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Slow Lorises: Venomous Primates and a Related Cat Secretion

Linda Crampton is a writer and experienced science teacher with an honors degree in biology. She enjoys writing about science and nature.

Unique and Interesting Primates

Slow lorises may move slowly, as their name suggests, but they are fascinating animals. They live in Southeast Asia and are often considered to be very appealing creatures. Unfortunately, they are sometimes kept as pets, which can be a major problem for them, and the wild populations are facing difficulties. The animals have a special claim to fame. They are the only venomous primates. Scientists have recently discovered a striking similarity between an important protein in their venom and the Fel D1 protein that cause allergies in cats.

Venom is a substance that enters our body via a bite or a sting. A poison is a substance that enters the body when we eat the substance containing it. Scientists refer to the special secretion of a slow loris as venom because it's transferred by a bite. It isn’t injected into the body via fangs as happens in a venomous snake bite, however, so the use of the term "venom" is somewhat controversial. Whatever it's called, the slow loris's secretion can produce very unpleasant and potentially serious effects in humans.

Some Java or Javan slow lorises have a darker coat than the one shown above.

Some Java or Javan slow lorises have a darker coat than the one shown above.

Biological Classification of Slow Lorises

Slow lorises belong to the order Primates, like us. They are classified in the suborder Strepsirrhini. Humans, apes, and monkeys are classified in the suborder Haplorhini. Slender lorises belong to the same suborder as slow lorises but to a different family. In this article, the word "lorises" refers to the latter animals.

The table below shows that there are eight species of slow lorises and that they all belong to the genus Nycticebus. The classification system in the table was established by biologists Rachel Munds, Anna Nekaris, and Susan Ford.

Sometimes a five-species system is used for slow lorises. The Bangka and Bornean animals were once considered to be subspecies of the Philippine species (Nycticebus menagensis). The Kayan River animal was once considered to be the same as the Philippine one and wasn't given a distinct name. Some sources still use this older system of classification.

Classification changes can be confusing but are sometimes advisable as scientists learn more about an animal and its features. Additional changes in slow loris classification may appear. The animals are not as well known or understood as might be expected. As the San Diego Zoo says, their biological classification is currently "fluid."

Slow Loris Species (Genus nycticebus)

Each common name ends in "slow loris", which is represented by the ditto sign. Each scientific name begins with "Nycticebus". A genus name is often abbreviated after it has been written once.

Common NameScientific Name

Bangka slow loris

Nycticebus bancanus

Bengal ''

N. bengalensis

Bornean ''

N. borneanus

Sunda ''

N. coucang

Javan ''

N. javanicus

Kayan River ''

N. kayanem

Philippine ''

N. menagensis

Pygmy ''

N. pygmaeus

Physical Features of the Animals


Slow lorises have a noticeably rounded face compared to that of lemurs, which also belong to the suborder Strepsirrhini. The large eyes of a loris are often outlined in black. A white stripe travels between their eyes and reaches their nose. Their fur is predominately a shade of brown, grey, or cream, depending on the species. There may be darker markings on the background color. The animals have a tail, but it's a tiny stump that is hidden by fur. The loris's coat often looks woolly.


The eyes of slow lorises have a tapetum lucidum. The tapetum (as it's often called) is a reflective layer behind the retina in the eyeball. Light rays in the environment hit the retina, which is the part of the eye that detects light and sends a signal to the brain. Light that passes through the retina hits the tapetum. It's then reflected back to the retina, where it gets another chance to stimulate the light-sensitive cells. The tapetum lucidum, therefore, improves the night vision of a nocturnal animal. When light shines on the animal at night, its eyes glow due to the reflection by the tapetum. The phenomenon is called eyeshine.

Tooth Comb

The animals have a tooth comb in their mouth. The comb is a group of tightly arranged teeth in the lower jaw (incisors and canines) that slopes forward. It delivers venom to a victim by capillary action or the movement of a liquid through a narrow space.

Eyeshine in a Kayan River slow loris

Eyeshine in a Kayan River slow loris

Locomotion Facts

Lorises walk on four legs. As can be seen in the video above, they use their front limbs as arms and hands when they aren't walking. The hands have opposable thumbs, and their fingers bear nails. The second digit on their hands is shorter than the others. Their second toe bears a grooming claw.

The walking movement of slow lorises is not only slow but also very deliberate. It gives the impression that they are thinking carefully about where to place each foot. The animals sometimes look like they're crawling instead of walking. They can move quickly when necessary, however.

The animals hang from branches as well as walk over them, but they don't leap. They have a group of blood vessels called the retia mirabile in their arms and legs. These networks enable the animal to hang in apparent comfort from a branch for a long time.

The facts in this article probably apply to all of the slow loris species, but there may be exceptions. Further studies by scientists are required.

Diet and Behavior

Food Choices

Slow lorises are nocturnal and live in trees in various types of forests. They rarely come to the ground. The animals start to feed around sunset and have an omnivorous diet. They eat tree sap and gum, nectar, flower parts that contain nectar, some fruits, insects, spiders, and perhaps other animals. The pygmy slow loris (and perhaps other species) can catch insects in the air with its hands. It also deliberately wounds trees so that they exude material that the animal can eat.

Foraging Behavior

Slow lorises are often solitary as they search for food. Some researchers believe that they may be more social than is generally realized, however. At least in the pygmy slow loris, the animals communicate with other members of their species by calls and scent markings as they travel. Lorises, in general, deposit urine to mark their territories.

Sleeping Routine

During the day, a slow loris curls up in a ball in a tree and sleeps. It chooses an area hidden by branches and leaves or enters a hole in the tree. It generally sleeps alone but may sometimes sleep with one or more companions. A single animal uses many different sites as a sleeping area.

Reproduction and Lifespan

The slow loris is thought to be polygamous. The details about breeding time and frequency seem to depend on the species. Gestation lasts for around six months and nursing for about three to six months. The litter size is small and consists of just one or two animals. The mother may coat a baby with venom to protect it from predators just before she leaves to forage on her own. The animal lives between twenty and twenty-five years (if it isn't killed by a predator or disease).

A real-life photo of the defensive posture in three species can be seen below. The fingers of some slow loris species have a more humanoid appearance than those of other species.

N. menagensis, N. javanicus, and N. coucang in the defensive posture

N. menagensis, N. javanicus, and N. coucang in the defensive posture

Slow Loris Venom and Defensive Behavior

Slow lorises are not aggressive animals, but like most creatures, they will try to protect themselves when necessary. The animal's venom is produced by its brachial gland. This gland is found on the inner side of each elbow.

The Defensive Posture

When a slow loris is scared, it sometimes raises its bent arms and rests them against its head, as shown in the illustration and photos above. The pose may give the impression that the animal is trying to hide or disguise its appearance. It has another benefit, however. It enables the mouth to reach the brachial glands.

The animal licks the brachial glands to obtain the venom. Research suggests that the combination of venom and saliva is more dangerous than the venom alone. When the slow loris bites an attacker, the venom and saliva in its mouth enter the wound.

Mimicking a Cobra

At least one group of scientists has proposed that the defensive posture evolved not only because it made it easier for the animal to reach its brachial glands but also because it enabled it to mimic a cobra. The loris often hisses when it assumes the defensive posture. The scientists say that the animal's posture and markings resemble that of the expanded hood of a cobra, especially in the dim light present when the loris is active. The animal's hissing and the fact that it also undulates its body resembles the behavior of a cobra that is about to attack. The loris has several extra vertebrae compared to other primates, which helps it to create serpentine movement.

Effects of the Venom in Humans

Slow loris venom is often harmful to humans and potentially dangerous. It seems that some people experience more severe effects from the venom than others, however. An article in the Journal of Venom Research documented a survey of eighty people working with various species of slow lorises in zoos, rescue centers, and the wild over one year.

  • 54 people experienced a bite during the year. 26 did not.
  • 42 of the people who were bitten experienced symptoms from the bite.
  • 15 of these people required medical attention
  • 12 people who were bitten experienced no symptoms. Nine of these people were wearing gloves at the time of the bite. (I've read one report of a slow loris bite that penetrated the finger of a glove, however.)
  • Symptoms of the bite may include pain at the wound site, which is sometimes severe, swelling, inflammation, and/or infection. Symptoms may extend beyond the wound and include one or more of nausea, a headache, and malaise (a general feeling of ill health). Potentially very serious effects include swelling of the face and airways and difficulty in breathing.

Some people have developed anaphylaxis after a slow loris bite. Anaphylaxis is a severe allergic reaction that affects the whole body. The condition can lead to anaphylactic shock (very low blood pressure) and be life-threatening. There is one report in the literature of a slow loris bite causing a person to die from anaphylactic shock.

We analyzed the DNA sequence of the protein in slow loris venom, discovering that it's virtually identical to the allergenic protein on cats.

— Dr Alan Fry, University of Queensland

DNA (deoxyribonucleic acid) is a chemical in the nucleus of cells that contains the genetic code for creating an organism and its constituents. The code exists in the form of a specific sequence of smaller chemicals in the DNA molecule. These chemicals are known as nitrogenous bases.

Scientists from the University of Queensland in Australia have been studying slow lorises rescued from the pet trade. They have discovered that the code for an important protein in slow loris venom is "virtually identical" to the one that codes for a protein found in cat skin and saliva. Other scientists have explored the structure of the relevant protein (which is called Fel D1 in cats) and have found that the version in both animals is very similar.

Sebaceous glands in cat skin and salivary glands in their mouth secrete the Fel D1 protein. The protein is found in cat dander (dead skin cells), fur, and saliva. While exposure to the chemical causes no problems for some people, in others, it triggers an allergic response. The researchers suspect that the ancestors of domestic cats evolved the ability to make the protein because it protected them from predators.

There may be more harmful substances in loris venom than the one resembling the Fel D1 protein. The method of application of the chemical may also be significant. In general, symptoms of cat allergies are less severe than the ones caused by slow loris venom. An exception might occur when an allergy to cats causes an asthma attack.

Cats and slow lorises are mammals, but other than this, they aren't closely related. The similarity in their protein may have evolved separately in the lineage of each animal. It's a fascinating idea to consider.

Slow Lorises in the Pet Industry

Some people keep slow lorises in captivity under ethical conditions (as far as captivity can be considered ethical). Rescue centers may be an example. Zoos that provide a dark environment for the animals when they are active may be another example. Slow lorises are sometimes kept as pets, however, which is illegal in many places and is frequently a horrible situation for them.

The teeth of the animals designated to be pets are often removed without anesthetic via pliers or another instrument. This must be a very painful process. The removal of the teeth may reduce the chance that a bite from the animal will break a person's skin and transmit venom into their body. It doesn't eliminate the possibility of venom transfer, however. Anna Nekaris is a scientist at Oxford Brookes University who studies the animals. She says that the jaws of a slow loris are strong and can create a wound even without the presence of teeth.

The wounds created by tooth removal may cause serious blood loss and infection in lorises. If the animals survive the process and are rescued, they must often remain in captivity. Without their teeth, they can't follow their normal diet and may not be able to defend themselves from every predator that attacks them.

Slow lorises are nocturnal animals, but in captivity, they are often forced to interact with humans during the day. The light of the daytime environment is almost certainly stressful for them. In nature, they would be curled up in a hidden area and asleep during this time.

Behavior that humans may consider to be cute—such as raising their arms— may actually be signs of distress in the animals. Their diet is often far from satisfactory or completely unsuitable. In the wild, they travel long distances to find food. In captivity, they are usually confined in a cage for much of the time. According to slow loris experts, the animals seen in online videos often appear to be unhealthy or sick.

In a 2016 study, researchers from Oxford Brookes University examined a hundred online videos of pet lorises and concluded that all the animals were distressed, sick, or exposed to unnatural conditions.

— Jani Actman, "National Geographic"

Population Status of the Species

The Red List of the International Union for Conservation of Nature (IUCN) classifies animals according to their nearness to extinction. The population status of the slow loris species in their database is based on a 2015 assessment. The species are classified as vulnerable, endangered, or critically endangered. In addition to the eight species listed above, the IUCN recognizes a ninth species: the Sumatran slow loris or Nycticebus hilleri.

One reason why slow lorises are in trouble is the loss of their forest habitat. Land in their habitat is being cleared for agriculture, as it is in many parts of the world. Their popularity as cute and furry animals has caused them to be in high demand in the pet trade. Their intact bodies and the components of their bodies are popular in traditional customs and medicine, which is also a drain on their population.

Increasing Our Knowledge

Slow lorises are sometimes described as "neglected" animals with respect to scientific studies. We need to learn more about them and about the differences between the species. Understanding their features, habits, and requirements is important, and conflicting ideas need to be clarified. For example, the animals are often described as solitary, but some researchers say that they are actually social animals. We need to know whether this is the case for some species, all of them, or none of them.

Dissuading or preventing people from making use of the animals is also very important. Education of the public may be helpful. Strategies for balancing the needs of humans and those of the animals may be useful in the natural habitat of the loris. In addition, new population assessments are needed for them. Based on what we know so far, the animals need our help.


  • Slow loris fact sheet from the National Primate Research Center, University of Wisconsin - Madison (This article is useful, but it uses an older classification system for the animals and lacks the most recent information about them.)
  • Facts about the pygmy slow loris from the San Diego Zoo
  • The venomous slow loris may have evolved to mimic cobras from Popular Science
  • Ecology and biochemistry of slow loris venom from Nekaris et al. and the Journal of Venomous Animals and Toxins including Tropical Diseases (article and images published under a creative commons license)
  • An allergic reaction in a wildlife biologist bitten by a slow loris from Mongabay
  • The scientific report about the bite from the NIH (National Institutes of Health)
  • Survey of people bitten by slow lorises from the Journal of Venom Research and the NIH
  • Primate venom mimics a cat allergen from the news service
  • Pet allergy facts (including information about a cat allergy in people) from the Mayo Clinic
  • Facts about slow lorises kept as pets from International Animal Rescue
  • Population status of the pygmy slow loris from the IUCN (The web page has a search box in which the names of other species of slow loris can be entered.)

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2020 Linda Crampton


Linda Crampton (author) from British Columbia, Canada on May 28, 2020:

Thank you very much for the comment.

anonymous on May 28, 2020:

Fascinating read, Linda, and really augmented nicely by the videos. The slow loris is a really cute creature, and the fact that it's venomous makes it intriguing, as well. I appreciate the education...great article!

Linda Crampton (author) from British Columbia, Canada on March 03, 2020:

You've raised a good point, Mel. Cuteness can be deceptive!

Mel Carriere from Snowbound and down in Northern Colorado on March 03, 2020:

Cuteness can be deceptive in nature. I have a mild allergic reaction to cats, so these little buggers might not be good for me. Great article.

Linda Crampton (author) from British Columbia, Canada on February 28, 2020:

Thank you very much for the visit and the comment, Eddy.

Eiddwen from Wales on February 28, 2020:

A great article Linda on a subject I knew little about despite my love for all animals. Well researched and equally well written,

Linda Crampton (author) from British Columbia, Canada on February 24, 2020:

I appreciate your visit and comment, Eman.

Eman Abdallah Kamel from Egypt on February 24, 2020:

A very interesting article. Thank you, Linda, for sharing all this information about slow lorises. I enjoyed reading this article.

Linda Crampton (author) from British Columbia, Canada on February 20, 2020:

Hi, Adrienne, The fact that the teeth are pulled is horrible. I hope the situation changes soon. Thanks for the visit.

Adrienne Farricelli on February 20, 2020:

They are rather cute-looking, never imagined that slow lorises would bite and that their venom could pose dangers to humans. Sad to hear that their teeth, need to be pulled out (without anesthetic!) just to make them safer as pets.

Linda Crampton (author) from British Columbia, Canada on February 19, 2020:

Hi, Sal. I hope the animals survive for a long time. They are fascinating, as you say.

Sal Santiago from Minnesota on February 19, 2020:

Enjoyed reading this article about slow lorises. Fascinating creature indeed. Hope they can continue to survive.

Linda Crampton (author) from British Columbia, Canada on February 19, 2020:

Hi, Meg. Yes, they are lovely creatures. The way in which we treat other species is often worrying. Thank you for the visit.

DreamerMeg from Northern Ireland on February 19, 2020:

I had no idea that slow lorises were the only venomous primate! Lovely creatures but not well-known, as you say. Humans can be very cruel to other species on this beautiful planet. :(

Linda Crampton (author) from British Columbia, Canada on February 14, 2020:

Thank you, Devika. They are interesting animals.

Devika Primic on February 14, 2020:

These creatures are fluffy and cute. You share everything important to know of them and with great thought here.

Linda Crampton (author) from British Columbia, Canada on February 13, 2020:

Thank you for such a kind comment, Heidi. I hope you have a wonderful Valentine's Day!

Heidi Thorne from Chicago Area on February 13, 2020:

There is one thing for certain. If I am ever stranded in the wild, I want you to be there to identify all the flora and fauna around me. Sheesh! Your depth of knowledge of the biological world is incredible. Thank you for sharing your expertise with us! Happy Valentine's Day!

Linda Crampton (author) from British Columbia, Canada on February 12, 2020:

Hi, Manatita. We treat many animals in a horrible way. It's a very sad situation. Thank you for the visit.

manatita44 from london on February 12, 2020:

A fascinating report. It is sad that we treat them this horrible way but then we put men in the arena with lions for entertainment.

They look really cute with small heads and bright eyes. Interesting to read about their venom.

Linda Crampton (author) from British Columbia, Canada on February 11, 2020:

Hi, Flourish. Yes, their treatment is heartbreaking. I hope the animals have a better future.

FlourishAnyway from USA on February 11, 2020:

They are so beautiful and it’s heartbreaking to read about their exploitation for the pet trade and endangerment. Let’s hope that when people know better they do better.

Linda Crampton (author) from British Columbia, Canada on February 11, 2020:

I agree, Liz. It's a very sad price to pay. I appreciate your visit.

Linda Crampton (author) from British Columbia, Canada on February 11, 2020:

Hi, Dipali. I love animals, too.

Liz Westwood from UK on February 11, 2020:

The slow lorises look very cute, so I can understand why they are wanted by some as pets, but the removal of their teeth and disruption of their sleep cycle is a sad price to pay. This is a very well-researched and informative article. I have learnt a lot.

Dipali Ingle from Nandura on February 11, 2020:

I love animals

Linda Crampton (author) from British Columbia, Canada on February 10, 2020:

That's an interesting thought, Penny. It will be interesting to read about future discoveries.

Penny Leigh Sebring from Fort Collins on February 10, 2020:

I wonder if the similarity between the venom and the allergen in cats could lead to a new solution for cat allergies?

Linda Crampton (author) from British Columbia, Canada on February 10, 2020:

I appreciate your visit and comment very much, Maren.

Linda Crampton (author) from British Columbia, Canada on February 10, 2020:

Thank you, Peggy. I hope we can protect the animals, too. Learning more about them and their role in the forest would be very interesting.

Maren Elizabeth Morgan from Pennsylvania on February 10, 2020:

Fascinating info which you make easy to understand. Thank you!

Peggy Woods from Houston, Texas on February 10, 2020:

Slow lorises are fascinating animals. I have only seen photos of them. You provided much information regarding them that I never knew. The loss of habitat for them is serious. I hope that we can help protect them and continue to learn from them. Thanks for assembling this information, Linda.

Linda Crampton (author) from British Columbia, Canada on February 10, 2020:

Hi, Fran. Thanks for the visit. The animals live in Southeast Asia.

fran rooks from Toledo, Ohio on February 10, 2020:

What an interesting article! I had never heard of this animal. Where is their habitat? They are certainly a unique animal. Thanks for the info.

Linda Crampton (author) from British Columbia, Canada on February 10, 2020:

Thanks, Bill. It's a fascinating animal!

Bill Holland from Olympia, WA on February 10, 2020:

You stumped me on this one. I have never heard of this primate. Fascinating information, Linda!

Linda Crampton (author) from British Columbia, Canada on February 09, 2020:

Thank you, Chitrangada. I always appreciate your comments.

Chitrangada Sharan from New Delhi, India on February 09, 2020:

A very well written and informative article about Lorises. I have seen them in the zoo only. Good to know about their features and the other details.

Thank You for providing all the interesting information.

Linda Crampton (author) from British Columbia, Canada on February 09, 2020:

I agree, Denise. It's a horrible procedure.

Blessings to you, too.

Denise McGill from Fresno CA on February 09, 2020:

How cruel to pull their teeth! That's worse than declawing cats. I hate that they would do that to a wild animal.



Linda Crampton (author) from British Columbia, Canada on February 09, 2020:

Thanks for the visit and the comment, Pamela. The lorises do look fluffy and cute, but I think they shouldn't be kept as pets, even if it's legal in a particular place. The capture and treatment of the animals before they are sold is often horrible. In addition, it would be very hard to keep the animals both happy and healthy in a home. There may be some exceptional caretakers of the animals in a few places, but I suspect that these are few and far between.

Pamela Oglesby from Sunny Florida on February 09, 2020:

Linda, I don't think I have ever seen a lorise even in the zoo. They look so fluffy and it was so cute eating. I see why people might like them as a pet. I wouldn't want to get bit and the venom could be a problem too. This was such an interesting article as I was not familiar with the lorises before now.