The only venomous primate brews its toxin by licking its own arm
Slow lorises make their venom in two steps. A gland on the arm secretes a fluid related to a cat allergen, and when the loris licks it, saliva activates it. The resulting bite was long assumed to be a defence against predators, but lorises mostly use it on each other, in fights between rivals.
Slow lorises are nocturnal primates of the genus Nycticebus, ranging from Bangladesh and northeast India to the Sulu Archipelago in the Philippines, and from Yunnan down to Java. The genus name, coined by Étienne Geoffroy Saint-Hilaire in 1812, means night monkey in Greek. They have round heads, big eyes, a long flexible torso and hands built for a pincer grip that can hold a branch for hours. They move slowly and silently, and when threatened they freeze. Documented predators include snakes, changeable hawk-eagles and orangutans.
Their bite is rare among mammals and unmatched among primates. Beyond the arm secretion, wild animals may add toxins picked up from their diet. Males guard territories fiercely, scent marks carry messages, and infants are sometimes parked on branches while the parents forage for small animals, fruit and tree gum.
Naming them has been a two-century tangle. The Dutchman Arnout Vosmaer described one in 1770 and lumped it with sloths, which Buffon disputed. Buffon had introduced the word loris in 1765 from a Dutch term that, according to a later physician, meant clown. In 1939 Reginald Pocock folded every slow loris into one species; the count has since climbed back to at least eight. In 2012 Rachel Munds, Anna Nekaris and Susan Ford split the Bornean form into four species using facial markings, and in 2022 the pygmy slow loris was moved into its own genus, Xanthonycticebus.
A single tooth from Thailand, about 18 million years old, is the earliest Asian loris fossil, and molecular clocks suggest the living species began diverging roughly 10 million years ago, reaching the Sunda islands across land bridges exposed at low sea level. Every species assessed before 2012 is rated vulnerable or endangered. Forest loss and fragmentation hurt them, but demand from the exotic pet trade and traditional medicine has done the most damage.
Source: Slow loris
