research Group and, since 2011, has continued to concentrate on the conservation of all loris species, including the Sunda, as an independent enterprise. Through the research it has conducted with both wild and captive slow lorises, it has distinguished itself as an expert in their care and rehabilitation. In addition to running educational programs that promote public and international awareness about the cruelties of slow loris trafficking, LFP acts as a consultant for zoos and rescue centers that house slow lorises, helping such establishments to design adequate and appropriate enclosures for their charges. It has even established a set of dietary and housing guidelines for them to follow, setting an important standard of protocols and procedures.

LFP takes great pride in the noninvasive techniques it uses to conduct its research on slow lorises. Anesthetic is notoriously bad for slow lorises, who are highly stressed by its effects and aftereffects. By developing ways to handle creatures quickly and concisely, the organization has been able to forego the use of anesthetic when measuring and collaring slow lorises. LFP researchers also exclusively use red lights when out in the field. This practice not only protects slow lorises’ eyes, but helps the lorises to distinguish researchers from potential poachers.


Written by Zachary Lussier, August 2019. Conservation status updated July 2020.