0:00:34 > 0:00:38Modern Australia - it seems a familiar sort of place...
0:00:39 > 0:00:42..but step outside these cities
0:00:42 > 0:00:46and you could almost be on another planet,
0:00:46 > 0:00:50because Australia is the strangest continent on Earth.
0:00:55 > 0:01:01It's wildlife is so weird that, at first, some people thought that the animals were a hoax,
0:01:01 > 0:01:04or the work of the devil.
0:01:05 > 0:01:08It's a paradox, a place of extremes -
0:01:08 > 0:01:11its centre a burning desert,
0:01:11 > 0:01:16but also with rugged mountains covered in deep, winter snow.
0:01:19 > 0:01:24It has endless horizons of magical, timeworn landscapes.
0:01:30 > 0:01:34And in them, an amazing variety of wildlife.
0:01:38 > 0:01:42More species of animals than Europe and America combined.
0:01:42 > 0:01:47Almost all of them unique - they live nowhere else on Earth.
0:01:58 > 0:02:02It's a place that likes to do things differently,
0:02:02 > 0:02:05and, somehow, this remarkable mix of wildlife
0:02:05 > 0:02:10manages to survive on the harshest, driest inhabited continent on Earth.
0:02:12 > 0:02:16So how did Australia come to be so special?
0:02:18 > 0:02:23To answer that, you need to travel back in time
0:02:23 > 0:02:28to when this was a very different type of place, covered in trees.
0:02:30 > 0:02:33One hundred million years ago,
0:02:33 > 0:02:38massive forces shattered the supercontinent of Gondwana,
0:02:38 > 0:02:42and gradually a giant fragment floated off northwards
0:02:42 > 0:02:44with a unique cargo of wildlife.
0:02:44 > 0:02:47Australia was born.
0:02:49 > 0:02:54This was an extraordinary world, lush, green and dripping with life.
0:02:54 > 0:03:00Today, there are still a few places in Australia where you can get a feel for that past.
0:03:04 > 0:03:08These are the rainforests of Tasmania.
0:03:11 > 0:03:15They're ancient, mysterious places,
0:03:15 > 0:03:21and some of Australia's oddest animals live here, like the Tasmanian devil.
0:03:22 > 0:03:26They're scavengers, sort of antipodean hyenas,
0:03:26 > 0:03:30and they use their powerful jaws to crush up every bit of a carcass.
0:03:32 > 0:03:35You may get a dozen or so around a dead wallaby.
0:03:38 > 0:03:43They find it hard to share, let alone be sociable.
0:03:43 > 0:03:47With such lethal teeth, manners like these can be very dangerous.
0:03:53 > 0:03:57Screaming at each other is safer, but, better still,
0:03:57 > 0:04:01is bum-barging your neighbour with a few powerful blows from behind.
0:04:14 > 0:04:18This competitive spirit starts early in life.
0:04:18 > 0:04:22Devils are marsupials - their babies develop inside a pouch -
0:04:22 > 0:04:27and while this mother is jostling for a meal, the young are tucked away inside,
0:04:27 > 0:04:30doing much the same thing.
0:04:34 > 0:04:40Mothers produce about twenty embryos and they have to fight for just six teats, so competition is fierce.
0:04:40 > 0:04:45Even the ones that survive still have to fight for a drink.
0:04:48 > 0:04:52Only three or four usually make it out of the pouch.
0:04:52 > 0:04:59By then, the competitive spirit is well-established and will stay with them for the rest of their lives.
0:05:11 > 0:05:15Dense forests are not just confined to Tasmania.
0:05:15 > 0:05:20They spread right up the eastern coast of the continent,
0:05:20 > 0:05:26because soon after Australia became an island, its eastern side was buckled into mountains.
0:05:26 > 0:05:30These trapped rain, blowing in from the ocean.
0:05:38 > 0:05:42So their lowest slopes are covered in thick forest.
0:05:45 > 0:05:48Higher up, there are rugged peaks.
0:05:52 > 0:05:55And in the south,
0:05:55 > 0:05:58in winter, the rain falls as snow.
0:05:59 > 0:06:04These are the Australian Alps, snow-covered for months of the year.
0:06:04 > 0:06:07In places, it drifts up to 30m deep.
0:06:22 > 0:06:29It's not something you'd expect to see in a land which is mostly dusty and hot,
0:06:29 > 0:06:33but this weather can be ferocious and unpredictable.
0:06:36 > 0:06:38Sometimes there are blizzards.
0:06:44 > 0:06:49But even here, there are marsupials determined to make a living.
0:06:49 > 0:06:54A wombat doubles up as a snowplough in an attempt to find food.
0:07:01 > 0:07:06Wombats are world-class diggers and use strong front legs and snout
0:07:06 > 0:07:10to bulldoze through the snow in search of grass beneath.
0:07:13 > 0:07:18They're normally nocturnal, but now it's too cold to come out at night,
0:07:18 > 0:07:23so they forage during the day, even in the worst of the weather.
0:07:32 > 0:07:37It's a tough place, but there are other marsupials up here as well -
0:07:37 > 0:07:40dainty little wallabies.
0:07:45 > 0:07:49Surprisingly, the wallaby AND the wombat
0:07:49 > 0:07:53have young families in these conditions.
0:07:53 > 0:07:56But there's a good reason for this.
0:07:56 > 0:07:59These joeys will emerge in spring,
0:07:59 > 0:08:03just in time to feed on the new green shoots.
0:08:05 > 0:08:10Meantime, a centrally-heated pouch is the warmest place to be.
0:08:12 > 0:08:16Even the world's weirdest mammal, the platypus,
0:08:16 > 0:08:21makes a living in the icy waters of these mountains.
0:08:26 > 0:08:29Uniquely Australian, it has a duck's bill,
0:08:29 > 0:08:34an otter's tail and webbed feet with claws.
0:08:34 > 0:08:38Males have poisonous spurs, and females lay eggs, like birds.
0:08:38 > 0:08:43It's no surprise that early reports of them were treated as hoaxes.
0:08:45 > 0:08:51It's a monotreme, a typically Australian group of mammals.
0:08:54 > 0:08:58That weird-looking bill is highly specialised,
0:08:58 > 0:09:04with tiny sensors to detect electrical signals from the muscles of its prey.
0:09:04 > 0:09:09It's so sophisticated, it can swim with its eyes and ears closed.
0:09:14 > 0:09:19Swinging its head, it builds up a radar-like map of the stream,
0:09:19 > 0:09:22pinpointing the shrimp and worms it wants.
0:09:31 > 0:09:37It's a very adaptable animal, making its home in forest streams like these,
0:09:37 > 0:09:41all the way up the east coast of Australia.
0:09:45 > 0:09:51From the snowy mountains of the south right up to these tropical rainforests in the north.
0:10:00 > 0:10:03Like the Tasmanian forests,
0:10:03 > 0:10:08these are also ancient and have been here before Australia was born.
0:10:08 > 0:10:15The land they cover today is relatively small, just 1/1000 of the continent.
0:10:15 > 0:10:21They have just about the richest mixture of wildlife of any of Australia's environments.
0:10:42 > 0:10:45It's here, of all places,
0:10:45 > 0:10:49you can see what a truly strange place Australia is.
0:10:49 > 0:10:54Here more than anywhere, you see how its original cargo of wildlife
0:10:54 > 0:10:58has evolved into such a variety of unique species.
0:11:10 > 0:11:14Improbable giants, like this flightless cassowary.
0:11:20 > 0:11:26And marsupials in every shape and form, including the possums.
0:11:26 > 0:11:31One of the most striking is the striped possum,
0:11:31 > 0:11:35which scampers over tree trunks, looking for grubs and nectar.
0:11:35 > 0:11:40There is no better source of nectar than the bumpy satin ash,
0:11:40 > 0:11:44covered in tiny blossoms, growing straight from the trunk.
0:11:44 > 0:11:47The possum gets a sticky meal
0:11:47 > 0:11:52and it picks up pollen on its fur, transferring it from tree to tree.
0:12:03 > 0:12:10There are 26 species of possum in Australia and almost half of them live in these rainforests.
0:12:10 > 0:12:14Some have found ingenious ways to move around.
0:12:20 > 0:12:22This is a sugar glider.
0:12:36 > 0:12:40Flying through the air, or perhaps just falling with style,
0:12:40 > 0:12:45they use their built-in skydiving suits to glide from tree to tree
0:12:45 > 0:12:48for up to 50m.
0:12:49 > 0:12:53They can steer, even change direction, by 90 degrees,
0:12:53 > 0:12:58by adjusting their flaps of skin and using their tails as a rudder.
0:13:08 > 0:13:11When it's time to land,
0:13:11 > 0:13:15they just lower their flaps and put out their landing gear.
0:13:18 > 0:13:21Although touchdown could be better!
0:13:22 > 0:13:26But why did some possums evolve to glide?
0:13:30 > 0:13:35When Australia became an island, its climate started to dry out.
0:13:35 > 0:13:43The thick, tangled forest that had covered most of Australia long began to thin out into open woodland.
0:13:50 > 0:13:55It was a change that stamped the character of today's bush.
0:13:55 > 0:14:00The lush rainforest was replaced by eucalypts or gum trees.
0:14:00 > 0:14:06With trees now further apart, some possums evolved to glide across gaps.
0:14:06 > 0:14:10And there was now space for other types of travel, too.
0:14:16 > 0:14:20Kangaroos evolved in woodlands just like these.
0:14:20 > 0:14:26You need room to bounce like this - a uniquely Australian solution to budget travel.
0:14:32 > 0:14:39At certain speeds, a hopping kangaroo is more efficient than any horse or antelope.
0:14:39 > 0:14:45They live in family groups called mobs, and females can be impressive breeding machines.
0:14:45 > 0:14:52There are 50 million kangaroos in Australia, more than twice the human population.
0:14:58 > 0:15:02Having a successful design is all very well,
0:15:02 > 0:15:05but you need to know how to use it.
0:15:05 > 0:15:09Days out of the pouch, this joey has more than just a spring in his step.
0:15:22 > 0:15:28Learning to get about on two super-charged pogo sticks is no mean feat.
0:15:50 > 0:15:53That was exhausting! Time for a nap.
0:15:58 > 0:16:03But as you grow older, fitting those legs inside isn't easy.
0:16:03 > 0:16:06In two months, he'll be out for good.
0:16:08 > 0:16:15Up in the gum trees is another marsupial, with a less energetic approach to life.
0:16:21 > 0:16:25It has the laid-back Aussie love for leisure.
0:16:26 > 0:16:31This koala is putting his back into taking it easy.
0:16:34 > 0:16:40Koalas eat gum leaves, which are full of toxins and hard to digest.
0:16:40 > 0:16:45To survive on this diet, they turned napping into a national sport.
0:16:45 > 0:16:50It looks like dozing, but they are working hard to digest their meal.
0:16:53 > 0:17:01Bu at one time of the year, this all changes. It's spring, and the males want to mate.
0:17:01 > 0:17:03GROWLS AND SNORTS
0:17:03 > 0:17:06To start the season, they begin calling.
0:17:06 > 0:17:09But if your date is almost comatose,
0:17:09 > 0:17:12that may not be enough.
0:17:22 > 0:17:30For some older males, this is already too much hard work. They can't keep the mood going for long.
0:17:36 > 0:17:41For those who CAN gather enough energy, the chase is on.
0:17:43 > 0:17:48But this female, with a baby on her back, is not ready to mate.
0:17:48 > 0:17:53For a koala, this is really getting a move on.
0:17:53 > 0:17:55MALE CALLS
0:17:55 > 0:17:58But males can be very determined.
0:18:04 > 0:18:07Gentlemanly courtship is not his style.
0:18:08 > 0:18:13SHE GROWLS Nor is she willing to give in.
0:18:15 > 0:18:20His only skill is the ability to turn a drama into a crisis.
0:18:20 > 0:18:23THEY GROWL AND GRUNT
0:18:34 > 0:18:40The baby is now in serious danger and gets separated from its mother.
0:18:55 > 0:18:58But it gets even worse.
0:18:58 > 0:19:02In the confusion, the youngster ends up dangling from the male.
0:19:04 > 0:19:08This farce could easily turn into tragedy.
0:19:08 > 0:19:11SQUEALING
0:19:14 > 0:19:18The male has bungled the whole episode. It's time to exit,
0:19:18 > 0:19:23but as he slams into reverse, he takes the baby with him.
0:19:34 > 0:19:38Escape at last, but the baby isn't out of danger yet.
0:19:38 > 0:19:42Koalas depend on their mothers until a year old,
0:19:42 > 0:19:46and this one is too small to survive on its own.
0:19:46 > 0:19:49MOTHER CALLS
0:19:49 > 0:19:54Encouraged by her calls, though, he manages to sprint the last metres
0:19:54 > 0:19:56back into her arms.
0:20:03 > 0:20:05Now he's safe.
0:20:15 > 0:20:22Raising babies, with or without rampaging males, is not easy in these eucalypt woodlands.
0:20:22 > 0:20:26They're tough places - dusty and dry, without a lot of food.
0:20:29 > 0:20:33Especially with mouths like these to feed.
0:20:39 > 0:20:45This is a kookaburra, and these chicks are demanding customers.
0:20:45 > 0:20:48They want round-the-clock room service.
0:20:48 > 0:20:53It's a problem for parents to provide this on their own,
0:20:53 > 0:20:59so last year's brood helps. It's a sort of kookaburra catering corps,
0:20:59 > 0:21:04with work experience thrown in. They learn all about bringing up chicks.
0:21:04 > 0:21:08Kookaburras are the largest kingfishers in the world.
0:21:08 > 0:21:14Being Australian, they don't always catch fish and don't always live near rivers.
0:21:14 > 0:21:19To keep the brood well fed, they catch everything they can find.
0:21:19 > 0:21:22Spiders, snakes, sometimes small mammals.
0:21:22 > 0:21:25Anything to keep the noise down.
0:21:36 > 0:21:40With the entire family working together on constant dinner duty,
0:21:40 > 0:21:44they can deliver food round the clock.
0:21:45 > 0:21:49But it seems the faster they shovel it in, the louder the babies cry.
0:22:05 > 0:22:10Now and then, though, a big mouthful of lizard seems to do the trick.
0:22:16 > 0:22:22These parched woodlands aren't just tough places to live in and bring up a family,
0:22:22 > 0:22:25they're dangerous as well.
0:22:30 > 0:22:34They're tinder-dry and easily ignite.
0:22:37 > 0:22:41When a spark hits the volatile oils in their leaves and bark,
0:22:41 > 0:22:45gum trees burst into flame. In minutes, the woodland is a fireball.
0:22:50 > 0:22:53Animals that can move fast get out quick.
0:23:08 > 0:23:15If the wind gets up, it can fan the blaze, causing crown fires that race through the tree tops.
0:23:25 > 0:23:28And afterwards...Armageddon.
0:23:39 > 0:23:44The morning after, there may be some dead insects around, the odd shoot,
0:23:44 > 0:23:49but any animals that survived will have to move on.
0:23:53 > 0:23:55And they may have a long way to go.
0:23:55 > 0:24:00Hundreds of kilometres of woodland can disappear in days.
0:24:00 > 0:24:05Three million hectares a year are incinerated by fires like this.
0:24:13 > 0:24:17But then something extraordinary happens.
0:24:18 > 0:24:22Many gum trees have evolved to survive bush fires.
0:24:22 > 0:24:28And some have energy stores beneath their bark, so they burst back into life.
0:24:28 > 0:24:35Within a week or two, their trunks are covered in dazzling green foliage.
0:24:43 > 0:24:48The drying out of Australia's climate over millions of years
0:24:48 > 0:24:53not only had a major effect on its forests, but also on its rivers.
0:24:54 > 0:25:01Long ago, Australia had a network of mighty rivers, stretching right into the heart of the continent.
0:25:01 > 0:25:05But when the climate dried, they dried up, too.
0:25:05 > 0:25:10Today, the largest river system left is the Murray-Darling.
0:25:11 > 0:25:15And here it is - barely wider than the average road.
0:25:18 > 0:25:24It's extraordinary that a 2,500km river should be so narrow.
0:25:24 > 0:25:26And this is in full flood.
0:25:33 > 0:25:40Even in a year, less water flows down the Murray-Darling than down the Amazon in a single day.
0:25:50 > 0:25:54Most of Australia's rivers are even smaller.
0:25:54 > 0:26:01Many are streams that dry out for part of the year. Others are creeks that haven't seen water for years.
0:26:12 > 0:26:17But in many river beds, water remains in pools called billabongs.
0:26:17 > 0:26:25In a parched landscape, these stand out as irresistible lures, drawing in wildlife from every direction.
0:26:37 > 0:26:43Many animals live or die by their skills at finding vital billabongs.
0:26:45 > 0:26:50None arrive in greater numbers than corella parrots.
0:26:50 > 0:26:53BIRDS SCREECH
0:26:56 > 0:26:59These turn up in their thousands.
0:27:00 > 0:27:07In flocks so huge that early explorers in search of water learnt to look for them on the horizon.
0:27:08 > 0:27:13In this early-evening rush hour, they're joined by budgies -
0:27:13 > 0:27:17tough little nomads, who will travel a long way for water.
0:27:36 > 0:27:41By the end of the day, thousands of birds have gathered here,
0:27:41 > 0:27:45and every available tree seems packed with budgies and corellas.
0:27:59 > 0:28:05Most animals in the outback get at least some water from their food,
0:28:05 > 0:28:09but corellas and budgies eat seeds, which are very dry,
0:28:09 > 0:28:11so they need to drink every day.
0:28:27 > 0:28:30Kangaroos can survive longer without water,
0:28:30 > 0:28:33but rarely stray far from it.
0:28:39 > 0:28:41On the other hand,
0:28:41 > 0:28:45emus may have followed a trail for over 100km.
0:28:45 > 0:28:48They use cues like distant clouds
0:28:48 > 0:28:51or thunder to help them find water.
0:28:51 > 0:28:55And it's not just vital for daily life.
0:28:55 > 0:28:57Animals need it for breeding, too.
0:28:59 > 0:29:04Because rain is so unpredictable, kangaroos breed when they can.
0:29:04 > 0:29:08When there's water, females move into mass production.
0:29:08 > 0:29:15She may be suckling an older joey, with another in the pouch, and an embryo inside her as well.
0:29:18 > 0:29:21Budgies, too, make the most of it.
0:29:21 > 0:29:26When they find water, they set up home and raise a family instantly.
0:29:26 > 0:29:30But they have some rather annoying neighbours.
0:29:30 > 0:29:36All the activity at this budgie household seems too much for the corellas.
0:29:36 > 0:29:39They are intelligent birds,
0:29:39 > 0:29:44but they also enjoy sticking their beaks into other people's business.
0:29:44 > 0:29:49For the budgies, they're the neighbours from hell.
0:29:54 > 0:30:01The corellas are just being nosy, but it is best for the budgie chicks to stay in their hole.
0:30:06 > 0:30:13These are playful birds, and after a few drinks at the billabong, they like a bit of fun.
0:30:15 > 0:30:19Fooling around helps strengthen their relationships.
0:30:22 > 0:30:25But some of it's just showing off.
0:30:42 > 0:30:44While the water lasts,
0:30:44 > 0:30:49they make the most of this time off in the cooler evening light.
0:31:05 > 0:31:12Although much of Australia has very little water, there's one area that's awash with it.
0:31:12 > 0:31:18Since becoming an island, Australia has drifted north at 5cm a year,
0:31:18 > 0:31:21so its top end's now in the tropics,
0:31:21 > 0:31:24right in the path of the tropical monsoon.
0:31:24 > 0:31:29This is one of the most powerful weather systems on the planet.
0:31:39 > 0:31:42It lasts for only a few months each year.
0:31:42 > 0:31:47While it does, Northern Australia becomes a very different place.
0:31:47 > 0:31:49It has a dramatic wet season.
0:31:52 > 0:31:54For a short time,
0:31:54 > 0:31:59rain falls so hard that rivers turn into raging torrents.
0:32:10 > 0:32:16When they burst out of their gorges, they flood out onto open plains,
0:32:16 > 0:32:20creating some of the world's largest tropical wetlands.
0:32:24 > 0:32:28The most famous of these is called Kakadu.
0:32:30 > 0:32:35Every year, huge numbers of birds arrive to feed and breed.
0:32:35 > 0:32:39Two million magpie geese alone jostle for space
0:32:39 > 0:32:43with ducks, herons, ibis and other water birds,
0:32:43 > 0:32:48some feeding on the flooded grass, others on shrimps and small fish.
0:32:58 > 0:33:01But birds aren't the only animals here.
0:33:04 > 0:33:08In the quiet streams on the edge of the swamp,
0:33:08 > 0:33:12are residents who live here all year round.
0:33:12 > 0:33:18This prehistoric-looking reptile is an amphibious lizard called Merton's Water Monitor.
0:33:23 > 0:33:28They're graceful swimmers, spending some time completely submerged,
0:33:28 > 0:33:33propelled by a long, powerful tail, which doubles up as a rudder.
0:33:38 > 0:33:45They're scavengers and, even under water, they can taste the scent of rotting food.
0:34:08 > 0:34:13Finally, it finds the meal it's been looking for - a dead fish.
0:34:20 > 0:34:23There are other reptiles here, too.
0:34:23 > 0:34:28Freshwater crocodiles, also uniquely Australian.
0:34:28 > 0:34:34These daintier cousins of the giant saltwater crocs feed on small prey,
0:34:34 > 0:34:36like fish and crustaceans.
0:34:41 > 0:34:49This is boom time, but it won't be long before the monsoon ends and the blazing sun takes over again.
0:35:01 > 0:35:05As the water evaporates, the swamp congeals
0:35:05 > 0:35:08into an ocean of sticky mud.
0:35:08 > 0:35:13On the margins of Kakadu, streams dwindle into pools of sludge.
0:35:13 > 0:35:16The monitors can move back on land
0:35:16 > 0:35:20but these freshies rely on water to keep cool.
0:35:20 > 0:35:25Their situation is beginning to look increasingly sticky.
0:35:25 > 0:35:30Before they get stuck fast, these crocs must do something - quickly.
0:35:36 > 0:35:38As the evening heat dies down,
0:35:38 > 0:35:41they slide to the edge of the pool.
0:35:41 > 0:35:47Their only chance of surviving is to travel overland in search of water.
0:35:47 > 0:35:50They'll need to find it before sunrise.
0:35:55 > 0:35:58Instead of the normal crocodile belly crawl,
0:35:58 > 0:36:03they march overland with this unusual high walk.
0:36:03 > 0:36:09It's the fastest way to travel if they're going to find water by dawn.
0:36:14 > 0:36:19When the sun comes up, they're in real danger of overheating.
0:36:19 > 0:36:21But freshies have one last trick.
0:36:26 > 0:36:29With a unique gallop,
0:36:29 > 0:36:32they make an Olympic dash
0:36:32 > 0:36:35and become the fastest crocodiles in the world.
0:36:46 > 0:36:49With any luck, a deep pool like this will survive
0:36:49 > 0:36:52until the monsoon returns.
0:36:58 > 0:37:01But most of the streams and pools
0:37:01 > 0:37:06will have all water sucked out of them by the burning tropical sun.
0:37:11 > 0:37:16Throughout its long history, Australia has dried out so much
0:37:16 > 0:37:19that half the continent is desert -
0:37:19 > 0:37:22in places, so arid and alien,
0:37:22 > 0:37:26it looks more like the surface of Mars.
0:37:43 > 0:37:45In the harshest areas,
0:37:45 > 0:37:48there are vast lakes of dry salt.
0:37:55 > 0:38:01With almost no vegetation, the bones of the continent are laid bare.
0:38:03 > 0:38:05Like a gigantic ribcage,
0:38:05 > 0:38:10these parallel sand dunes stretch for hundreds of kilometres.
0:38:13 > 0:38:19At the heart of the desert - Uluru, one of the world's largest rocks.
0:38:20 > 0:38:23And THIS is just the tip -
0:38:23 > 0:38:26the rest extends 6km below ground.
0:38:26 > 0:38:29In such a dry landscape,
0:38:29 > 0:38:34it seems bizarre that Uluru was actually weathered into shape
0:38:34 > 0:38:37by millions of years of rain.
0:38:39 > 0:38:44At first glance, there's not much sign of life in the desert.
0:38:44 > 0:38:46But during the day,
0:38:46 > 0:38:52sensible Australians stay out of the sun - including the planigale.
0:38:52 > 0:38:56It's one of Australia's smallest marsupials and one of the toughest.
0:38:56 > 0:39:01It needs to be. Most of its meals are larger than it.
0:39:05 > 0:39:10Dwarfed even by this moth, the planigale doesn't give in.
0:39:10 > 0:39:13With true outback grit,
0:39:13 > 0:39:19it tries to wrestle this oversize meal to the ground - and fails.
0:39:20 > 0:39:25In these underground cracks, it's almost 15 degrees cooler
0:39:25 > 0:39:30than in the sun. The planigale can hunt for a smaller meal in comfort.
0:39:36 > 0:39:39Or so he thinks.
0:39:42 > 0:39:45This is no time to relax
0:39:45 > 0:39:50when above you is the world's deadliest snake - the inland taipan.
0:39:59 > 0:40:02This snake scares even Australians.
0:40:02 > 0:40:04It's loaded with venom -
0:40:04 > 0:40:09enough to kill thousands of planigales and you or me in minutes.
0:40:10 > 0:40:13NOW being small has its advantages.
0:40:15 > 0:40:17With a specially flattened head,
0:40:17 > 0:40:20it can squeeze into tiny crevices.
0:40:27 > 0:40:32Even the world's most venomous snake can't always get a meal.
0:40:34 > 0:40:37The Australian desert is full of deadly snakes.
0:40:37 > 0:40:42In fact, all sorts of reptiles flourish here - especially lizards.
0:40:42 > 0:40:46Australia has more than any other continent.
0:40:46 > 0:40:50A single sand dune can support 40 species.
0:40:50 > 0:40:54This really is the land of the lizard.
0:40:54 > 0:40:57The largest are more than a metre long.
0:40:57 > 0:41:01This is a sand goanna, also known as a racehorse goanna -
0:41:01 > 0:41:04for obvious reasons.
0:41:14 > 0:41:18Lizards are much more successful here than mammals
0:41:18 > 0:41:21because they need less food.
0:41:23 > 0:41:28Meals can be scarce and goannas will eat almost anything they can catch -
0:41:28 > 0:41:31even scorpions.
0:41:57 > 0:42:03Goannas do get stung but they seem to be immune to the poison.
0:42:03 > 0:42:08It may not be much but this could be its last meal for weeks.
0:42:08 > 0:42:13Animals don't come much tougher than the adult goanna
0:42:13 > 0:42:15but their eggs are more vulnerable.
0:42:15 > 0:42:19They need protection from the harsh climate
0:42:19 > 0:42:23and termite mounds make perfect incubators.
0:42:24 > 0:42:27These eggs were laid about nine months ago
0:42:27 > 0:42:31and now they're ready to hatch.
0:42:44 > 0:42:47Fully formed, miniature adults emerge.
0:42:55 > 0:42:59The termite mounds gave perfect protection
0:42:59 > 0:43:03but now they're a barrier to the outside world
0:43:03 > 0:43:06and these babies need to get out.
0:43:11 > 0:43:14The walls can be rock-hard.
0:43:22 > 0:43:26But the youngsters are already as determined as adults.
0:43:31 > 0:43:36One by one, they clamber out to one of the toughest habitats on earth.
0:43:43 > 0:43:47Over its long history, Australia has dried out so much
0:43:47 > 0:43:53that, in places, its desert heart has expanded right up to the coast.
0:44:02 > 0:44:05Millions of years of drying
0:44:05 > 0:44:09has had an enormous impact on the character of Australia.
0:44:09 > 0:44:14But one further event put the finishing touches to its shape.
0:44:14 > 0:44:18Just 10,000 years ago,
0:44:18 > 0:44:23at the end of the Ice Age, sea levels around the world rose,
0:44:23 > 0:44:26Australia's coastline was flooded,
0:44:26 > 0:44:29creating thousands of beautiful islands.
0:44:33 > 0:44:38This flooding also helped shape the world's largest living structure -
0:44:38 > 0:44:41the Great Barrier Reef.
0:44:41 > 0:44:43This reef was once dry land.
0:44:43 > 0:44:47Aborigines might even have hunted kangaroos here.
0:44:47 > 0:44:50Now, at over 2,000km long,
0:44:50 > 0:44:54it's the greatest coral complex to have ever existed.
0:44:54 > 0:44:59It's hard to imagine a more colourful contrast
0:44:59 > 0:45:02to the dry, crusty old continent.
0:45:08 > 0:45:12Over 400 different corals, in every shape and size,
0:45:12 > 0:45:15support more than 2,000 species of fish.
0:45:18 > 0:45:20And just for a few days in spring,
0:45:20 > 0:45:25the reef bursts into a special frenzy of activity.
0:45:31 > 0:45:36With precision timing, using cues from the moon and the tides,
0:45:36 > 0:45:39many fish begin to breed.
0:45:39 > 0:45:43Thousands of them condense their courtship and spawning
0:45:43 > 0:45:48into just a few minutes of frantic fertilisation.
0:46:00 > 0:46:02But on just a few nights each year,
0:46:02 > 0:46:06an even more remarkable event takes place.
0:46:07 > 0:46:10On certain tides, just after the full moon,
0:46:10 > 0:46:13the reef itself begins to erupt.
0:46:24 > 0:46:262,000km of coral takes part
0:46:26 > 0:46:30in a synchronised release of eggs and sperm
0:46:30 > 0:46:33in vast quantities.
0:46:40 > 0:46:44No-one knows quite how so many billions of eggs
0:46:44 > 0:46:50are timed to release on the same night, so precisely.
0:46:58 > 0:47:03It's the biggest synchronised breeding event on the planet.
0:47:22 > 0:47:25It seems extraordinary that Australia -
0:47:25 > 0:47:30the harshest, driest inhabited continent on earth -
0:47:30 > 0:47:34has also produced such a colossal, vibrant, growing structure.
0:47:34 > 0:47:38But from the moment Australia became an island,
0:47:38 > 0:47:43its isolation and history have made it into this continent of extremes.
0:47:43 > 0:47:46It is a land of fantastic diversity,
0:47:46 > 0:47:49the weirdest mix of animals and plants
0:47:49 > 0:47:55living in some of the toughest, most beautiful, landscapes imaginable.
0:48:03 > 0:48:07This really is the strangest continent on earth.
0:48:23 > 0:48:29Next week, Wild Down Under takes you to Australia's desert heart,
0:48:29 > 0:48:34a place where only the hardiest animals survive.
0:48:34 > 0:48:40But this extraordinary landscape is full of natural secrets.
0:48:40 > 0:48:45From ancient mountains to disappearing inland seas,
0:48:45 > 0:48:50this is a journey across the most surprising desert in the world.