Slow Loris Facts: Meet the World's Only Venomous Primate

The slow loris, with its big eyes, slow crawl, and grip strong enough to hang all night from a branch, looks like a stuffed animal that wandered out of a toy store. But don't be fooled by the cute face. This tiny primate is the only venomous one on Earth, and its story is much more complex than the viral videos suggest.

The slow loris is not a monkey, though many people confuse the two. It is a small nocturnal primate found in South and South-east Asia, from Indonesia, Vietnam, Thailand, Cambodia and parts of the forests of India, and is part of the Lorisidae family. Depending on the taxonomy you follow, there are about nine to eleven recognised species, from the tiny pygmy slow loris (about 10 inches long) to the larger Sunda slow loris, which can stretch past a foot.

All species have the same basic look: round, saucer-like eyes adapted for night vision, a short snout, dense woolly fur, and dark rings around the eyes like a racoon's mask. Instead of leaping from branch to branch as most primates do, they crawl slowly and deliberately, moving on all fours.

And this is where most people are shocked: the slow loris is the only venomous primate in the world. It doesn't make venom like a snake does. Instead, it has a small gland near its elbow that secretes an oily toxin. When the loris licks that gland and mixes the oil with its saliva, it becomes venomous. It can deliver that mixture through a bite from its sharp lower teeth.

That bite is more than a nuisance. The venom can kill insects and small animals. In humans, it typically causes severe pain and swelling and, rarely, anaphylactic shock due to a severe allergic reaction. This defence against predators and rival lorises is rarely used against people, so slow lorises are non-aggressive animals. Nevertheless, there is a good reason to admire this animal from a distance.

Slow lorises are almost entirely arboreal, spending nearly their whole lives in the trees. They rarely come down to the forest floor, only to urinate and defecate, and scientists believe this may be a means to avoid leaving a scent trail for predators.

They are strictly nocturnal. By day, a slow loris curls up tight into a ball in a tree hollow or mass of vines, nearly invisible. It slowly makes its way through the canopy at night, seeking food, always keeping at least three limbs on a branch. That slow, deliberate movement isn't laziness; it's a survival tactic. The loris moves slowly and quietly to avoid attracting the attention of owls, snakes and other predators that hunt by sound and motion.

Slow lorises are omnivores and prefer tree gum and sap, which they scrape from bark with a specialised row of teeth called a "tooth comb." They also eat:

• Fruit and nectar

• Insects and minor invertebrates

• Bird eggs sometimes

• Little lizards

That gum-and-sap habit is more important than it sounds—it connects slow lorises to the health of certain tree species in their forest, which is one reason habitat loss is considered such a direct threat to the species by conservationists.

All slow loris species are under threat, the two main drivers being deforestation and the illegal wildlife trade. When forest developers and farmers clear forests for farmland and development, lorises lose the connected canopy they need to move, feed, and hide from predators. They are slow movers, and this makes it difficult for them to cross open terrain in search of new habitat after a forest has been fragmented.

The illegal pet trade is even easier. The slow loris's large eyes and placid appearance have made it a favorite on social media and in videos, which drives up demand for the animal as a pet—yet it's illegal to keep one in most countries, and it's harmful to the animal. Captured lorises' teeth are often pulled out without anesthesia to avoid bites. This brutal practice kills many animals before they're ever sold. Some cultures use lorises in traditional medicine, but there is no scientific proof.

Conservation groups now classify most species of slow loris as vulnerable, endangered, or critically endangered. Rescue and rehabilitation efforts are in place, but researchers have found that releasing rescued lorises back into the wild without careful assessment of the habitat and monitoring can actually reduce their chances of survival—rescue is more than just letting them go.

The slow loris is proof that adorable and dangerous are not mutually exclusive. The slow-moving, big-eyed forest dweller has a truly toxic bite, a diet centered around tree sap, and a conservation story that deserves more attention than it usually gets on the internet. How best to help? Never support the pet trade, and never share videos of lorises being handled as pets—each view adds fuel to a demand that's driving this one-of-a-kind primate closer to extinction.

🌿 Bio4Climate – Slow Loris Feature

Learn more about slow lorises from Biodiversity for a Livable Climate's featured creature series.

✓ Species information • Conservation • Unique adaptations • Pollination role

🐵 Primates & Wildlife