Sloth Versus Slow Loris
The slow loris, or ‘loris perezoso’ in Spanish (literally ‘sloth loris’), is a fascinating creature. Despite living on the opposite side of the world from sloths, they share many similarities. Let’s delve into the world of the only venomous primate and explore how it compares to the sloth!
What is a Slow Loris?
Slow lorises are small, nocturnal primates exclusively found in South and Southeast Asia. They are known for their large, round eyes, short snouts, compact bodies, and dense fur. Like sloths, they also display distinctive facial markings and slow deliberate movements!
There are a total of nine species of slow lorises, all of which belong to the same genus Nycticebus, and each species shares many similar characteristics and behaviors. The species include the Philippine slow loris, Bengal slow loris, Greater slow loris, Kayan slow loris, Bangka slow loris, Bornean slow loris, Sumatran slow loris, Javan slow loris, and Pygmy slow loris.
Slow and lazy enters scientific literature
The first known mention in scientific literature dates back to the 18th century by Dutchman Arnout Vosmaer, who described a specimen of what is recognized today as N. bengalensis. This initial classification was later debated by French naturalist Georges-Louis Leclerc, Comte de Buffon, who believed the animal was more aligned with the lorises of Ceylon (now Sri Lanka) and Bengal, rather than sloths. The term “loris” was introduced by Buffon in 1765, derived from the Dutch word “loeris,” meaning “clown.”
By the way, George Louis Leclerc, Comte Buffon, is well know in the house; he’s the same person who described sloths as:
“Slowness, habitual pain, and stupidity are the results of this strange and bungled conformation. These sloths are the lowest form of existence. One more defect would have made their lives impossible.”
Where do they live?
All nine species of slow lorises are native to the rainforests of South and Southeast Asia, specifically in regions spanning Indonesia, Malaysia, Thailand, the Philippines, Vietnam, and parts of Cambodia, Laos, and Myanmar. They inhabit tropical and subtropic forests, dense jungles, and wooded areas.
Are Slow Loris and Sloths related?
Often mistaken as closely related due to their similar names and arboreal lifestyle, sloths and slow lorises are, in fact, distinctly different creatures. Sloths, native to Central and South America, belong to the order Pilosa and share genetic ties with anteaters and armadillos. They are characterized by their slow-moving behavior, specialized limbs for hanging upside down, and a diet primarily consisting of leaves.
In contrast, slow lorises are primates belonging to the family Lorisidae, sharing closer genetic ties with lemurs, tarsiers, and other primates. While both species exhibit certain ecological similarities, such as arboreal lifestyles and slow movements, their evolutionary paths diverged long ago, placing them on separate branches of the evolutionary tree.
A Life on the Trees
Sloths and slow lorises share common adaptations for their arboreal life in the trees.
Slow lorises possess opposable thumbs on all four legs, helping them grip branches and navigate through the dense canopy to forage for food. Their specialized blood vessels provide extra oxygen to muscles, allowing them to cling to trees for hours on end without fatigue.
In contrast, sloths have hooked-shaped fingers, with some species possessing two or three fingers, allowing them to hang effortlessly from tree branches.
This unique adaptation allows sloths to perform essential activities such as eating, sleeping, and even giving birth while suspended in the canopy, sometimes remaining in the same position even after death.
Slow Loris, the only venomous primate in the world!
Interestingly, slow loris are considered the world’s only venomous and potentially lethal primate as well. This unique feature stems from a small, raised bald patch underneath their inner upper arm that secretes oil. When threatened, slow lorises lick the oil, and combined with their saliva, produce a venom strong enough to kill small arthropods and mammals.
In humans, a bite from a slow loris can cause anaphylactic shock, irregular heartbeats, and death. However, despite their ability to injure predators and kill small prey, they reserve their toxic bite for members of their own species, typically during territorial disputes, maternal defense, or mating competition.
Sloths are not venomous, but their bites can cause severe damage, and due to the bacteria present in their mouths, the bite can lead to a serious infection.
Slow versus Lazy
Slow lorises are predominantly nocturnal, often found curled up in tree hollows or clinging to branches during the day. Research indicates that during cooler months, they may spend up to 19 hours asleep each day, entering a state of torpor to conserve energy.
Sloths typically sleep between 8-10 hours per day. While they were once considered nocturnal, recent studies suggest they are actually cathemeral, meaning their activity levels can vary throughout the day and night, depending on the individual.
Slow lorises, known for their unusually low basal metabolic rate—about 40% of the expected value for placental mammals of their size, similar to sloths—consume a high-calorie diet available year-round. It has been proposed that their slow metabolism mainly serves to process and eliminate toxic compounds found in their food.
Scientific Studies
Relatively little is known about slow lorises compared to other primates, largely due to their elusive nature and their nocturnal habits, which pose challenges to researchers. However, despite this setback, scientists are still exploring questions regarding their movements, as well as their behavior and how they evolved.
Current ongoing research seeks to understand various aspects of their behavior, ecology, and physiology, such as research on their dispersal behavior and investigation of their nasal cavity characteristics. Other studies include learning about their sleeping patterns and handedness preferences.
Similar studies are conducted on sloths, employing field observations, radio telemetry, VHF collars, camera trapping, and genetic studies to uncover more about these fascinating creatures.
Sloths, Loris, and Viral Videos
The ‘cuteness’ of slow lorises has made them stars of many viral animal videos on YouTube. For example, by March 2011, a video of a slow loris holding a cocktail umbrella had amassed over two million views, while an older video of one being tickled reached over six million views.
However, these videos often mislead viewers. Many are unaware that it is illegal in most countries to keep slow lorises as pets and that their docility in these videos typically results from their passive defense response to stress or threat. This misinterpretation of their behavior is similar to how sloths are used as photo props for selfies; in both cases, the animals are likely experiencing stress and fear.
It’s important to understand that sharing or commenting on such videos can inadvertently promote animal mistreatment by boosting the visibility of the content through social media algorithms. Instead, if you encounter videos where wild animals are used as props, consider reporting the video and blocking the account to help discourage this harmful practice.
Conservation status
Slow lorises and sloths face numerous threats in the wild, including habitat loss due to deforestation, human encroachment, and illegal wildlife pet trade. Slow lorises, in particular, are hunted and traded for various purposes, including food, pseudo-medical therapies, and the exotic pet trade. Both species are also exploited in the tourist industry, where they may be used as photo props.
According to the International Union for Conservation of Nature (IUCN), all species of slow lorises face conservation challenges, with populations decreasing across the board. Under their Red List of Threatened Species, their status is:
- Philippine slow loris: Vulnerable
- Bengal slow loris: Endangered
- Greater slow loris: Endangered
- Kayan slow loris: Vulnerable
- Bangka slow loris: Critically Endangered
- Bornean slow loris: Vulnerable
- Sumatran slow loris: Endangered
- Javan slow loris: Critically Endangered
- Pygmy slow loris: Endangered
Unfortunately, sloths face a similar grim outlook, with their populations decreasing as well, highlighting the urgent need for conservation action to prevent further decline.
What can be done to protect both species?
Protecting slow lorises and sloths is essential for maintaining biodiversity and ecosystem health in their respective habitats. Conservation efforts should focus on preserving their natural habitats, and combating illegal wildlife trade.
Additionally, research and education play crucial roles in understanding these species and developing effective conservation strategies. Advocacy for stronger laws and regulations to protect these animals is also essential in ensuring their long-term survival.
-Darlene Buibas
SloCo Collaborator
