The Secret of the Savannah Secrets of our Living Planet

Ten million species live on planet Earth.

Each one is remarkable.

But none can survive on its own.

All life depends upon connections...

..unexpected, invariably complex,

beautiful relationships between millions of plants and animals.

This time, in our grasslands,

I want to show you why these antelope need these rhino...

..why this lone wolf...

needs an ant...

SNARLS

..and the incredible secret that lies buried beneath them all.

Connections like these create the planet's great ecosystems.

They're vital for all life.

I want to show you our world as you've never seen it before.

Central Kenya...

..and this is whistling acacia grassland.

The whistling actually comes from the breeze

blowing across the holes in these hollow galls...

..and they're home to one of the grasslands' most intriguing creatures.

This lizard is the aptly named dwarf gecko,

and this one has laid a couple of eggs

down here in this gall on the tree.

The perfect place for a nest, you might think.

But this tiny lizard can only safely lay its eggs here

thanks to one of Africa's largest, most iconic and bizarre animals,

the giraffe.

The story of why the gecko needs the giraffe is wonderful,

and it will take us on a journey across the world,

to some of our most breathtaking grasslands.

They are habitats which occupy a quarter of the land surface of our planet.

They support some of our most spectacular wildlife...

and yet grasslands lack one of the basic ingredients for life...

..a truly precious element.

It's this -

nitrogen,

a colourless, tasteless gas.

It's only when we chill it down to 196 degrees below zero

that we can actually see it.

I can tell you

that almost everything that happens out here in this grassland ecosystem

is governed by a craving for this rare resource.

In fact, I'd go so far as to say that grasslands can only function

because they can cope so ingeniously with so little of it.

So, for once, perhaps this will make the ecologist's job a little easier,

because to understand how grasslands work,

all we need to do is follow the nitrogen.

Australia.

The grasslands here have some of the lowest levels of nitrogen on the planet,

which makes the local wildlife perfect for demonstrating why it's so important.

Nitrogen is the magic ingredient.

When you add it to carbohydrate, you get protein.

And protein is what you need to make living tissue.

Protein is the building block for life, all life.

A baby eastern grey kangaroo.

When he was born, he weighed less than a one-pence piece.

His dad, on the other hand, is one of the heaviest marsupials in the world.

Which means that joey has a lot of growing up to do.

In fact, from birth to adulthood,

he'll increase his body size by 100,000 times.

And all of that will be built with protein.

And you can't make protein without nitrogen.

Right now, he gets most of his protein from his mother,

and she gets all of her protein from a diet of grass.

At the moment, these kangaroos are just hanging out,

and they look like a typical population of kangaroos,

but I can assure you they're not.

Because this is not your typical Australian grassland.

It's Anglesea Golf Club near Melbourne.

Kangaroos were here when the golf course was built 60 years ago,

but since then, their population has boomed.

At a recent count, there were 359 of them.

That's nearly 20 for each hole.

And the secret of their success is down to these immaculate fairways.

This grass is so green and so lush because it's had something added to it.

This.

Nitrogen fertiliser.

And I know it's a product of the industrial revolution

that's therefore led to all of this lushness,

but it certainly proves a point - the power of nitrogen in a grassland.

It's added once a month.

It seeps into the soil, is quickly taken up by the roots

and then converted into proteins for stronger, healthier grass.

Great for golf but perfect for the joey.

The extra protein means that he can grow faster,

become healthier and live longer

and that's the power of nitrogen.

On the plains of East Africa, there's an animal

that you might think is the least likely to be affected

by nitrogen levels in the grassland.

SNARLING

Nitrogen, or indeed the lack of it,

plays a decisive role in any grassland ecosystem.

It's even intrinsically entwined with the ecology of large predators

like these lions.

GROWLING

This close, and I'm in no doubt

that these animals are at the very top of their food chain.

But to find out how nitrogen affects predators,

I need to start at the bottom of the food chain...

..and it all begins with a very special plant...

..one of the great unsung heroes of our planet,

grass.

The really great thing about grass is that it's simple.

Compared to other flowering plants, shrubs and trees,

it requires minimal protein to build.

So it can take all of the nitrogen from its roots

and put it not into bulky structures but organise it efficiently, yet simply,

to maximise photosynthesis to produce its food.

So grass leaves have protein at much lower concentrations.

But this gives grazing animals a real problem.

Impala are one of Africa's commonest antelope,

a favourite prey of big cats.

But their biggest challenge is a much more basic one...

..how to survive on nothing more than grass.

The key is being very fussy about the sort of grass you eat,

because some grass is richer in nitrogen than other grass.

This impala is actually cherry-picking the leaves

with the highest concentration of nitrogen.

Even so, she'll have to work hard to extract it.

Just watch her neck closely.

Any moment now, she's going to regurgitate

a ball of partially digested grass...

..and she'll process it all over again.

It's called chewing the cud.

By digesting grass not once...

..but twice,

these animals can extract as much of the nitrogen as possible,

but it still only works on the very best grass.

Antelope, like these impala,

can only survive on a diet of grass which is relatively high in nitrogen -

grass like this. We call it sweet grass.

This long grass, on the other hand, is known as sour grass,

because the nitrogen in its leaves occurs at even lower concentrations.

Antelope can't live here.

They simply can't get enough nitrogen out of sour grass to survive.

But there is an animal here that can change that...

..a very rare one.

This is what I've been looking for.

The animal that has deposited this dung

processes grass through its gut in a very different way than antelope,

and I'm sure I can demonstrate that.

Here is some antelope poo,

and if I take just one of these and break it open here,

you can see that what remains is pretty much nothing more than dust.

Whereas this, on the other hand, is very different.

If I break this one in half...

..the grass is still very visible.

RHINO SNORTS

The white rhino.

What an animal!

Their sheer scale...

I mean, they're the closest thing perhaps that we have on the planet

to mammalian dinosaurs.

And of course, they have a reputation for being pretty feisty,

so I'm being very careful and not moving too quickly and keeping my voice down.

In fact, this one's getting a little bit close,

so I'm going to stop moving and talk...talking altogether.

Their eyesight is poor, so if I'm still, they may not notice me.

But they do have a great sense of smell.

If the wind changes, they could charge.

Absolutely fabulous things.

Now, one of these animals has got no horns.

It hasn't lost them in a scrap.

They've been deliberately removed by the park rangers here,

as these horns can have a tremendous value.

Rhinos with horns are prized by poachers.

The month before I arrived, they killed one in this very park.

Cutting off her horn could save her life,

and it's hoped that this practice will save the entire species.

Losing a species like this

would have a drastic impact on the entire grassland ecosystem.

Her huge size allows her to live on grass where antelope just can't.

Her body houses a massive gut, a fermentation chamber,

so she can make up for the low quality of sour grass

by digesting vast quantities of it.

All of which means she produces a lot of dung...

..which she drops in a very specific place -

a midden.

For rhinos, this is important. It's how they communicate.

Rhinos come here from far and wide.

By smelling the pile, they can tell who's around,

how they're doing and who is ready to mate.

It's a sort of faecal Facebook but with added value.

It brings nitrogen-rich manure from all over the grassland to one place.

So the grass growing here becomes increasingly sweeter

until, as if by magic, rhinos have created

a grazing lawn of sweet grass,

perfect for fussy eaters like impala.

Rhinos are ecosystem engineers upon which many other animals depend.

That, surely, is their true value.

That's why they're worth much more alive than dead.

Right across the world,

it's sweet grass that is crucial for most grassland grazers...

..and it's this quest for sweet grass

that drives one of the largest movements of animals on our planet.

Every year, one and a half million wildebeest migrate 3,000 kilometres,

all because of nitrogen.

And this is when its impact reaches the top of the food chain.

INSECTS BUZZING

BONES CRUNCHING

So, what has a lion kill got to do with nitrogen?

Well, basically two things.

You see, the lions here have identified

the richest source of nitrogen available out here in the grassland -

large herbivores.

You see, their bodies are made up of principally proteins,

and that protein is where the nitrogen is.

Then it's the sweet grass which dictates where lions like to hunt.

PURRS

King of beasts they may be, but their lives are ruled by nitrogen.

But how would a grassland predator survive

if there were no sweet grass to hunt in?

Depending on where you are in the world, the grassland always has a special name.

In Africa, the savannah.

In the US, it's the prairies.

Here in South America, it's the cerrado.

There's one animal that lives here that I'd love to show you.

It's...it's really special.

I've never seen one in the wild,

but it's a truly fantastic animal by anyone's standards.

This is Emas National Park.

The name comes from the Brazilian for this bird...

..the rhea.

BIRDSONG

But it's not a rhea that I'm after.

What I'm after is a wolf.

Maned wolves are one of the largest predators in South America,

but their home ranges, their territories, are huge,

so they're not easy to find or see.

This wolf has a problem on her paws.

You see, these grasslands are so low in nitrogen

that they can't support herds of grazing animals,

like impala or wildebeest.

In fact, the wolf's survival here

is all thanks to a relationship

with one of the cerrado's smallest inhabitants.

It's this, an ant.

And the story of why the wolf needs the ant is an amazing one,

and it's all down to the way

that grassland ecosystems survive against the odds.

Other species of canids - dogs, wolves - hunt in packs,

but her life is a lonely one.

There's just not enough nitrogen here for even two maned wolves,

so one of them has to go.

Hunting on her own means that even the odd deer is off the menu.

Instead, she has to catch more modest prey.

She may have walked miles just for that mouse...

..and such meagre pickings won't sustain a wolf.

So she has put herself on a bizarre dietary supplement.

This is a lobeira fruit, from the word "lobo", which means wolf,

and wolves love these things.

They make the perfect midnight snack.

Lobeira fruit make up about half of her diet.

True, they don't have much nitrogen,

but they are packed with vitamins and carbohydrates.

So eating fruit means she needs to catch fewer mice.

SNIFFING

And that actually means that she can survive

in this nitrogen-starved grassland.

But it gets even better.

The maned wolf is also helping the fruit.

Wolves like to mark their territory, and maned wolves are no exception,

and they like to choose high spots to do so.

But, of course, here on the flat cerrado,

such places are in short supply.

So, the one they turn to is this,

and this mound of soil here is the nest of leaf-cutter ants.

When the wolf poos on the mound, it has an immediate effect.

Soon most of the colony are out in force.

The ants will salvage anything.

They'll even try what's left of a mouse.

But one of them has just found the real prize...

..a seed from the lobeira fruit.

The nutrient-rich coating from these seeds will be fed to the ant larvae.

And, buried in the safety of the nest, those seeds will germinate.

They've even got added fertiliser.

So what we have here is an interaction

between three totally disparate species -

the ant, the fruit and the wolf.

Now, the ants, they get food delivered straight to their door.

The fruit has found something to disperse its seeds

and something else to ensure that they germinate perfectly.

And the wolves? Well, they're effectively farming their own food.

What a story. What a story!

It's stories like that

that mean that you can always entertain

a lifelong fascination with nature.

And, you know, every single leaf-cutter ant nest out here on the cerrado

has a lobeira fruit tree growing next to it.

It works.

And, you know, the most exciting thing for me

is that none of the players in this system,

the ant, the fruit or the wolf,

has any knowledge or regard for what it's doing,

and yet it works perfectly.

Fantastic.

These connections are not just important for the creatures concerned.

Because of the way they move precious nitrogen around,

they are crucial for the entire grassland ecosystem.

Relationships between species evolve over millennia,

but they can be destroyed in just a matter of years.

And it's happened a lot in Australia's grasslands.

This is Mount Rothwell Research Centre in Victoria.

It's 400 hectares of high-security grassland.

Scientists here are trying to restore animal relationships

and thus mend a broken ecosystem.

It's surrounded by 11 kilometres of fencing.

7,500 volts protect the perimeter...

..and it's patrolled every day.

I'm feeling a little imprisoned.

But then, this fence is not designed to keep things in.

It's actually designed to keep things out.

You see, in here

is the largest piece of native Australian grassland left in this region,

and this fence is helping keep out

a whole load of animals that they don't want in here.

CAT MIAOWS

This moggy is, or was, someone's pet,

but she's also an alien predator that didn't evolve in this ecosystem.

CAT MIAOWS

You see, Australia has no native cats of any kind.

Down under, she's an unstoppable killer

along with feral dogs and foxes.

These carnivores would do anything to get their jaws and claws on what's in here.

This is a brush-tailed rock wallaby.

And because of these introduced predators,

he is now one of the rarest mammals in the world,

and the extinction of just a few key creatures like him

has had a catastrophic impact.

Crucial ecological relationships are in tatters here,

and as a result, this native grassland

is now far more endangered than any tropical rainforest.

The question is, if you remove all of the alien animals

and reintroduce the key native ones,

could Australia's grasslands be brought back to life?

On the inside of this fence,

a relatively small community of animals and plants has been saved,

and I've got to say, some of them really are pretty odd,

and to stand any chance of seeing them,

I'm going to have to wait until after dark.

INSECTS DRONE

Welcome to the weird world of the native Aussie night.

This is a southern brown bandicoot...

..and I'm getting a superb view of it.

I'm so close that I can actually see the saliva glistening in its mouth

as it's chewing its food.

It's one of about 20 different species of bandicoot,

and they all come equipped with this long, pointed and sensitive snout.

And they're principally insectivores, meat eaters,

but they do play a very important role

when it comes to maintaining the plant community in this ecosystem.

He spends all of his time digging for food.

By the end of the night, he'll have covered the grassland

with lots of snout-shaped conical pits.

Here's one of the pits, here.

And when the wind blows, grass seeds are caught in here

along with a lot of other detritus, all of which is rich in nitrogen.

So they become a perfect place for germination.

This is a bettong, otherwise known as a rat kangaroo.

They're herbivores.

At the moment, if you listen carefully,

you can hear it munching on some roots or tubers that it's eating.

All of these animals are so tame

that's it's no wonder foreign cats and foxes have almost wiped them out.

As it feeds, it effectively ploughs this hard soil,

allowing air and water in,

vital for the plants that live here.

But so that the herbivores don't do too much damage,

this miniature Serengeti also has its own mini lion.

SNIFFING

This is an eastern quoll...

..a pocket-sized marsupial predator.

Don't be fooled by his size.

He can take prey much larger than himself.

What's important is that unlike cats and foxes,

quolls have co-evolved with their prey

so they are a critical part of this ecosystem.

The Rothwell experiment is working.

Rare species of plants, birds and mammals, the entire grassland,

is making a comeback here.

The secret to healthy grasslands is having the right species in the right place...

..and there's one animal that benefits grasslands more than any other on Earth.

These monoliths dominate the cerrado in South America.

There can be as many as 40,000 in one square kilometre.

From the outside, these things appear entirely lifeless.

In fact, you could sit down here alongside one and see nothing move all day.

But living on the inside

is perhaps the most important animal in this entire ecosystem.

They are grasslands' secret weapon in the battle for nitrogen.

Termites, half-blind distant cousins of cockroaches.

There are so many millions living in this grassland

that their combined weight is far greater

than that of all of the mammals living here put together.

And yet you would have no idea they were even here

if they didn't build these huge mounds.

They build them as cooling towers,

to keep the temperature of the colony on the inside

at an optimum 30 degrees centigrade,

and they are remarkably efficient,

normally accurate plus or minus a single degree.

Not bad for a colony of primitive insects.

But then, building these mounds all over the landscape

is the least of their accomplishments.

CAWING

Because, one way or another,

termites are fundamentally important to almost all life here.

Especially the strangest of all, the giant anteater.

These animals are related to armadillos and sloths.

They're part of a group called edentates, which basically means "without teeth".

But whilst armadillos and sloths do have rudimentary teeth,

if you were to perform a dental examination on one of these guys,

which would be difficult because their mouth is so small,

you'd find no teeth at all.

But it's not teeth he needs to unlock the termites' secret.

If you look at its front feet,

you can see it's got these two huge claws on each one of them,

and they can break into just about any substrate.

It also uses them for defence.

It's said that if it's attacked by a larger predator,

it will stand back on its tail and lash out with those claws.

He uses his tongue, which is over 50cm long,

flicking it in and out at around 150 times a minute.

Giant anteaters eat 35,000 termites a day.

Nevertheless, you could be forgiven for thinking

that no matter how many they hoover up, or how quickly,

they could never sustain an animal this size.

But they do.

By weight, termites are the most protein-rich food that you can find.

There's more protein in these little insects

than there is in beans, nuts, cheese, chicken, even roast beef.

And what's interesting is that termites occur in ecosystems all over the world,

and wherever they do, there are creatures like this

that have evolved to feed exclusively on termites.

The reason termites are so rich in protein

is all down to some very intimate relationships.

The first is with a fungus.

Deep within the mound,

the fungus breaks down dead grass so the termites can digest it.

Not much else could eke a living out of this stuff.

The second is more remarkable still.

You see, termites can obtain nitrogen

directly from the air.

And they achieve this through another symbiotic relationship,

an even more intimate one.

Because living inside their digestive systems

are amazing nitrogen-trapping bacteria,

and it's this that gives termites their special powers.

So using the nitrogen they get from that bacteria,

the nutrients they get from the fungus,

they're able to turn

this dead, woody material into a productive food source.

This stuff, which is so low in nitrogen, so low in protein,

they can turn into edible protein,

and that's how they can form these vast colonies.

The termite mound becomes a nitrogen hot spot.

That's good for anteaters

but also for all the surrounding plants and for all the other animals living here.

The incredible actions of termites nurture grasslands all over the world...

..including Kenya's whistling acacia savannah.

Here, the impact of termites goes right to the top...

..all the way to the world's tallest land animal.

When I was a child, we thought there was just one type of giraffe,

but now we know there are six different species.

This one's a reticulated giraffe.

He can reach anything,

but of all the plants here, he's chosen to eat the whistling acacia tree.

But just look at it.

It's one of the best-defended plants in the whole of Africa.

But why are these trees so well armed

against browsing animals like these giraffes?

Well, the answer, you won't be surprised, comes down to nitrogen.

You see, these trees' leaves are absolutely packed with nitrogen.

That's why they are the botanical equivalent of Fort Knox.

At the base of many of these acacias are colonies of African termites.

The acacias' roots are boring under the mounds,

tapping into a rich well of nitrogen.

As a result, these acacias become an oasis in a nitrogen desert.

So it's really no wonder

that the thorns alone don't deter giraffes from tucking in.

So, not to be beaten, the tree employs another line of defence,

its own private army.

Now, just watch this.

I'm going to pretend to be a giraffe browsing on this branch here.

So I'm going to pull at the leaves, shake it about a bit,

try and not get jabbed by the thorns here.

But just look at this.

Very quickly,

a whole mass of these Crematogaster ants swarms out and covers my hand.

And I can tell you that, if you were a giraffe browsing on this,

you wouldn't want these things all over your tongue.

Each ant is armed with a chemical weapon.

It's capable of squirting venom.

Each gall houses a separate colony of ants,

and each branch might have a dozen or more of these galls.

So the only way a giraffe can get an ant-free meal

is to grab a quick snack and then move on.

The tree has evolved to produce these hollow thorns,

and they are the perfect structures for the ants to make their colonies inside.

And in return for the plant's investment,

it gets these insects as vigorous defenders.

But this is just the beginning of a truly amazing web of relationships.

These are patas monkeys.

As grassland specialists, they're the fastest-running primates in the world.

In the 100-metre sprint, they'd beat any Olympian by three seconds.

To fuel their energetic lifestyles,

their favourite food is Crematogaster ants and their larvae.

The trick is finding them in just the right position.

He could easily have his eye out on those thorns.

Once ripped open, the ants abandon the gall,

but this act of primate vandalism only serves to enrich this mini ecosystem.

You see, a short while later, a new occupant has moved in.

Here, protected from predators and the harsh sun,

a dwarf gecko has laid two eggs.

Because she isn't a threat to either them or the acacia, the ants mostly ignore her.

After four months, a perfect miniature gecko hatches out.

It's completely defenceless,

but luckily, it's found itself in the perfect nest.

It couldn't possibly appreciate all of the creatures here on the grassland

that have come together to put a safe roof over its head.

The giraffe eats the acacia tree,

so it continually produces those galls which form the geckos' home.

The acacia tree needs the ants to protect its leaves and keep it healthy,

and in turn, the patas monkey needs those ants and their larvae as food.

And all of this can only happen

because the tree has managed to accumulate nitrogen

from a grassland that's evolved to prosper

despite the fact that this element is always in short supply.

It's often said that you can only tell who your real friends are in times of need.

This is also true in nature.

You might ask if it really matters if an animal becomes extinct.

Well, so intricate are the connections in the natural world

that there's no way to predict the impact of adding or removing species

until it's too late.

Who would have thought that a bettong would need a bandicoot,

that a leaf-cutter ant would need a maned wolf,

or, indeed, that a gecko would need a giraffe?

Now, the complex web of relationships that we've seen

have evolved over millions of years,

but we've only scratched the surface of a myriad of stories

that, when they come together, make these grasslands functional ecosystems,

and it's here that I've learned to see the real beauty in nature.

You see, for me, it's not in the minute detail.

It's in the bigger picture.

Because this works perfectly, and that is beautiful.

If you'd like to know more about the fascinating web of links between species,

the Open University has produced some material both to inform and inspire you.

For your free copy,

or to find out more about Open University programmes, ring:

Or go to the website:

And then follow the links to Open University.

And join me next time,

when I'll be travelling to the world's greatest seasonal forest.