"In this driest of continents there's a vast green landscape that stretches for thousands of kilometers round Australia's edge." "This is the Australian bush - its most characteristic landscape." "The first European settlers, pushing through it 200 years ago, didn't like the bush." "It was daunting and alien, and so big you could get lost and die." "In these hot, endless forests, the very trees seemed to droop - these, they said, were 'forests in rags'." "And from one end of the country to another, they all looked strangely alike." "Because these thousands of kilometers of green are dominated by just one kind of tree - the eucalypt, or gum tree." "And around these trees live Australia's oddest and most charismatic animals." "The eucalypt has transformed itself into 700 different species, some growing monstrously tall." "Some thrive in the baking north, some in the chilly south, and some even grow in the snow." "Wherever they find a foothold, gum trees attract a vast assortment of wildlife." "Australia is the eucalypt's native home - it was born here." "But how has this peculiar tree managed to spread itself over the entire continent?" "And why is it that so much lives around it?" "Fifty million years ago, when the climate was wetter, much of Australia was covered in rainforest." "In this lush land eucalypts barely existed." "But the continent was gradually drying out and the eucalypts seized their chance." "Far better able to cope with the harsh new conditions, they rushed out and thrived." "Now eucalypt bushland encircles Australia in an almost unbroken line." "But in this vast land every gum-tree landscape is different." "The tropical north is Crocodile Dundee country, where the year swings between months of crackling dryness and weeks of pouring rain." "It's a hot and sultry place." "But eucalypts thrive here." "And up in these trees live big and watchful lizards." "A frilled lizard can spot its prey from 3 metres up a tree." "All it has to do then is jump down and catch it." "For their size and big teeth, frilled lizards have moderate tastes." "They eat almost nothing but insects." "A good feeding area like this is worth hanging onto." "A frilled lizard won't tolerate a rival in its territory." "Competing males hiss and lash their tails, raising their frills to make themselves look bigger than they really are." "But it's dangerous down there on the ground." "Whistling kites eat frilled lizards round here." "All that frill-waving and hissing forgotten, the lizards make a two-legged dash back to the safety of their trees." "The eucalypt's rough bark helps them get a grip as they climb." "Once safely back up there, they make themselves look as small and inconspicuous as possible." "And for 90 % of their lives, this is where they stay, using the gum trees as lookout posts and bolt-holes." "In these tropical northern woodlands, the temperature most days can top 30 degrees Celsius." "But Australia is a land of enormous contrasts." "Move from the far north to the far south, at the same time of year, and the change couldn't be more extreme." "Here it's mountainous, and metres deep in snow." "Australia is so big, it can have baking heat in one place and winter in another." "And eucalypts can cope with both." "On the ancient mountains of Australia's southern Alps grow woodlands of snow gums." "They can tolerate temperatures as low as minus 20, twisted and dwarfed by the wind and the cold." "And in these snowy uplands, among these hardy trees, there are parrots." "Gang-gang cockatoos feast on the eucalypt's hard seed capsules, cracking them open with their strong beaks." "Many birds move to lower ground in winter, but gang-gangs brave the cold to take advantage of this valuable food." "Up here, the weather can quickly turn nasty." "The mountains are snowbound for months of the year." "This is no place for wimps." "But wombats, with their thick fur, trudge out to dig for grass buried under the snow." "And up in the trees the gang-gangs keep on feeding, even with their jaunty feathers all caked in ice." "The red-headed males, grey-headed females and blushing juveniles pick away together at the gum tree feast." "Australia's south-eastern mountains trap the cold and soaking air that blows in from the southern seas." "Moisture falls as snow and rain." "Australia may be the driest inhabited continent on earth, but here there's plenty of water." "And on the lower slopes of these misty mountains, the trees grow monumentally tall." "With wetter weather and slightly better soil, they reach a height of more than a hundred metres." "Towering above the rest of the forest greenery, these trees can grow over a metre a year." "These are the tallest hardwood trees in the world - and they're eucalypts." "The first British settlers called them mountain ash, because they were homesick for the old country." "And they do have the feeling of lush European forests - until the inhabitants turn up." "From the dense, damp undergrowth comes a strange recital." "Not a flock of different birds, but just one." "The superb lyrebird is striking up." "Male lyrebirds mimic the other birds around them, pulling their songs together into an impressive repertoire." "Wattlebirds, honeyeaters, whipbirds, kookaburras - he does them all!" "His powerful voice can carry as much as a kilometre through the forest." "Clearing a stage for himself on a mound of earth, he belts out his performance." "All this effort is to attract as many females as possible, and he'll carry on like this for hours." "When darkness falls, and the lyrebirds are asleep up in the trees, a different set of wildlife emerges." "Mountain ash can live to be 300 years old, and many are full of holes." "At night, these holes produce some curious animals." "Australia has no monkeys - instead it has these." "They're possums, and just after dark they come out of their gum tree nests, to feed." "Tiny Leadbeater's possums zip through the lower trees looking for insects and sap." "They're sociable animals, and eight or more may share a single hollow." "Hollow eucalypts are desirable homes, but to live in these big trees you have to be agile." "Mountain brush-tailed possums are far bigger and slower, but they're competent climbers." "They're tree-dwellers, but they spend a fair bit of time on the forest floor, coming down in the darkness to eat fungi and fallen seeds." "It's tricky enough having to negotiate these dense trees by yourself, but imagine what it's like having to haul a baby around with you." "This female has carried her baby in her pouch for six months, and it will ride on her back for another two." "But alongside her, and safe from attack by owls, it learns all the skills it will need for a life on its own." "For now it can feast on fallen seeds, and it might even have a quick suckle while mum's busy grooming herself with her huge tree-climber's feet." "And before daylight comes, mother and baby will disappear into the safety of their gum tree den." "These giant eucalypts thrive here because there's more water, and fractionally better soil, than in other parts of Australia." "But though eucalypts do well in the wetter fringes of the land, they don't just stop there." "The further you move inland, the more arid the scenery becomes." "The typical Australian landscape is hot, dry and sandy, not an easy place to put down roots." "But gum trees pop up almost everywhere." "They grow alongside trickles of inland rivers, where there's barely any water flowing, putting down deep roots to suck what moisture there is." "They grow in the outback, where conditions couldn't be more different from the misty highlands." "Here there's only a tenth of the rainfall, and the soil is thin, worn down by sheer age." "A white trunk reflects the glare of the sun, and leaves hang down to avoid overheating." "But when daytime temperatures climb to 40 plus, red kangaroos are grateful for even this thin shade." "Once parked, a big red will spend its day under the trees, until the sun goes down and the land cools again." "Even here, among the red rocks of the Centre, gum trees have a toehold." "This most ethereal tree is a ghost gum, and it grows in Australia's heart." "It clings to crumbling gorges, where water is scarce and only the hardiest survive." "This is one tough tree." "But even the scrawniest of eucalypts in the most desiccated places have a surprise." "They produce the most beautiful, nectar-filled flowers." "The colours and shapes are as diverse as the trees themselves, each attractive to different animal visitors." "Many flowers are cup-shaped, allowing insects inside to gather pollen and nectar." "Blossoms appear on different trees at different times of the year, providing an ever-moving feast." "Lorikeets and honeyeaters are energetic nectar specialists, always on the lookout for new flowers to drink at." "Eucalypts are such a draw that flying foxes in the tropical north will fly fifty kilometres every night, moving from flowering tree to flowering tree to feed." "In return for this feast of nectar, the trees use these big bats as couriers, covering them in pollen, which they'll pass on to the flowers of next tree they visit." "Even if you can't fly, eucalypt flowers are worth the climb." "The tiny Western pygmy possum in southern Australia emerges at nightfall." "It eats plenty of insects, but it's also very partial to nectar." "Weighing little more than a boiled sweet, and not much bigger than the flowers themselves, it laps up the nectar with a tongue shaped like a little brush." "This possum is a strictly nocturnal animal." "Come the dawn, it retires to its tree-hollow nest - made of gum leaves." "Nectar is cheap for these trees to produce, and they give it away freely." "But their leaves are another story." "They're precious in a land where nutrients are in short supply, and the eucalypts do their best to hang on to them." "They're hard, and full of toxic chemicals, including the oils, which give them their distinctive smell." "It's enough to stop most animals eating them, but not all." "And this is the classic gum eater." "In fact it doesn't eat much else." "Koalas evolved with the eucalypts, and they're just about able to cope with their leaves, thanks to a large and complicated digestive system." "But it has to be careful - before it eats, it has a sniff to check the chemical strength." "And those leaves are so hard, it has to chew more than sixteen thousand times a day to break them down." "An old koala will eventually wear out its teeth completely." "It's all such hard work for so little nutrients, that koalas have to sleep for 20 hours a day, just to save energy." "This is a highly specialised way of life." "A tiny baby koala, barely out of the pouch, won't be able to cope with eating gum leaves straight away." "First it must have a snack of its mother's special droppings." "Disgusting as it may seem, the baby koala wouldn't survive otherwise." "By eating 'pap', it's taking in vital bacteria passed from its mother's gut, which will later help it digest those leaves." "It's a bit like eating live yoghurt." "When you're this tiny, it's sometimes hard to work out which way is up, which is especially hazardous when you're ten metres above the ground." "And koala mothers are pretty laid-back when it comes to childcare." "But at six months, this baby has to get used to a life in the trees." "If it's lucky it will live to be fifteen years old." "Young koalas stay dependent on their mothers for a whole year, but as they grow, they start to become more adventurous." "In spite of the hazards, most koalas survive their childhood, and the bond with their mothers is usually broken only when she gives birth to her next baby." "Koalas don't make dens, so a mother has nowhere that she can leave her offspring in safety." "The only option is to carry it round with her as she moves from tree to tree." "Most mothers carry their children on their back, but others have slightly more unconventional ways." "And when your baby can be a quarter of your weight, that's a lot to heave around." "It's all very hard work." "Gum trees tend to grow widely spaced apart - but there are other woodland dwellers that seem to have cracked the problem of getting around." "They glide." "A yellow-bellied glider can sail as far as 120 metres from tree to tree, making strange noises in the night." "It spends its days inside hollow trees, only emerging when darkness falls." "A cape of skin stretches from wrists to ankles, and this is what gives it lift." "As it comes in to land, it swings its limbs forward, touching down with all four feet together." "Gripping toes and big claws help it to hang on." "It's out and about to feed." "Yellow-bellied gliders are fond of insects, and eucalypt nectar when they can get it." "But they also bite notches in the bark of trees and eat the oozing sap, often in the company of a few relatives." "On such a meagre diet, gliding is a low-energy way to travel." "This is an economical place." "Eucalypts are almost all evergreen, and evergreen leaves are expensive to produce when soil nutrients are low." "But they do last for a good long time." "Eucalypts stand dusty and ragged, with leaves that may be several years old." "And even when they do fall, something is sure to want to put them to good use." "In the arid gum-tree shrublands of southern Australia, the mallee fowl is busy." "The female has laid her eggs in a huge mound of soil and dead leaves that she and her mate have carefully scraped into shape." "As this pile rots down, the heat generated incubates the buried eggs." "Too much or too little heat and the eggs will die, so the birds keep on adjusting the mound to keep it at a steady 34 degrees." "Both birds have temperature sensors in their mouths - a quick taste keeps things monitored." "Two months after they're laid, the eggs begin to hatch." "The chick bursts out and starts its journey upwards." "When you're buried a metre down, this is no picnic." "It can take two days to get to the surface, and it gets no help at all from its parents." "This is one tough little chick!" "When it finally gets out, it's able to walk immediately, and it toddles off into the bush." "It can even feed itself, and it'll be able to fly within a day." "It's just as well it's so self-sufficient, because from now on, it's on its own." "And with all those dry, dead leaves around, the bush is a dangerous place to be..." "Of all that gum trees have to endure, this surely seems the most devastating." "Australia's landscape has been dramatically shaped by fires." "They happen right across the country - and in some areas very frequently." "Whether started by lightning or careless matches, bushfires are a fact of life." "In dry conditions, the fires quickly take hold." "Strips of bark peel away in flames, carried off in the wind to start new fires as much as thirty kilometres away." "In eucalypt woodlands the litter that collects round the trees is highly flammable, and can create a fire as hot as a thousand degrees centigrade." "It may look like a disaster for the trees, but the bizarre truth is, eucalypts seem to encourage their surroundings to burst into flames." "Many have thick and insulating bark, able to withstand all but the most ferocious fires." "Some gums actually need a really good blaze to release their seeds, and provide a fertile bed of ash on which they'll later sprout." "This dry old country has been burning like this for millennia." "Although it may not look like it, the gum-trees have the situation well under control." "And this devastation is a prelude to something quite remarkable." "Within weeks of a fire that seems to have killed them, many gum trees start popping out fresh green shoots." "They grow from buds underneath the bark, where they'd been protected from the intense heat." "Bare and blackened branches are suddenly green again, and the trees carry on as normal." "It's almost like a magic trick." "In this volatile country, eucalypts seem able to cope with anything." "To add to the damage begun by fire and rain, they are chewed away by millions of termites." "Australia's gum trees are among the most termite-ridden in the world." "Some are completely hollowed out by the activities of these little insects." "But with so many termites around, there are other animals ready to eat them." "Including these." "They're Numbats and they live in the woodlands of Australia's southwest." "Numbats have tiny mouths and their teeth are not particularly effective." "But as they only eat termites, all they need is a good sense of smell and the right tongue - sticky, manoeuvrable, and very, very long." "It can flick termites into its mouth and swallow them whole." "Most of Australia's small mammals are nocturnal, but numbats don't get out of bed until the sun has warmed the ground, and the termites are active just below the surface." "Numbats are solitary animals, but these are young ones, out and about together." "When they're old enough they'll feed on their own, like their parents, getting through 20,000 termites a day." "These youngsters will stay together for a few months, learning to fend for themselves." "Until then, the slightest danger, real or imaginary, will send them fleeing to their den, in the safety of a gum tree hollow." "Hollow trees are a real feature of the bush." "There was once a man who lived inside a giant gum tree - and raised a family of four there." "Tall trees, strange tales." "There is a particular type of gum that thrives on the banks of the Murray River of southern Australia." "The river red gum grows here in enormous forests, and some of the trees may be 500 years old." "The oldest trees are full of holes, and they're especially popular with parrots." "Regent parrots make their homes here." "In the breeding season, the male brings food to the female, who is never far away from the nest." "And that nest may be more than five metres down inside the tree." "It may seem like hard work to have to climb so far, but it's sensible - it protects the eggs and young from the elements, and from other hazards." "There are thieves around." "Given the chance, a lace monitor would easily make a meal of an egg or a chick." "In the nesting season, they're a major part of its diet." "And it knows where they live..." "The danger passes, and the lace monitor turns its attentions elsewhere." "These gum tree forests flank the river for hundreds of kilometres, and they're full of wildlife." "Some of it has the oddest behaviour." "When night falls, a strange, savage little marsupial makes its appearance." "It's a yellow-footed antechinus." "The size of a mouse, it's a voracious and feisty little carnivore." "Thus fortified, this male has a busy time ahead of him." "It's a bizarre life cycle." "These animals have just one short, sharp mating season, and competition for females during that time is so strong that the males even give up food." "Each mating can last twelve hours, and it's a bit of a free for all, with the females having a pretty rough time of it." "The stress is all so much that after 2 weeks of frantic activity, all the males drop dead." "The pregnant females are left to carry on alone " "...but with the males out of the way, it does mean there will be more food left for mother and the kids." "It's a perilous environment, this gum tree bushland - in more ways than one." "These giant old red gums have been nicknamed 'widow-makers'." "And this is why." "They have an alarming tendency to drop their branches, without warning, on the calmest of days." "The wood is so heavy that if it falls into the river, it sinks like a stone." "And so the river is full of 'snags' - a tangle of fallen branches and collapsed trees." "But even these drowned limbs have their uses." "Waterbirds use them as lookout posts." "These underwater woodlands are also the perfect hideout for Australia's biggest freshwater fish." "The Murray cod can reach more than a metre long - even bigger, if fishermen's tales are true - and weigh more than a man." "Under these snags it can hide from predators, rest from the flow of the river and shelter from the sun, while it lives to be a hundred years old." "In the Australian bush, even the fish live in trees." "The Murray river is shallow and the banks are low." "Once every few years, when spring rains are especially heavy, and snow melts fast in the mountains upstream, the big river breaks its banks." "And it moves into the surrounding forest." "It looks like a beautiful disaster." "But the bushland inhabitants are surprisingly adaptable." "When put to it, a kangaroo can swim." "And the gum trees themselves are perfectly at home." "In this dry place, where rainfall is generally so low, these big trees would die of thirst without floods from time to time." "For now, they can drink deep and put on a spurt of green growth." "For a while, the forest is transformed into a wetland - a maze of swamps and billabongs." "Where just a few days ago kangaroos browsed in grassy clearings, now there are spoonbills and egrets fishing among the trees." "Floods like these are less frequent than they once were." "The Murray's flow has been altered by people, because the water was needed elsewhere." "But when they do happen, the results are spectacular." "The wildlife is tuned to events like these." "Fish begin to breed, and thousands of waterbirds are prompted to start nesting around the flooded trees." "This is the driest inhabited continent in the world, and yet here are kangaroos up to their knees in water!" "The Australian bush is nothing if not contradictory." "The first European settlers had dismissed these vast green swathes as just 'forests in rags'." "But as they got to grips with the curious land, the bush, with its resilience and strange wildlife, became the essence of Australia." "It's a land of pioneers, where adaptability and tenacity are the keys to survival." "And gum trees seem to suit it very well."