Loris: Adorable Mammal With a Deadly Bite


It's Loris Awareness Week! If you're already aware of lorises, it's probably because you've seen one of those viral videos of someone's pet. But if all you know is that they're cute, you're still unaware of what really makes lorises fascinating. The slow loris is one of the world's only venomous mammals, and those apparently adorable behaviors in the videos aren't quite what they seem.

Loris Basics

Ten species of loris are found in Southeast Asia, and their closest more-familiar relatives are the lemurs. "Lemurs and lorises are both categorized in the same group of primates called prosimians," says Chris Smith of the Duke Lemur Center. "Pro- means pre, simian means monkeys."

Lemurs and lorises evolved before other primates and share some unique characteristics. Their hands are less developed than those of monkeys and apes. "They can make fists, but they lack precision grip, so they couldn't pick up a piece of rice," says Smith. They also have what's called a tooth comb: six teeth on the bottom jaw that grow out instead of straight up.

And there's a connection between their lack of fine finger control and the existence of the tooth comb. "They can't use their hands to groom themselves like we think of chimps or gorillas sitting behind each other and picking insects off using their fingers," says Smith. "So they open the mouth and rake the toothcomb through each other's fur."

They've also essentially got two tongues. "Under the tongue toward the back of the mouth is a small piece of cartilage, not quite as flexible as the tongue," he says, which is used to clean out the toothcomb.

Lorises have an amazing grip, which they need because they can't jump, even over short distances. "I've seen them hold on to a vertical tree branch with their feet and extend their body completely perpendicular to the branch, only holding on with their feet," Smith says. "I don't know how many crunches in a day you'd need to do to do that."

Cute but Deadly

The slow loris is one of the very few venomous mammals. Its toxic bite is produced in an unusual way, by licking a gland on the arm that exudes an oil that mixes with their saliva.

Interestingly, the toxic protein that's formed by the combination is related to the one that causes people to be allergic to cats, and its effect is similar to a deadly allergic reaction. One case involved an Australian herpetologist, who, although well acquainted with similarly dangerous creatures, had no idea that the loris was venomous. So he thought it was kind of funny to have been bitten by this cute little mammal — till he started to swell up and his legs began to go numb.

"He took photos every fifteen minutes till he got to a hospital," says loris researcher Anna Nekaris. "By then his lips were thirty times their normal size and his tongue was so swollen he couldn't swallow."

Loris venom didn't originally evolve to affect humans, of course. "Mother lorises will put it on their hands and coat their infants with it," says Smith. "It seems to work as a predator deterrent." This is vital because unlike most primates, they leave their infants behind when they go out to forage.


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