Credit: Little Fireface Project

The slow loris, a tiny creature from the jungle with oh-so-probing eyes, looks like a furry cartoon character. Few had ever heard of this animal until it became a YouTube sensation, attracting millions of views, but that is what's threatening the animal's existence.

Dr. Anna Nekaris, a primatologist at Oxford Brookes University and one of the world's only slow loris experts, met "Nightline" at one of the few zoos that keeps lorises, the Paignton Zoo in Southwest England. She said this nocturnal primate, found in indo-China, Vietnam and Cambodia, is endangered - up to 90 percent have been wiped out.

For all 10 species of lorises, illegal trade "is their number one threat," she said.

Credit: Little Fireface Project

The BBC and Animal Planet followed the elusive and obscure slow loris into the jungle with Nekaris as she studied them on the Indonesian island of Java. She is hoping to find out what can be done to save the slow loris from extinction, and why the loris is the only mammal with a venomous bite - something she found out the hard way six years ago.

"It's not a pleasant experience because, like a snake bite, it can decay and fester and the wound takes quite a long time to heal," she said. "It can throb for days and days. They can bite straight through your fingernail and into the bone."

In Southeast Asia, villagers say a loris bite can be lethal. Nekaris explained that when the animal goes into a "defensive posture," it will raise its arms above its head and squeeze them tightly. This pulls oil from its armpits into its mouth, she said, mixing it with saliva, to deliver its venomous bite. Its growl even mimics a cobra.

But while she was studying its venom, Nekaris also discovered the loris is rapidly disappearing from the jungle, and those heart-melting Youtube videos are part of the problem.

Credit: Little Fireface Project

Credit: Little Fireface Project

The adorable lorises have become coveted pets, especially in Japan, Russia and the Persian Gulf. On the illegal animal Asia market, Nekaris said their venomous teeth are removed with nail clippers and are sold for $25. When smuggled out of the country, they can be worth thousands.

"People don't understand that these are illegal pets," she said. "They think they can have one. They see it as being cute."

Animal Planet's world premiere of "Frontier Earth" airs on Tuesday, Nov. 20 at 8 p.m. ET. Watch ABC's Jeffrey Kofman's report on the slow loris HERE: