- [Narrator] The animal kingdom is remarkably diverse.

Two million species and counting.

In every corner of the planet, they have adapted to their surroundings, finding miraculous ways to survive and thrive.

Despite the fact that rainforests, or jungles, cover just 6% of the land on Earth, they contain the lion's share of life.

Well over half of all known terrestrial species call these lush, green oases home.

From the highest boughs in the canopy to the dense undergrowth below, each layer within these extraordinary jungles provide shelter and food for the masses.

And opportunities for humans to connect to nature and its remarkable ark of animals.

(light orchestral music) Here in the tropical far north of Australia, heavy rain and high temperatures conspire to create ideal conditions for huge trees to grow.

With only a thin layer of fertile soil to nourish their shallow roots, these giants have thrown down buttresses to support their expanding girths.

Their heads are literally lost in the clouds, seeking light to photosynthesize.

If these treetops could talk, they would have truly epic tales to tell.

For they've been around for a very long time.

Their ancestors would have sheltered dinosaurs.

Indeed some would argue these magnificent forests still do.

With its killer claws and bizarre head casque, the Southern Cassowary certainly looks the part, roaming through the oldest tropical rainforest on Earth.

Cassowaries are thought to have been on the planet for 25 million years.

They can only be found in four places today, in Papua New Guinea and three pockets of rainforest in Australia.

The most accessible of these, is the Daintree in far north Queensland, a botanical treasure 180 million years in the making.

Female cassowaries are larger than males.

They can be as tall as two meters and weigh up to 75 kilos.

They have thick, muscly legs covered in scaly skin and huge three-toed feet with massive dagger-like claws on their inside toes.

Up to 12 centimeters long, these claws have two main functions, to dig for fruit buried on the forest floor and to defend their territory and honor.

Cassowaries do not roam through the jungle looking for a fight, but they can be a little feisty, especially when there are chicks around.

The males aggressively guard their young.

Cassowaries have a strange helmet called a casque.

Scientists are not 100% sure what it's for, but many believe it's a sexual ornament, helping both sexes to evaluate the quality and fitness of a potential partner.

It's spongy in texture rather than bony, so it possibly acts as a resonating device, helping to amplify the low booming sound cassowaries make when danger threatens.

It's impossible to overstate how important these ancient birds are to the survival of the rainforest.

Cassowaries eat fruit and lots of it, so they play an essential role in dispersing seeds, complete with a load of fertilizer.

One cassowary scat can contain hundreds of seeds, which means potentially hundreds of new trees.

But it's not just the quantity that counts, it's the variety.

These hungry birds eat over 230 different species of fruit.

The cassowary has become the accidental farmer of the rainforest.

Many scientists believe that if these birds were not around, the complex rainforest ecosystem would just cease to exist.

Cassowaries are generally solitary birds.

Each female has a home range which overlaps that of several males.

During mating season, the female will mate with one or more of the males in her home range.

After a brief courtship she will lay her eggs, then leave the male to guard and incubate them.

Assuming he does that successfully, after 50 days, three to five stripy chicks will emerge.

The male cassowary then spends the next eight to 18 months raising his offspring before they are ready to fend for themselves.

It takes another year and a half for young cassowaries to reach maturity, to be able to breed themselves, and in so doing, contribute to the recovery of their population in the wild.

(light orchestral music) While many creatures in the jungle may frighten or repel, there's one species we humans have no trouble at all relating to, the orangutan.

We share a whopping 28 physical characteristics with orangutans, leading some scientists to believe they are our nearest relatives.

Orangutans live on one of two remote islands in Southeast Asia, Sumatra and Borneo.

Borneo is a mysterious place, shrouded in mist and mystery.

It straddles the Equator so it's hot, wet, and covered in lush, dense rainforest.

The perfect home for these magnificent, intelligent animals.

Orangutans are the only great apes of Asia.

They spend at least 90% of their time in the forest canopy, eating, snoozing, or just hanging around.

Despite their laid back attitude, orangutans can move fast if they need to.

Their arms are long and strong and span nearly 2 1/2 meters.

Both hands and feet have opposable thumbs for gripping onto branches.

Their hands are very similar to ours, as is the enamel on their teeth, their long hair, and shoulder blades.

But curiously, orangutans do not have toenails on their big toes.

We share 97% of our DNA with them and just as much time as a species caring for our young.

Unlike most animals, female orangutans do not have babies until they are about 15 or 16 years old.

They carry their young for up to five years and are happy to breastfeed them until they are eight years old.

At 10 years old, the children leave home, but they regularly come back to visit their mothers for a further five years.

The theory is that a long childhood is linked to the animal's large brain.

It gives the young orangutans time to learn many skills and behavior patterns from their mothers.

Orangutan fathers play no direct role in rearing their offspring.

They live a solitary life, only getting together with the others to mate or to fight other males for a mate.

Dominant males can be easily identified by their hard-won battle scars and prominent flanges on their faces.

Males without these cheek flaps are subordinate and do not get to mate with a female.

The latest research suggests dominant males may exude a hormone that prevents the other males from reaching full maturity.

But once the top man dies, a subordinate male will grow in size and stature, developing the facial flanges to show his supremacy.

Getting close to orangutans is relatively easy.

Many zoos have them on display.

In fact, Singapore Zoo even has an enclosure where it's possible to have breakfast with a few very well habituated youngsters.

Those seeking a deeper encounter can volunteer at one of several rescue centers in Borneo where orphaned and injured orangutans are cared for.

Deforestation in Borneo, thanks to the global demand for palm oil, is destroying orangutan habitat.

And as a result, the species is listed as critically endangered.

If numbers continue to decline, they could be extinct within 50 years.

So every effort here to save a life improves their chances of surviving in the wild.

(light orchestral music) The tropical jungles in the heart of Borneo are home to over 350 different bird species, but the biggest drawcard among bird watchers are the extraordinary hornbills.

Eight of the world's 45 hornbill species can be found here, including the Oriental Pied Hornbill.

The males have an almost comically large bill with a pronounced casque.

Similar to the cassowary's multifunctional helmet, it too is thought to amplify sound.

Hornbills are the only bird family to have the first two vertebrae in their necks fused, most likely to support the weight of their top-heavy beaks.

Recent studies suggest they double as radiators, helping hornbills to regulate their body temperature, controlling the amount of heat they need to lose or conserve depending on the time of day and ambient conditions.

Hornbills have distinct eyelashes, modified feathers that protect the bird's eyes from flying insects and debris.

While many jungle animals spend the bulk of their lives in and around the treetops, others quietly prowl through the undergrowth.

This is a prime habitat for Borneo's top predator, the Clouded Leopard.

The smallest of the big cats, these striking felines are shy and secretive.

Of all the animals living in the jungles of Southeast Asia, great cats remain the most elusive.

Sightings of tigers in the wild are particularly rare and becoming rarer by the day as humans continue to encroach on their habitat and hunt them for their organs and pelts.

The largest of all cat species, tigers are the ultimate apex predators with muscular legs, retractable claws, and a mouth full of teeth tailored to specific tasks, taking down prey, tearing flesh from bone, and chewing.

They were once the kings of these jungles stretching from India to Northeast China and from the Russian Far East to Sumatra.

But over the last century, their numbers have fallen by 95%.

A global conservation campaign has stopped their numbers from diminishing further, but it will be years before they regain their standing in what remains of their natural domain.

With fewer than 4,000 tigers left in the wild, zoos now play an important role in ensuring their protection, giving visitors a chance to better understand their behavior and hunting prowess.

These Bengal Tigers live at Singapore Zoo.

Their white coloring is extremely rare.

For it to occur, both parents must carry the same unusual gene.

Their stripes are like fingerprints.

No two pelts are the same.

Unlike other big cats whose patterns only occur in their fur, a tiger's stripes go all the way through to their skin.

Tigers breed well in captivity, so there is a chance these cubs and their future offspring might one day play a role in ensuring the survival of wild populations throughout the world.

(light orchestral music) While many rainforest animals will do all they can to avoid being seen, our next jungle dweller is a veritable show off.

It's spent thousands of generations evolving the most ostentatious feathers of any bird on Earth.

There are around 40 different species of these striking birds, each with a unique combination of bright colors and ornate feathers.

Collectively, they are the Birds of Paradise.

Some live in tropical Australia and Eastern Indonesia, but most have made a home for themselves in Papua New Guinea.

Papua New Guinea is a very special place.

It's a land of extremes, the world's largest and highest tropical island.

New Guinea has massive ice-capped mountains and deep, steamy valleys filled with jungle.

It's a place of mystery, of unexplored valleys with species that are yet to be discovered, the perfect setting for Birds of Paradise.

Most females are a drab brown, but the males are simply resplendent.

The male will spend ages preparing a stage on which to perform.

It could be a branch of a tree or a clearing on the forest floor.

Once a potentially curious female arrives, the show begins in earnest.

Each species of bird puts on a unique dance to try to seduce the female, and some displays may last several hours.

Females can spend six weeks watching dance after dance before they select their mate.

After all this work, many males may not get selected at all.

Stunning feathers attract potential mates, but they also attract predation by humans.

Indigenous tribespeople, such as the Huli Wigmen of the Tari Highlands, have collected feathers for millennia, using them to decorate their headdresses and ritual objects, which are handed down from one generation to the next.

Their kinship to the Bird of Paradise is evident in the dances and chants they perform, mimicking the birds they so clearly revere.

Another feathered family living deep in the rainforests of Papua New Guinea and Australia are the Bowerbirds.

Many of the 18 species that comprise this group have beautiful feathers worthy of attention.

But the male bower bird's preferred method of seduction is architecture.

To attract a mate, the Satin Bowerbird will build an elaborate set.

It is not a nest, rather a stage where he will perform a special dance to show off to the ladies.

These are always located on the ground and can be up to two meters long.

The quality of the bower and the male's prowess on the dance floor determine courting success.

But in some species, females may also assess the feathers of a potential breeding partner as a glossy, satin-like sheen would indicate their overall health.

Bowers are decorated with colorful natural objects such as berries, snail shells, or feathers from other birds.

Where habitat borders suburbia, bottle tops, pegs, and bits of brightly colored glass and rubbish are used.

Many Satin Bowerbirds show a preference for blue objects, perhaps because this helps to accentuate their own color.

There is no honor among thieves, and male bowerbirds, even those of a different species, will sabotage another's bower and steal his treasures in an effort to have the best looking structure in the neighborhood.

(light orchestral music) The rainforests of Australia and Papua New Guinea are also home to the world's only Megabats, but some species are not restricted to this habitat.

Indeed some manage to live right in the heart of major cities.

The Botanic Garden in Sydney has long provided a safe roost for a huge number of gray headed flying foxes, the largest of the four megabat species.

It has a whopping one meter wingspan.

Bram Stoker never made it to Australia, but these creatures certainly look like they were the inspiration for Dracula.

Unlike vampire bats and those fictitious beasts in the horror movies, flying foxes do not drink blood.

In fact, they don't eat meat at all.

Their favorite foods are fruit, seeds, and nectar.

Every night, they fly out from their roosting sites in huge numbers to search for a feast, flying hundreds of kilometers if necessary to get to a favorite stand of trees in flower.

Here in Elsey National Park in the Northern Territory, flying foxes are forced to drink on the wing in an effort to reduce any associated risk.

Hiding just below the surface, freshwater crocodiles are waiting to capture their next meal.

Timing is everything on the part of the crocodiles and the flying foxes, whose lives can be snuffed out in a heartbeat.

The whole safety in numbers strategy won't work for everyone, but those that safely run the gauntlet return to their camps to rest during the day.

Flying foxes breed at a slower rate compared to other medium sized mammals.

Females take a year and a half to reach breeding age and generally give birth to one pup at a time.

But in large colonies such as this, that can mean a few thousand extra mouths to feed.

As the seasons progress, different tree species across the flying foxes' range bear flowers or fruit, so the colony will come into contact with a huge range of trees across a vast area.

As they eat, they pollinate the trees, and as they defecate on the wing, they disperse seeds far and wide.

Flying foxes are keystone species, an essential part of the rainforest's life cycle.

Without them, these forests would not be able to keep reproducing, and all the species that depend on these forests would not survive, either.

Their nomadic and migratory ways help drive biodiversity in this region.

It's hard to imagine looking at this mass of animals, but flying foxes are listed as vulnerable.

They are being wiped out by a perfect storm of causes.

Conservationists and scientists are suggesting that if things don't change and change quickly, the flying fox may well be extinct by 2050.

(light orchestral music) Australia's rainforests provide a home for a vast array of creatures.

And the best time to see many of them is at night.

With keen eyes and a powerful torch, it is possible to surprise many nocturnal creatures, particularly spiders and reptiles.

Forest huntsmen do not build webs to catch prey.

They hunt and forage for food, mainly insects and other invertebrates creeping through the undergrowth.

They hide during the day to avoid being eaten themselves, principally by birds.

A spotlight won't intimidate a forest huntsman, for despite having eight beady eyes, it detects prey through vibration.

The Amethystine or scrub python is Australia's largest snake, growing to eight meters long.

Like all pythons and boas, it's not a venomous snake.

It kills by coiling itself around its prey and squeezing until the victim's heart stops beating.

Heat-sensing pits along its lips allow it to detect warm-blooded prey, and flexible muscles and ligaments in its lower jaw stretch so the python can swallow large animals such as birds, bats, and wallabies.

Because the Amethystine can eat large prey, it doesn't have to eat very often, maybe once or twice a year.

Despite its enormous size, the Amethystine poses no major threat to humans.

They are quite shy and unlikely to attack unless threatened or accidentally disturbed.

The Boyd's Forest Dragon is another handsome reptile that is relatively easy to find and observe on a spotlighting tour in the wet tropics.

This particular dragon is unique among lizards as it does not need to draw energy from the sun to survive.

It regulates its body temperature to the surrounding vegetation, a handy skill to have to counteract the heat-sensing ability of the Amethystine.

These well-camouflaged lizards like to eat stick insects that have a preference for eating new leaves.

When a Boyd's Forest Dragon needs to feed, it will hang around in a spot it knows the stick insects will find irresistible, patiently waiting for a potential meal to arrive.

As they have less stored energy to expend, they will stay quite still for a long time, fixed to a tree limb or vine, so it's easy to get a close and prolonged encounter with one in the wild.

The most spectacular looking python in the Queensland rainforest is the Green Tree Python.

It is small by Australian snake standards, around 1 1/2 half meters long, but it is very good at ambushing its prey.

Tree pythons will often lie motionless on a low branch, waiting for a potential meal to wander within striking distance.

Young pythons are not born green, but begin life bright yellow or orange, so whether young or mature, this beautiful snake is a real jewel of the jungle.

(light orchestral music) Most jungle animals can be hard to see in the wild.

When they hear us coming, they run or fly away.

But one creature that has difficulty effecting an escape is the Sloth.

It's the slowest mammal in the world.

They live in South America in the most famous jungle of all, the Amazon.

Their top speed is a glacial two meters per minute.

Sloths are so slow-moving, fungi and plants grow in their fur, creating a viable habitat for hundreds of beetles and other crawling insects.

This mini ecosystem affects the color of their fur, allowing them to blend into the forest foliage.

The sights and smells of the rainforest in South and Central America can be overwhelming, but the thing that surprises people most is the noise.

The soundtrack to these jungles is deafening.

Insects make a constant din, but that cacophony of ear-piercing whoops, howls, and chatter you hear comes from monkeys.

The monkeys in this part of the world come in all shapes and sizes.

They represent five different primate families and are collectively referred to as New World Monkeys.

Most New World Monkeys are color blind.

They have similar-looking noses, and many have prehensile tails, perfect for charging around the canopy, swinging from tree to tree.

The best swingers in the jungle are the Spider Monkeys.

These graceful animals can move effortlessly at high speeds, thanks to their very long limbs and tail.

You'll probably hear them before you see them, as they're known for their distinctive screeches and barks.

The loudest animal in the jungle is the aptly named Howler Monkey.

You'll be able to hear these foghorns of the forest from over five kilometers away.

Scientists think the loud howls prevent fights between troops by announcing the size and location of each group of animals.

Male howlers have evolved to magnify sound.

They have oversized throats and shell-shaped vocal chambers.

The jungles of Colombia are home to one of the smaller New World Monkeys, the very punk-looking Cotton-Top Tamarin.

These beautiful animals are one of the most sociable in the new world order and one of the most critically endangered, so sightings like this in the wild are a rare privilege.

Woolly Monkeys are far more common in the upper Amazon Basin, and they are quite large for a tree-dwelling species.

Feeding primarily on fruits, they put their prehensile tails to good use acting as a safety anchor while their limbs are otherwise engaged.

Another familiar face in the wilds of South America belongs to the Cheeky Capuchin.

They are thought to be the most intelligent of all the New World monkeys.

Demonstrating an ability to problem-solve, they use rocks as tools, crushing fruit in order to get at the delicious, nutty kernel within.

Another amazing place to encounter new- and old-world monkeys is South Africa, specifically in Monkeyland, the world's first free-roaming multi-species primate sanctuary.

The staff here are on a mission to educate and foster greater understanding of our primate cousins.

The animals are not caged, so looking for them is all part of the adventure.

There are well over 700 primates living in the sanctuary, spider monkeys and capuchins from South America, gibbons from South East Asia, lemurs from Madagascar.

Indeed, it's the United Nations of primates.

These species would never encounter one another in the wild, but somehow they all seem to get along.

Rangers do not try to tame the monkeys, and visitors are asked not to touch or feed them.

Many inmates have been rescued from captive situations.

They may have been mistreated as pets or experimented on in laboratories.

When they first arrive, they are given a thorough check up before they're allowed to socialize with their new friends.

Initially, a new resident will be placed in a cage for their own protection, allowing the other animals to get used to them and vice versa.

Other than daily food and water checks, rangers try to avoid interacting with a new monkey.

This encourages them to become independent and ready for release into the sanctuary.

Rangers still keep a distant eye on a newcomer, but contact is kept to a minimum.

One of the most distinctive Monkeyland residents is the male Proboscis Monkey from Borneo.

Scientists believe their rather large noses act as echo chambers, amplifying the calls they make to intimidate rivals or alternatively attract females.

The crowd favorite here and in many primate exhibits around the world are the Ring-Tailed Lemurs from the African island of Madagascar.

They spend more than a third of their time on the ground, which is unusual among the lemur family... often striking a very yoga-like pose as they take in warmth from the sun.

There are fewer than 2,000 of these enigmatic animals living in the wild, but they breed well in captivity, so their populations in zoos around the world are thriving.

Their trademark tails are longer than their bodies with 12 or 13 white rings and 13 or 14 black rings.

They cannot grip with their tails as many of their primate cousins do... but they do use them for balance and communication.

Females are dominant and assertive and will enforce their status through biting and lunging or rearing up on their back legs, but clearly there's little need for that here at the Monkey U.N.

(light orchestral music) There's one rainforest creature that well and truly shows there's safety and power in great numbers.

And its behavior has taught the local humans to be the most careful drivers in the world.

The red crabs of Christmas Island.

Christmas Island is the top of an underwater volcano in the Indian Ocean.

The closest nation is Indonesia, but it's an Australian territory.

And these bright red crabs have put the island on the map.

They're land crabs and spend most of the year living in the jungle away from the coast.

But around Christmas time, the crabs stage a remarkable event.

They march to the sea in their millions.

Much of the coast of Christmas Island becomes a carpet of red crabs.

The crabs are a wonderful sight to behold and people travel all the way to this remote island just to witness this spectacular migration.

Human infrastructure can present challenges for armies of small crabs on the move.

But the locals do their best to assist them.

Plastic fences and funnels guide the crabs to safe crossing points.

The migration is the only time red crabs break out of their lonely lives to get together.

The first wave of crabs consists of the males.

They head from their inland homes to the coast and quickly dig themselves a temporary burrow.

The females join them, selecting their mate for the season.

And after copulating, the males head back to the jungle, leaving the females to look after the developing eggs in their burrows.

Within about two weeks, the eggs have developed and are ready for the next remarkable stage of the great red crab journey.

At high tide, they carry their eggs to the water's edge and release them into the ocean before returning home to the jungle.

Within a month, the eggs have hatched and matured and are ready to begin the air-breathing phase of their lives.

Each crab is only five millimeters across, but there are so many, they often form a moving carpet several centimeters thick.

Once they reach the rainforest, they find a good hiding place where they can feed and grow.

Red crabs are a keystone species.

The entire rainforest depends on them to disperse seeds and fertilize the soil with their droppings and to aerate the ground with their burrows.

It's amazing that something so small should play such an important part in the ecology of Christmas Island.

(light orchestral music) The cloud-capped mountains and secluded valleys of Rwanda form the backdrop for one of the most extraordinary, life-changing animal encounters on the planet... a chance to see the last of the great Silverback Gorillas.

Mountain gorillas were first seen by Europeans in 1902.

Unfortunately, this discovery led to a century of gorilla decimation.

They were hunted for trophies, bush meat, and live young.

At the same time, their habitat was being compromised to make way for more agricultural land.

As a species, they were clearly imperiled.

When naturalist Dian Fossey arrived in Rwanda to study the mountain gorilla, she estimated there were only 240 remaining.

Today, the gorillas' fortunes have turned, thanks to the truly heartening efforts of a new generation of activists, conservationists and hardworking locals.

Zoologists believe there are now about 900 mountain gorillas in the wild.

Mountain gorillas are the largest gorilla species.

A big male can weigh 160 kilos and be over a meter and a half tall.

One troop usually consists of a dominant male, the Silverback, a few young males, some females, and their offspring.

The Silverback rules the troop, organizing the day with activities such as eating roots and leaves, building nests to rest in, and moving around the small home range.

Troop home ranges often overlap, but mountain gorillas do not fight to defend their territory.

They only get aggressive when their troop needs protecting.

Newborn gorillas are tiny, weighing in at only a kilo and a half.

They will stay with their mother for at least six years, first clinging to her fur and then riding on her back before they are big enough to play, like children, really, in the surrounding forest.

Tourism is the key to the survival of these beautiful creatures.

Rwanda has about 19 gorilla troops living in the Volcanoes National Park and 10 of those are used to human visitation.

A permit to visit these remarkable animals in the wild is expensive, but a portion of the funds raised helps to support schools and medical centers in the region.

Protecting the gorillas' habitat and guiding work keeps many of the local villagers employed, so the whole undertaking is sustainable, a win-win for the community and of course, the magnificent mountain gorillas.

The jungles of the world are some of the hardest places to get to, requiring time and often great physical effort.

But they contain such an incredible profusion of life.

They never fail to impress and inspire.

The sights, the sounds, and the smells of the world's tropical jungles conspire to create multi-sensory experiences that are unique and often profound.

(jungle animal noises and grunts with birds cawing) (light orchestral music)