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08:58source of food, and enough pollen sticks to their whiskers and fur to make these tiny
09:04bats gentle and reliable go-betweens.
09:20The trees derive no benefit from this possum. The Herbert River ringtail relishes the flowers
09:26as a welcome break from its usual fair of leaves. Possums first evolved in the rainforests,
09:38and over time they diversified into many specialised kinds.
09:49For arboreal animals, lemuroid possums aren't all that agile.
10:11While most of the larger species feed on leaves and other plant food, this small and elusive
10:17striped possum prefers insects. Searching along the rotting and dying trees, it tears the
10:24bark with sharp teeth and digs out wood-boring grubs. Its hands tap along the wood for the
10:34hollow sounds that betray the presence of borers. The fourth finger on each hand is much longer
10:48than the others, and it's tipped with a sharp claw to skewer fat and juicy grubs from deep
10:54inside the rotting timber.
11:02Today, this pretty striped possum is hard to find. Although the rot and decay that's so
11:08much part of this dense and wet forest gives it a good living here, its special way of life
11:13left it no match for a dramatic change which began to gather pace 15 million years ago.
11:26Australia started to dry out, and most of the rainforests and their inhabitants vanished.
11:33But among the plants were some that adapted, plants that already had evolved features to survive
11:39in places where the soil was poor. And it was these marginal, hardier plants that took over,
11:47while the ancestral forests retreated to a few pockets. From among the new plants rose a group
11:54that spread around Australia in splendid variety, the eucalypts, the gums.
12:03They reach their most majestic form in the mountain ash. Growing to 100 metres, it's the tallest
12:09flowering plant in the world, and with its light and airy crown, it's the king of the eucalypts.
12:20The open canopy lets through much more light than the rainforest it replaced. And in these
12:26higher, wetter areas, it allows an understory of tree ferns to flourish. A backdrop of green
12:32lace for what sounds like a great chorus of birds.
12:45In fact, all the songs have but one singer, the lyrebird, a uniquely Australian master of both mimicry
12:53and display. The aim is to persuade females nearby that the cockbird is a fine and healthy specimen,
13:11well worthy of fathering their chicks.
13:14withinters.
13:16Through the same thing.
13:32Do the same thing.
13:35Here we go.
13:35Let's go.
13:40And the tale of the garden of the youth, where the beetle's a wind,
13:42Here we go.
13:54This hen seems to have heard it all before, and she's more interested in the insects hiding in the litter.
14:00But in time, the display will work its spell.
14:09Eucalypt forests are spacious and uncluttered, and that gave some of the possums added impetus to turn leaping into gliding
14:17as a means of getting around.
14:29Folds of skin that stretched between the fore and hind limbs of the leaping possums evolved into strong and supple
14:35membranes to carry sugar gliders and their kin on long flights through the open forests.
14:58A
15:25Gliding doesn't use as much energy as climbing,
15:27and it's an economical way for possums to harvest a special food provided by some kinds of widely scattered gums.
15:37In these uncommon trees, a sugary sap flows so close to the outer skin
15:42that a slash of sharp teeth has it oozing out to become a rich and sustaining food.
15:50The sap trees are few and far between, and so sugar gliders band together to defend this precious resource.
15:58As a result, they've become the most social of the possums.
16:03It's a society where the chief language is not sound, but smell, and a complex idiom it is.
16:13Whenever gliders meet, they stop to sniff and refresh their communal scent.
16:17The glands are in the most unlikely places, under the chin, on the forehead, even under the feet.
16:29As well as the tribal odour, there are subtle blends that tell who's who in the social order, and details
16:36of sex.
16:37For instance, whether this female is ready to mate.
16:52The unfamiliar odour all around warns this stranger that he's in the wrong place.
17:08To warn all comers that this is occupied territory, the resident males smear pungent trails around the tribal range.
17:23A strong scent from glands around the vent is mixed with drops of urine.
17:35Again, it's scent, or rather the lack of a familiar one, that marks out an intruder.
17:41His body odour declares him to be a male, but a very young one, and so no real threat.
18:00Before dawn breaks, the gliders make their way to the communal den.
18:10Such a tight squeeze keeps out larger possums, and gives protection against whatever enemies might come prowling by.
18:27Inside the eucalypt hollow, it's also a fairly snug fit.
18:31Some colonies have as many as eight gliders bedding down together.
18:36Sharing body warmth saves energy, and helps to pass around the all-important tribal scent.
18:57The eucalypt's distinctive dull green foliage is much more open than that of the rainforest trees from which they evolved,
19:05with smaller, hardier leaves to withstand the climate.
19:11The leaves hang angled away from the sun to keep water loss down.
19:16And to make them unpalatable, they're loaded with potent cocktails of toxins and oils.
19:25Despite this, some animals have found ways of breaching the eucalypt's defences,
19:30and they form a web of life that extends even to the streams flowing through the forest.
19:40The leaves fall all year round, and almost the moment they hit the water,
19:45the first of a long line of insect shredders gets to work.
19:53Caddisfly larvae, armoured in a suit of sand grains and plant fragments,
19:57reduce the leaf to a skeleton, carefully munching their way around the poisonous oil glands.
20:06The bits of leaf get broken down further, and are swept downstream,
20:11some to fetch up in a tiny net, spun by another kind of Caddisfly larvae.
20:17Instead of having a portable suit of armour, this one builds a fortress out of tiny pebbles.
20:23It's such a good spot that another larva mounts an assault on the miniature castle, and takes over.
20:38The usurper's first task is to improve and strengthen the structure.
21:07One side of the keep serves to anchor the net.
21:10And with all the rebuilding, it's become rather tattered and torn.
21:15When the last pebble is securely in place, the caddis sets about reweaving its gossamer snare,
21:21producing sticky threads, much like a spider's.
21:38The net is delicate but tough, only five millimetres across,
21:42yet sturdy enough to catch and hold the bits of broken down leaf swept into it by the strong current.
21:49The creatures that inhabit these streams belong to very ancient families.
21:55It's only the nature of the leaves on which all their lives depend that's changed,
21:59from rainforest to eucalypt.
22:09The leaf shredders and net spinners become food for larger insects and crustaceans.
22:15And there are enough of those to help feed the platypus,
22:18which lives much as it did when these streams were still fed, not by eucalypts, but by rainforest.
22:29Change becomes more apparent further downstream, in the drier woodland of the lower rainfall country.
22:36The soils are poorer here, and the gum trees don't grow as tall.
22:41They're more gaunt and spare than the eucalypts of the higher ranges.
22:46This is the characteristic bush.
22:50Unlike their rainforest ancestors, gums don't make fleshy fruit.
22:55Instead, seeds are packed in woody cases to stop them drying out.
23:19A colourful company of cockatoos, parakeets and lorikeets feeds on gum nuts and berries,
23:26deftly peeling them with tongue and beak.
23:40The open canopy allows a lot of sun to reach the ground.
23:44There's plenty of light and space for seeds to germinate and grow.
23:48And the eucalypts have no need to bribe birds to carry the seeds away.
23:53Though many are eaten by parrots, many more survive.
23:59But sun also dries the litter as it builds up, accumulating fuel for another powerful force that moulded the nature
24:08of Australia.
24:10Fire.
24:23Astonishingly, the eucalypts came to thrive on fire.
24:27Features that developed first to cope with poor soils and then with drought, now stand them in good stead in
24:34dealing with flames.
24:38Western
24:59In the aftermath the bush looks black and lifeless…
25:04But it's far from dead. Already, the wombats which hid from the flames in their burrows are out, squabbling over
25:12bits of plant food left unburned.
25:37The eucalypts live on. The reserve shoots and buds under the bark and the main branches begin to sprout. And
25:44within weeks, the gums are veiled in green again.
26:08The fresh growth attracts armies of insects, for leaves are best eaten when they're young and tender, even though they're
26:15already loaded with defensive toxins.
26:28A vast array of suckers, cutters, nibblers and munchers goes to work. They're mostly the larvae of moths and butterflies.
26:36And they consume great quantities of leaves. Some simply nibble their way around the chemical defences. Others are immune.
26:53Because the eucalypts can put out new growth repeatedly, they seem to suffer more insect attack than many other trees.
27:02¶¶
27:09¶¶
27:50Fire, insects, and still the trees survive.
27:54Indeed, they do attract some allies in the insect wars,
27:57though even a legion of praying mantises wouldn't take much of a bite out of the hosts of leaf eaters.
28:05The intervention of this bell miner actually works against the trees.
28:11The reason for that is its fondness of these small sugary domes that form on the leaves of some eucalypts.
28:19They're called lerps, and they're made by the larvae of psyllid insects
28:23to protect their soft bodies from the sun while they suck the sap from the leaves.
28:35The psyllids digest what they need from the sap and use the waste to build their sunshades.
28:42At first, the material is soft and pliable, and the larva can work it into shape.
28:47The larvae of psyllid insects
28:50The larvae of psyllid insects
28:56The larvae of psyllid insects
29:21Eventually, the fruit of two hours' patient labour sits into a tiny house of sweet glass.
29:37Bell miners relish the stuff and carefully remove the domes, leaving the insects to manufacture
29:43more.
29:43They chase other birds away, birds that eat the insects as well as their shelters.
29:50And that's a problem for the eucalypts, for with the bell miners protecting the psyllids
29:55and taking their domes, the insects' appetite for leaf sap is constantly being stimulated
30:01to become ever more voracious.
30:09The eucalypts can't count this bird among their friends either.
30:13It's gone into partnership with a parasitic plant, the mistletoe.
30:29The mistletoe taps into the eucalypts for its own growth and it employs the mistletoe bird
30:35to spread its seeds and gain a root hold.
30:40The bird and its chicks have the gut specially designed so that the berries go directly into
30:45the intestine and bypass the stomach.
30:47That way they go through very quickly and when the partly digested berries emerge, they're
30:53still sticky.
30:55the seeds are dropped high in another tree and sprout.
31:13One eucalypt may carry several mistletoes and struggle to survive itself.
31:23The mistletoe is at the centre of another, even more remarkable relationship.
31:29At the base of some host trees, the caterpillars of azure butterflies are tended by sugar ants,
31:36which give them shelter in their own nest.
31:42Every night the grubs go on a long and dangerous trek to the top of the tree to feed on
31:47the mistletoe
31:48leaves.
31:49The ants go with them and their presence guards against spiders and other enemies.
31:56In return, the grubs supply the ants with a rich sugary liquid from their body glands.
32:07In their rise to dominance over the last two million years, the eucalypts formed a range
32:12of extraordinary associations.
32:14But most involve birds and insects, which either avoid or cope with the toxic leaves.
32:21By contrast, only a few leaf-eating marsupials have been able to adapt.
32:32Of all the rainforest ring-tailed possums, only the common ring-tail thrives in these drier
32:38woodlands.
32:40It's successful because its digestion can cope with the oils and toxins in the eucalypt foliage,
32:46which is the most abundant food here.
32:57As soon as they're out of the pouch, the baby possums start weaning on the tough plant food.
33:02That'll be their adult fare.
33:20That grasping tail helps them reach the fragile outer branches bearing the fresh new leaf growth,
33:26and it also makes a handy carrier for nesting material.
33:36The leaves that pose the marsupials with such a digestive challenge make a dry, hard litter,
33:42which takes a long time to break down.
33:45But enough insects and other invertebrates live amongst it to provide a good living for
33:50this Antichinus.
33:52Its hunting skill is extraordinary.
34:22Speed and a single-minded ferocity enable it to tackle almost any kind of prey.
34:28But it's the Antichinus' sex life that's even more remarkable.
34:33There too, ferocity is the hallmark.
34:36With the advent of the mating season, males competing for females fight each other to a
34:42standstill.
34:43There it is.
35:15The male sex drive is especially urgent with antichinus, as well it might be, for they
35:21have only one season to reproduce. It makes their couplings fairly brutal, more like a
35:28rape, and lengthy they are too.
35:54All this frantic breeding is lethal. It takes tremendous energy and produces great tension
36:01and males hardly eat. Their teeth fall out, they get gastric ulcers, and their stress hormones
36:08rise to levels so high that their immune system fails, like AIDS. By the end of the season,
36:15they are all dead, leaving only the pregnant females. It's a high price to pay for breeding
36:24success, but there is sense in it. Small mammals don't live long anyway, and among the antichinus,
36:31evolution has favoured males which put all their reproductive effort into their first and only
36:37mating season. Success lies not in personal survival, but in how many young are fathered,
36:43to ensure that the line is carried on.
37:01The challenge of procreation in these woodlands has fashioned other equally intriguing strategies.
37:11Many of the birds here form extended families to share the task of rearing young. Several generations
37:22of kookaburras, older brothers, sisters, unattached uncles and aunts, pitch in with feeding and even
37:29help to incubate the eggs. Communal breeding is a way of giving chicks a better chance in an environment
37:40where food supplies aren't always reliable. But animals don't usually do anything for nothing.
37:46Perhaps the return comes later, when the helpers get help with their own young.
38:01The galah's strategy is to form a lifelong bond with one mate. Pairs come back to nest
38:07in the same tree hollow year after year. Hollows are fairly safe places, but no bond is strong
38:22enough to guard against lace monitors on the prowl. Though they're only active for a short time each day,
38:36their acutely sensitive taste and smell make them the most feared predator in these parts.
39:10The
39:18It's just another meal for the lace monitor, but for the galahs, it's the end of their
39:23chance to rear a family this season.
39:32Beneath the eucalypts live banksias, ancient plants going back to the primeval rainforest.
39:46They are inhabited by pygmy possums.
39:49Vacant bird nests often provide a home, and some of their food comes from insects.
39:55So, I'm going to take a few minutes.
40:03I'm going to take a few minutes.
40:26Insects are relished, but the banksias themselves provide their small guests with even more important
40:32nourishment.
40:32The pygmy possums feed on the nectar, and in so doing, help pollinate the flowers.
40:49The possum babies soon get the hang of clambering around.
40:53After all, the pygmy possums and banksias evolve together over an immensely long time.
40:58The shape of the flowers suits these nocturnal pollinators.
41:02Each spike has hundreds of tiny flowers, densely packed together to provide support, and plenty
41:09of nectar and pollen.
41:17Banksias and their relatives come splendidly into their own in the heathlands, especially
41:22here in Western Australia.
41:33In these ancient leached soils, so poor they're almost pure sand, climatic hardships created
41:40an evolutionary nursery without parallel.
41:49So many flowers eager to attract pollinators have fostered a matching diversity of insects.
41:56Many, like these jewel beetles, are rewarded with nectar.
42:00But some plants show even greater entrepreneurial flair.
42:06Honey eaters make good go-betweens, and many plants employ them.
42:12Even more recruit insects, and the result is a wonderful assortment of shapes designed
42:18to suit the various visitors.
42:31Certain plants even resort to fraud to seduce insects.
42:36One group of orchids cunningly exploits the sexual habits of this wasp, habits remarkable
42:42enough in themselves.
42:44The female has no wings, and when she's ready to mate, she rubs off chemical signals for
42:51a male to come and fly off with her.
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43:11Very lonely.
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43:22But the body we want to get precise and pén to take a deep house afterìn Bow,
43:23mate on the wing and still coupled end to end he takes her to some nectar rich flowers now he
43:33feeds
43:33dragging his partner behind him she can't feed herself but when he's had his fill he rubs her
43:43abdomen which prompts her to curl forward and receive a few drops from his mouth
44:00feeding her is his investment in the eggs now forming in her body the whole method hangs on
44:09the chemical signals she sends out and the orchids have evolved almost identical signals
44:15to trick the male wasps into trying to copulate with them and so become their pollen carriers
44:27this flower looks as well as smells like a sexy female wasp and he keeps on trying to mate even
44:35when the orchid flips him onto its pollen bearing part such mimicry is an economic way of seducing
44:44pollinators without having to supply nectar a great advantage in these poor soils the plants
44:52that use birds do give a reward but the flowers are shaped so that the visitor has to collect a
44:57dab of pollen as well the honey eaters are also matched to the task inside the long bill is a
45:07long
45:07pollen tongue tipped with a brush to soak up the nectar rather than opt for one particular kind of
45:16pollinator banksias play the field their dense blooms are arranged to tempt various honey eaters reward
45:23them with nectar and ensure they carry away pollen but those same blooms also support a much more ancient
45:40partnership with this extraordinary animal much smaller than a mouse the marsupial honey possum is one of
45:50the very few mammals in the world designed to feed exclusively on nectar and pollen like the honey eating birds
45:57it has
45:58a long tongue fitted with a brush at the end the partnership began in the ancestral rain forests and while
46:07many other
46:08plants and animals vanished the honey possum stayed with the banksias as they became transformed into these hardy plants of
46:15the bush
46:25in the eucalypts that fringe the heathlands lives another very specialized marsupial the numbat its survival is linked closely to
46:34the termites that became abundant as the australian landscape dried out
46:48uniquely among marsupials they become active only by day because that's when the termites upon which they feed move near
46:56the surface and into the fallen timber
47:01the stripes are good camouflage but having to step out in broad daylight still makes the numbats very cautious
47:17this kind of eucalypt woodland provides a plentiful supply of the wood eating termites that the numbats prefer and they're
47:26well equipped to harvest
47:27them with a tongue that unrolls to half their body length it's a specialized way of life and it's enabled
47:35the numbats to live through the ever drying climate that made the bush
47:42the rise of the eucalyptus
47:44the rise of the eucalypts offered a secure place for any marsupial that could stomach their foliage
47:49some possums managed it but it's the koala that's come to typify the supreme gum specialist
47:57its gut has special bacteria to extract all it needs from just a few types of eucalypt leaves
48:04it means koala life revolves around a small range of gums that's where they fight feed and mate
48:11mating is what's on the mind of this old dominant bull right now
48:16the female is still carrying last year's young and she sees the approach as a threat to herself and her
48:22joey
48:39it means those Nichter
48:42it means they cannot do it
48:49it means they havecko
48:51theOSS
48:51caer
49:05She's much lighter, and she can move out to the thinner branches where he daren't follow.
49:12The awkward way they clamber around suggests that they haven't been tree dwellers all that long.
49:18In fact, their closest relatives are wombats.
49:27The old bull is about to suffer more frustration.
49:30A young rival has come into his range with designs on a virgin female.
49:34A young whale!
50:07The commotion sends the king koala hurrying to protect his mating rights.
50:11If this intruder manages to impregnate one of his consorts,
50:16there's one less chance of fathering a royal cub.
50:50The old male is an experienced campaigner.
50:53His tactic is to drive the young rival far out on a slender limb.
51:05Now the choice is to fall or risk an escape past the royal rage.
51:34Peace returns, but the tension remains.
51:37Sooner or later, the young male will try his luck again.
51:41He may even displace the old bull and become the new ruler.
51:44It'll make no difference to the females.
51:47They'll continue to care for their young,
51:49and when the time is right, receive the seed for the next generation.
52:05It's important for Joey to stay close to mother,
52:08not only for milk, but also to be fed with some of her faeces.
52:13It's a pap that will prime the young with the special bacteria to process gum leaves.
52:18It's sole food in adult life.
52:47Of all the marsupials,
52:48the koalas have tied their fortunes most closely to the eucalypts.
52:53It's the quintessential partnership in the bush,
52:56a partnership that could only have evolved in Australia.
53:01Inland from the wooded margins,
53:03the drying centre of the continent posed animals and plants
53:06with an even greater challenge.
53:08And that's the theme of our next programme.
53:28The theme of our next programme is
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