[0:05]This is the story of Earth's oldest tropical rainforest. Of an ancient island. Home to giant apes and tiny bears. To plants that kill. And jellyfish that farm. Where day length never changes. The sun's strength never wanes. And abundant rainfall provides perfect conditions for life. But do not be fooled. For the island's breathtaking diversity is born not of bounty, but of extreme adversity. Of an intense struggle for existence. That gives rise to bizarre species, and extraordinary relationships.
[1:11]This is Borneo. Earth's Ancient Eden.
[1:28]These are some of the richest, most complex rainforests on the planet.
[1:41]And if one being defines life here, this is it.
[1:50]The orangutan.
[1:56]Few know the island secrets as they.
[2:05]To survive here, takes great ingenuity. For life in Borneo is utterly unique.
[2:16]There's so much to learn, but passing your secrets on is a full-time job. This youngster won't leave his mother's side for eight long years. It may not be until his teens that he finally sets off for good. Until that day, they'll share a remarkable bond.
[2:50]He stays in close contact, watching and learning from mum's every move.
[3:04]After all, simply navigating their treetop world takes great care and consideration.
[3:16]She rarely moves more than one hand or foot at a time and she never jumps.
[3:31]Instead, she uses her weight to bend trunks and branches across any gaps.
[3:44]It takes two years before youngsters begin climbing for themselves.
[4:02]Though his confidence grows with each day, he's still not strong or heavy enough to bend branches the way mum can. He won't master that until he's at least six.
[4:30]Until then, she's remarkably patient. He needs to use her body as a bridge between the trees.
[4:43]So complex is their jungle home, the carving out your own path is no easy task. Making the orangutans the longest childhood of any wild primate.
[5:00]With many secrets to pass on, few relationships on earth share the intimacy of theirs.
[5:22]And quite how life here became so challenging is all to do with the unique conditions of their ancient island home.
[5:35]Borneo has everything life needs to prosper. It straddles the equator, having been positioned in the tropics for well over a hundred million years. Temperature and day length here barely changes.
[5:59]The tropical sun provides plants with all the energy they need to grow.
[6:07]And there's a daily pattern which has been the same for millennia.
[6:14]As morning wears on, water vapor is drawn up from the forests and surrounding seas.
[6:36]And when afternoon arrives, the clouds break, releasing torrents of rain.
[6:58]To live in these forests is to endure relentless rainfall.
[7:07]For Borneo's most iconic residence, there's little choice but to sit it out.
[7:39]The sun will return tomorrow and the cycle will begin again.
[7:51]In every part of the island, species find surprising ways to deal with all the water.
[8:00]For some, it's as simple as getting noticed over all the noise.
[8:10]At times, calling just doesn't work out.
[8:19]Waving your arms and legs is a much better way to catch the eye of a potential mate.
[8:33]For the tiny rock frogs, the noise may be an inconvenience. But there are places here where the rains create far greater challenges.
[8:48]So much rain falls on Borneo's highest peaks, that little is able to survive.
[9:00]All the water washes away nutrients, starving the already poor soils of the basic ingredients for life.
[9:37]To live here, some plants take extreme measures. One even turns the rainfall to its advantage.
[10:04]It draws in ants with an offer of sweet nectar.
[10:14]Getting them right where it wants them.
[10:28]All it needs is a single drop.
[10:43]There's no way out.
[10:47]Their bodies will dissolve.
[10:52]The plant belongs to an extraordinary family which modified their leaves to trap and kill prey.
[11:03]The leaf central vein extends outwards.
[11:13]It keeps on growing until one day, it stops.
[11:24]Next, the tip begins to inflate.
[11:53]Finally, after several weeks it opens, revealing a deadly liquid-filled trap.
[12:08]These are the Nepenthes, the carnivorous pitcher plants. Borneo is home to a greater diversity of them than anywhere else. And they go to astonishing lengths to trap prey.
[12:34]Nepenthes hemleyana has modified the back wall of its pitcher to perfectly reflect the sonar of a small bat.
[12:57]Surely a deception too far, even for a carnivorous plant.
[13:06]But it's not the bat Nepenthes hemleyana desires.
[13:14]Merely, its poo.
[13:20]Nepenthes hemleyana and the bat have evolved an amazing partnership. The plant gets essential nitrogen from the poo and, in return, offers the bat a perfect resting place.
[13:39]Strange things happen with species forced to compete for limited resources.
[13:47]And while the water washes away nutrients, it also eats into the rock itself, carving out immense underground caverns.
[14:11]Cathedral-like spaces.
[14:21]Some of the largest caves on earth.
[14:38]Little light penetrates here and yet it is full of life.
[15:02]An army of cockroaches.
[15:08]They live only on this giant mound of bat droppings, some a hundred meters long.
[15:18]There are millions of them, dependent entirely on these nutrients brought in from the outside world, recycling everything. Even the bodies of the bats themselves.
[15:37]Nothing here goes to waste.
[15:45]Others use the cave, too.
[15:55]Cave swiftlets. A primitive form of echolocation helps them find their way. They nest high up on the cave walls. And these nests draw yet more life into the darkness.
[16:18]Over several hours, teams haul rope and rattan ladders into position.
[16:36]Next, a perilous ascent begins. With no safety harness, collectors head some 60 meters above the cave floor.
[16:55]They work in almost total darkness, remaining up here for the entire day.
[17:05]A single slip spells certain death. But the prize is worth the risk. The swiftlet nests are a delicacy. The main ingredient in bird's nest soup.
[17:24]And those from Borneo's ancient caves are among the most valuable on Earth.
[17:33]With the day shift ending, wrinkle lip bats begin to stir.
[17:42]They're preparing for a night's hunting in the forest beyond. And outside, other hunters are expecting them. A Wallace's Hawk Eagle. Each evening, it takes up position near the cave's entrance.
[18:07]But today there's a disturbance. The local gang of Pied Hornbills.
[18:23]The male seemed to be testing their prowess against each other. A source of great frustration for the Hawk Eagle.
[18:57]Hopefully that's the last of them.
[19:07]This is the moment the Hawk Eagle has been waiting for.
[19:14]The nightly exodus of hundreds of thousands of bats. A reliable feast. If you're able to catch one. They leave in such spectacular numbers that it even distracts the rowdy hornbills.
[19:41]For the Hawk Eagle, it's game on.
[19:50]Diving into the crowd, it's in its element.
[19:57]They're still watching.
[20:14]For a bird that mostly eats fruit, the hornbills seem unusually interested in the bats.
[20:26]What exactly is he doing?
[20:41]He is. He's trying to catch one.
[20:50]This is unheard of.
[20:56]These are birds with giant beaks for picking off fruit, not bats in flight.
[21:07]The expert shows exactly how it's done.
[21:44]But once in a while, even amateurs strike lucky.
[21:55]A completely new behavior, never recorded here before.
[22:05]Fruit eaters with blood on their bills. It seems Borneo still has secrets to reveal.
[22:16]So many bats stream from the cave that all the predators have little effect on their numbers.
