Seas of Grass The Living Planet

These beautiful flowers belong to one of the most successful,

the most widespread and the commonest of plants.

There are about 10,000 species in this one family,

and they claim over a quarter of all the vegetated land on Earth.

They are pollinated by the wind, they need far less water than most trees,

and they can survive both burning and freezing. They are the grasses.

These tough, persistent plants continue to grow even when they're trimmed

day after day by grazing teeth.

They are able to withstand all this rough treatment

because the point from which a grass leaf grows is at its base

close to the ground and is permanently active.

So grass provides a continuous banquet for creatures big and small.

Down among the tangled grass stems live not only creatures that eat grass

but others that feed on the grass-eaters.

Lizards snap up small insects and mantis munch grasshoppers.

Spiders tackle almost any creature that moves

and dung beetles clear up the droppings from above.

Among the most industrious of these tiny labourers are the termites.

On many tropical grasslands, they flourish in such numbers that,

one way or another, they consume more of the grass

than big creatures like antelope, cows or kangaroo.

In the savannas of Brazil, there are more termite mounds on an acre

than anywhere else in the world. And termites are highly nutritious -

so much so that the giant anteater is able to exist by feeding on them

and nothing else whatever.

This creature has very poor eyesight and very poor hearing,

and finds its way around mostly by smell, so, as long as I keep

downwind of it, there's no reason

why it should be particularly disturbed by my presence.

You might think that that would make it very vulnerable to enemies.

The fact is, out on the savannas here, it's got very few enemies.

The only things that might attack it are a jaguar or a puma, or if it was a baby,

a savannah fox.

And it has a very good defence against such creatures.

Those huge forelegs, with enormous muscles on them and gigantic claws,

are quite powerful enough to rip the stomach from a puma or a jaguar.

It was always thought that those legs

are actually for ripping open termite hills,

and they may be used to some extent for that purpose.

But it seems more likely now that they are primarily defensive weapons,

because when they actually come to feed,

this creature doesn't do so much of a sweep with its front claws

as to use them very, very carefully to open the exit tunnels in the termite hills.

Once it has done that, it pokes its nose into the tunnel entrance

and flicks out its 20-inch-long tongue, coated with sticky mucus,

and picks off the worker termites clinging to the tunnel walls.

After about half a minute, before the soldier termites, which have powerful bites,

can rally to the defence of the opened tunnel, the anteater moves on.

It is a wanderer, always on the move, sleeping at night out in the open,

blanketed against the cold by its huge hairy tail.

Having no permanent den, the female carries her youngster with her,

piggyback.

Other termite hunters live on the surface of the mounds themselves.

Beetle larvae lurk in burrows and lure flying ants and other insects to them

by the luminous glow of their heads.

Sometimes the termite mounds are attacked at their very foundations.

This is the biggest insect-eater on Earth, the giant armadillo,

a massive animal that weighs over a hundredweight.

There are few more powerful diggers.

It's no finicky feeder like the giant anteater,

but rips its way through the ground into the heart of the termite hill.

With its defences breached, the termite colony is very vulnerable.

This mouse, oxymicterus, has a particular fondness for termites

and regularly follows in the wake of the giant armadillo.

But the termites' biggest enemies are even smaller.

Carnivorous ants regularly raid the colonies, carrying off the helpless,

pallid termite larvae.

The defenders of the colony, the soldier termites, engage the enemy ants.

These termite warriors have jaws so specialised for fighting

that they can't feed for themselves and have to be tended by the workers.

Each species is armed in its own way.

Some have short nippers, some sharp shears.

Others have blades that strike outwards and others nozzles on their forehead

through which they squirt a sticky poison spray.

Other ants are vegetarians, like the termites,

and use their jaws to demolish the living grass plants, scissoring up the leaves,

sawing through the stems and carrying off the plant piecemeal.

Grass consists largely of cellulose and that is a very difficult

substance to digest.

Termites do it with the help of bacteria in their gut.

The grass-cutting ants have another and quite extraordinary method

of making its nutriment digestible.

Laboriously, they haul the pieces of grass back to their nest,

which may be as much as 100 yards away and have several hundred

small entrances.

Inside an entrance, a tunnel leads down into a vast labyrinth of corridors

that may extend for 80 or 90 feet in a horizontal direction

and lead to as many as 2,000 interlinked chambers.

Such a nest may contain as many as 20 million ants.

The workers carry their cuttings deeper and deeper into the nest.

And here, 15 feet below the surface of the ground, in special chambers,

they feed the grass to a fungus.

This fungus forms crumbly white lumps and grows nowhere else

but in these nests.

Carefully, the ant gardeners clean every fragment of grass.

Meticulously, they remove every spore of any other fungus

that might grow down here if it got the chance. Weeds, as you might say.

The waxy skin that covers the leaf surface is stripped away

and then the pieces are cut up into even smaller fragments.

The gardeners push the prepared morsels of grass into the mass

of the fungus.

The fungus digests it, cellulose and all, and grows,

and the ants then feed on the fungus, which, unlike grass, they can digest.

The ants tend their gardens with great care.

Dead pieces of fungus and coarse, unsuitable fragments of leaves

are carefully removed and carried away.

With unflagging energy, porter lines of ants carry the waste down

the long corridors to the lowest chambers of all, 20 feet below ground,

that serve as the colony's refuse tips.

These are not only rubbish dumps, but cemeteries,

for here they also bring the bodies of dead workers.

Dawn on the grasslands of Brazil, the campo.

It's still chilly and the dew lies heavily.

But the rising sun will soon dry out the pasturage and rouse

the daytime inhabitants.

The grassland birds have no trees from which to sing. Some make do

with grass stems.

Others, like the scissor-tailed flycatcher, proclaim their territorial rights by visual

display, flying incessantly and conspicuously above their chosen plots.

The seriama, a catcher of snakes and insects, surveys the day's prospects

from the top of a termite hill.

The tapir has browsed throughout the night, but now, as the sun rises,

it makes its way back to the forest that grows in the moist ground

beside the river, for it greatly prefers the shady obscurity down there to

the hot conspicuousness of the daytime plains.

On the other hand, the savannah deer has slept all night and only begins

to graze when it is light.

It prefers to be able to see its enemies.

The armadillo is no grass-eater. It's looking for insects, roots and

birds' eggs, and even a lizard or a small snake.

As the day warms up, reptiles become active.

The tegu lizard is sufficiently powerful to be able to take on all-comers.

Just what it likes, and no small bird, no matter how aggressive,

is able to repel a hungry tegu.

Eggs on the ground are very much at risk to creatures like this.

But where else can you put them? There are few trees on the grassland.

But there are termite hills.

The flicker is a kind of woodpecker and drills into termite hills

just as efficiently as its cousins do into tree trunks.

And when the flicker has finished with its hole, kestrels often take it over.

The male has a lizard.

Softly, he summons the female, who is incubating her eggs in the hole beneath.

The burrowing owls nest in holes in the ground,

taking over ones that have been abandoned by armadillos

or even digging them for themselves.

The male perches on a termite hill on guard,

for the chicks are about to emerge.

Danger - a harrier.

Now it's safe once more.

As long as the chicks can't fly, they're in danger from armadillos,

tegus and other predators.

So it is very important that they get their flight feathers as quickly as possible,

and already, only a couple of weeks after hatching,

they are showing through the down.

Out in the fresh air, there is space to preen and a chance to sunbathe.

Once more there is an alarm... It's the spur-winged plovers.

The plovers are quarrelsome birds.

Even though each pair has established its claims over a patch of grassland,

the birds continually dispute with their neighbours.

Rivals display aggressively, running along the frontier between

their territories and dive-bombing one another.

CONSTANT SQUAWKING

Their nest is probably as safe as it would be even if they remained sitting

on it, for their eggs are marvellously camouflaged and very difficult to see.

The adult tinamou, on the other hand, is just as well-disguised as

the plover's eggs. Its strategy is to stay put and freeze.

Just as well, for its eggs are very conspicuous, a brilliant shiny purple.

One ground-nester on the open plains, however, fears nothing.

It's big enough and strong enough to take on even an armadillo or a tegu.

The rhea, the South American ostrich.

It's the male that makes the nest and incubates the eggs.

And he is polygamous, with half a dozen or so females, all of whom

will lay in his nest.

But with so many contributors, the compiling of a clutch can be

a tricky business.

Sometimes several females, each with an egg ready to be laid,

will turn up at the same time

and there's some confusion as to who's going to have the first turn.

He doesn't seem to want them to lay in the main clutch.

Perhaps he's worried about them treading on his eggs,

so they'll have to sit outside.

The first female goes down.

Once laid, the egg has to be brought in to join the rest of the clutch

if he is to incubate it properly.

Another female settles down to lay.

And another egg joins his collection.

His final clutch may be huge, up to 50 or so.

They've come from many different females and been laid over a period

of eight days, but all hatch together.

The young pipe to one another while they're still inside their shells,

stimulating the eggs that are a bit behind to speed up their development.

The advantage of hatching simultaneously is that the young,

soon after they emerge,

can go off and feed together under Father's watchful eye.

The 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.

The maned wolf will certainly take one if it gets the chance.

It hunts alone, never forming packs, seldom even seen with its mate.

It maintains contact with others of its kind by an occasional bark

and by leaving its scent on bushes and termite mounds, spraying its urine

high up so that the wind will pick up the smell and broadcast it.

This wolf's tastes are, oddly, strongly vegetarian.

Fruit forms a large part of its diet.

But it certainly takes birds if it can, and the tinamou is particularly

vulnerable, for it's almost flightless.

Trees don't grow on the open plains of Argentina and Brazil because,

for much of the year, there is too little rain.

During the dry season, the shallow lakes are reduced

to stretches of baked mud.

Capybara, giant semi-aquatic guinea pigs, crowd into the few

shrinking pools that remain.

Cayman are compelled to spend much of their time out of water,

and turtles jostle for places along the contracting margins with the capybara.

But during April, the clouds begin to gather and in June they burst.

THUNDER AND RAIN

It's a testing time for many of the grassland creatures.

2,000 miles north of the Brazilian campo, the grasslands of Venezuela,

the Ilanos, flood over great areas, for the ground is full of clay

and holds the water.

For some, this is exactly what they want.

The Ilanos are flooded like this for almost half the year.

That's all right for those capybara.

They are almost as much at home in the water as they are on land.

Some creatures, even such an unlikely-looking swimmer as

the giant anteater, manage to struggle to dry ground.

The armadillo, too, is very competent in the water.

Many others, such as burrowing rodents that might otherwise crop

the grass of the plains,

can't do so because they can't survive being flooded like this every year.

The grass, however, grows tall and lives through even this hardship.

2,000 miles farther north still, water lies on the plains for many months on end,

as snow on the prairies of North America.

Here the temperature can drop to 46 degrees below zero centigrade.

The resistant grass survives it but few animals can.

The ground squirrels retreat to their burrows and go into a state of

suspended animation.

Their temperature falls and their breathing rate slows - they hibernate,

using the absolute minimum of their body reserves accumulated

during the summer.

A 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 can find.

The 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.

Things are happening, however, below ground.

The pocket gopher is still hard at work.

Its winter food is roots, and very nourishing they are,

for many plants in autumn withdraw much of their substance from

withering leaves and store it in their roots.

The bison manages to survive even the coldest weather out on the prairie.

Big animals are not as easily chilled as small ones,

and the bison is the most massive animal in North America.

A bull can weigh a tonne.

The 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.

The bison, being so big, have no difficulty in sweeping away the snow

and reaching the frozen tufts.

Bison share the prairies with pronghorn antelope which, in winter,

often visit areas that the bison have just cleared of snow.

They are the swiftest animals in North America, capable of speeds

of 50 mph at full stretch.

Coyotes, a small relation of the wolf, have little chance of catching a young

healthy pronghorn.

But that doesn't mean they won't try, and by chasing, they can discover

if there are any antelope in the group that are less than healthy

and therefore catchable.

Another joins the chase.

The bitter cold and the shortage of food kills many animals at this time.

For the coyotes, a carcass is precious, a mass of meat in an otherwise

barren land.

A pair has already taken possession of this dead elk.

A third arrives. There will be trouble.

They signal their threats with bristling fur, snarling lips

but surprisingly little sound.

As spring approaches, the temperature rises, even below ground,

and the winter sleepers begin to awake.

Rattlesnakes, forced to take shelter from the cold, frequently take over

the deeper burrows made by prairie dogs and there, ten feet below ground,

sit out the winter beyond the reach of the lethal frost.

Sometimes as many as 200 or 300 will share the same hole.

As the spring sun warms the air, so they too slowly come to life.

The prairie chickens leave the tall grass country where they spent the winter

and assemble on shorter turf,

for they are about to start their spring dances.

CHATTERING REPEATED CALLS

LOW, BOOMING CALLS

Each male stays on a small patch of ground that is his dancing stage,

and there erects his feathery horns, inflates his wattles and starts

his stamping dance.

DRUMMING RHYTHM

The prairie dogs live in such concentrations and such numbers

that their patch of the prairie is called a town.

They mated below ground back in February.

The youngsters were born a month later and now, in the sunshine

of early summer, they get their first view of the world.

The bison, too, have their young.

The thick woollen coat that protected them through the winter is now far

too hot, and the animals begin to shed it in sheets and tatters.

The bison, being such a big animal, has a long gestation period, nine months.

So, soon after the young are born, courting starts again,

and for the bulls that involves battling with rivals.

These jousts, which can be very punishing and even end in death,

establish a ranking among the bulls.

The victors can then seek access to the cows, which is another problem.

The bison herds have a particular liking for the grazing around

the prairie dogs' towns, for the prairie dogs are good farmers.

They deliberately cut down unpalatable plants and remove dead material,

and their constant cropping means that the grass leaves around their burrows

are all young and succulent, and the bison like that

just as much as the prairie dogs do.

The rattlesnakes also haunt the town, on the lookout for young prairie dogs.

The shortness of the cropped turf makes it easy for the town sentinels

to see approaching danger.

What to do about it is another question.

Bolting down a burrow is no defence against a rattlesnake.

It will simply follow. The only thing to do is retreat

and whistle a warning to the neighbours.

HIGH-PITCHED CALL

Bison are cattle. Like antelope and sheep, they are ruminants, dealing with

the problem of digesting cellulose by regurgitating pellets of grass they graze

and giving it all a second chew.

They also maintain a digestive broth of bacteria in their huge stomachs.

Only 150 years ago, they live in such numbers on the prairies

that a herd could stretch from one horizon to another.

How many there were altogether is uncertain. Thirty million is one

of the lower estimates.

That was a measure of the great fertility of these natural grasslands.

Today, most of the prairie has been turned over to the raising of

domesticated cattle for beef,

or ploughed up to grow domesticated grass, wheat.

By the beginning of this century, less than a thousand wild bison were left.

But today, thanks to careful conservation, there are some

35,000 living in reserves.

The prairies receive comparatively little rain because they lie in the centre

of a huge continent and the Rocky Mountains screen off the rain.

Across the northern Pacific, the biggest continental mass of all, Eurasia,

also contains a heartland where relatively little rain falls -

the grass-covered steppes of Russia and Eastern Europe.

And here another grass feeder survives that once formed vast herds,

an extraordinary antelope, the saiga.

Its huge nose contains, internally, a convoluted arrangement of passages

lined with mucous glands that apparently serve to warm and moisten

the dry air of the steppes and filter out the dust.

The steppes are not as fertile as the prairie

and are ravaged by regular and disastrous droughts.

But the saiga seem to have adapted to this and have a quite extraordinary

rate of reproduction that enables them to recover their numbers after

such a catastrophe with great speed.

The females, when they are a mere four months old and only half-grown,

mate and produce their first calf.

After it is weaned, they grow rapidly, so that by the beginning of the next

breeding season, they are full-size, and then they quickly breed again,

and this time three quarters of them will produce twins.

These animals, too, were hunted close to extinction,

but when people realised that these natural inhabitants of the steppes

could turn their grass into meat much more efficiently than any

domesticated animal, indiscriminate hunting was stopped and now

there are over two million in the Soviet Union.

Travel south west from the steppes of central Eurasia, the greatest of all temperate grasslands,

across territory where there is so little rain that not even grass can grow,

and you come to the greatest of all tropical grasslands - in Africa.

Here there is enough rain to create rivers and waterholes, so in the moist soils

around them and on rocky outcrops, a few trees manage to grow.

In the more regularly watered parts, thorn trees stand, distanced from

one another, their widespread root systems managing to collect just

enough water to sustain them.

Elsewhere, there is only enough rainfall for grass.

But young trees are threatened not only by drought but by fire.

It sweeps rapidly over the plains, killing the tree seedlings

but leaving the growing buds of the grasses, close to the ground,

quite unharmed, and green shoots of grass appear within days.

So the fire, which starts so easily in withered grass stems,

is one of the factors that keeps the country open, for grass.

The grasslands of Africa stretch in an immense and almost continuous arc

from the Sahara in the north down through East Africa

and on to the great game plains of Southern Africa and the Cape.

During the eight million years or so of recent history, they've varied

quite a lot in their extent.

At the moment, they are not as big as they have been in the past.

But during this period of time, the grasslands have developed,

and as they have done so, the animals that lived on them have evolved,

the nature of one reacting on the nature of the other.

Today, there's a greater variety and a bigger concentration of grass-living

creatures on these African plains than anywhere else in the world.

Different lengths of neck, different sets of teeth, different appetites,

such variety means that almost every growing leaf, short or long,

of every kind of plains plant, is eaten by something.

This vast tonnage of meat on the hoof has led, inevitably,

to the appearance of an abundance of meat-eaters.

And they too are varied, to exploit the variety of meat available.

The serval seeks mice.

The lions, hunting in teams, butcher wildebeest and zebra.

Hunting dogs do the same.

The cheetah goes for animals its own size, gazelle.

Before grass spread over the plains, the ancestors of grazing antelopes

must have lived in bush country, rather as dik-dik do today.

The bushes don't produce many leaves, but they are highly nutritious

and there are enough in an acre or so to sustain a pair of these tiny antelope.

So the dik-dik mate for life and are permanent residents of their territory.

They know it intimately and have their own trails and hiding places,

and they mark out its frontiers with special notices.

The ritual is nearly always the same. The female visits the midden first.

The buck is stimulated to follow and habitually goes through exactly the

same sequence of smelling, urinating, scratching and dunging.

When the ceremony is over, the buck marks the nearby bushes

with a sticky perfumed wax from a gland just below his eyes.

Impala, however, live in more open country and feed not only

on bushes but on grass.

Here they can't hide and they find their safety in numbers.

With so many sharp eyes and acute ears, it's very difficult for a hunter

to approach them undetected.

But such a lifestyle obviously makes it impossible for the animals to live

in permanent pairs on their own territory as the dik-dik do.

Instead, the males and females form separate herds.

The bucks then battle among themselves.

Those that win will leave the bachelor herds and set up individual territories.

When the victors have established themselves, the does visit them,

one after the other.

It is a very exhausting business for the bucks, repeatedly mating

and fighting off challengers.

After about three months of this, the once dominant bucks are worn out.

They yield to other, fresher males and return to the bachelor herd to recover.

Wildebeest live on grass alone.

But the patchy distribution of rain over the African plains

means that they can't stay permanently in the same place.

They 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.

So the wildebeest are constantly on the move and their social

arrangements have to be different from the dik-dik and impala.

During the short breeding season, the males set up small territories

along the migration routes.

They advertise their pretensions by prancing around and snorting,

seeking showy contests with rivals to demonstrate their virility

to passing females.

The problem then is to keep the females in their territory

and prevent them from moving on to a rival's patch.

The young calves, born only a few months before, adopt very early

the jaunty, slightly crazy way of carrying on affected by their fathers.

Within two weeks, the majority of the females are mated.

And then, suddenly, almost overnight, the whole herd, hundreds of thousands

strong, vanishes. They've gone in search of fresh pastures.

The varying growth of the grass over the year affects the lives of people

as well as animals.

In the eastern part of the grasslands, in the Sudan,

the people keep herds of semi-domesticated cattle.

These are their pride and their wealth and their livelihood.

At night they pen them in enclosures made from uprooted thorn bush,

to keep out lion.

The people can't settle in permanent villages, for their cattle exhaust the

meagre pasture, just as wildebeest do, so periodically they too have to move.

It is a nice question as to whether the animals are being driven by the people

or whether the people are, willy-nilly, following the herds.

Many 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.

The white-eared kob, the males black and white, the females a delicate tan,

live in the southern Sudan.

Here, during the rainy season, the does give birth to their young.

As 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.

As they go, the herds are funnelled together

by two rivers that flow closer and closer to one another until eventually they join

and the kob have no alternative but to attempt to cross it

and here the Merle people await them.

For the Merle, this is an annual bonanza and a great celebration.

Families have travelled from all over the tribal territory to take part

and to claim their share in their harvest of meat.

If all goes well, there will be great feasting. But that's by no means a certainty.

If the herds don't appear, there will be real hunger in the tribe.

In the early morning, the hunters cross the river to set up their ambush.

There's no guarantee that the kob will come this way.

If the rivers are low, they may well try to cross on a much broader

front upstream.

SHOUTING

For the kob now, there is no going back. They have to cross.

SHOUTING CONTINUES

Day after day, the kob that have arrived at this crossing attempt

to run the gauntlet.

It takes several weeks for the whole migration to pass through.

A million kob will make the journey. 5,000 of them will be killed.

The Merle not only feast well now, they sun-dry the meat so that

the families will have full stomachs for many months to come.

In spite of the Merle's ambush, the vast majority of the kob reach

the northern grasslands.

There they will find enough food to sustain them throughout the critical

months of the dry season.

And there, too, they mate, so that next year herds will reappear to make

the river crossing and provide the Merle, once more, with meat.

And the grass, too, will spring again,

this remarkable plant that can survive intense grazing and burning and flooding.

The one thing it can't tolerate is drought.

If there is 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.

And then it's reduced to little more than sand and the land becomes a desert.

And it's to deserts that we're going in the next programme.