0:01:05 > 0:01:08These beautiful flowers belong to one of the most successful,
0:01:08 > 0:01:12the most widespread and the commonest of plants.
0:01:15 > 0:01:19There are about 10,000 species in this one family,
0:01:19 > 0:01:23and they claim over a quarter of all the vegetated land on Earth.
0:01:23 > 0:01:28They are pollinated by the wind, they need far less water than most trees,
0:01:28 > 0:01:33and they can survive both burning and freezing. They are the grasses.
0:01:41 > 0:01:45These tough, persistent plants continue to grow even when they're trimmed
0:01:45 > 0:01:49day after day by grazing teeth.
0:01:50 > 0:01:52They are able to withstand all this rough treatment
0:01:52 > 0:01:56because the point from which a grass leaf grows is at its base
0:01:56 > 0:01:59close to the ground and is permanently active.
0:01:59 > 0:02:05So grass provides a continuous banquet for creatures big and small.
0:02:11 > 0:02:16Down among the tangled grass stems live not only creatures that eat grass
0:02:16 > 0:02:19but others that feed on the grass-eaters.
0:02:19 > 0:02:25Lizards snap up small insects and mantis munch grasshoppers.
0:02:36 > 0:02:40Spiders tackle almost any creature that moves
0:02:40 > 0:02:44and dung beetles clear up the droppings from above.
0:02:44 > 0:02:49Among the most industrious of these tiny labourers are the termites.
0:02:49 > 0:02:52On many tropical grasslands, they flourish in such numbers that,
0:02:52 > 0:02:55one way or another, they consume more of the grass
0:02:55 > 0:02:59than big creatures like antelope, cows or kangaroo.
0:03:03 > 0:03:07In the savannas of Brazil, there are more termite mounds on an acre
0:03:07 > 0:03:11than anywhere else in the world. And termites are highly nutritious -
0:03:11 > 0:03:16so much so that the giant anteater is able to exist by feeding on them
0:03:16 > 0:03:18and nothing else whatever.
0:03:22 > 0:03:28This creature has very poor eyesight and very poor hearing,
0:03:28 > 0:03:33and finds its way around mostly by smell, so, as long as I keep
0:03:33 > 0:03:36downwind of it, there's no reason
0:03:36 > 0:03:40why it should be particularly disturbed by my presence.
0:03:40 > 0:03:44You might think that that would make it very vulnerable to enemies.
0:03:44 > 0:03:48The fact is, out on the savannas here, it's got very few enemies.
0:03:48 > 0:03:53The only things that might attack it are a jaguar or a puma, or if it was a baby,
0:03:53 > 0:03:55a savannah fox.
0:03:55 > 0:03:59And it has a very good defence against such creatures.
0:03:59 > 0:04:05Those huge forelegs, with enormous muscles on them and gigantic claws,
0:04:05 > 0:04:11are quite powerful enough to rip the stomach from a puma or a jaguar.
0:04:13 > 0:04:15It was always thought that those legs
0:04:15 > 0:04:18are actually for ripping open termite hills,
0:04:18 > 0:04:22and they may be used to some extent for that purpose.
0:04:22 > 0:04:27But it seems more likely now that they are primarily defensive weapons,
0:04:27 > 0:04:29because when they actually come to feed,
0:04:29 > 0:04:33this creature doesn't do so much of a sweep with its front claws
0:04:33 > 0:04:40as to use them very, very carefully to open the exit tunnels in the termite hills.
0:04:40 > 0:04:44Once it has done that, it pokes its nose into the tunnel entrance
0:04:44 > 0:04:48and flicks out its 20-inch-long tongue, coated with sticky mucus,
0:04:48 > 0:04:52and picks off the worker termites clinging to the tunnel walls.
0:04:58 > 0:05:02After about half a minute, before the soldier termites, which have powerful bites,
0:05:02 > 0:05:08can rally to the defence of the opened tunnel, the anteater moves on.
0:05:08 > 0:05:12It is a wanderer, always on the move, sleeping at night out in the open,
0:05:12 > 0:05:16blanketed against the cold by its huge hairy tail.
0:05:22 > 0:05:26Having no permanent den, the female carries her youngster with her,
0:05:26 > 0:05:27piggyback.
0:05:44 > 0:05:48Other termite hunters live on the surface of the mounds themselves.
0:05:48 > 0:05:53Beetle larvae lurk in burrows and lure flying ants and other insects to them
0:05:53 > 0:05:55by the luminous glow of their heads.
0:06:22 > 0:06:26Sometimes the termite mounds are attacked at their very foundations.
0:06:26 > 0:06:31This is the biggest insect-eater on Earth, the giant armadillo,
0:06:31 > 0:06:34a massive animal that weighs over a hundredweight.
0:06:34 > 0:06:36There are few more powerful diggers.
0:06:36 > 0:06:38It's no finicky feeder like the giant anteater,
0:06:38 > 0:06:43but rips its way through the ground into the heart of the termite hill.
0:06:46 > 0:06:50With its defences breached, the termite colony is very vulnerable.
0:06:50 > 0:06:55This mouse, oxymicterus, has a particular fondness for termites
0:06:55 > 0:06:58and regularly follows in the wake of the giant armadillo.
0:07:00 > 0:07:03But the termites' biggest enemies are even smaller.
0:07:04 > 0:07:08Carnivorous ants regularly raid the colonies, carrying off the helpless,
0:07:08 > 0:07:10pallid termite larvae.
0:07:11 > 0:07:16The defenders of the colony, the soldier termites, engage the enemy ants.
0:07:22 > 0:07:26These termite warriors have jaws so specialised for fighting
0:07:26 > 0:07:30that they can't feed for themselves and have to be tended by the workers.
0:07:30 > 0:07:33Each species is armed in its own way.
0:07:36 > 0:07:39Some have short nippers, some sharp shears.
0:07:39 > 0:07:45Others have blades that strike outwards and others nozzles on their forehead
0:07:45 > 0:07:48through which they squirt a sticky poison spray.
0:08:06 > 0:08:09Other ants are vegetarians, like the termites,
0:08:09 > 0:08:14and use their jaws to demolish the living grass plants, scissoring up the leaves,
0:08:14 > 0:08:18sawing through the stems and carrying off the plant piecemeal.
0:08:21 > 0:08:26Grass consists largely of cellulose and that is a very difficult
0:08:26 > 0:08:27substance to digest.
0:08:27 > 0:08:31Termites do it with the help of bacteria in their gut.
0:08:31 > 0:08:35The grass-cutting ants have another and quite extraordinary method
0:08:35 > 0:08:37of making its nutriment digestible.
0:08:37 > 0:08:41Laboriously, they haul the pieces of grass back to their nest,
0:08:41 > 0:08:45which may be as much as 100 yards away and have several hundred
0:08:45 > 0:08:46small entrances.
0:08:48 > 0:08:53Inside an entrance, a tunnel leads down into a vast labyrinth of corridors
0:08:53 > 0:08:58that may extend for 80 or 90 feet in a horizontal direction
0:08:58 > 0:09:01and lead to as many as 2,000 interlinked chambers.
0:09:05 > 0:09:10Such a nest may contain as many as 20 million ants.
0:09:18 > 0:09:22The workers carry their cuttings deeper and deeper into the nest.
0:09:26 > 0:09:32And here, 15 feet below the surface of the ground, in special chambers,
0:09:32 > 0:09:35they feed the grass to a fungus.
0:09:35 > 0:09:40This fungus forms crumbly white lumps and grows nowhere else
0:09:40 > 0:09:41but in these nests.
0:09:44 > 0:09:47Carefully, the ant gardeners clean every fragment of grass.
0:09:47 > 0:09:51Meticulously, they remove every spore of any other fungus
0:09:51 > 0:09:56that might grow down here if it got the chance. Weeds, as you might say.
0:09:56 > 0:10:00The waxy skin that covers the leaf surface is stripped away
0:10:00 > 0:10:03and then the pieces are cut up into even smaller fragments.
0:10:09 > 0:10:13The gardeners push the prepared morsels of grass into the mass
0:10:13 > 0:10:14of the fungus.
0:10:14 > 0:10:19The fungus digests it, cellulose and all, and grows,
0:10:19 > 0:10:24and the ants then feed on the fungus, which, unlike grass, they can digest.
0:10:35 > 0:10:38The ants tend their gardens with great care.
0:10:38 > 0:10:42Dead pieces of fungus and coarse, unsuitable fragments of leaves
0:10:42 > 0:10:45are carefully removed and carried away.
0:10:52 > 0:10:56With unflagging energy, porter lines of ants carry the waste down
0:10:56 > 0:11:01the long corridors to the lowest chambers of all, 20 feet below ground,
0:11:01 > 0:11:05that serve as the colony's refuse tips.
0:11:16 > 0:11:20These are not only rubbish dumps, but cemeteries,
0:11:20 > 0:11:24for here they also bring the bodies of dead workers.
0:11:36 > 0:11:41Dawn on the grasslands of Brazil, the campo.
0:11:54 > 0:11:57It's still chilly and the dew lies heavily.
0:11:57 > 0:12:01But the rising sun will soon dry out the pasturage and rouse
0:12:01 > 0:12:03the daytime inhabitants.
0:12:29 > 0:12:34The grassland birds have no trees from which to sing. Some make do
0:12:34 > 0:12:36with grass stems.
0:12:36 > 0:12:41Others, like the scissor-tailed flycatcher, proclaim their territorial rights by visual
0:12:41 > 0:12:47display, flying incessantly and conspicuously above their chosen plots.
0:13:02 > 0:13:07The seriama, a catcher of snakes and insects, surveys the day's prospects
0:13:07 > 0:13:09from the top of a termite hill.
0:13:11 > 0:13:15The tapir has browsed throughout the night, but now, as the sun rises,
0:13:15 > 0:13:18it makes its way back to the forest that grows in the moist ground
0:13:18 > 0:13:23beside the river, for it greatly prefers the shady obscurity down there to
0:13:23 > 0:13:26the hot conspicuousness of the daytime plains.
0:13:31 > 0:13:36On the other hand, the savannah deer has slept all night and only begins
0:13:36 > 0:13:37to graze when it is light.
0:13:37 > 0:13:40It prefers to be able to see its enemies.
0:13:42 > 0:13:47The armadillo is no grass-eater. It's looking for insects, roots and
0:13:47 > 0:13:50birds' eggs, and even a lizard or a small snake.
0:13:56 > 0:14:00As the day warms up, reptiles become active.
0:14:03 > 0:14:08The tegu lizard is sufficiently powerful to be able to take on all-comers.
0:14:09 > 0:14:13Just what it likes, and no small bird, no matter how aggressive,
0:14:13 > 0:14:16is able to repel a hungry tegu.
0:14:30 > 0:14:34Eggs on the ground are very much at risk to creatures like this.
0:14:34 > 0:14:37But where else can you put them? There are few trees on the grassland.
0:14:37 > 0:14:40But there are termite hills.
0:14:44 > 0:14:48The flicker is a kind of woodpecker and drills into termite hills
0:14:48 > 0:14:52just as efficiently as its cousins do into tree trunks.
0:14:54 > 0:14:58And when the flicker has finished with its hole, kestrels often take it over.
0:15:04 > 0:15:06The male has a lizard.
0:15:06 > 0:15:12Softly, he summons the female, who is incubating her eggs in the hole beneath.
0:15:21 > 0:15:25The burrowing owls nest in holes in the ground,
0:15:25 > 0:15:28taking over ones that have been abandoned by armadillos
0:15:28 > 0:15:30or even digging them for themselves.
0:15:30 > 0:15:33The male perches on a termite hill on guard,
0:15:33 > 0:15:35for the chicks are about to emerge.
0:15:42 > 0:15:44Danger - a harrier.
0:15:55 > 0:15:58Now it's safe once more.
0:15:58 > 0:16:02As long as the chicks can't fly, they're in danger from armadillos,
0:16:02 > 0:16:04tegus and other predators.
0:16:04 > 0:16:08So it is very important that they get their flight feathers as quickly as possible,
0:16:08 > 0:16:11and already, only a couple of weeks after hatching,
0:16:11 > 0:16:13they are showing through the down.
0:16:21 > 0:16:26Out in the fresh air, there is space to preen and a chance to sunbathe.
0:16:57 > 0:17:03Once more there is an alarm... It's the spur-winged plovers.
0:17:14 > 0:17:16The plovers are quarrelsome birds.
0:17:16 > 0:17:20Even though each pair has established its claims over a patch of grassland,
0:17:20 > 0:17:24the birds continually dispute with their neighbours.
0:17:24 > 0:17:27Rivals display aggressively, running along the frontier between
0:17:27 > 0:17:31their territories and dive-bombing one another.
0:17:31 > 0:17:34CONSTANT SQUAWKING
0:17:42 > 0:17:46Their nest is probably as safe as it would be even if they remained sitting
0:17:46 > 0:17:51on it, for their eggs are marvellously camouflaged and very difficult to see.
0:17:56 > 0:18:00The adult tinamou, on the other hand, is just as well-disguised as
0:18:00 > 0:18:03the plover's eggs. Its strategy is to stay put and freeze.
0:18:03 > 0:18:08Just as well, for its eggs are very conspicuous, a brilliant shiny purple.
0:18:13 > 0:18:17One ground-nester on the open plains, however, fears nothing.
0:18:17 > 0:18:22It's big enough and strong enough to take on even an armadillo or a tegu.
0:18:22 > 0:18:26The rhea, the South American ostrich.
0:18:28 > 0:18:31It's the male that makes the nest and incubates the eggs.
0:18:31 > 0:18:35And he is polygamous, with half a dozen or so females, all of whom
0:18:35 > 0:18:36will lay in his nest.
0:18:43 > 0:18:47But with so many contributors, the compiling of a clutch can be
0:18:47 > 0:18:48a tricky business.
0:18:48 > 0:18:52Sometimes several females, each with an egg ready to be laid,
0:18:52 > 0:18:54will turn up at the same time
0:18:54 > 0:18:58and there's some confusion as to who's going to have the first turn.
0:18:58 > 0:19:01He doesn't seem to want them to lay in the main clutch.
0:19:01 > 0:19:03Perhaps he's worried about them treading on his eggs,
0:19:03 > 0:19:06so they'll have to sit outside.
0:19:11 > 0:19:14The first female goes down.
0:19:27 > 0:19:30Once laid, the egg has to be brought in to join the rest of the clutch
0:19:30 > 0:19:33if he is to incubate it properly.
0:19:35 > 0:19:38Another female settles down to lay.
0:19:43 > 0:19:45And another egg joins his collection.
0:20:05 > 0:20:09His final clutch may be huge, up to 50 or so.
0:20:09 > 0:20:12They've come from many different females and been laid over a period
0:20:12 > 0:20:15of eight days, but all hatch together.
0:20:15 > 0:20:19The young pipe to one another while they're still inside their shells,
0:20:19 > 0:20:24stimulating the eggs that are a bit behind to speed up their development.
0:20:44 > 0:20:47The advantage of hatching simultaneously is that the young,
0:20:47 > 0:20:49soon after they emerge,
0:20:49 > 0:20:52can go off and feed together under Father's watchful eye.
0:21:25 > 0:21:30The open grassland is full of dangers and there are very few places to hide
0:21:30 > 0:21:33from the many enemies that lie in wait for the chicks.
0:21:33 > 0:21:37The maned wolf will certainly take one if it gets the chance.
0:21:41 > 0:21:46It hunts alone, never forming packs, seldom even seen with its mate.
0:21:46 > 0:21:50It maintains contact with others of its kind by an occasional bark
0:21:50 > 0:21:54and by leaving its scent on bushes and termite mounds, spraying its urine
0:21:54 > 0:21:58high up so that the wind will pick up the smell and broadcast it.
0:22:00 > 0:22:04This wolf's tastes are, oddly, strongly vegetarian.
0:22:04 > 0:22:07Fruit forms a large part of its diet.
0:22:30 > 0:22:34But it certainly takes birds if it can, and the tinamou is particularly
0:22:34 > 0:22:37vulnerable, for it's almost flightless.
0:23:22 > 0:23:26Trees don't grow on the open plains of Argentina and Brazil because,
0:23:26 > 0:23:30for much of the year, there is too little rain.
0:23:30 > 0:23:32During the dry season, the shallow lakes are reduced
0:23:32 > 0:23:34to stretches of baked mud.
0:23:34 > 0:23:39Capybara, giant semi-aquatic guinea pigs, crowd into the few
0:23:39 > 0:23:41shrinking pools that remain.
0:23:41 > 0:23:45Cayman are compelled to spend much of their time out of water,
0:23:45 > 0:23:50and turtles jostle for places along the contracting margins with the capybara.
0:23:52 > 0:23:57But during April, the clouds begin to gather and in June they burst.
0:23:57 > 0:24:00THUNDER AND RAIN
0:24:08 > 0:24:12It's a testing time for many of the grassland creatures.
0:24:23 > 0:24:282,000 miles north of the Brazilian campo, the grasslands of Venezuela,
0:24:28 > 0:24:33the Ilanos, flood over great areas, for the ground is full of clay
0:24:33 > 0:24:34and holds the water.
0:24:36 > 0:24:38For some, this is exactly what they want.
0:24:45 > 0:24:49The Ilanos are flooded like this for almost half the year.
0:24:49 > 0:24:52That's all right for those capybara.
0:24:52 > 0:24:56They are almost as much at home in the water as they are on land.
0:24:56 > 0:25:00Some creatures, even such an unlikely-looking swimmer as
0:25:00 > 0:25:04the giant anteater, manage to struggle to dry ground.
0:25:04 > 0:25:07The armadillo, too, is very competent in the water.
0:25:12 > 0:25:15Many others, such as burrowing rodents that might otherwise crop
0:25:15 > 0:25:17the grass of the plains,
0:25:17 > 0:25:22can't do so because they can't survive being flooded like this every year.
0:25:22 > 0:25:26The grass, however, grows tall and lives through even this hardship.
0:25:27 > 0:25:332,000 miles farther north still, water lies on the plains for many months on end,
0:25:33 > 0:25:37as snow on the prairies of North America.
0:25:38 > 0:25:42Here the temperature can drop to 46 degrees below zero centigrade.
0:25:42 > 0:25:47The resistant grass survives it but few animals can.
0:25:48 > 0:25:52The ground squirrels retreat to their burrows and go into a state of
0:25:52 > 0:25:53suspended animation.
0:25:53 > 0:25:58Their temperature falls and their breathing rate slows - they hibernate,
0:25:58 > 0:26:02using the absolute minimum of their body reserves accumulated
0:26:02 > 0:26:03during the summer.
0:26:14 > 0:26:18A cousin of the ground squirrel, another rodent called the prairie dog,
0:26:18 > 0:26:23does remain active, and during milder spells it ventures out onto the snow
0:26:23 > 0:26:25to nibble what leaves it can find.
0:26:28 > 0:26:33The prairie chicken, actually a grouse, is one of the few birds to stay on
0:26:33 > 0:26:36the winter prairies, for although there are no insects to be had now,
0:26:36 > 0:26:40it can survive on nothing but seeds and leaves.
0:26:43 > 0:26:46Things are happening, however, below ground.
0:26:49 > 0:26:52The pocket gopher is still hard at work.
0:26:54 > 0:26:58Its winter food is roots, and very nourishing they are,
0:26:58 > 0:27:01for many plants in autumn withdraw much of their substance from
0:27:01 > 0:27:05withering leaves and store it in their roots.
0:27:09 > 0:27:14The bison manages to survive even the coldest weather out on the prairie.
0:27:14 > 0:27:17Big animals are not as easily chilled as small ones,
0:27:17 > 0:27:20and the bison is the most massive animal in North America.
0:27:20 > 0:27:22A bull can weigh a tonne.
0:27:28 > 0:27:32The extreme temperatures have, in effect, put the grass into deep freeze,
0:27:32 > 0:27:36so that, although it's frozen solid, such nutriment as it contained
0:27:36 > 0:27:37is preserved.
0:27:37 > 0:27:41The bison, being so big, have no difficulty in sweeping away the snow
0:27:41 > 0:27:44and reaching the frozen tufts.
0:27:45 > 0:27:50Bison share the prairies with pronghorn antelope which, in winter,
0:27:50 > 0:27:53often visit areas that the bison have just cleared of snow.
0:27:53 > 0:27:56They are the swiftest animals in North America, capable of speeds
0:27:56 > 0:27:59of 50 mph at full stretch.
0:28:01 > 0:28:06Coyotes, a small relation of the wolf, have little chance of catching a young
0:28:06 > 0:28:07healthy pronghorn.
0:28:07 > 0:28:11But that doesn't mean they won't try, and by chasing, they can discover
0:28:11 > 0:28:14if there are any antelope in the group that are less than healthy
0:28:14 > 0:28:16and therefore catchable.
0:28:47 > 0:28:50Another joins the chase.
0:29:02 > 0:29:06The bitter cold and the shortage of food kills many animals at this time.
0:29:06 > 0:29:11For the coyotes, a carcass is precious, a mass of meat in an otherwise
0:29:11 > 0:29:12barren land.
0:29:12 > 0:29:15A pair has already taken possession of this dead elk.
0:29:16 > 0:29:19A third arrives. There will be trouble.
0:29:24 > 0:29:28They signal their threats with bristling fur, snarling lips
0:29:28 > 0:29:30but surprisingly little sound.
0:30:05 > 0:30:10As spring approaches, the temperature rises, even below ground,
0:30:10 > 0:30:13and the winter sleepers begin to awake.
0:30:16 > 0:30:21Rattlesnakes, forced to take shelter from the cold, frequently take over
0:30:21 > 0:30:25the deeper burrows made by prairie dogs and there, ten feet below ground,
0:30:25 > 0:30:29sit out the winter beyond the reach of the lethal frost.
0:30:29 > 0:30:34Sometimes as many as 200 or 300 will share the same hole.
0:30:34 > 0:30:39As the spring sun warms the air, so they too slowly come to life.
0:30:44 > 0:30:48The prairie chickens leave the tall grass country where they spent the winter
0:30:48 > 0:30:50and assemble on shorter turf,
0:30:50 > 0:30:53for they are about to start their spring dances.
0:30:53 > 0:30:55CHATTERING REPEATED CALLS
0:30:58 > 0:31:00LOW, BOOMING CALLS
0:31:14 > 0:31:18Each male stays on a small patch of ground that is his dancing stage,
0:31:18 > 0:31:23and there erects his feathery horns, inflates his wattles and starts
0:31:23 > 0:31:24his stamping dance.
0:31:24 > 0:31:29DRUMMING RHYTHM
0:32:13 > 0:32:17The prairie dogs live in such concentrations and such numbers
0:32:17 > 0:32:20that their patch of the prairie is called a town.
0:32:20 > 0:32:23They mated below ground back in February.
0:32:23 > 0:32:27The youngsters were born a month later and now, in the sunshine
0:32:27 > 0:32:30of early summer, they get their first view of the world.
0:32:54 > 0:32:56The bison, too, have their young.
0:32:56 > 0:32:59The thick woollen coat that protected them through the winter is now far
0:32:59 > 0:33:04too hot, and the animals begin to shed it in sheets and tatters.
0:33:12 > 0:33:16The bison, being such a big animal, has a long gestation period, nine months.
0:33:16 > 0:33:21So, soon after the young are born, courting starts again,
0:33:21 > 0:33:24and for the bulls that involves battling with rivals.
0:33:24 > 0:33:28These jousts, which can be very punishing and even end in death,
0:33:28 > 0:33:31establish a ranking among the bulls.
0:33:33 > 0:33:38The victors can then seek access to the cows, which is another problem.
0:34:11 > 0:34:15The bison herds have a particular liking for the grazing around
0:34:15 > 0:34:19the prairie dogs' towns, for the prairie dogs are good farmers.
0:34:19 > 0:34:23They deliberately cut down unpalatable plants and remove dead material,
0:34:23 > 0:34:27and their constant cropping means that the grass leaves around their burrows
0:34:27 > 0:34:30are all young and succulent, and the bison like that
0:34:30 > 0:34:34just as much as the prairie dogs do.
0:34:46 > 0:34:51The rattlesnakes also haunt the town, on the lookout for young prairie dogs.
0:34:51 > 0:34:56The shortness of the cropped turf makes it easy for the town sentinels
0:34:56 > 0:34:57to see approaching danger.
0:35:09 > 0:35:11What to do about it is another question.
0:35:29 > 0:35:32Bolting down a burrow is no defence against a rattlesnake.
0:35:32 > 0:35:35It will simply follow. The only thing to do is retreat
0:35:35 > 0:35:38and whistle a warning to the neighbours.
0:35:38 > 0:35:40HIGH-PITCHED CALL
0:35:46 > 0:35:51Bison are cattle. Like antelope and sheep, they are ruminants, dealing with
0:35:51 > 0:35:56the problem of digesting cellulose by regurgitating pellets of grass they graze
0:35:56 > 0:35:58and giving it all a second chew.
0:35:58 > 0:36:03They also maintain a digestive broth of bacteria in their huge stomachs.
0:36:03 > 0:36:07Only 150 years ago, they live in such numbers on the prairies
0:36:07 > 0:36:10that a herd could stretch from one horizon to another.
0:36:10 > 0:36:14How many there were altogether is uncertain. Thirty million is one
0:36:14 > 0:36:15of the lower estimates.
0:36:15 > 0:36:20That was a measure of the great fertility of these natural grasslands.
0:36:20 > 0:36:23Today, most of the prairie has been turned over to the raising of
0:36:23 > 0:36:25domesticated cattle for beef,
0:36:25 > 0:36:29or ploughed up to grow domesticated grass, wheat.
0:36:29 > 0:36:33By the beginning of this century, less than a thousand wild bison were left.
0:36:33 > 0:36:37But today, thanks to careful conservation, there are some
0:36:37 > 0:36:4035,000 living in reserves.
0:36:41 > 0:36:45The prairies receive comparatively little rain because they lie in the centre
0:36:45 > 0:36:49of a huge continent and the Rocky Mountains screen off the rain.
0:36:53 > 0:36:58Across the northern Pacific, the biggest continental mass of all, Eurasia,
0:36:58 > 0:37:02also contains a heartland where relatively little rain falls -
0:37:02 > 0:37:06the grass-covered steppes of Russia and Eastern Europe.
0:37:06 > 0:37:10And here another grass feeder survives that once formed vast herds,
0:37:10 > 0:37:13an extraordinary antelope, the saiga.
0:37:17 > 0:37:22Its huge nose contains, internally, a convoluted arrangement of passages
0:37:22 > 0:37:26lined with mucous glands that apparently serve to warm and moisten
0:37:26 > 0:37:29the dry air of the steppes and filter out the dust.
0:37:38 > 0:37:41The steppes are not as fertile as the prairie
0:37:41 > 0:37:44and are ravaged by regular and disastrous droughts.
0:37:44 > 0:37:48But the saiga seem to have adapted to this and have a quite extraordinary
0:37:48 > 0:37:52rate of reproduction that enables them to recover their numbers after
0:37:52 > 0:37:54such a catastrophe with great speed.
0:37:54 > 0:37:59The females, when they are a mere four months old and only half-grown,
0:37:59 > 0:38:02mate and produce their first calf.
0:38:02 > 0:38:05After it is weaned, they grow rapidly, so that by the beginning of the next
0:38:05 > 0:38:09breeding season, they are full-size, and then they quickly breed again,
0:38:09 > 0:38:13and this time three quarters of them will produce twins.
0:38:14 > 0:38:17These animals, too, were hunted close to extinction,
0:38:17 > 0:38:21but when people realised that these natural inhabitants of the steppes
0:38:21 > 0:38:24could turn their grass into meat much more efficiently than any
0:38:24 > 0:38:27domesticated animal, indiscriminate hunting was stopped and now
0:38:27 > 0:38:30there are over two million in the Soviet Union.
0:38:33 > 0:38:38Travel south west from the steppes of central Eurasia, the greatest of all temperate grasslands,
0:38:38 > 0:38:42across territory where there is so little rain that not even grass can grow,
0:38:42 > 0:38:46and you come to the greatest of all tropical grasslands - in Africa.
0:38:54 > 0:38:59Here there is enough rain to create rivers and waterholes, so in the moist soils
0:38:59 > 0:39:03around them and on rocky outcrops, a few trees manage to grow.
0:39:05 > 0:39:09In the more regularly watered parts, thorn trees stand, distanced from
0:39:09 > 0:39:13one another, their widespread root systems managing to collect just
0:39:13 > 0:39:15enough water to sustain them.
0:39:15 > 0:39:18Elsewhere, there is only enough rainfall for grass.
0:39:20 > 0:39:23But young trees are threatened not only by drought but by fire.
0:39:23 > 0:39:27It sweeps rapidly over the plains, killing the tree seedlings
0:39:27 > 0:39:30but leaving the growing buds of the grasses, close to the ground,
0:39:30 > 0:39:35quite unharmed, and green shoots of grass appear within days.
0:39:35 > 0:39:39So the fire, which starts so easily in withered grass stems,
0:39:39 > 0:39:42is one of the factors that keeps the country open, for grass.
0:39:46 > 0:39:52The grasslands of Africa stretch in an immense and almost continuous arc
0:39:52 > 0:39:56from the Sahara in the north down through East Africa
0:39:56 > 0:40:01and on to the great game plains of Southern Africa and the Cape.
0:40:01 > 0:40:05During the eight million years or so of recent history, they've varied
0:40:05 > 0:40:07quite a lot in their extent.
0:40:07 > 0:40:11At the moment, they are not as big as they have been in the past.
0:40:11 > 0:40:15But during this period of time, the grasslands have developed,
0:40:15 > 0:40:19and as they have done so, the animals that lived on them have evolved,
0:40:19 > 0:40:23the nature of one reacting on the nature of the other.
0:40:23 > 0:40:28Today, there's a greater variety and a bigger concentration of grass-living
0:40:28 > 0:40:32creatures on these African plains than anywhere else in the world.
0:40:45 > 0:40:50Different lengths of neck, different sets of teeth, different appetites,
0:40:50 > 0:40:54such variety means that almost every growing leaf, short or long,
0:40:54 > 0:40:59of every kind of plains plant, is eaten by something.
0:41:10 > 0:41:14This vast tonnage of meat on the hoof has led, inevitably,
0:41:14 > 0:41:17to the appearance of an abundance of meat-eaters.
0:41:19 > 0:41:23And they too are varied, to exploit the variety of meat available.
0:41:24 > 0:41:27The serval seeks mice.
0:41:43 > 0:41:47The lions, hunting in teams, butcher wildebeest and zebra.
0:41:51 > 0:41:53Hunting dogs do the same.
0:41:56 > 0:42:00The cheetah goes for animals its own size, gazelle.
0:42:28 > 0:42:32Before grass spread over the plains, the ancestors of grazing antelopes
0:42:32 > 0:42:36must have lived in bush country, rather as dik-dik do today.
0:42:36 > 0:42:39The bushes don't produce many leaves, but they are highly nutritious
0:42:39 > 0:42:43and there are enough in an acre or so to sustain a pair of these tiny antelope.
0:42:43 > 0:42:48So the dik-dik mate for life and are permanent residents of their territory.
0:42:48 > 0:42:51They know it intimately and have their own trails and hiding places,
0:42:51 > 0:42:54and they mark out its frontiers with special notices.
0:42:56 > 0:43:00The ritual is nearly always the same. The female visits the midden first.
0:43:01 > 0:43:05The buck is stimulated to follow and habitually goes through exactly the
0:43:05 > 0:43:10same sequence of smelling, urinating, scratching and dunging.
0:43:30 > 0:43:33When the ceremony is over, the buck marks the nearby bushes
0:43:33 > 0:43:38with a sticky perfumed wax from a gland just below his eyes.
0:43:41 > 0:43:45Impala, however, live in more open country and feed not only
0:43:45 > 0:43:47on bushes but on grass.
0:43:47 > 0:43:51Here they can't hide and they find their safety in numbers.
0:43:51 > 0:43:56With so many sharp eyes and acute ears, it's very difficult for a hunter
0:43:56 > 0:43:58to approach them undetected.
0:43:58 > 0:44:02But such a lifestyle obviously makes it impossible for the animals to live
0:44:02 > 0:44:05in permanent pairs on their own territory as the dik-dik do.
0:44:05 > 0:44:09Instead, the males and females form separate herds.
0:44:09 > 0:44:12The bucks then battle among themselves.
0:44:12 > 0:44:17Those that win will leave the bachelor herds and set up individual territories.
0:44:27 > 0:44:31When the victors have established themselves, the does visit them,
0:44:31 > 0:44:32one after the other.
0:44:32 > 0:44:36It is a very exhausting business for the bucks, repeatedly mating
0:44:36 > 0:44:38and fighting off challengers.
0:45:00 > 0:45:04After about three months of this, the once dominant bucks are worn out.
0:45:04 > 0:45:09They yield to other, fresher males and return to the bachelor herd to recover.
0:45:14 > 0:45:17Wildebeest live on grass alone.
0:45:17 > 0:45:21But the patchy distribution of rain over the African plains
0:45:21 > 0:45:25means that they can't stay permanently in the same place.
0:45:25 > 0:45:29They quickly exhaust pasture on one patch of the plains and must move on
0:45:29 > 0:45:33to an area where rain has recently fallen and the grass is springing again.
0:45:33 > 0:45:38So the wildebeest are constantly on the move and their social
0:45:38 > 0:45:42arrangements have to be different from the dik-dik and impala.
0:45:42 > 0:45:46During the short breeding season, the males set up small territories
0:45:46 > 0:45:48along the migration routes.
0:45:48 > 0:45:52They advertise their pretensions by prancing around and snorting,
0:45:52 > 0:45:57seeking showy contests with rivals to demonstrate their virility
0:45:57 > 0:45:59to passing females.
0:46:08 > 0:46:11The problem then is to keep the females in their territory
0:46:11 > 0:46:15and prevent them from moving on to a rival's patch.
0:46:32 > 0:46:37The young calves, born only a few months before, adopt very early
0:46:37 > 0:46:42the jaunty, slightly crazy way of carrying on affected by their fathers.
0:47:01 > 0:47:05Within two weeks, the majority of the females are mated.
0:47:11 > 0:47:16And then, suddenly, almost overnight, the whole herd, hundreds of thousands
0:47:16 > 0:47:21strong, vanishes. They've gone in search of fresh pastures.
0:47:22 > 0:47:27The varying growth of the grass over the year affects the lives of people
0:47:27 > 0:47:28as well as animals.
0:47:28 > 0:47:31In the eastern part of the grasslands, in the Sudan,
0:47:31 > 0:47:35the people keep herds of semi-domesticated cattle.
0:47:35 > 0:47:38These are their pride and their wealth and their livelihood.
0:47:41 > 0:47:45At night they pen them in enclosures made from uprooted thorn bush,
0:47:45 > 0:47:47to keep out lion.
0:47:51 > 0:47:56The people can't settle in permanent villages, for their cattle exhaust the
0:47:56 > 0:48:01meagre pasture, just as wildebeest do, so periodically they too have to move.
0:48:01 > 0:48:05It is a nice question as to whether the animals are being driven by the people
0:48:05 > 0:48:10or whether the people are, willy-nilly, following the herds.
0:48:13 > 0:48:18Many people in the Sudan regard not only their semi-wild cattle
0:48:18 > 0:48:20as their own personal property,
0:48:20 > 0:48:25but also the fully wild game that regularly passes through their territory.
0:48:26 > 0:48:31The white-eared kob, the males black and white, the females a delicate tan,
0:48:31 > 0:48:34live in the southern Sudan.
0:48:34 > 0:48:37Here, during the rainy season, the does give birth to their young.
0:48:39 > 0:48:44As the rains end and the plains begin to dry out, the herds begin to move north,
0:48:44 > 0:48:48following the new flush of grass that springs from the receding waters.
0:48:51 > 0:48:53As they go, the herds are funnelled together
0:48:53 > 0:48:59by two rivers that flow closer and closer to one another until eventually they join
0:48:59 > 0:49:03and the kob have no alternative but to attempt to cross it
0:49:03 > 0:49:06and here the Merle people await them.
0:49:11 > 0:49:15For the Merle, this is an annual bonanza and a great celebration.
0:49:15 > 0:49:19Families have travelled from all over the tribal territory to take part
0:49:19 > 0:49:22and to claim their share in their harvest of meat.
0:49:22 > 0:49:26If all goes well, there will be great feasting. But that's by no means a certainty.
0:49:26 > 0:49:30If the herds don't appear, there will be real hunger in the tribe.
0:49:39 > 0:49:43In the early morning, the hunters cross the river to set up their ambush.
0:49:43 > 0:49:46There's no guarantee that the kob will come this way.
0:49:46 > 0:49:49If the rivers are low, they may well try to cross on a much broader
0:49:49 > 0:49:51front upstream.
0:50:02 > 0:50:04SHOUTING
0:50:22 > 0:50:27For the kob now, there is no going back. They have to cross.
0:50:42 > 0:50:43SHOUTING CONTINUES
0:50:53 > 0:50:58Day after day, the kob that have arrived at this crossing attempt
0:50:58 > 0:50:59to run the gauntlet.
0:51:43 > 0:51:47It takes several weeks for the whole migration to pass through.
0:51:48 > 0:51:54A million kob will make the journey. 5,000 of them will be killed.
0:51:54 > 0:51:58The Merle not only feast well now, they sun-dry the meat so that
0:51:58 > 0:52:01the families will have full stomachs for many months to come.
0:52:12 > 0:52:16In spite of the Merle's ambush, the vast majority of the kob reach
0:52:16 > 0:52:19the northern grasslands.
0:52:19 > 0:52:23There they will find enough food to sustain them throughout the critical
0:52:23 > 0:52:24months of the dry season.
0:52:24 > 0:52:28And there, too, they mate, so that next year herds will reappear to make
0:52:28 > 0:52:33the river crossing and provide the Merle, once more, with meat.
0:52:34 > 0:52:37And the grass, too, will spring again,
0:52:37 > 0:52:43this remarkable plant that can survive intense grazing and burning and flooding.
0:52:43 > 0:52:46The one thing it can't tolerate is drought.
0:52:46 > 0:52:52If there is just a little less rain, then its leaves wither, its roots shrivel
0:52:52 > 0:52:56and can no longer hold the soil together, so that the wind can catch it
0:52:56 > 0:52:59and blow away the small nutritious particles.
0:52:59 > 0:53:04And then it's reduced to little more than sand and the land becomes a desert.
0:53:04 > 0:53:08And it's to deserts that we're going in the next programme.