1 00:00:34,633 --> 00:00:38,399 In this driest of continents there's a vast green landscape 2 00:00:38,604 --> 00:00:42,836 that stretches for thousands of kilometers round Australia's edge. 3 00:00:43,442 --> 00:00:47,902 This is the Australian bush - its most characteristic landscape. 4 00:00:52,518 --> 00:00:54,247 The first European settlers, 5 00:00:54,453 --> 00:00:57,752 pushing through it 200 years ago, didn't like the bush. 6 00:00:58,190 --> 00:00:59,782 It was daunting and alien, 7 00:01:00,159 --> 00:01:02,719 and so big you could get lost and die. 8 00:01:04,964 --> 00:01:09,333 In these hot, endless forests, the very trees seemed to droop - these, 9 00:01:09,501 --> 00:01:12,061 they said, were 'forests in rags'. 10 00:01:12,238 --> 00:01:14,502 And from one end of the country to another, 11 00:01:14,740 --> 00:01:17,174 they all looked strangely alike. 12 00:01:21,180 --> 00:01:24,172 Because these thousands of kilometers of green are dominated 13 00:01:24,350 --> 00:01:29,253 by just one kind of tree - the eucalypt, or gum tree. 14 00:01:29,421 --> 00:01:33,949 And around these trees live Australia's oddest and most charismatic animals. 15 00:01:36,896 --> 00:01:41,094 The eucalypt has transformed itself into 700 different species, 16 00:01:41,367 --> 00:01:43,426 some growing monstrously tall. 17 00:01:47,940 --> 00:01:51,740 Some thrive in the baking north, some in the chilly south, 18 00:01:52,044 --> 00:01:54,478 and some even grow in the snow. 19 00:02:02,721 --> 00:02:04,245 Wherever they find a foothold, 20 00:02:04,490 --> 00:02:07,789 gum trees attract a vast assortment of wildlife. 21 00:02:09,795 --> 00:02:13,390 Australia is the eucalypt's native home - it was born here. 22 00:02:14,400 --> 00:02:19,360 But how has this peculiar tree managed to spread itself over the entire continent? 23 00:02:19,905 --> 00:02:23,466 And why is it that so much lives around it? 24 00:02:30,983 --> 00:02:33,781 Fifty million years ago, when the climate was wetter, 25 00:02:34,286 --> 00:02:37,050 much of Australia was covered in rainforest. 26 00:02:39,758 --> 00:02:42,818 In this lush land eucalypts barely existed. 27 00:02:43,295 --> 00:02:48,358 But the continent was gradually drying out and the eucalypts seized their chance. 28 00:02:51,570 --> 00:02:56,906 Far better able to cope with the harsh new conditions, they rushed out and thrived. 29 00:03:01,180 --> 00:03:06,117 Now eucalypt bushland encircles Australia in an almost unbroken line. 30 00:03:12,558 --> 00:03:16,460 But in this vast land every gum-tree landscape is different. 31 00:03:22,301 --> 00:03:25,099 The tropical north is Crocodile Dundee country, 32 00:03:25,404 --> 00:03:27,599 where the year swings between months of crackling 33 00:03:27,773 --> 00:03:30,503 dryness and weeks of pouring rain. 34 00:03:36,982 --> 00:03:39,280 It's a hot and sultry place. 35 00:03:41,253 --> 00:03:43,653 But eucalypts thrive here. 36 00:03:43,822 --> 00:03:47,155 And up in these trees live big and watchful lizards. 37 00:03:49,628 --> 00:03:53,428 A frilled lizard can spot its prey from 3 metres up a tree. 38 00:03:54,133 --> 00:03:57,762 All it has to do then is jump down and catch it. 39 00:04:07,646 --> 00:04:09,375 For their size and big teeth, 40 00:04:09,681 --> 00:04:11,945 frilled lizards have moderate tastes. 41 00:04:12,117 --> 00:04:14,551 They eat almost nothing but insects. 42 00:04:20,692 --> 00:04:23,889 A good feeding area like this is worth hanging onto. 43 00:04:24,129 --> 00:04:27,121 A frilled lizard won't tolerate a rival in its territory. 44 00:04:37,342 --> 00:04:39,776 Competing males hiss and lash their tails, 45 00:04:39,978 --> 00:04:43,311 raising their frills to make themselves look bigger than they really are. 46 00:04:46,051 --> 00:04:48,246 But it's dangerous down there on the ground. 47 00:04:56,762 --> 00:04:59,526 Whistling kites eat frilled lizards round here. 48 00:05:09,408 --> 00:05:11,399 All that frill-waving and hissing forgotten, 49 00:05:11,577 --> 00:05:15,741 the lizards make a two-legged dash back to the safety of their trees. 50 00:05:23,889 --> 00:05:27,552 The eucalypt's rough bark helps them get a grip as they climb. 51 00:05:37,603 --> 00:05:38,968 Once safely back up there, 52 00:05:39,238 --> 00:05:43,038 they make themselves look as small and inconspicuous as possible. 53 00:05:49,882 --> 00:05:53,283 And for 90 % of their lives, this is where they stay, 54 00:05:53,585 --> 00:05:57,043 using the gum trees as lookout posts and bolt-holes. 55 00:06:07,733 --> 00:06:09,462 In these tropical northern woodlands, 56 00:06:09,635 --> 00:06:13,230 the temperature most days can top 30 degrees Celsius. 57 00:06:15,574 --> 00:06:18,737 But Australia is a land of enormous contrasts. 58 00:06:19,478 --> 00:06:23,744 Move from the far north to the far south, at the same time of year, 59 00:06:24,016 --> 00:06:27,417 and the change couldn't be more extreme. 60 00:06:33,225 --> 00:06:37,127 Here it's mountainous, and metres deep in snow. 61 00:06:37,429 --> 00:06:38,828 Australia is so big, 62 00:06:39,064 --> 00:06:42,761 it can have baking heat in one place and winter in another. 63 00:06:43,135 --> 00:06:45,729 And eucalypts can cope with both. 64 00:06:47,506 --> 00:06:50,066 On the ancient mountains of Australia's southern Alps 65 00:06:50,242 --> 00:06:52,608 grow woodlands of snow gums. 66 00:06:56,515 --> 00:06:59,382 They can tolerate temperatures as low as minus 20, 67 00:07:00,786 --> 00:07:04,187 twisted and dwarfed by the wind and the cold. 68 00:07:08,327 --> 00:07:13,788 And in these snowy uplands, among these hardy trees, there are parrots. 69 00:07:25,043 --> 00:07:29,139 Gang-gang cockatoos feast on the eucalypt's hard seed capsules, 70 00:07:29,314 --> 00:07:31,339 cracking them open with their strong beaks. 71 00:07:33,652 --> 00:07:35,950 Many birds move to lower ground in winter, 72 00:07:36,288 --> 00:07:41,055 but gang-gangs brave the cold to take advantage of this valuable food. 73 00:07:45,664 --> 00:07:48,656 Up here, the weather can quickly turn nasty. 74 00:07:49,801 --> 00:07:52,736 The mountains are snowbound for months of the year. 75 00:07:53,038 --> 00:07:55,165 This is no place for wimps. 76 00:07:58,944 --> 00:08:01,208 But wombats, with their thick fur, 77 00:08:01,446 --> 00:08:05,177 trudge out to dig for grass buried under the snow. 78 00:08:09,721 --> 00:08:12,622 And up in the trees the gang-gangs keep on feeding, 79 00:08:12,791 --> 00:08:16,227 even with their jaunty feathers all caked in ice. 80 00:08:21,166 --> 00:08:23,634 The red-headed males, grey-headed females 81 00:08:23,969 --> 00:08:28,770 and blushing juveniles pick away together at the gum tree feast. 82 00:08:46,992 --> 00:08:50,792 Australia's south-eastern mountains trap the cold and soaking air 83 00:08:50,962 --> 00:08:53,123 that blows in from the southern seas. 84 00:08:53,432 --> 00:08:55,866 Moisture falls as snow and rain. 85 00:08:58,837 --> 00:09:01,897 Australia may be the driest inhabited continent on earth, 86 00:09:02,074 --> 00:09:04,668 but here there's plenty of water. 87 00:09:12,184 --> 00:09:14,675 And on the lower slopes of these misty mountains, 88 00:09:14,886 --> 00:09:17,286 the trees grow monumentally tall. 89 00:09:22,794 --> 00:09:25,092 With wetter weather and slightly better soil, 90 00:09:25,397 --> 00:09:28,389 they reach a height of more than a hundred metres. 91 00:09:29,968 --> 00:09:32,232 Towering above the rest of the forest greenery, 92 00:09:32,637 --> 00:09:35,902 these trees can grow over a metre a year. 93 00:09:37,409 --> 00:09:40,242 These are the tallest hardwood trees in the world - 94 00:09:40,879 --> 00:09:43,109 and they're eucalypts. 95 00:09:49,087 --> 00:09:52,022 The first British settlers called them mountain ash, 96 00:09:52,290 --> 00:09:54,952 because they were homesick for the old country. 97 00:09:57,662 --> 00:10:00,756 And they do have the feeling of lush European forests - 98 00:10:01,099 --> 00:10:03,727 until the inhabitants turn up. 99 00:10:14,780 --> 00:10:18,409 From the dense, damp undergrowth comes a strange recital. 100 00:10:18,784 --> 00:10:21,548 Not a flock of different birds, but just one. 101 00:10:21,720 --> 00:10:24,689 The superb lyrebird is striking up. 102 00:10:29,194 --> 00:10:31,788 Male lyrebirds mimic the other birds around them, 103 00:10:32,197 --> 00:10:35,496 pulling their songs together into an impressive repertoire. 104 00:10:35,901 --> 00:10:39,166 Wattlebirds, honeyeaters, whipbirds, kookaburras - 105 00:10:39,738 --> 00:10:41,296 he does them all! 106 00:10:56,354 --> 00:11:00,450 His powerful voice can carry as much as a kilometre through the forest. 107 00:11:03,261 --> 00:11:05,627 Clearing a stage for himself on a mound of earth, 108 00:11:05,797 --> 00:11:08,163 he belts out his performance. 109 00:11:08,533 --> 00:11:11,764 All this effort is to attract as many females as possible, 110 00:11:12,270 --> 00:11:15,000 and he'll carry on like this for hours. 111 00:11:24,816 --> 00:11:28,377 When darkness falls, and the lyrebirds are asleep up in the trees, 112 00:11:28,753 --> 00:11:31,586 a different set of wildlife emerges. 113 00:11:33,758 --> 00:11:36,454 Mountain ash can live to be 300 years old, 114 00:11:36,795 --> 00:11:38,387 and many are full of holes. 115 00:11:38,763 --> 00:11:42,529 At night, these holes produce some curious animals. 116 00:11:46,505 --> 00:11:50,601 Australia has no monkeys - instead it has these. 117 00:11:51,776 --> 00:11:52,743 They're possums, 118 00:11:53,178 --> 00:11:57,410 and just after dark they come out of their gum tree nests, to feed. 119 00:11:59,718 --> 00:12:02,881 Tiny Leadbeater's possums zip through the lower trees 120 00:12:03,054 --> 00:12:04,885 looking for insects and sap. 121 00:12:11,496 --> 00:12:12,986 They're sociable animals, 122 00:12:13,231 --> 00:12:15,859 and eight or more may share a single hollow. 123 00:12:23,041 --> 00:12:25,066 Hollow eucalypts are desirable homes, 124 00:12:25,577 --> 00:12:28,774 but to live in these big trees you have to be agile. 125 00:12:36,187 --> 00:12:39,384 Mountain brush-tailed possums are far bigger and slower, 126 00:12:39,624 --> 00:12:41,091 but they're competent climbers. 127 00:12:41,526 --> 00:12:42,515 They're tree-dwellers, 128 00:12:42,694 --> 00:12:45,720 but they spend a fair bit of time on the forest floor, 129 00:12:45,897 --> 00:12:49,663 coming down in the darkness to eat fungi and fallen seeds. 130 00:12:56,808 --> 00:13:00,335 It's tricky enough having to negotiate these dense trees by yourself, 131 00:13:00,645 --> 00:13:03,876 but imagine what it's like having to haul a baby around with you. 132 00:13:06,384 --> 00:13:09,512 This female has carried her baby in her pouch for six months, 133 00:13:09,988 --> 00:13:12,786 and it will ride on her back for another two. 134 00:13:22,267 --> 00:13:25,134 But alongside her, and safe from attack by owls, 135 00:13:25,403 --> 00:13:28,839 it learns all the skills it will need for a life on its own. 136 00:13:32,010 --> 00:13:34,274 For now it can feast on fallen seeds, 137 00:13:34,679 --> 00:13:36,203 and it might even have a quick suckle 138 00:13:36,381 --> 00:13:40,977 while mum's busy grooming herself with her huge tree-climber's feet. 139 00:13:52,397 --> 00:13:53,796 And before daylight comes, 140 00:13:54,065 --> 00:13:58,934 mother and baby will disappear into the safety of their gum tree den. 141 00:14:13,284 --> 00:14:15,013 These giant eucalypts thrive here 142 00:14:15,186 --> 00:14:18,019 because there's more water, and fractionally better soil, 143 00:14:18,189 --> 00:14:20,089 than in other parts of Australia. 144 00:14:20,959 --> 00:14:23,655 But though eucalypts do well in the wetter fringes of the land, 145 00:14:23,928 --> 00:14:25,418 they don't just stop there. 146 00:14:38,309 --> 00:14:42,370 The further you move inland, the more arid the scenery becomes. 147 00:14:46,418 --> 00:14:50,218 The typical Australian landscape is hot, dry and sandy, 148 00:14:50,655 --> 00:14:53,123 not an easy place to put down roots. 149 00:14:53,291 --> 00:14:56,226 But gum trees pop up almost everywhere. 150 00:14:56,928 --> 00:14:59,362 They grow alongside trickles of inland rivers, 151 00:14:59,631 --> 00:15:01,360 where there's barely any water flowing, 152 00:15:01,666 --> 00:15:04,692 putting down deep roots to suck what moisture there is. 153 00:15:08,740 --> 00:15:09,968 They grow in the outback, 154 00:15:10,175 --> 00:15:13,303 where conditions couldn't be more different from the misty highlands. 155 00:15:13,778 --> 00:15:15,837 Here there's only a tenth of the rainfall, 156 00:15:16,214 --> 00:15:19,809 and the soil is thin, worn down by sheer age. 157 00:15:29,427 --> 00:15:31,952 A white trunk reflects the glare of the sun, 158 00:15:32,297 --> 00:15:35,164 and leaves hang down to avoid overheating. 159 00:15:37,769 --> 00:15:40,761 But when daytime temperatures climb to 40 plus, 160 00:15:40,972 --> 00:15:44,840 red kangaroos are grateful for even this thin shade. 161 00:16:02,127 --> 00:16:05,927 Once parked, a big red will spend its day under the trees, 162 00:16:06,397 --> 00:16:10,128 until the sun goes down and the land cools again. 163 00:16:17,876 --> 00:16:23,337 Even here, among the red rocks of the Centre, gum trees have a toehold. 164 00:16:26,851 --> 00:16:29,752 This most ethereal tree is a ghost gum, 165 00:16:29,921 --> 00:16:31,980 and it grows in Australia's heart. 166 00:16:33,191 --> 00:16:35,125 It clings to crumbling gorges, 167 00:16:35,293 --> 00:16:39,559 where water is scarce and only the hardiest survive. 168 00:16:44,335 --> 00:16:46,326 This is one tough tree. 169 00:16:50,275 --> 00:16:52,209 But even the scrawniest of eucalypts 170 00:16:52,377 --> 00:16:56,006 in the most desiccated places have a surprise. 171 00:16:58,183 --> 00:17:01,846 They produce the most beautiful, nectar-filled flowers. 172 00:17:10,395 --> 00:17:13,831 The colours and shapes are as diverse as the trees themselves, 173 00:17:13,998 --> 00:17:16,694 each attractive to different animal visitors. 174 00:17:17,101 --> 00:17:18,728 Many flowers are cup-shaped, 175 00:17:18,903 --> 00:17:22,737 allowing insects inside to gather pollen and nectar. 176 00:17:28,379 --> 00:17:31,473 Blossoms appear on different trees at different times of the year, 177 00:17:31,716 --> 00:17:33,650 providing an ever-moving feast. 178 00:17:34,319 --> 00:17:37,652 Lorikeets and honeyeaters are energetic nectar specialists, 179 00:17:37,822 --> 00:17:40,450 always on the lookout for new flowers to drink at. 180 00:17:58,443 --> 00:17:59,933 Eucalypts are such a draw 181 00:18:00,178 --> 00:18:04,581 that flying foxes in the tropical north will fly fifty kilometres every night, 182 00:18:05,083 --> 00:18:08,985 moving from flowering tree to flowering tree to feed. 183 00:18:24,435 --> 00:18:26,369 In return for this feast of nectar, 184 00:18:26,638 --> 00:18:29,004 the trees use these big bats as couriers, 185 00:18:29,307 --> 00:18:30,501 covering them in pollen, 186 00:18:30,975 --> 00:18:34,376 which they'll pass on to the flowers of next tree they visit. 187 00:18:46,424 --> 00:18:49,916 Even if you can't fly, eucalypt flowers are worth the climb. 188 00:18:50,495 --> 00:18:55,194 The tiny Western pygmy possum in southern Australia emerges at nightfall. 189 00:18:55,833 --> 00:18:59,769 It eats plenty of insects, but it's also very partial to nectar. 190 00:19:14,719 --> 00:19:16,414 Weighing little more than a boiled sweet, 191 00:19:16,621 --> 00:19:18,612 and not much bigger than the flowers themselves, 192 00:19:18,990 --> 00:19:22,187 it laps up the nectar with a tongue shaped like a little brush. 193 00:19:32,670 --> 00:19:35,138 This possum is a strictly nocturnal animal. 194 00:19:35,406 --> 00:19:36,202 Come the dawn, 195 00:19:36,374 --> 00:19:39,901 it retires to its tree-hollow nest - made of gum leaves. 196 00:19:51,255 --> 00:19:54,952 Nectar is cheap for these trees to produce, and they give it away freely. 197 00:19:55,326 --> 00:19:57,726 But their leaves are another story. 198 00:20:02,767 --> 00:20:05,861 They're precious in a land where nutrients are in short supply, 199 00:20:06,237 --> 00:20:08,728 and the eucalypts do their best to hang on to them. 200 00:20:09,207 --> 00:20:11,232 They're hard, and full of toxic chemicals, 201 00:20:11,609 --> 00:20:14,635 including the oils, which give them their distinctive smell. 202 00:20:15,146 --> 00:20:19,014 It's enough to stop most animals eating them, but not all. 203 00:20:24,489 --> 00:20:26,821 And this is the classic gum eater. 204 00:20:27,191 --> 00:20:28,886 In fact it doesn't eat much else. 205 00:20:36,467 --> 00:20:38,799 Koalas evolved with the eucalypts, 206 00:20:39,170 --> 00:20:41,661 and they're just about able to cope with their leaves, 207 00:20:42,040 --> 00:20:45,305 thanks to a large and complicated digestive system. 208 00:20:47,311 --> 00:20:48,539 But it has to be careful - 209 00:20:49,013 --> 00:20:49,980 before it eats, 210 00:20:50,348 --> 00:20:53,044 it has a sniff to check the chemical strength. 211 00:20:55,620 --> 00:20:57,053 And those leaves are so hard, 212 00:20:57,288 --> 00:21:01,622 it has to chew more than sixteen thousand times a day to break them down. 213 00:21:02,260 --> 00:21:06,128 An old koala will eventually wear out its teeth completely. 214 00:21:15,573 --> 00:21:18,565 It's all such hard work for so little nutrients, 215 00:21:18,876 --> 00:21:21,902 that koalas have to sleep for 20 hours a day, 216 00:21:22,246 --> 00:21:23,907 just to save energy. 217 00:21:44,302 --> 00:21:46,827 This is a highly specialised way of life. 218 00:21:47,271 --> 00:21:50,206 A tiny baby koala, barely out of the pouch, 219 00:21:50,374 --> 00:21:53,673 won't be able to cope with eating gum leaves straight away. 220 00:21:55,279 --> 00:21:58,476 First it must have a snack of its mother's special droppings. 221 00:22:06,757 --> 00:22:08,190 Disgusting as it may seem, 222 00:22:08,493 --> 00:22:11,053 the baby koala wouldn't survive otherwise. 223 00:22:11,229 --> 00:22:12,457 By eating 'pap', 224 00:22:12,797 --> 00:22:16,733 it's taking in vital bacteria passed from its mother's gut, 225 00:22:17,001 --> 00:22:19,697 which will later help it digest those leaves. 226 00:22:22,907 --> 00:22:25,068 It's a bit like eating live yoghurt. 227 00:22:40,625 --> 00:22:44,186 When you're this tiny, it's sometimes hard to work out which way is up, 228 00:22:44,795 --> 00:22:48,561 which is especially hazardous when you're ten metres above the ground. 229 00:23:01,546 --> 00:23:05,209 And koala mothers are pretty laid-back when it comes to childcare. 230 00:23:05,616 --> 00:23:09,950 But at six months, this baby has to get used to a life in the trees. 231 00:23:10,121 --> 00:23:13,284 If it's lucky it will live to be fifteen years old. 232 00:23:19,363 --> 00:23:22,491 Young koalas stay dependent on their mothers for a whole year, 233 00:23:22,900 --> 00:23:26,267 but as they grow, they start to become more adventurous. 234 00:23:42,420 --> 00:23:45,821 In spite of the hazards, most koalas survive their childhood, 235 00:23:46,123 --> 00:23:48,591 and the bond with their mothers is usually broken only 236 00:23:48,759 --> 00:23:51,250 when she gives birth to her next baby. 237 00:23:55,299 --> 00:23:56,766 Koalas don't make dens, 238 00:23:57,268 --> 00:24:01,136 so a mother has nowhere that she can leave her offspring in safety. 239 00:24:01,739 --> 00:24:06,369 The only option is to carry it round with her as she moves from tree to tree. 240 00:24:19,290 --> 00:24:21,485 Most mothers carry their children on their back, 241 00:24:21,859 --> 00:24:25,090 but others have slightly more unconventional ways. 242 00:24:35,606 --> 00:24:38,006 And when your baby can be a quarter of your weight, 243 00:24:38,476 --> 00:24:40,068 that's a lot to heave around. 244 00:24:52,757 --> 00:24:54,019 It's all very hard work. 245 00:24:56,093 --> 00:24:58,391 Gum trees tend to grow widely spaced apart - 246 00:24:58,863 --> 00:25:00,524 but there are other woodland dwellers 247 00:25:00,698 --> 00:25:03,292 that seem to have cracked the problem of getting around. 248 00:25:06,370 --> 00:25:07,530 They glide. 249 00:25:12,143 --> 00:25:16,978 A yellow-bellied glider can sail as far as 120 metres from tree to tree, 250 00:25:17,381 --> 00:25:19,576 making strange noises in the night. 251 00:25:26,757 --> 00:25:29,191 It spends its days inside hollow trees, 252 00:25:29,427 --> 00:25:31,987 only emerging when darkness falls. 253 00:25:41,238 --> 00:25:46,335 A cape of skin stretches from wrists to ankles, and this is what gives it lift. 254 00:25:47,478 --> 00:25:50,311 As it comes in to land, it swings its limbs forward, 255 00:25:50,481 --> 00:25:53,177 touching down with all four feet together. 256 00:25:54,719 --> 00:25:57,381 Gripping toes and big claws help it to hang on. 257 00:26:05,296 --> 00:26:07,127 It's out and about to feed. 258 00:26:07,598 --> 00:26:09,828 Yellow-bellied gliders are fond of insects, 259 00:26:10,000 --> 00:26:12,230 and eucalypt nectar when they can get it. 260 00:26:12,603 --> 00:26:16,630 But they also bite notches in the bark of trees and eat the oozing sap, 261 00:26:17,708 --> 00:26:20,040 often in the company of a few relatives. 262 00:26:30,354 --> 00:26:31,753 On such a meagre diet, 263 00:26:32,056 --> 00:26:34,354 gliding is a low-energy way to travel. 264 00:26:44,402 --> 00:26:46,233 This is an economical place. 265 00:26:49,940 --> 00:26:52,033 Eucalypts are almost all evergreen, 266 00:26:52,410 --> 00:26:57,040 and evergreen leaves are expensive to produce when soil nutrients are low. 267 00:26:58,516 --> 00:27:00,677 But they do last for a good long time. 268 00:27:06,056 --> 00:27:10,584 Eucalypts stand dusty and ragged, with leaves that may be several years old. 269 00:27:11,429 --> 00:27:15,957 And even when they do fall, something is sure to want to put them to good use. 270 00:27:22,306 --> 00:27:25,207 In the arid gum-tree shrublands of southern Australia, 271 00:27:25,409 --> 00:27:27,001 the mallee fowl is busy. 272 00:27:27,845 --> 00:27:31,576 The female has laid her eggs in a huge mound of soil and dead leaves 273 00:27:31,949 --> 00:27:35,112 that she and her mate have carefully scraped into shape. 274 00:27:41,325 --> 00:27:45,785 As this pile rots down, the heat generated incubates the buried eggs. 275 00:27:46,297 --> 00:27:49,357 Too much or too little heat and the eggs will die, 276 00:27:49,733 --> 00:27:54,329 so the birds keep on adjusting the mound to keep it at a steady 34 degrees. 277 00:27:57,408 --> 00:27:59,933 Both birds have temperature sensors in their mouths - 278 00:28:00,344 --> 00:28:02,835 a quick taste keeps things monitored. 279 00:28:10,855 --> 00:28:14,689 Two months after they're laid, the eggs begin to hatch. 280 00:28:24,835 --> 00:28:28,532 The chick bursts out and starts its journey upwards. 281 00:28:29,139 --> 00:28:32,472 When you're buried a metre down, this is no picnic. 282 00:28:32,910 --> 00:28:35,242 It can take two days to get to the surface, 283 00:28:36,547 --> 00:28:39,380 and it gets no help at all from its parents. 284 00:28:48,726 --> 00:28:50,887 This is one tough little chick! 285 00:29:05,409 --> 00:29:08,435 When it finally gets out, it's able to walk immediately, 286 00:29:08,612 --> 00:29:10,876 and it toddles off into the bush. 287 00:29:11,081 --> 00:29:15,108 It can even feed itself, and it'll be able to fly within a day. 288 00:29:30,768 --> 00:29:32,998 It's just as well it's so self-sufficient, 289 00:29:33,404 --> 00:29:36,498 because from now on, it's on its own. 290 00:29:38,208 --> 00:29:40,335 And with all those dry, dead leaves around, 291 00:29:40,744 --> 00:29:43,212 the bush is a dangerous place to be... 292 00:29:48,886 --> 00:29:51,411 Of all that gum trees have to endure, 293 00:29:51,722 --> 00:29:54,282 this surely seems the most devastating. 294 00:30:06,704 --> 00:30:10,731 Australia's landscape has been dramatically shaped by fires. 295 00:30:11,141 --> 00:30:13,006 They happen right across the country - 296 00:30:13,477 --> 00:30:16,071 and in some areas very frequently. 297 00:30:18,515 --> 00:30:21,245 Whether started by lightning or careless matches, 298 00:30:21,652 --> 00:30:23,677 bushfires are a fact of life. 299 00:30:24,922 --> 00:30:27,948 In dry conditions, the fires quickly take hold. 300 00:30:30,094 --> 00:30:32,528 Strips of bark peel away in flames, 301 00:30:32,763 --> 00:30:37,530 carried off in the wind to start new fires as much as thirty kilometres away. 302 00:30:49,613 --> 00:30:51,046 In eucalypt woodlands the litter 303 00:30:51,215 --> 00:30:53,979 that collects round the trees is highly flammable, 304 00:30:54,385 --> 00:30:58,321 and can create a fire as hot as a thousand degrees centigrade. 305 00:31:08,465 --> 00:31:12,333 It may look like a disaster for the trees, but the bizarre truth is, 306 00:31:12,703 --> 00:31:16,662 eucalypts seem to encourage their surroundings to burst into flames. 307 00:31:22,613 --> 00:31:24,604 Many have thick and insulating bark, 308 00:31:25,015 --> 00:31:28,007 able to withstand all but the most ferocious fires. 309 00:31:31,855 --> 00:31:35,689 Some gums actually need a really good blaze to release their seeds, 310 00:31:35,959 --> 00:31:39,793 and provide a fertile bed of ash on which they'll later sprout. 311 00:31:46,003 --> 00:31:49,530 This dry old country has been burning like this for millennia. 312 00:31:56,013 --> 00:31:57,344 Although it may not look like it, 313 00:31:57,715 --> 00:32:01,173 the gum-trees have the situation well under control. 314 00:32:09,927 --> 00:32:14,387 And this devastation is a prelude to something quite remarkable. 315 00:32:15,032 --> 00:32:17,398 Within weeks of a fire that seems to have killed them, 316 00:32:17,868 --> 00:32:20,996 many gum trees start popping out fresh green shoots. 317 00:32:21,572 --> 00:32:23,563 They grow from buds underneath the bark, 318 00:32:24,041 --> 00:32:26,942 where they'd been protected from the intense heat. 319 00:32:35,986 --> 00:32:38,887 Bare and blackened branches are suddenly green again, 320 00:32:39,056 --> 00:32:41,149 and the trees carry on as normal. 321 00:32:41,525 --> 00:32:43,322 It's almost like a magic trick. 322 00:32:49,566 --> 00:32:53,969 In this volatile country, eucalypts seem able to cope with anything. 323 00:32:54,638 --> 00:32:57,232 To add to the damage begun by fire and rain, 324 00:32:57,608 --> 00:33:00,304 they are chewed away by millions of termites. 325 00:33:06,150 --> 00:33:10,314 Australia's gum trees are among the most termite-ridden in the world. 326 00:33:10,654 --> 00:33:15,148 Some are completely hollowed out by the activities of these little insects. 327 00:33:17,461 --> 00:33:21,898 But with so many termites around, there are other animals ready to eat them. 328 00:33:23,734 --> 00:33:24,826 Including these. 329 00:33:25,469 --> 00:33:29,633 They're Numbats and they live in the woodlands of Australia's southwest. 330 00:33:38,248 --> 00:33:42,480 Numbats have tiny mouths and their teeth are not particularly effective. 331 00:33:43,053 --> 00:33:44,714 But as they only eat termites, 332 00:33:45,222 --> 00:33:48,658 all they need is a good sense of smell and the right tongue - 333 00:33:49,126 --> 00:33:52,584 sticky, manoeuvrable, and very, very long. 334 00:33:57,868 --> 00:34:01,395 It can flick termites into its mouth and swallow them whole. 335 00:34:15,252 --> 00:34:17,948 Most of Australia's small mammals are nocturnal, 336 00:34:18,488 --> 00:34:21,924 but numbats don't get out of bed until the sun has warmed the ground, 337 00:34:22,159 --> 00:34:24,821 and the termites are active just below the surface. 338 00:34:44,414 --> 00:34:46,245 Numbats are solitary animals, 339 00:34:46,750 --> 00:34:49,651 but these are young ones, out and about together. 340 00:34:50,220 --> 00:34:52,484 When they're old enough they'll feed on their own, 341 00:34:52,789 --> 00:34:57,123 like their parents, getting through 20,000 termites a day. 342 00:35:05,602 --> 00:35:08,264 These youngsters will stay together for a few months, 343 00:35:08,505 --> 00:35:10,200 learning to fend for themselves. 344 00:35:11,909 --> 00:35:15,401 Until then, the slightest danger, real or imaginary, 345 00:35:15,646 --> 00:35:19,878 will send them fleeing to their den, in the safety of a gum tree hollow. 346 00:35:27,391 --> 00:35:30,189 Hollow trees are a real feature of the bush. 347 00:35:30,827 --> 00:35:33,523 There was once a man who lived inside a giant gum tree - 348 00:35:33,830 --> 00:35:36,321 and raised a family of four there. 349 00:35:36,800 --> 00:35:39,633 Tall trees, strange tales. 350 00:35:50,881 --> 00:35:52,678 There is a particular type of gum 351 00:35:52,849 --> 00:35:56,285 that thrives on the banks of the Murray River of southern Australia. 352 00:35:57,254 --> 00:36:00,781 The river red gum grows here in enormous forests, 353 00:36:01,158 --> 00:36:03,922 and some of the trees may be 500 years old. 354 00:36:07,831 --> 00:36:09,492 The oldest trees are full of holes, 355 00:36:09,933 --> 00:36:12,993 and they're especially popular with parrots. 356 00:36:20,444 --> 00:36:22,378 Regent parrots make their homes here. 357 00:36:24,114 --> 00:36:27,208 In the breeding season, the male brings food to the female, 358 00:36:27,517 --> 00:36:29,348 who is never far away from the nest. 359 00:36:40,931 --> 00:36:44,765 And that nest may be more than five metres down inside the tree. 360 00:37:05,922 --> 00:37:10,552 It may seem like hard work to have to climb so far, but it's sensible - 361 00:37:10,894 --> 00:37:13,795 it protects the eggs and young from the elements, 362 00:37:13,997 --> 00:37:16,192 and from other hazards. 363 00:37:18,168 --> 00:37:19,897 There are thieves around. 364 00:37:30,414 --> 00:37:36,182 Given the chance, a lace monitor would easily make a meal of an egg or a chick. 365 00:37:43,860 --> 00:37:47,728 In the nesting season, they're a major part of its diet. 366 00:37:47,998 --> 00:37:50,296 And it knows where they live... 367 00:38:19,229 --> 00:38:25,168 The danger passes, and the lace monitor turns its attentions elsewhere. 368 00:38:30,040 --> 00:38:33,942 These gum tree forests flank the river for hundreds of kilometres, 369 00:38:34,311 --> 00:38:36,040 and they're full of wildlife. 370 00:38:36,480 --> 00:38:38,880 Some of it has the oddest behaviour. 371 00:38:41,585 --> 00:38:42,517 When night falls, 372 00:38:42,853 --> 00:38:46,584 a strange, savage little marsupial makes its appearance. 373 00:38:51,061 --> 00:38:53,552 It's a yellow-footed antechinus. 374 00:38:55,298 --> 00:38:59,894 The size of a mouse, it's a voracious and feisty little carnivore. 375 00:39:19,022 --> 00:39:22,753 Thus fortified, this male has a busy time ahead of him. 376 00:39:33,904 --> 00:39:35,565 It's a bizarre life cycle. 377 00:39:35,906 --> 00:39:39,467 These animals have just one short, sharp mating season, 378 00:39:39,709 --> 00:39:43,201 and competition for females during that time is so strong 379 00:39:43,547 --> 00:39:45,913 that the males even give up food. 380 00:39:50,120 --> 00:39:52,213 Each mating can last twelve hours, 381 00:39:52,656 --> 00:39:54,021 and it's a bit of a free for all, 382 00:39:54,491 --> 00:39:57,255 with the females having a pretty rough time of it. 383 00:40:25,188 --> 00:40:29,386 The stress is all so much that after 2 weeks of frantic activity, 384 00:40:29,693 --> 00:40:31,456 all the males drop dead. 385 00:40:32,596 --> 00:40:35,326 The pregnant females are left to carry on alone - 386 00:40:40,904 --> 00:40:42,565 ...but with the males out of the way, 387 00:40:42,973 --> 00:40:46,431 it does mean there will be more food left for mother and the kids. 388 00:40:50,513 --> 00:40:56,076 It's a perilous environment, this gum tree bushland - in more ways than one. 389 00:40:59,222 --> 00:41:03,488 These giant old red gums have been nicknamed 'widow-makers'. 390 00:41:03,727 --> 00:41:05,285 And this is why. 391 00:41:08,999 --> 00:41:11,365 They have an alarming tendency to drop their branches, 392 00:41:11,534 --> 00:41:14,628 without warning, on the calmest of days. 393 00:41:25,315 --> 00:41:30,116 The wood is so heavy that if it falls into the river, it sinks like a stone. 394 00:41:34,724 --> 00:41:36,715 And so the river is full of 'snags' - 395 00:41:37,093 --> 00:41:40,585 a tangle of fallen branches and collapsed trees. 396 00:41:45,568 --> 00:41:48,162 But even these drowned limbs have their uses. 397 00:41:48,938 --> 00:41:51,736 Waterbirds use them as lookout posts. 398 00:41:59,883 --> 00:42:03,319 These underwater woodlands are also the perfect hideout 399 00:42:03,486 --> 00:42:06,512 for Australia's biggest freshwater fish. 400 00:42:07,490 --> 00:42:11,586 The Murray cod can reach more than a metre long - even bigger, 401 00:42:11,761 --> 00:42:13,820 if fishermen's tales are true - 402 00:42:13,997 --> 00:42:15,828 and weigh more than a man. 403 00:42:18,768 --> 00:42:21,362 Under these snags it can hide from predators, 404 00:42:21,771 --> 00:42:25,138 rest from the flow of the river and shelter from the sun, 405 00:42:25,542 --> 00:42:28,443 while it lives to be a hundred years old. 406 00:42:34,284 --> 00:42:37,981 In the Australian bush, even the fish live in trees. 407 00:43:18,628 --> 00:43:22,064 The Murray river is shallow and the banks are low. 408 00:43:22,632 --> 00:43:26,466 Once every few years, when spring rains are especially heavy, 409 00:43:26,803 --> 00:43:29,431 and snow melts fast in the mountains upstream, 410 00:43:29,839 --> 00:43:35,971 the big river breaks its banks. And it moves into the surrounding forest. 411 00:44:01,404 --> 00:44:03,463 It looks like a beautiful disaster. 412 00:44:04,073 --> 00:44:07,702 But the bushland inhabitants are surprisingly adaptable. 413 00:44:14,617 --> 00:44:17,643 When put to it, a kangaroo can swim. 414 00:44:48,651 --> 00:44:51,984 And the gum trees themselves are perfectly at home. 415 00:44:52,355 --> 00:44:55,882 In this dry place, where rainfall is generally so low, 416 00:44:56,392 --> 00:45:00,260 these big trees would die of thirst without floods from time to time. 417 00:45:00,830 --> 00:45:05,665 For now, they can drink deep and put on a spurt of green growth. 418 00:45:12,208 --> 00:45:15,769 For a while, the forest is transformed into a wetland - 419 00:45:16,112 --> 00:45:18,444 a maze of swamps and billabongs. 420 00:45:34,197 --> 00:45:38,395 Where just a few days ago kangaroos browsed in grassy clearings, 421 00:45:38,768 --> 00:45:42,829 now there are spoonbills and egrets fishing among the trees. 422 00:46:00,156 --> 00:46:03,125 Floods like these are less frequent than they once were. 423 00:46:03,793 --> 00:46:06,159 The Murray's flow has been altered by people, 424 00:46:06,596 --> 00:46:08,996 because the water was needed elsewhere. 425 00:46:09,566 --> 00:46:13,366 But when they do happen, the results are spectacular. 426 00:46:14,137 --> 00:46:16,605 The wildlife is tuned to events like these. 427 00:46:17,273 --> 00:46:18,706 Fish begin to breed, 428 00:46:19,042 --> 00:46:23,877 and thousands of waterbirds are prompted to start nesting around the flooded trees. 429 00:46:52,675 --> 00:46:55,769 This is the driest inhabited continent in the world, 430 00:46:56,079 --> 00:46:59,674 and yet here are kangaroos up to their knees in water! 431 00:47:00,650 --> 00:47:04,746 The Australian bush is nothing if not contradictory. 432 00:47:48,898 --> 00:47:51,196 The first European settlers had dismissed 433 00:47:51,367 --> 00:47:55,599 these vast green swathes as just 'forests in rags'. 434 00:47:56,105 --> 00:47:59,268 But as they got to grips with the curious land, the bush, 435 00:47:59,609 --> 00:48:01,839 with its resilience and strange wildlife, 436 00:48:02,178 --> 00:48:04,408 became the essence of Australia. 437 00:48:04,914 --> 00:48:06,609 It's a land of pioneers, 438 00:48:06,983 --> 00:48:10,282 where adaptability and tenacity are the keys to survival. 439 00:48:10,787 --> 00:48:14,314 And gum trees seem to suit it very well.