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00:00Transcription by CastingWords
00:30CastingWords
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02:59And these aren't the only wild animals that have been painted on these rocks.
03:06A giraffe.
03:09A kind of wild goat, probably a mouflon.
03:13And antelope.
03:15Obviously, at the time these pictures were painted, there was good grazing here.
03:20Indeed, there was sufficient vegetation to sustain not only wild animals, but whole herds of cattle.
03:27We don't know exactly who drew these pictures.
03:32The artists may have been the ancestors of the nomads, who today follow their herds of long-horned, piebald cattle just south of the Sahara.
03:40But we do know what they look like, because they left their own portraits.
03:44They lived here, it seems, some 5,000 years ago.
03:47But eventually the rains began to fail, the pastures disappeared, and with it, the cattle and their keepers.
03:53But there are one or two living survivors from that time.
03:57This ancient cypress, to judge from the number of rings in the trunks of others like it, is probably between 2,000 and 3,000 years old.
04:09In fact, it was probably already growing here at the time when the last of the paintings were being made.
04:15It still bears fertile seed, but there are no little seedlings growing around here to replace it.
04:21The land now is far, far too dry for them.
04:25Indeed, the cypress itself only survives because it sends its huge roots deep into the ground to tap underground water.
04:32The drying out of the Sahara seems to be connected with the great changes in climate that overtook the world at the end of the last ice age.
04:41As the glaciers retreated northwards across Europe, so the belt of rains that fell regularly along their southern edge left Africa and moved up into Europe.
04:51Indeed, it seems to be that most, if not all, of the great deserts of the world were formed around that time,
05:01and most, if not all of them, are therefore comparatively recent environments.
05:05To see why deserts lie where they do, we can look at the Sahara from the west.
05:12The equator runs away from us, across the width of Africa.
05:16It's along this line that the sun's rays strike from directly overhead, and therefore with the greatest strength.
05:24The heated air rises along the equator and flows away north and south to cooler parts of the world.
05:30Because it's warm, it carries with it a lot of moisture.
05:33But as it rises and cools, the moisture condenses first to form clouds and then to fall as rain.
05:41By the time the air comes down again over the Sahara to the left and the Kalahari to the right,
05:46it's lost most of its moisture and creates very few clouds.
05:50So the Sahara, with few clouds to shield it from the sun, becomes roastingly hot during the day.
05:56And at night, with no blanket of clouds to keep in its warmth, it gets desperately cold.
06:03Deserts are not placed symmetrically around the world because the continents themselves are distributed in a very irregular way.
06:11They are ridged with great mountain ranges, which interfere with the even flow of air,
06:16and the spin of the planet itself creates vast eddies in the atmosphere, which further complicates things.
06:22But even so, deserts do lie in two broad zones on either side of the equator.
06:28The pattern in Africa, with the Sahara in the north and the Kalahari and the Namib in the south,
06:33has its equivalent in the Americas.
06:38South of the lush equatorial jungles of the Amazon, beyond the great range of the Andes, lies the Atacama Desert.
06:47On the other side of the equator, beyond the drenched tropical rainforests of Panama,
06:52stretch the deserts of Mexico and Arizona.
06:54Across the Pacific, the greatest expanse of water on the globe, lies south of the equator, Australia,
07:04most of which is covered by desert.
07:07Its northern tip gets close enough to the equator to collect some rain.
07:12Far the north still, beyond the jungle that blankets Indonesia and Malaysia, Thailand and Burma,
07:17across the great snow-covered range of the Himalayas, stretch the vast deserts of Central Asia, Mongolia and the Gobi.
07:26And beyond them, as we complete the circuit of the globe, the huge desert of the Middle East,
07:31that covers Iran, Iraq and Jordan, Syria and Israel, the vast sandy emptiness of Arabia,
07:39and runs on to join the Sahara.
07:47This is the biggest expanse of waterless land on Earth.
07:53Here, as in deserts everywhere, almost nothing moves during the heat of the day.
08:00But animals are here.
08:02If you want to see what made these tracks, you have to wait until the sun sinks and the desert begins to cool.
08:19A striped hyena, one of the commonest of the bigger desert animals in this part of the world.
08:44A fennec fox.
08:49Fennecs usually live in small family groups and clearly enjoy one another's company.
09:08But there's not much time for frolicking.
09:11Food must be found.
09:12Faint smells from the sand tell them who has moved where since they were last out.
09:17Food must be found.
09:47Food must be found.
09:48Food must be found.
09:49Food must be found.
09:50Food must be found.
09:51Food must be found.
09:52Food must be found.
09:53Food must be found.
09:54Food must be found.
09:55Food must be found.
09:56Food must be found.
09:57Food must be found.
09:58Food must be found.
09:59Food must be found.
10:00Food must be found.
10:01Food must be found.
10:02Food must be found.
10:03Food must be found.
10:04Food must be found.
10:05Food must be found.
10:06Food must be found.
10:07Food must be found.
10:08Food must be found.
10:09Food must be found.
10:10Food must be found.
10:11Food must be found.
10:12Food must be found.
10:13Food must be found.
10:14Food must be found.
10:15Food must be found.
10:17Another little seed-eating rodent, a gerbil.
10:23And a caracal, a kind of cat,
10:26which loves both gerbils and jerboas, if it can get them.
10:29A smaller hunter, but nonetheless a deadly one, a scorpion.
10:49It is searching for beetles or other small insects,
10:53but sometimes the hunter becomes the hunted.
10:56A black widow spider has set her snare of silk underneath a thorn bush.
11:26In the intense struggle, the black widow loses one of her legs.
11:32She manages to get more ropes of silk around the scorpion, hampering it still further.
12:08But to no purpose. The battle is as good as lost.
12:23Methodically, the spider trusses up her victim and hangs it in her larder.
12:28Wolves, perhaps surprisingly, are quite common in these Middle Eastern deserts.
12:39But they're not the same as the wolves from farther north.
12:42They're smaller, lighter-coloured, and with only the thinnest fur.
12:46And they scavenge as much as they hunt.
12:54The cool night is coming to an end. Hunting is over.
12:57The animals must go back to their dens and hiding places
13:00to shelter from the heat that is to come.
13:12The sun returns. And very soon, the desert will be heating up once again.
13:30The mammals that were active during the night will have to go for shelter.
13:34And the day will belong not to them,
13:36but to those creatures that get their heat directly from the sun.
13:40The reptiles.
13:41This is the desert of the American West in Arizona.
13:45And we've come here to look at one very special desert reptile.
13:49This one.
13:53This is the Gila monster.
13:55One of only two poisonous lizards in the world.
13:59Actually, he very seldom uses his poison in defence.
14:08And in any case, it's still quite early in the morning
14:11and he's so cold that he isn't very active.
14:15But in only about an hour, an hour and a half,
14:18the desert will get so hot that he won't be able to stand it
14:21and he too will have to go and seek shade.
14:24So in this short period of the early morning
14:27and in the cool of the evening is the time when he hunts.
14:45A tortoise.
14:46But he's far too big and well-armoured for a Gila monster to tackle.
14:50This great nest of sticks, however, looks much more promising.
15:05The victim, a desert mouse.
15:24The tortoise is on the lookout for food too.
15:40But it is a vegetarian.
15:54The day is now several hours old.
16:01Cool dawn is changing to baking noon.
16:05It's time for even a reptile to get out of the sun.
16:15Movement generates heat.
16:17So now nothing moves unless it absolutely has to.
16:21And there are some creatures that remain motionless
16:24even when you get within a few inches of them.
16:27One of them is sitting down on the ground right in front of me now.
16:32Though you may find it difficult to see
16:34because it's so well camouflaged.
16:36It's a poor will.
16:39A kind of nightjar.
16:45Fluttering the throat evaporates moisture from the mouth
16:48and so cools the bird.
16:49And it consumes much less energy than heaving the chest and panting
16:53as many mammals would do in this situation.
16:57The sand grass of Africa uses the same trick.
17:06The sand grouse chicks start doing it almost as soon as they emerge from the shell.
17:17They also immediately peck for seeds.
17:19But there's little moisture in a seed
17:21and unless they get a drink they will die.
17:24The responsibility for providing that rests entirely with the male.
17:29Every day he flies to water maybe as much as 25 miles from the nest.
17:34First he fills his own stomach with water.
17:42But then very deliberately he soaks his belly feathers.
17:51These feathers have a special spongy structure
17:54so that they can absorb a great deal of water.
17:57And once he's got a full load on board
17:59he flies back to his family.
18:04At last the chicks get their drink.
18:14No other bird has such an ingenious water carrying device.
18:18The road runner of the American deserts provides water for its chicks in a quite different way.
18:34This parent bird has collected a cicada for its family.
18:39Its nest is up in a cholla cactus.
18:41The parent doesn't give its chicks their food immediately.
18:51The chick is gulping.
18:53The parent bird is producing liquid from its stomach
18:56and letting it trickle down its beak.
18:58Each youngster gets its share.
19:02Each youngster gets its share.
19:06Another ration of solid food, this time a lizard.
19:24And each time, before the meal is handed over, the chicks get a drink, whether they like it or not.
19:41During the heat of the day, the parents sit on the nest, not to keep the chicks warm,
19:57but on the contrary, to keep them cool, by shading them.
20:01And the sitting bird not only flutters its throat, but protects itself from the sun by using its tail as a parasol.
20:12The ground squirrel of the Namib desert in southern Africa does the same thing,
20:16and very effectively too, carefully angling itself as far as possible to keep its body in the shade.
20:22Many animals keep their blood cool with radiators.
20:37The hedgehog that lives in the desert of the Middle East has unusually large ears.
20:42Blood circulates through capillaries close to the surface of the skin and is cooled by the breeze.
20:52The fennec fox's huge ears serve the same purpose.
21:01And so do those of the American jackrabbit,
21:03which perhaps has the biggest ears of all in proportion to its body.
21:13The Dorcas gazelle also has radiator ears and is one of the best adapted of all desert mammals.
21:19It's one of the very few that can survive without a drink at all.
21:23It gets all the liquid it needs from the vegetation.
21:29It doesn't waste liquid as urine, but gets rid of its uric acid as small dry pellets.
21:35It's now approaching noon, the hottest time of the day.
21:42It's summer, the hottest time of the year, and I'm in one of the hottest places on Earth.
21:50Death Valley in the Western United States.
21:51Death Valley in the Western United States.
21:53A thermometer on the ground here has risen to 201 degrees Fahrenheit.
21:56That's about 94 degrees centigrade.
21:59It's so hot that no creature can survive permanently out here.
22:06Even at the edge of these sand flats where the ground is a little more broken,
22:09there is no sign of an accident.
22:10It's so hot that no creature can survive permanently out here.
22:14Even at the edge of these sand flats where the ground is a little more broken,
22:27there is no sign of animal life whatever.
22:30All animals now have sought the shade and shelter from this ferocious sun.
22:36But there are some organisms that can't get out of the sun.
22:42Plants being fixed to the ground have to stay out in the heat of the day and simply endure.
22:50But all of them have special devices to help them to do so.
22:54The Desert Holly, its leaves grow at about 70 degrees to the vertical
22:59so that in the morning when it's less hot and in the evening and the plant needs light,
23:05it presents the face of its leaves to the light.
23:08But during the middle of the day, it shows only the edges and so it doesn't heat up so much.
23:14Not only that, but the plant extracts salt from the salt-laden ground
23:20and excretes it as a white coating on the surface of the leaf,
23:24which like the white costume of an athlete reflects the heat
23:28and so keeps the plant that much cooler.
23:31And this, the creosote bush.
23:34This is one of the most widespread of plants in American deserts.
23:39And its roots are better at extracting the last molecule of water from these parched sand
23:45than those of any other American plant.
23:48And this has led to a most extraordinary state of affairs that's only just been discovered.
23:53It seems that the creosote bush was the first plant to establish itself in the arid sand of the Mojave Desert
24:00when the desert first appeared.
24:02And once it had established its extensive root system,
24:05it extracted moisture from the sand so efficiently that it was extremely difficult for any other plant to grow alongside it.
24:13And that applied not only to any other kind of plant, but also to its own seedlings.
24:20So, an individual creosote bush tended to spread not by setting seeds and producing a new generation,
24:29but by sending out new stems around its base.
24:33And as these spread outwards, so the stems in the middle tended to die away,
24:38and the bush grew into a ring shape like this.
24:42So these are not separate individual creosote bushes as it might appear,
24:48but this is just one big ring-shaped individual plant.
24:55Over the centuries, the rings widened and changed their shape,
25:00until now some are over 25 yards across, like this one.
25:06Of course, the individual stems and leaves of this plant are not very ancient.
25:13The first ones to grow that appeared in the middle have decayed and disappeared,
25:17a long time ago.
25:19But now it's estimated that this plant started growing between 10 and 12,000 years ago.
25:26In fact, when the Mojave Desert first appeared.
25:30And that makes it the oldest known living organism in the world.
25:40In the Mojave, the plants may have to survive for as long as 10 years without rain.
25:46But if rain falls just a little more frequently, as it does nearby in Arizona,
25:51plants can have different survival strategies.
25:55To many of us, the very symbol of the desert is the cactus.
25:59But in fact, this family of fleshy-stemmed plants lives only in the Americas.
26:05There are several hundred species of them, but among the biggest is the saguaro.
26:11The saguaro has solved the problems of surviving in great heat and drought very successfully indeed.
26:20Its stem is pleated like an accordion, so that when rain does fall, the cactus can expand
26:26and quickly absorb as much of the water as possible before it disappears.
26:30After a single storm, a saguaro can take up as much as a ton in a few days.
26:37Its leaves have become thorns, so reducing the surface area from which the plant might lose water by evaporation.
26:44The stem itself is green and has taken over the job of photosynthesis.
26:49The thorns protect the young plant from browsers, but they also break up the wind currents,
26:55so that the cactus is wrapped, as it were, in still air,
26:58and evaporation of moisture from the stem is kept very low.
27:02These huge saguaro cacti can live for over 200 years and stand nearly 50 feet high.
27:10A big one like this may weigh as much as eight tons, and 90% of that is water.
27:17If I was dying of thirst in this desert, I'd be tempted to cut inside that saguaro and raid its reservoir of water.
27:26But that would probably be a mistake, because the water in the saguaro contains a poison.
27:31But there are lots of desert living plants which do have drinkable water within them.
27:37And desert living people all over the world have become expert botanists,
27:42able to recognise from just the tiniest little leaflet or straggling stem where they can get a good drink.
27:51None are more skilled than the bushman people of the Kalahari.
28:01None are more skilled than the bushman people of the Kalahari.
28:09By the end of the dry season, all their water holes have usually dried up.
28:13For liquid, they must now rely almost entirely on plants,
28:17and their ability to recognise the right ones.
28:20This tuber is a kind that provides good drinking water.
28:32This much larger one is also full of liquid,
28:45but unfortunately it's so bitter it's undrinkable.
28:48But it's worth having nonetheless.
28:54To extract the water, the roots must be grated and pulped.
28:57The water is diggested and pulped.
29:15.
29:21The bigger root is grated as well.
29:37Drier though it is, it still contains valuable fluid.
29:47Since it cannot be drunk, the people use it to moisten their skin
29:51and as it evaporates, it brings a delicious, refreshing coolness.
30:15200 miles to the west of the Kalahari lies an even hotter, drier desert.
30:20The namib.
30:22Very few plants indeed can survive in these parched sands.
30:26Patches of grass sprouted after a rare shower of rain
30:29and lived for a few weeks, but that was over four years ago
30:33and now only the dusty withered stems are left.
30:36There is one plant that grows here though and indeed nowhere else
30:39and one that is very odd indeed.
30:42The scientist who first described this extraordinary plant
30:50was an Austrian called Dr. Vellvich who came to this part of Africa
30:54in the middle of the last century.
30:56He discovered many plants in Africa, but this perhaps is his most famous
31:01and the one that bears his name being called Vellvichia.
31:04There are male plants and female plants.
31:07This one is a female and these are the female structures.
31:11These are young ones which sprouted this year
31:14and these are the fully developed ones from last year.
31:17In structure, they're very like the cones of a fir tree.
31:22The male plant has growths rather like stamens which produce pollen.
31:29So Vellvichia seems to be a kind of link
31:31between coniferous trees and true flowering plants.
31:38But the oddest thing about it perhaps are its leaves.
31:42They grow from the top of its central trunk
31:44and what's more do so extremely slowly
31:47so that this length of leaf would have taken about 70 years to be produced.
31:52But if it hadn't frayed at the edges, it would be about 400 yards long
31:57because this individual plant is thought to be about 1,500 years old.
32:05It's these amazing leaves that enable the plant to collect water in this rainless country.
32:11The Namib lies close to the western coast of Africa.
32:15At dawn, fogs regularly roll in from the Atlantic.
32:18As they swirl around the Vellvichia, their moisture condenses on the plant's huge leaves.
32:24Some droplets are absorbed through cracks in the leaves' skin.
32:28The rest of the water is channelled down to the ground
32:34where it's sucked up by roots just below the surface of the sand.
32:39The fog also provides life-saving drinks for some of the desert animals.
32:44These are darkling beetles.
32:47On foggy mornings, they climb to the top of the dunes
32:50and stand in lines, head down, abdomen up, slowly marking time.
32:55Droplets of water from the fog collect on legs and antennae
33:20and then, as the beetle lifts its feet, trickle down towards its mouth.
33:31The Namib's fogs never penetrate very far inland.
33:35Those deserts that lie a long way from the sea, therefore,
33:38can never receive moisture in such a way.
33:41Their water must come from the clouds.
33:43Only too often, the clouds that do build up above a desert
33:50sail off elsewhere without bursting,
33:53and the land remains parched.
34:04But when eventually rain does come,
34:07it's the trigger for immediate and urgent action.
34:13One or two drops are all that's necessary
34:15to activate these dead stems.
34:28Within half a minute, they're upright.
34:35Other plants begin to open their seed heads.
34:38None of these plants is alive.
34:49All their movements are simply the result
34:51of the dead tissues absorbing water.
34:53The dead seed heads have held the seeds securely during the drought.
35:11Now, since there's been rain,
35:13and there's a chance of them germinating,
35:15they can be distributed.
35:18For some plants, the heavy raindrops are enough
35:21to dislodge the seeds.
35:23Others utilize the physical effects of absorbing water
35:45to shoot the seeds away.
35:47Now the seeds themselves, lying on the ground,
36:00begin to move.
36:07As the hares absorb water, they swell and stiffen,
36:10so raising the seed into the right position
36:13for its first rootlets
36:14to strike straight downwards into the ground.
36:20But sometimes in the Arizona desert,
36:23maybe once in several years,
36:24there are real cloudbursts,
36:26and the desert is transformed.
36:28So as the area of water permeates what they wanna do,
36:30you know,
36:33the rescue of their,
36:33and so early navires to enter the town,
36:34and all about these lights.
36:35To piper what you know about the country had a level?
36:36What can happenage?
36:37How long have people thought that
36:38what we don't know about Gradeu?
36:39You can see an apresentation
36:40with water urged moments on the night before the day,
36:40too.
36:41You can see the seaacji regarding the ocean.
36:42The bayous partes on the ground,
36:42as at night before the sea will draw their squares.
36:44So the sea and that could you look at,
36:44then ask them to assume in yourorsch farm
36:45is the only called the três and the sea,
36:46and from what the sea we made.
36:47down on this point.
36:48The
36:51seaksam Liebe,
36:52all those things nickel and the sea,
36:52In the aftermath of the flood, new faces appear.
37:22A spade-foot toad.
37:35The males are the first to emerge from the soil where they've been buried for the past year or more.
37:47Hastily, they make their way down to one of the temporary pools that have appeared in the desert,
37:51and there they begin calling, summoning the females.
37:56There is great urgency. If they don't mate on this night, they may have lost their chance.
38:01. . .
38:08Within 24 hours, the eggs have been laid and fertilized and are beginning to hatch.
38:24. . .
38:35A day later, and the pool is full of tadpoles.
38:38. . .
38:42Other creatures have appeared as if from nowhere.
38:45. . .
38:45Fairy shrimp have hatched from tiny eggs, blown with the dust all over the desert.
38:49. . .
38:55The tadpoles are growing fast.
38:57These, with small mouths, feed on algae and bacteria, a diet usually abundant in these desert pools.
39:04. . .
39:12But other individuals that hatched from the same batch of eggs develop bigger heads and more powerfully muscle jaws.
39:18They have become meat-eaters.
39:20. . .
39:25Not all pools will provide enough food for them, but here they are fortunate.
39:31. . .
39:40They even eat their vegetarian brothers.
39:47With such a protein-rich diet, they grow even faster than the algal feeders.
39:54Here they are the favored few, more likely to survive if the pool evaporates very quickly indeed.
39:59They are an insurance for the continuation of the species for which the payments are their vegetarian brothers.
40:06. . .
40:08But now the pool is shrinking fast.
40:10Another couple of days and it's almost gone.
40:13Unless there's another shower of rain, all the tadpoles will die.
40:23If they do die, their bodies will not be wasted.
40:26They will decompose and fertilize the sand, so ensuring that when the next rains come,
40:31and another pool collects in this particular hollow, the algae will grow fast and well.
40:36. . .
40:39Ants are quick to attack these stricken tadpoles . . .
40:42. .
40:44. .
40:46But at the last minute there is a reprieve, a short shower of rain.
40:50Some of the tadpoles, even though they still have a tail, do now have legs,
40:54and they're able to leave the puddle just two weeks after hatching.
41:02. .
41:05Even among this tiny proportion of survivors, the mortality will be huge.
41:10But with luck, a few will join the adults as the desert dries
41:14and bury themselves to wait for the next shower of rain many months from now.
41:34For several weeks after the rains, the desert blooms.
41:45The seeds, shed by the shriveled plants, have sprouted and burst into flower.
41:50And so deserts after rain all over the world, in Arizona and Australia,
41:55the Namib and the Sahara, put on one of the most dazzling displays of colour
42:00that you can see anywhere.
42:04The Kingdom of Jesus
42:07For the
42:25For the
42:30Deserts are shaped by the sun and the wind.
42:50The roasting of the rocks during the day,
42:52their chilling during the cold nights,
42:54eventually makes their surface crumble.
42:56Some of their minerals splinter and fray into dust,
42:59but quartz, the commonest, is very hard,
43:01and that remains as grains of sand.
43:04The wind catches them, sweeps from the way,
43:07and collects them together as sand dunes.
43:29Dunes may be hundreds of feet high.
43:40If the wind is more or less constant,
43:42it blows the grains up the gently sloping side
43:45and over the steep front,
43:47so that the dune marches slowly across the desert.
43:50Trudging up the face of a dune like this is extremely hard work.
44:09The sand is so dry
44:12and the grains are so polished by the wind rubbing them together
44:16that the surface is continuously on the move
44:20and it's quite impossible to get any firm foothold.
44:24And, of course, that problem faces not just me,
44:28but all the animals that live among these dunes.
44:31And some of them have developed
44:33some extremely ingenious solutions to the difficulty.
44:37These extraordinary tracks have been made
44:41by one of the swiftest movers across the dunes.
44:48The Sidewinder, a kind of rattlesnake,
44:51it skims across the surface
44:53by throwing its body into a series of loops
44:55which only touch the sand at two points.
44:58This not only enables it to move very fast,
45:01but keeps most of its body off the hot surface.
45:03In the middle of the day,
45:11the sand is so hot that it's painful to touch.
45:14The Namib fringed-toed lizard
45:16prevents its feet from scorching by gymnastics.
45:19But eventually it gets so hot,
45:39the only thing to do
45:40is to shelter beneath the surface
45:41where the sand is very cool.
45:43But burrowing through this kind of sand
45:48also has its problems.
45:49An animal can't construct a tunnel
45:52like a mouse hole or a rabbit burrow
45:54because the sand is so smooth
45:55it simply falls in behind it.
45:57So instead, it has to wriggle through the sand
46:00almost as though it's swimming.
46:02And that's precisely what this little creature does.
46:05It may look like a worm,
46:07but in fact, it's a lizard that has lost its legs.
46:10And you can see that it's a lizard
46:12when you look closely at its face.
46:16For it has a mouth and two eyes
46:18covered by transparent scales
46:20that protect them in the sand.
46:21It's a blind skink.
46:23It lives by hunting for insects
46:25below the sand's surface
46:26and when I put it down,
46:29it'll wriggle away just like an eel.
46:31The most extremely specialised
46:40of these hunters in the dunes
46:42is not perhaps a reptile,
46:44but a mammal.
46:46It's very rarely seen
46:47and your best chance of finding it
46:48is at night.
46:54These are its tracks.
46:57And that depression,
46:58a place where it caught something.
47:01And this is where it has burrowed again
47:10and where, with luck,
47:11and if I dig very fast,
47:13I might catch it.
47:23Here it is,
47:24a golden mole.
47:28This one is a baby,
47:29but like its parents,
47:31it's totally blind.
47:32Eyes are of no use
47:33beneath the sand.
47:35Nor are ears,
47:36and it hasn't got those either.
47:37Its head ends
47:38in a kind of leathery wedge
47:40with which it pushes its way
47:41through the sand
47:42or, alternatively,
47:43through my fingers.
47:44golden moles will eat quite large creatures,
48:01a blind skink
48:02if it encounters one
48:03within the dune
48:04or other creatures
48:05that might be wandering
48:06unsuspectingly
48:07across the surface.
48:08a cricket
48:09would do nicely.
48:10A cricket
48:11would do nicely.
48:24a cricket
48:25would do nicely.
48:56The great sandy deserts of the world, in Arabia, Central Australia and the Sahara, have repelled even the hardiest of human travellers.
49:23Few people have managed to survive in them for long, totally unaided.
49:27But some manage to make regular journeys through these wildernesses.
49:31These are the Touareg.
49:38They travel from one side of the Sahara to the other, carrying great cakes of salt, which they trade for cloth and grain and dates.
49:45But even the Touareg can only make these journeys with the help of an animal desert specialist, the camel.
50:06They have to take all the food that they and their camels will need with them.
50:12Water is carried in skins slung beneath the camel's bellies to minimise evaporation and keep it as cool as possible.
50:23The camel itself is marvellously adapted to life in the desert.
50:29Its toes are reduced to two, but they're connected by skin so that they splay out on the sand and don't sink deeply into it.
50:36Their nostrils are closeable, so they can shut out sand grains during a sandstorm.
50:49The hair on their body is restricted to the top, where it serves as a shield against the sun.
51:03But elsewhere, for coolness, their skin is virtually naked.
51:07Their hump is full of fat, which, in emergencies, can be converted to water.
51:11But the process wastes a lot of the fat's calories, and the camel only does it when it hasn't drunk for a very long time.
51:18It can, in fact, live without liquid water for four times as long as a donkey and ten times as long as a man.
51:25But eventually, even a camel has to drink.
51:33At one or two places in the Sahara, water can be reached by digging deep into the ground.
51:42Here, camels can at last refill their stomachs, and they take a lot of filling.
51:47There are 30 people in the head.
51:53There are 30 people in the village in the寺院.
51:55There are 40 people in the island.
51:56Here we are.
51:58Here, Camel, I will Nunnum.
52:01Theākram.
52:04Theākram, a어주, theākram.
52:07Theākram, a stone, a stone, a stone.
52:09Theākram.
52:12Theākrams, theākram, a stone, a stone.
52:15But if the Touareg can't cross the Sahara without the camel,
52:22the camel can't do so without the Touareg,
52:24for only men can dig wells and haul up the essential water.
52:31Spring water is the key which unlocks abundant fertility.
52:35At Saharan oases like this one,
52:38all kinds of crops can be produced from the sand if it's watered.
52:42Dates and vegetables and fruit.
52:44Insects whiz and buzz over the gurgling irrigation channels
52:48and birds sing in the palm trees.
52:52But these small islands of life are under constant threat.
52:57If the wind veers and blows steadily from another direction,
53:01nothing can stop the sand.
53:02Eventually, the advancing dunes may well overwhelm this oasis,
53:18and then this small world that's been brought into existence
53:21in the middle of the desert by the presence of water will be extinguished.
53:25The force that drives the dune, of course, is the wind.
53:30And the wind, too, has its own world of living organisms.
53:33Many of the spiders and beetles and other insects
53:37that live in the oasis here will have arrived by air,
53:40and many of the plants, too,
53:42coming either as wind-blown seeds or carried on the feet of birds.
53:46And that world, the world of the wind and the sky,
53:49we'll be exploring next time.
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52:46
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