Life on Earth’s Wildest Frontiers with David Attenborough (4K Documentary)

To understand the diversity of life on Earth, we must travel to the remotest parts of our planet. In these extreme locations, varied habitats allow certain species to thrive. They are places of protection from climate and predators, where survival is easier. Australia's Great Barrier Reef is one of the most unique natural environments on the planet, attracting creatures in search of sanctuary from the wilderness of the open ocean. The Great Barrier protects its visitors in many different ways. That becomes clear when you look at the reef from above. This part of tropical Australia lies right in the path of regular seasonal cyclones. This tangle of limestone walls acts as a barrier against the open ocean. Between it and the land, the waters are warm and shallow, an ideal haven for visitors. A global community of animals rely on this great wilderness, and that makes it one of the most important and influential habitats on the planet. Every year, the Great Barrier Reef attracts over a million migrating animals. But there are still large animals whose movements remain something of a mystery. Manta rays are the nomads of the reef. They're huge creatures. They can measure 15 feet, five meters across, and weigh almost one and a half tons. They come to the reef to feed on plankton, but they also use it as a sanctuary where they can breed or get a good clean. Mantas have travelled hundreds of miles up the eastern coast of Australia to get here. Many make their way to the waters that surround Lady Elliot Island on the southern end of the Great Barrier. For the visiting manta rays, this is a paradise, a place where these ocean giants can get a little pampering. These are the beauty salons of the reef, and they're often run by a pair of wrasse. These committed cleaners regularly tend to a host of different creatures. They provide a vital service, removing the dead skin and parasites from outside and even inside their clients' bodies. It may seem like a thankless task, but the cleaner fish are getting a good meal out of it. And of all their clients, the manta rays are their star customers. When businesses risk, they patiently wait in line. Like planes in a holding pattern, they circle until an opportunity arrives. When it's their turn, the manta rays surrender themselves completely. Within seconds, a host of fish rush to their side. Manta rays are rarely left waiting for long. Each fish tends to a very specific part of the manta's body. And the cleaning can last a full hour. For the most part, the service is second to none. But occasionally, the cleaners can get a little carried away. A female wrasse has taken a nibble out of the manta ray's flesh. She's broken the rules, and there's a price to pay. Her partner chases after her. It's the cleaner fish equivalent of a stern telling off. Scientists believe males do this to protect future business. If the bite is a one-off, the manta ray will return. But research has shown that if it happens too often, the pair risks driving regular visitors away. Fortunately, it seems her indiscretion hasn't put their client off. The manta is back, and business has resumed. For the visiting mantas, the Great Barrier Reef really is a sanctuary. Here, this ocean giant is properly protected. Animals will travel huge distances across our planet in search of the perfect environment to breed and seek shelter for their young. Along the length of the Great Barrier Reef, there are 900 isolated islands to choose from, and a habitat to suit every visitor. This is Heron Island, and every year, it attracts thousands of birds seeking somewhere safe to nest. The warm waters of the Barrier Reef are full of fish, full of food, as far as birds are concerned. So there are immense numbers of seabirds throughout the year on the reef. But the moment comes in the year when, in fact, a bird has to lay, and to do that, it has to go onto land. And the number of sites where they can build a nest are very limited. So they will put up with a great deal of crowding, and even with intruders like myself, without deserting their nest. Hello. Noddies are very protective parents. Very little deters them from their chick-rearing duties. Over one and a half million birds come to the Great Barrier Reef every year to breed. To see one of the most intriguing, we'll have to wait until after dark. The first indication that this secretive character has arrived is its rather unusual song. The old sailors used to call it the Ghost Bird because of its extraordinary call. More properly known as the Wedge-tailed Shearwater. The bird's haunting calls guide me to their breeding grounds. These are true seafaring birds. Out at sea when they're feeding, they are very expert at flying just above the surface, or indeed, swimming on the surface, catching their fish. But when they come in to land, well, they have to come in in the dark for a start, and their landing is sometimes not very expert. Night vision cameras probably give us better pictures of their landing ground than they seem to have. These birds have travelled an extraordinary 4,000 miles to get here. After spending months feeding at sea, they've had to come to land in order to breed. Once paired, they're devoted couples, and both male and female share the tasks of parenthood. Even though there are trees here, the Shearwaters prefer to make their nests underground. At the bottom of the nest hole, their three-week-old chick is waiting for its next meal. Being a Shearwater parent is a demanding job. Their young requires constant feeding. Its demands compel the adults to continually fly out to sea and come back again with more food. And their take-offs are often just as clumsy as their landings. Fortunately for their nestlings, there's no shortage of fish in the summer months. In the waters just beyond Heron Island, there's a rich swirling current known as the Capricorn Eddy. As it spins clockwise, it pulls up cool waters from below, which bring rich nutrients to the surface. That fuels the growth of huge blooms of tiny marine creatures, plankton, the foundation of the entire marine food web. So this part of the reef is particularly rich with fish, vital food for the hungry young. By choosing Heron Island as a nesting ground, the birds can give their nestlings the best possible start in life. Corals are not new to the planet. They've been around for at least 500 million years. The new reefs provided homes for thousands of animals and very quickly, a whole new community began to establish itself. Today, the Great Barrier Reef has one of the most diverse communities of animals on the planet. And it's the story of these remarkable reef residents that I want to investigate next. This is Blizzard Island. It's one of the 600 continental islands scattered across the Great Barrier Reef. And its shallow lagoon is known for its exceptional biodiversity. Here, for the past few decades, there has been a research station where scientists can study continuously and in detail the full complexity of the community of animals that makes up the reef. Thanks to their research, we now know that coral reefs rival rainforests in the vast numbers of species they support. The first question is, where does all that diversity come from? Blizzard Island reefs owe their richness to the special plants that, in places, fringe the shores. They link land and sea and they're vital to the coral reef community. They're mangroves. Taking shelter amongst the roots are thousands of juvenile fish of all shapes and sizes. Many of these little fish look harmless enough, but when they grow up, they will become some of the most ferocious predators on the reef. Indeed, the existence of these mangrove nurseries is one of the reasons why the fish populations of the reef are among the most varied and richest in the world. The mangroves are not only nurseries, they're playgrounds. The aim of the game here is to survive the most vulnerable stage of any animal's life, being a juvenile. Baby turtles, rays, and even sharks take refuge here. These juvenile blacktips are just a few weeks old and only one-sixth of the size they will be when they make it out onto the reef as adults. For the first year of their lives, the mangroves play a vital role in keeping them safe. As infants, they're vulnerable to predation from larger sharks. But the tangle of mangrove roots keeps the big predators out and stops them making meals of the youngsters. When the young are ready, they will eventually leave this sheltered world behind and make their way to the reef beyond the mangrove roots. The next challenge will be to find their place in one of the most crowded ecosystems on the planet. All over the world, there are creatures which adapt to their surroundings to make a home that keeps them safe. In the ancient rainforests of Borneo, there's an animal that has created its perfect habitat. It's achieved this by developing a remarkable ability. The creatures I'm looking for find their food not by sight or smell, but by using a very different and highly advanced guidance system. One way to find them is to search for their ideal home. A place like that deep black cave beneath me. This is Gomantong. The cave is a vast network of underground tunnels and cathedral-sized caverns. It was carved out by streams of water over millions of years. And now it's home to a remarkable community of cave-dwelling specialists. High on the rocky cave ceiling above me, hidden in the darkness, there are vast numbers of bats. You can get some idea of how many there must be because of this huge dune behind me. That's formed of their droppings. Some people think there are a million bats up here in this cave. It's impossible to see them in the gloom. But special night vision cameras can reveal them. Densely packed crowds hanging from the ceiling. Their tiny eyes are adapted to low light, but they cannot penetrate the blackness. Millions of years ago, however, these bats evolved an extraordinary guidance system known as echolocation, or sonar. A bat produces extremely high-pitched sounds in its throat and then projects them forward. They bounce off the walls as echoes and are detected by the bat's huge ears. These are in constant movement and enable the bat to map its surroundings with remarkable precision. Every evening, as dusk arrives, the bats leave the safety of their secluded home to hunt. And now the bats are beginning to use their echolocation skill to fly out from their roosts in the depths of the cave, coming close to the ceiling and then whizzing out through this little entrance here. They don't collide with the roof, they don't collide with one another, or even with me. All through that echolocation. There they go. But this is just a trickle. The main exodus is taking place up a chimney that's deeper in the cave. I'm being hauled up 200 feet into the funnel, which serves as one of the cave's main exits, to watch close up the way the bats achieve their million-strong mass departure. At the top, there is a gaping hole. And now the bats are preparing to leave. They've assembled in a relatively small chamber close to the exit, and are flying round and round in a great swirling crowd, waiting for daylight to fade. And now, off they go. Outside, danger awaits. Hunters belonging to that other great group of animals with which they've shared the skies. Birds. Hawks, eagles, and kites. They are why the bats were reluctant to leave, and why they now do so in one continuous torrent. There is safety in numbers. But some will pay the price. The vast majority, of course, make it out over the forest canopy. And there they can use that skill of echolocation to find food. All species are most vulnerable in the early stages of life. And making it through to adulthood is the biggest challenge of all. So animals must find inventive ways of protecting themselves if they're to survive. One ingenious creature can be found here, in the jungles of Borneo. Butterflies. They hatch from eggs as little worms with legs. Of course, a little thin-skinned, fat-filled sausage is a tempting morsel for any bird or reptile. So caterpillars have to have ways of defending themselves. This one, which is the caterpillar of a lovely swallowtail butterfly, has disguised itself as a bird dropping. And if that doesn't deceive a bird, and a bird goes for it, it has another form of defense. It's emitted a rather unpleasant smell as well. In the struggle to survive long enough to become winged adults, caterpillars have developed other equally ingenious forms of defense. Concealed within these fluffy strands are short, stinging spikes. And this one is armed with long spines which have really painful stings. Not only that, it has these bright warning colors to tell any potential predator that they'll be in trouble if they attack. This caterpillar may appear to be dangerous, but it is in fact a fraud. The spines don't sting at all. It's relying on its disguise to make a potential predator think twice. And leave it alone. Or you can simply hide. These little tents have been made by the caterpillars of a skipper butterfly. Each caterpillar has started by making a circular cut in the edge of the leaf, but it's left one segment uncut so it can act as a hinge. Then it pulls over the whole segment and hides beneath to munch away at the tissues of the leaf. And if I just pull it up, there's a caterpillar. Caterpillars that survive this hazardous stage can now build their wings and turn into adults. They undergo a truly radical transformation. A caterpillar first surrounds itself with a protective shell to act as a sort of changing room within which it dismantles and then completely reconstructs its body. After around 10 days, it emerges as a butterfly. Now fluid pumps along veins in the wings to stretch them out to their full size. And then it is ready to fly. The combined front and hind wings of a butterfly not only constitute very effective flying mechanism, they can also carry messages. In fact, they carry some of the loveliest advertisements in the whole of the animal kingdom. Like, for example, this beautiful golden birdling butterfly from Borneo. The butterfly's huge wings provide a spacious canvas on which to display fantastically elaborate designs. So how are these flying advertisements created? The secret lies in the microscopic structure of the wing's surface. These overlapping scales, lined up like tiles on a roof, have evolved from bristles that were once tiny sensors. Some contain tiny packets of pigment that give the wings colour. Others have a complex structure which splits the light so that when viewed from a particular angle, it reflects a brilliant iridescence. There are over 18,000 species of butterfly around the world and each has wings with their own distinctive design. These ravishing colours and delectable patterns, of course, enable a male butterfly and a female butterfly to know whether or not they belong to the same species. And a mature adult ready to mate can identify a suitable partner from surprising distances. When a male and female eventually meet, they flutter around each other in a ritual dance. Each is checking out the flying skills and wing patterns of the other. If both pass the test, they mate. Millions of years ago, plants colonised the surface of the Earth, taking hold of the land to pave the way for the many creatures we see today. An astonishing example of these plant pioneers can be seen on the islands of the Galapagos. This is a place of wonders. Galapagos, islands born of fire. With inhabitants that have transformed our understanding of the whole of life on Earth. This is Santa Cruz in the centre of the archipelago. It has the ability to create its own weather. Its slopes are covered by a mantle of green. Humid oceanic winds blowing across the Pacific hit this mountain of lava and are so forced upwards. That cools them so that they can no longer hold their load of moisture and it condenses as mist and rain. And that allows plants to thrive. This might seem to be a forest of giant trees supporting a rich population of animals of all kinds. But this being Galapagos, this forest is different. These plants are not true trees. Fate placed these islands in a unique spot on this planet. They lie plumb on the equator with its year-long warmth and sunshine. But perhaps more importantly, they also lie at the crossroads between two competing winds. The southeast trade winds blow up from South America and the northeast trades come down from the Caribbean and Central America. These two winds are the lifeblood of the Galapagos. They carried the earliest settlers to the emerging volcanic islands. Seeds falling from trees in South and Central America were blown across hundreds of miles of ocean. Most were lost at sea. Of those few that reached the islands, many fell on sterile, baking hot rocks. But just a few were luckier. This extraordinary species is related to dandelions and it's found a way to grow where there is neither soil nor rain. A windblown seed arrives and drops in a crevice in the lava. Moisture collects and causes it to germinate. With its tiny leaves, it manages to collect more moisture and the infinitesimal quantities of nutrients that moisture from the skies might contain. Some of these leaves may look dead. And indeed they are. The plant is deliberately shedding them. It's ensuring that nothing it produces is wasted. It's creating its own soil. And eventually, after 80 to 100 years, it produced this. Scalesia, which seems to grow straight out of naked rock. Without competition from other trees, Scalesia grew big. This, you could say, is a forest of giant dandelions. There's no groundwater in these thin volcanic soils but the Scalesia tree is tall enough to collect moisture from the skies, from clouds and from mist. And that is sufficient to sustain a whole community of plants and animals. It's become the host for a community that could not exist without it. Because Scalesia performs a conjuring trick that gives life to the rest of the forest. High in the canopy, mist condenses on the spindly crisscross branches. Water trickles down their woody trunks. Ferns root themselves in the damp moss that clings to their bark. The moisture creates conditions where spiders and other small creatures can live. And on the forest floor, pools appear. Here, dragonflies thrive and, once again, they belong to a species that occurs nowhere else but here. As islands mature, their habitats change. Landscapes weather. Rocks erode and beaches emerge. On the island of Española, the ocean has carved out a sandy coastline. This is a natural bathing beach for Galapagos sea lions. They are just one of the very few mammal species that are unique to the Galapagos. And the beach of an aging island provides them with an excellent nursery. Here, sea lion pups can suckle in complete safety. Though they can be a little irritating. And in a protected cove close by the beach, parents can teach their youngsters to swim. After a swimming lesson, the beach is a perfect place to relax. Sea lions seem to have an idyllic life, but there is just one irritant. Flies. On younger islands with rocky coastlines, sea lions have help to keep the flies at bay. Larvae lizards. But on the sandy beaches of Española, the larvae lizards are nowhere to be seen. They prefer the nearby rocks, which are warmer. So here, the sea lions must deal with the fly problem by themselves. Little lizards like this are found throughout the archipelago. Each island has its own distinct species. And they differ not so much in the way they look as the way they behave. This is a larva lizard. There are lots of them on the rocks around here. And in the breeding season, which is now, the males are competing with one another, both for territory and for females. And the way they do so is with press-ups. Watch. Actually, this is a model that is used by scientists to investigate the way in which these lizards communicate with one another. Let's see how he gets on. And there's a response. These press-ups vary both in the number and the intensity, the speed at which they do it, and how high they bob their heads. The interesting thing is that the responses vary from species to species. In other words, each species has its own language of gestures. There are slight physical differences between the species of larva lizard on different islands. But now, because they have developed different gestures, they can't interbreed even if they meet. They're separated by a language barrier. Millions of years before humans inhabited the Earth, strange creatures dominated. But it was the skies that were populated by the most successful animals, the pterosaurs. Today, along our coastlines, there are still traces of how these extraordinary animals survived. Birds today are the masters of the skies. But they were not the first creatures to fly. This prehistoric creature, it's called capybara. It had a simply enormous head crest. Swans and geese today sometimes lift their wings to catch gusts of air, a behaviour called goose winging. So perhaps capybara did something similar. But big head crests had a much more likely function. There are clues of what that might be in animals alive today, like this colony of gannets on Bass Rock off the coast of Scotland. Pterosaurs, doubtless, would have lived in great groups around the ancient coastlines. And living in tightly packed communities, then as now, must have led to all kinds of dramas, just as it does in communities like this one. Gannets, nesting close to one another, squabble with their neighbours over food and territory. Pterosaurs, doubtless, also competed with one another for the attentions of the opposite sex. Perhaps capybara used its huge head crest in displays to its mate during the breeding season and indulged in the same sort of strutting performances that so many birds do today. After their courtship, pterosaurs, just like birds, laid eggs. This fossilised egg, which is about the same size as one of these gannet eggs, is actually the egg of a pterosaur. And although it's squashed flat, it's marvelously preserved, so you can see details of the bone inside. The head, as you would expect with a bird head, is quite well formed. It's amongst this mass of bones here. But whereas a bird's wings would hardly be formed at this stage, here the pterosaur wings have got these well-formed bones in them. And that leads us to one extraordinary conclusion. A pterosaur chick, when it hatched, was almost immediately able to fly. The bones of the pterosaur embryo reveal another extraordinary fact. They develop in a way quite different from birds. And what is more, they continue to do so even after the young have hatched. This led to some species becoming gigantic. This was Quetzalcoatlus. It lived 70 million years ago during the Cretaceous period. But how did this giant get off the ground? A modern glider is about the same size as that giant pterosaur. It too has long, slender wings, and it too is extremely light. This flying machine is so lightweight, it doesn't even need an engine. All it requires is a tow to get it into the air. This is the nearest I will ever get to experiencing the magic of Quetzalcoatlus in flight. With its giant wingspan, this was the largest animal ever to fly. Quetzalcoatlus kept its wing beats to a minimum. It was a living glider. We are controlling our flight using, at least in part, our tail. However, whereas powered aeroplanes have tails and birds have tails, advanced pterosaurs like Quetzalcoatlus didn't have a tail. So steering must have been much more difficult and would have required very considerable brain power. But there was, people think, a payoff to that. Because without a tail, Quetzalcoatlus was even more maneuverable than we are in this. Quetzalcoatlus doubtless used many of the techniques employed by human glider pilots. To maintain our height, we need to find a thermal. That's those columns of warm air that rise from patches of the landscape that heat well in the sun, like patches of rock. You can tell where they are because white, fluffy clouds form at the top of them. And there's one over there and we're going to have to get to it if we're going to maintain our height. It's been estimated that by exploiting thermals, Quetzalcoatlus could travel some 10,000 miles in a single flight. And that is almost half the circumference of the entire planet. It might even be that like some eagles today, these flying giants undertook long migratory journeys every year.