Slow Lorises, Primate Venom, and a Related Cat Secretion
Slow lorises may move slowly, as their suggests, but they are fascinating animals. They live in Southeast Asia and are often considered to be very appealing creatures. They are sometimes kept as pets, which is a major problem for them. 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 to cats.
A 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 a 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.
Biological Classification of Slow Lorises
Slow lorises belong to the order Primates, like us. They belong to the suborder Strepsirrhini while humans, apes, and monkeys belong to 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)
Bangka slow loris
Kayan River ''
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 colour. 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.
The animals have a tooth comb in their mouth. This is a group of tightly arranged teeth in the lower jaw (incisors and canines) that slopes forward. The toothcomb delivers the venom to a victim by capillary action, or the movement of a liquid through a narrow space.
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 as if they are thinking carefully about where to place each foot. The animals sometimes look 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 Behaviour
Slow lorises are nocturnal and live in trees in various types of forest. 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 animals are often solitary as they search for food. Slow lorises may be more social than is generally realized, however. At least in the pygmy slow loris, they communicate with other members of their species by calls and scent markings as they travel. The 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.
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 sleep with one or more companions. A single loris uses many different sites as a sleeping area.
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.
Slow Loris Venom and Defensive Behaviour
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 behaviour 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 centres, 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. 9 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.)
- 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
A Venom Protein and a Link to Cat Allergies
DNA (deoxyribonucleic acid) is a chemical in cells that contains the code for creating an organism and its constituents. The code exists in the form of a sequence of smaller chemicals in the DNA molecule. 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 centres 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.
Behaviour that humans may consider to be cute—such as raising the 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
The Red List of the International Union for Conservation of Nature (IUCN) classifies animals according to their nearness to extinction. The list uses the five-species classification system for slow lorises. Four of the species have been placed in the Vulnerable category and are said to have decreasing populations. In each case, the last assessment of their numbers was done in 2008, which is a long time ago. The population of the Javan slow loris (Nycticebus javanicus) was last assessed in 2013. This animal has been classified as critically endangered.
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 the wild animals. 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 uses an older classification system for the animals.)
- 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 phys.org news service
- Pet allergy facts (including information about a cat allergy) from the Mayo Clinic
- The problem of slow lorises in captivity from National Geographic
Questions & Answers
© 2020 Linda Crampton