Tree Kangaroos: Meet These Never-Before-Seen Creatures in the Wild "Nightline" travels to Papua New Guinea to see endangered species roam treetops.

Dec. 15, 2009 -- Deep in the mysterious rainforests of Papua New Guinea, hundreds of feet in the air, lives one of the most beautiful and rare creatures on the planet: the tree kangaroo. Locals refer to these elusive animals as the "ghosts of the forest."

Papua New Guinea is one of the only places in the world where you can find tree kangaroos. The only way to get an up-close look at the fuzzy marsupials is to climb way, way up into a towering tree. No one knows why or when this rare breed of kangaroos moved into the trees.

About a hundred live in zoos around the world, but these kangaroo hybrids have become endangered. Approximately 10,000 exist in the wild. Our cameras captured tree kangaroos in their natural habitat for the first time ever.

We traveled by helicopter to a remote region of the cloud forest. After a greeting ceremony, which included locals dressed as tree kangaroos, we entered a forest as pristine a movie set. As one writer once remarked, you almost expect to be approached by a hobbit from J. R. R. Tolkien's "The Lord of the Rings," in here.

Lisa Dabek, an American biologist who's dedicated her life to saving the tree kangaroo, was our guide. She said she first saw these creatures 20 years ago at the Woodland Park Zoo and was instantly hooked.

"I fell in love with them," she said. "They're beautiful and the more I learned about them, the more I wanted to help them."

But to help the tree kangaroos, first, you have to find them, which isn't an easy task. Dabek, whose research is funded by a National Geographic-Waitt grant, in addition to other funders such as Conservation International, went eight years without seeing one in the wild.

"For eight years we looked at their dung. That's it," she said. "It's so hard to find them."

But a few years ago, Dabek and her team finally managed to put radio collars on some tree kangaroos.

Led by locals, many of them hiking barefoot, we joined them on their journey, as they followed the signal of a female they named Trish.

We caught a glimpse of Trish, way up in the high branches, staring warily. She didn't seem too scared, but was very alert.

"She's watching us," Dabek said, "She's alerted and she's sort of wondering what we're going to do."

Scaring Tree Kangaroos Down From Treetops

Tree kangaroos spend most of their time in trees, but are adept on land. If startled, they'll leap down from the treetops, a move that factors into Dabek's plan.

"One guy will climb up closer to her and they'll make noise so she'll come down," Dabek told us. "She's going to try to figure out how to get away -- and what they do is to really get away from something, they leap down to the ground, and try to run away."

From treetops about 100 feet in the air, Trish jumped to the ground and appeared unscathed.

"They do that in the wild. ...When they land, they sort of stop for a second and that's when we get them," Dabek said.

Once Trish landed, men rushed in to grab her by the tail. For Dabek, as a conservationist, forcing an animal out of a tree and into a bag runs counter to her every instinct. But she said she believes the more we know about how these mysterious, endangered animals live, eat and breed, the easier it will be to protect them in the wild.

Next, men held Trish's ears to calm her and stop her from biting or clawing as Dabek measured the animal. They took off Trish's radio collar and for the first time ever, put on a tiny camera from National Geographic, called the "Crittercam."

Researchers have placed similar cameras on animals like squids and sharks and lions in the past. If it works, the cameras will record the world as Trish sees it.

It's intense and stressful work, but Dabek said it is worth it -- especially if the camera is a success.

"We have no idea what they do on top on the canopy -- so we want to see what plants they eat, what they're doing up there, so we're basically getting a window into her world," she said. "This is an animal we don't know a lot about."

Not long ago, villagers used to hunt and eat tree kangaroos. But with Dabek's help, they've now set aside over 180,000 acres of rain forest to protect the animals. It's part of a huge cultural shift.

World Through the Eyes of a 'Tree 'Roo'

The next day, we joined the team to look for another tree kangaroo, a young one who was recently captured for the first time. A few days earlier, the team fitted the animal with a camera. Researchers hope to get the first view of the world through the eyes of a "tree 'roo."

Finally, we spotted the animal. Again, it was way up in the trees. It was the same drill: Villagers chopped out an area safe enough for the tree 'roo to land and a man climbed up the tree to scare the animal down.

After they got the tree 'roo down and in the bag, they found that the camera -- with its much-anticipated roo's-eye video -- was gone.

It's was a huge disappointment for Dabek. Even as it began to pour, the locals combed the forest, searching under trees where the animal may have recently been. And against all odds, they found it.

Under a tarp in the pounding rain, the team entered the private world of the reclusive animal they've spent years of their lives trying to understand and protect.

It was oddly mesmerizing to watch as the 'roo climbs up trees, snacks on orchids and ferns and ventures out onto thin branches with dizzying views.

Dabek appeared to tear up as she watched. She was told it couldn't be done. But 15 years later, she's watching a breakthrough in the making.

And with that -- the tree 'roo goes scampering off -- a new, unwitting ambassador for a rare, endangered species.

To learn more about saving the tree kangaroos in Papua New Guinea, click here.