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00:00The
00:30These beautiful flowers belong to one of the most successful, the most widespread, and
00:39the commonest of plants. There are about 10,000 species in this one family, and they claim
00:49over a quarter of all the vegetated land on earth. They're pollinated by the wind, they
00:55need far less water than most trees, and they can survive both burning and freezing. They're
01:02the grasses.
01:10These tough, persistent plants continue to grow even when they're trimmed day after day
01:16by grazing teeth. They're able to withstand all this rough treatment because the point
01:22from which a grass leaf grows is at its base, close to the ground, and is permanently active.
01:28So grass provides a continuous banquet for creatures big and small.
01:40Down among the tangled grass stems live not only creatures that eat grass, but others that
01:45feed on the grass eaters. Lizards snap up small insects, and mantis munch grasshoppers.
01:52Spiders tackle almost any creature that moves, and dung beetles clear up the droppings from
01:57above. Among the most industrious of these tiny labourers are the termites. On many tropical
02:04grasslands, they flourish in such numbers that, one way or another, they consume more of the
02:08grass than big creatures like antelope, cows, or birds, or birds. They consume more of the
02:11grass than big creatures like antelope, cows, or birds. They consume more of the grass than
02:14big creatures like antelope, cows, or kangaroo. In the savannahs of Brazil, there are more termite
02:21mounds in an acre than anywhere else in the world, and termites are highly nutritious. So much so, that the
02:27giant anteater is able to exist, and the most industrious of these tiny labourers are the termites.
02:32On many tropical grasslands, they flourish in such numbers that, one way or another, they consume
02:36better than anywhere else in the world, and termites are highly nutritious. So much so, that the giant
02:42anteater is able to exist by feeding on them, and nothing else whatever.
02:51This creature has very poor eyesight, and very poor hearing, and finds its way around mostly by smell.
03:01So as long as I keep downwind of it, there's no reason why it should be
03:06particularly disturbed by my presence. You might think that that would make it very
03:11vulnerable to enemies. But the fact is that out on the savannahs here, it's got very few enemies.
03:17The only things that might attack it are a jaguar, or a puma, or perhaps if it was a baby, a
03:22savannah fox. And it has a very good defence against such creatures. Those huge forelegs, with enormous
03:30muscles on them, and gigantic claws, are quite powerful enough to rip the stomach
03:37from a puma or a jaguar. It's always thought that those legs are actually for ripping home
03:45termite hills. And they may be used to some extent for that purpose. But it seems much more
03:51likely now that they are primarily defensive weapons. Because when they actually come to feed,
03:57this creature doesn't do so much a sweep with its front claws as to use them very, very carefully
04:04to open the exit tunnels in the termite hills. Once it's done that, it pokes its nose into the tunnel
04:12entrance and flicks out its 20-inch-long tongue, coated with sticky mucus, and picks off the worker termites
04:18clinging to the tunnel walls. After about half a minute, before the soldier termites, which
04:30have powerful bites, can rally to the defence of the open tunnel, the anteater moves on.
04:36It's a wanderer, always on the move, sleeping at night out in the open, blanketed against
04:42the cold by its huge, hairy tail.
04:50Having no permanent den, the female carries her youngster with her, piggyback.
04:56Other termite hunters live on the surface of the mounds themselves.
05:16Beetle larvae lurk in burrows and lure flying ants and other insects to them by the luminous
05:22glow of their heads.
05:50Sometimes the termite mounds are attacked at their very foundations.
05:55This is the biggest insect-eater on earth, the giant armadillo, a massive animal that weighs over a hundredweight.
06:02There are a few more powerful diggers. It's no finicky feeder like the giant anteater,
06:07but rips its way through the ground into the heart of the termite hill.
06:15With its defences breached, the termite colony is very vulnerable.
06:18This mouse, Oxymyterus, has a particular fondness for termites and regularly follows in the wake of the giant armadillo.
06:28But the termites' biggest enemies are even smaller.
06:31Carnivorous ants regularly raid the colonies, carrying off the helpless, pallid termite larvae.
06:40The defenders of the colony, the soldier termites, engage the enemy ants.
06:44These termite warriors have jaws so specialised for fighting that they can't feed for themselves and have to be tended by the workers.
06:59Each species is armed in its own way.
07:01Some have short nippers, some sharp shears.
07:08Others have blades that strike outwards.
07:10And still others, nozzles on their forehead, through which they squirt a sticky poison spray.
07:16Other ants are vegetarians, like the termites, and use their jaws to demolish the living grass plants,
07:31scissoring up the leaves, sawing through the stems, and carrying off the plant piecemeal.
07:50Grass consists largely of cellulose, and that is a very difficult substance to digest.
07:55Termites do it with the help of bacteria in their gut.
08:00The grass-cutting ants have another and quite extraordinary method of making its nutriment digestible.
08:06Laboriously, they haul the pieces of grass back to their nest,
08:10which may be as much as a hundred yards away, and have several hundred small entrances.
08:17Inside an entrance, a tunnel leads down into a vast labyrinth of corridors
08:21that may extend for 80 or 90 feet in a horizontal direction,
08:26and lead to as many as 2,000 interlinked chambers.
08:34Such a nest may contain as many as 20 million ants.
08:38The workers carry their cuttings deeper and deeper into the nest.
08:55And here, 15 feet below the surface of the ground, in special chambers,
08:59they feed the grass to a fungus.
09:04This fungus forms crumbly white lumps, and grows nowhere else but in these nests.
09:13Carefully, the ant gardeners clean every fragment of grass.
09:17Meticulously, they remove every spore of any other fungus that might well grow down here,
09:21if it got the chance.
09:23Weeds, as you might say.
09:24The waxy skin that covers the leaf surface is stripped away,
09:28and then the pieces are cut up into even smaller fragments.
09:38The gardeners push the prepared morsels of grass into the mass of the fungus.
09:43The fungus digests it, cellulose and all, and grows.
09:46And the ants then feed on the fungus, which, unlike grass, they can digest.
10:04The ants tend their gardens with great care.
10:07Dead pieces of fungus and coarse, unsuitable fragments of leaves
10:11are carefully removed and carried away.
10:13With unflagging energy, portal lines of ants carry the waste down the long subterranean corridors,
10:26to the lowest chambers of all, 20 feet below ground,
10:30that serve as the colony's refuse tips.
10:32These are not only rubbish dumps, but cemeteries.
10:49For here, they also bring the bodies of dead workers.
10:52Dawn on the grasslands of Brazil, the campo.
11:09It's still chilly, and the dew lies heavily.
11:26But the rising sun will soon dry out the pasturage and rouse the daytime inhabitants.
11:31The grassland birds have no trees from which to sink.
11:33The grassland birds have no trees from which to sink.
11:35Some make do with grass stems.
11:36The grassland birds have no trees from which to sink.
11:37Some make do with grass stems.
11:38Others, like the scissor-tailed flycatcher,
11:41proclaim their territorial rights by visual display.
11:44The grassland birds have no trees from which to sink.
12:01Some make do with grass stems.
12:04Others, like the scissor-tailed flycatcher, proclaim their territorial rights by visual display,
12:11flying incessantly and conspicuously above their chosen plots.
12:15The seriyama, a catcher of snakes and insects, surveys the day's prospects from the top of a termite hill.
12:37The tapir has browsed throughout the night, but now, as the sun rises,
12:43it makes its way back to the forest that grows in the moist ground beside the river,
12:48for it greatly prefers the shady obscurity down there
12:51to the hot conspicuousness of the daytime plains.
13:00On the other hand, the savannah deer has slept all night
13:03and only begins to graze when it's light.
13:05It prefers to be able to see its enemies.
13:08The armadillo is no grass-eater.
13:13It's looking for insects, roots and birds' eggs,
13:16and even the lizard or a small snake.
13:24As the day warms up, reptiles become active.
13:27The tegu lizard is sufficiently powerful to be able to take on all comers.
13:37Just what it likes.
13:39And no small bird, no matter how aggressive, is able to repel a hungry tegu.
13:45Eggs on the ground are very much at risk to creatures like this.
14:02But where else can you put them?
14:04There are few trees on the grassland.
14:06But there are termite hills.
14:09The flicker is a kind of woodpecker and drills into termite hills
14:17just as efficiently as its cousins do into tree trunks.
14:22And when the flicker has finished with its hole,
14:25kestrels often take it over.
14:27The male has a lizard.
14:34Softly, he summons the female,
14:37who is incubating her eggs in the hole beneath.
14:40The burrowing owls nest in holes in the ground,
14:54taking over ones that have been abandoned by armadillos
14:57or even digging them for themselves.
14:59The male perches on a termite hill on guard,
15:02for the chicks are about to emerge.
15:10Danger. A harrier.
15:24Now it's safe once more.
15:27As long as the chicks can't fly,
15:29they're in danger from armadillos, tegus and other predators.
15:33So it's very important that they get their flight feathers as quickly as possible.
15:37And already, only a couple of weeks after hatching,
15:40they're showing through the down.
15:50Out in the fresh air, there's space to preen
15:53and a chance to sunbathe.
16:07Once more, there is an alarm.
16:28It's the spur-winged plovers.
16:32The plovers are quarrelsome birds.
16:45Even though each pair has established its claims over a patch of grassland,
16:49the birds continually dispute with their neighbours.
16:52Rivals display aggressively,
16:54running along the frontier between their territories
16:56and dive-bombing one another.
17:11Their nest is probably as safe as it would be,
17:13even if they remain sitting on it,
17:15for their eggs are marvellously camouflaged
17:17and very difficult to see.
17:24The adult tinamoo, on the other hand,
17:26is just as well disguised as the plovers' eggs.
17:29Its strategy is to stay put and freeze just as well,
17:33for its eggs are very conspicuous,
17:35a brilliant, shiny purple.
17:37One ground nester on the open plains, however, fears nothing.
17:45It's big enough and strong enough
17:47to take on even an armadillo or a tegu.
17:51The rear, the South American ostrich.
17:56It's the male that makes the nest and incubates the eggs.
17:59And he's polygamous, with half a dozen or so females,
18:02all of whom will lay in his nest.
18:11But with so many contributors,
18:13the compiling of a clutch can be a tricky business.
18:16Sometimes, several females,
18:18each with an egg ready to be laid,
18:20will turn up at the same time.
18:22And there's some confusion
18:23as to who's going to have the first turn.
18:25He doesn't seem to want them to lay in the main clutch.
18:29Perhaps he's worried about them treading on his eggs.
18:31So they'll have to sit outside.
18:40The first female goes down.
18:42Once laid, the egg has to be brought in to join the rest of the clutch,
18:59if he's to incubate it properly.
19:01Another female settles down to lay.
19:05And another egg joins his collection.
19:14His final clutch may be huge, up to 50 or so.
19:23They've come from many different females,
19:25and been laid over a period of eight days.
19:26But all hatched together.
19:27The young pipe to one another,
19:28while they're still inside their shells,
19:30stimulating the eggs that are a bit behind-hand
19:31to speed up their development.
19:32to speed up their development.
20:03The advantage of hatching simultaneously is that the young,
20:16soon after they emerge,
20:17can go off and feed together under father's watchful eye.
20:22So that is a fish.
20:24Not a fish.
20:25They're like,
20:27what a fish.
20:29So than a fish.
20:31So that's these little fish.
20:32And the green fish.
20:34Any fish.
20:35The open grassland is full of dangers and there are very few places to hide from the many enemies that lie in wait for the chicks.
21:02The maned wolf will certainly take one if it gets the chance.
21:11It hunts alone, never forming packs, seldom even seen with its mate.
21:15It maintains contact with others of its kind by an occasional bark and by leaving its scent on bushes and termite mounds,
21:23spraying its urine high up so that the wind will pick up the smell and broadcast it.
21:30This wolf's tastes are, oddly, strongly vegetarian. Fruit forms a large part of its diet.
22:00But it certainly takes birds if it can. And the tinamoo is particularly vulnerable for it's almost flightless.
22:30Trees don't grow on the open plains of Argentina and Brazil because, for much of the year, there is too little rain.
22:45During the dry season, the shallow lakes are reduced to stretches of baked mud.
22:52Capybara, giant semi-aquatic guinea pigs, crowd into the few shrinking pools that remain.
22:58Cayman are compelled to spend much of their time out of water, and turtles jostle for places along the contracting margins with the capybara.
23:13But during April, the clouds begin to gather, and in June they burst.
23:16It's a testing time for many of the grassland creatures.
23:20It's a testing time for many of the grassland creatures.
23:27It's a testing time for many of the grassland creatures.
23:352,000 miles north of the Brazilian Campo, the grasslands of Venezuela, the Llanos, flood over great areas, for the ground is full of clay and holds the water.
24:04For some, this is exactly what they want.
24:14The Llanos are flooded like this for almost half the year.
24:18That's all right for those capybara.
24:21They are almost as much at home in water as they are on land.
24:26Some creatures, even such an unlikely-looking swimmer as the giant anteater, manage to struggle to dry ground.
24:33The armadillo, too, is very competent in the water.
24:41Many others, such as burrowing rodents that might otherwise crop the grass of these plains, can't do so because they can't survive being flooded like this every year.
24:51The grass, however, grows tall and lives through even this hardship.
24:562,000 miles farther north still, water lies on the plains for many months on end, as snow on the prairies of North America.
25:06Here, the temperature can drop to 46 degrees below zero centigrade.
25:11The resistant grass survives it, but few animals can.
25:16The ground squirrels retreat to their burrows and go into a state of suspended animation.
25:22Their temperature falls and their breathing rate slows.
25:26They hibernate, using the absolute minimum of their body reserves accumulated during the summer.
25:31A cousin of the ground squirrel, another rodent called the prairie dog, does remain active, and during milder spells, it ventures out onto the snow to nibble what leaves it confined.
25:53The prairie chicken, actually a grouse, is one of the few birds to stay on the winter prairies, for although there are no insects to be had now, it can survive on nothing but seeds and leaves.
26:12Things are happening, however, below ground.
26:18The pocket gopher is still hard at work.
26:22It's winter food is roots, and of any nourishing they are, for many plants in autumn withdraw much of the substance from their withering leaves and store it in their roots.
26:37The bison manages to survive even the coldest weather out on the prairie.
26:43Big animals are not as easily chilled as small ones, and the bison is the most massive animal in North America.
26:50A bull can weigh a tonne.
26:56The extreme temperatures have, in effect, put the grass into deep freeze, so that, although it's frozen solid, such nutriment as it contained is preserved.
27:07The bison, being so big, have no difficulty in sweeping away the snow and reaching the frozen tufts.
27:13Bison share the prairies with pronghorn antelope, which in winter often visit areas that the bison have just cleared of snow.
27:22They're the swiftest animals in North America, capable of speeds of 50 miles an hour at full stretch.
27:28Coyotes, a small relation of the wolf, would have little chance of catching a young, healthy pronghorn, but that doesn't mean they won't try.
27:38And by chasing, they can discover if there are any antelope in the group that are less than healthy, and therefore catchable.
28:08Another joins the chase.
28:18The bitter cold and the shortage of food kills many animals at this time.
28:36For the coyotes, a carcass is precious, a mass of meat in an otherwise barren land.
28:41A pair have already taken possession of this dead elk.
28:46A third arrives. There will be trouble.
28:54They signal their threats with bristling fur, snarling lips, but surprisingly little sound.
29:06They are defunding fur.
29:35As spring approaches, the temperature rises, even below ground,
29:39and the winter sleepers begin to awake.
29:46Rattlesnakes, forced to take shelter from the cold,
29:49frequently take over the deeper burrows made by prairie dogs,
29:53and there, ten feet below ground, sit out the winter beyond the reach of the lethal frost.
29:58Sometimes as many as two or three hundred will share the same hull.
30:02As the spring sun warms the air, so they too slowly come to life.
30:13The prairie chickens leave the tall grass country where they spent the winter
30:17and assemble on shorter turf, for they are about to start their spring dances.
30:22Each male stays on a small patch of ground that is his dancing stage,
30:33and there he erects his feathery horns, inflates his wattles, and starts his stamping dance.
30:53The prairie chickens leave the tall grass.
30:54The prairie chickens leave the tall grass.
30:55The prairie chickens leave the tall grass.
30:56The prairie chickens leave the tall grass.
30:57The prairie chickens leave the tall grass.
30:58The prairie chickens leave the tall grass.
30:59The prairie chickens leave the tall grass.
31:00The prairie chickens leave the tall grass.
31:01The prairie chickens leave the tall grass.
31:02The prairie chickens leave the tall grass.
31:03The prairie chickens leave the tall grass.
31:04The prairie chickens leave the tall grass.
31:05The prairie chickens leave the tall grass.
31:06The prairie chickens leave the tall grass.
31:07The prairie chickens leave the tall grass.
31:08The prairie chickens leave the tall grass.
31:09The prairie chickens leave the tall grass.
31:10The prairie chickens leave the tall grass.
31:11The prairie chickens leave the tall grass.
31:12The prairie chickens leave the tall grass.
31:13BIRDS CHIRP
31:43BIRDS CHIRP
32:13BIRDS CHIRP
32:23The bison, too, have their young.
32:25The thick woolen coat that protected them through the winter is now far too hot,
32:30and the animals begin to shed it in sheets and tatters.
32:32The bison, being such a big animal, has a long gestation period, nine months.
32:46So soon after the young are born, courting starts again, and for the bulls, that involves battling with rivals.
32:53These jousts, which can be very punishing and even end in death, establish a ranking among the bulls.
33:02The victors can then seek access to the cows, which is another problem.
33:07The victors can be for as far as half an hour, and enlarge them in the car.
33:19The bison herds have a particular liking for the grazing around the prairie dog's towns.
33:45For the prairie dogs are good farmers.
33:48They deliberately cut down unpalatable plants and remove dead material, and their constant
33:54cropping means that the grass leaves around their burrows are all young and succulent,
33:59and the bison like that just as much as the prairie dogs do.
34:16The rattlesnakes also haunt the town, on the lookout for young prairie dogs.
34:21The shortness of the crop turf makes it easy for the town sentinels to see approaching danger.
34:38What to do about it is another question.
34:45Volting down a burrow is no defense against the rattlesnake.
35:01It will simply follow.
35:03The only thing to do is to retreat and whistle a warning to the neighbors.
35:07Bison are cattle.
35:17Like antelope and sheep, they're ruminants, dealing with the problem of digesting cellulose
35:22by regurgitating pellets of the grass they graze and giving it all a second chew.
35:27They also maintain a digestive broth of bacteria in their huge stomachs.
35:33Only 150 years ago they lived in such numbers on the prairies that a herd could stretch from
35:38one horizon to another.
35:40How many there were altogether is uncertain, 30 million is one of the lower estimates.
35:45That was a measure of the great fertility of these natural grasslands.
35:49Today most of the prairie has been turned over to the raising of domesticated cattle for beef,
35:55or ploughed up to grow domesticated grass wheat.
35:59By the beginning of this century, less than a thousand wild bison were left.
36:03But today, thanks to careful conservation, there are some 35,000 living in reserves.
36:10The prairies receive comparatively little rain because they lie in the center of a huge continent
36:16and the rocky mountains screen off the rain.
36:23Across the northern Pacific, the biggest continental mass of all, Eurasia, also contains a heartless
36:29land where relatively little rain falls.
36:32The grass-covered steppes of Russia and Eastern Europe.
36:35And here, another grass feeder survives that once formed vast herds.
36:40An extraordinary antelope, the saiga.
36:47Its huge nose contains internally a convoluted arrangement of passages lined with mucous glands
36:53that apparently serve to warm and moisten the dry air of the steppes and filter out the dust.
36:59The steppes are not as fertile as the prairie and are ravaged by regular and disastrous droughts.
37:13But the saiga seem to have adapted to this and have a quite extraordinary rate of reproduction
37:18that enables them to recover their numbers after such a catastrophe with great speed.
37:23The females, when they are a mere four months old and only half grown, mate and produce their first calf.
37:30After it's weaned, they grow rapidly so that by the beginning of the next breeding season, they're full size.
37:37And then they quickly breed again.
37:39And this time, three-quarters of them will produce twins.
37:44These animals, too, were hunted close to extinction.
37:46But when people realized that these natural inhabitants of the steppes could turn their grass into meat
37:51much more efficiently than any domesticated animal, indiscriminate hunting was stopped.
37:56And now there are over two million of them in the Soviet Union.
38:02Travel southwest from the steppes of central Eurasia, the greatest of all temperate grasslands,
38:07across territory where there's so little rain that not even grass can grow,
38:11and you come to the greatest of all tropical grasslands in Africa.
38:23Here, there is enough rain to create rivers and water holes,
38:27so in the moist soils around them and on rocky outcrops, a few trees manage to grow.
38:34In the more regularly-watered parts, thorn trees stand a distance from one another,
38:39their widespread root systems managing to collect just enough water to sustain them.
38:44Elsewhere, there's only enough rainfall for grass.
38:49But young trees are threatened not only by drought, but by fire.
38:53It sweeps rapidly over the plains, killing the tree seedlings,
38:56but leaving the growing buds of the grasses close to the ground quite unharmed.
39:01And green shoots of grass appear within days.
39:04So the fire, which starts so easily in withered grass stems,
39:08is one of the factors that keeps the country open for grass.
39:14The grasslands of Africa stretch in an immense and almost continuous arc,
39:21from the Sahara in the north, down through East Africa,
39:26and on to the great game plains of southern Africa and the Cape.
39:30During the eight million years or so of recent history,
39:34they've varied quite a lot in their extent.
39:36And at the moment, they're not as big as they have been in the past.
39:40But during this period of time, the grasslands have developed,
39:44and as they've done so, so the animals that lived on them have evolved.
39:48The nature of the one reacting on the nature of the other.
39:51Today, there's a greater variety and a bigger concentration of grass-living creatures
39:56on these African plains than anywhere else in the world.
40:15Different lengths of neck, different sets of teeth, different appetites.
40:19Such variety means that almost every growing leaf, short or long,
40:24of every kind of plains plant, is eaten by something.
40:39This vast tonnage of meat on the hoof has led, inevitably,
40:43to the appearance of an abundance of meat-eaters.
40:46And they, too, are varied, to exploit the variety of meat available.
40:54The serval seeks mice.
41:12The lions, hunting in teams, butcher, wildebeest and zeas.
41:16The zebra.
41:20Hunting dogs do the same.
41:26The cheetah goes for animals its own size, gazelle.
41:46Before grass spread over the plains, the ancestors of grazing antelopes must have lived in bush country, rather as Dick Dick do today.
42:04The bushes don't produce many leaves, but they're highly nutritious and there are enough in an acre or so to sustain a pair of these tiny antelope.
42:12So the Dick Dick mate for life and a permanent residence of their territory.
42:16They know it intimately and have their own trails and hiding places.
42:20And they mark out its frontiers with special notices.
42:24The ritual is nearly always the same.
42:26The female visits the midden first.
42:28The buck is stimulated to follow and habitually goes through exactly the same sequence of smelling, urinating, scratching and dunging.
42:38When the ceremony is over, the buck marks the nearby bushes with a sticky perfumed wax from a gland just below his eyes.
42:56Impala, however, live in more open country and feed not only on bushes but on grass.
43:16Here, they can't hide and they find their safety in numbers.
43:20With so many sharp eyes and acute ears, it's very difficult for a hunter to approach them undetected.
43:26But such a lifestyle obviously makes it impossible for the animals to live in permanent pairs on their own territory as the Dick Dick do.
43:34Instead, the males and females form separate herds.
43:38The bucks then battle among themselves.
43:41Those that win will leave the bachelor herds and set up individual territories.
43:45When the victors have established themselves, the does visit them, one after the other.
44:01But it's a very exhausting business for the bucks, repeatedly mating and fighting off challenges.
44:15After about three months of this, the once dominant bucks are worn out.
44:33They yield to other, fresher males and return to the bachelor herd to recover.
44:39Wildebeest live on grass alone.
44:46But the patchy distribution of rain over the African plains means that they can't stay permanently in the same place.
44:53They quickly exhaust pasture on one patch of the plains and must move on to an area where rain has recently fallen and the grass is springing again.
45:02So the wildebeest are constantly on the move.
45:05And their social arrangements have to be different from both the Dick Dick and the Impala.
45:10During the short breeding season, the males set up small territories along the migration routes.
45:17They advertise their pretensions by prancing around and snorting, seeking showy contests with rivals to demonstrate their virility to passing females.
45:28The problem then is to keep the females in their territory and prevent them from moving on into a rival's patch.
45:45The young calves, born only a few months before, adopt very early the jaunty, slightly crazy way of carrying on affected by their fathers.
46:10Within two weeks, the majority of the females are mated.
46:35And then suddenly, almost overnight, the whole herd, hundreds of thousands strong, vanishes.
46:47They've gone in search of fresh pastures.
46:50The varying growth of the grass over the year affects the lives of people as well as animals.
46:57In the eastern part of the grasslands in the Sudan, the people keep herds of semi-domesticated cattle.
47:04These are their pride and their wealth and their livelihood.
47:09At night, they pen them in enclosures made from uprooted thorn bush to keep out lion.
47:20The people can't settle in permanent villages, for their cattle exhaust the meagre pasture, just as wildebeest do.
47:27So periodically, they too have to move.
47:30And it's a nice question as to whether the animals are being driven by the people, or whether the people are, willy-nilly, following the herds.
47:38Many people in the Sudan regard not only their semi-wild cattle as their own personal property, but also the fully wild game that regularly passes through their territory.
47:53The white-eared cob, the males black and white, the females a delicate tan, live in the southern Sudan.
48:02Here, during the rainy season, the does give birth to their young.
48:06As the rains end and the plains begin to dry out, the herds begin to move north, following the new flush of grass that springs from the receding waters.
48:20As they go, the herds are funneled together by two rivers that flow closer and closer to one another, until eventually they join.
48:28And the cob have no alternative but to attempt a crossing.
48:32And here, the merli people await them.
48:40For the merli, this is an annual bonanza and a great celebration.
48:44Families have travelled from all over the tribal territory to take part,
48:48and to claim their share in their harvest of meat.
48:51If all goes well, there will be great feasting.
48:53But that's by no means a certainty.
48:55If the herds don't appear, there will be real hunger in the tribe.
49:08In the early morning, the hunters cross the river to set up their ambush.
49:12There's no guarantee that the cob will come this way.
49:15If the rivers are low, they may well try to cross on a much broader front upstream.
49:19Music
49:31Global
49:32Level
49:35Big
49:40Level
49:46The
49:49For the Kolp now, there is no going back. They have to cross.
50:19Day after day, the cob that have arrived at this crossing attempt to run the gauntlet.
50:49It takes several weeks for the whole migration to pass through.
51:17A million cob will make the journey. 5,000 of them will be killed.
51:23The Merle not only feast well now, they sun-dry the meat so that the families will have full stomachs for many months to come.
51:30In spite of the Merle's ambush, the vast majority of the cob reach the northern grasslands.
51:48There they will find enough food to sustain them throughout the critical months of the dry season.
51:53And there too they mate, so that next year the herds will reappear to make the river crossing and provide the Merle once more with meat.
52:01And the grass too will spring again, this remarkable plant that can survive intense grazing and burning and flooding.
52:13The one thing it can't tolerate is drought.
52:16If there's just a little less rain, then its leaves wither, its roots shrivel and can no longer hold the soil together so that the wind can catch it and blow away the small nutritious particles.
52:28And then it's reduced to little more than sand and the land becomes a desert.
52:34And it's to deserts that we're going in the next program.
52:37The end of the program.
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