0:00:04 > 0:00:08Ten million species live on planet Earth.
0:00:09 > 0:00:11Each one is remarkable.
0:00:13 > 0:00:15But none can survive on its own.
0:00:18 > 0:00:22All life depends upon connections...
0:00:24 > 0:00:27..unexpected, invariably complex,
0:00:27 > 0:00:31beautiful relationships between millions of plants and animals.
0:00:38 > 0:00:41This time, in our grasslands,
0:00:41 > 0:00:46I want to show you why these antelope need these rhino...
0:00:47 > 0:00:50..why this lone wolf...
0:00:50 > 0:00:52needs an ant...
0:00:52 > 0:00:53SNARLS
0:00:53 > 0:00:58..and the incredible secret that lies buried beneath them all.
0:00:59 > 0:01:04Connections like these create the planet's great ecosystems.
0:01:04 > 0:01:07They're vital for all life.
0:01:07 > 0:01:12I want to show you our world as you've never seen it before.
0:01:35 > 0:01:37Central Kenya...
0:01:39 > 0:01:43..and this is whistling acacia grassland.
0:01:51 > 0:01:54The whistling actually comes from the breeze
0:01:54 > 0:01:57blowing across the holes in these hollow galls...
0:01:59 > 0:02:05..and they're home to one of the grasslands' most intriguing creatures.
0:02:17 > 0:02:22This lizard is the aptly named dwarf gecko,
0:02:22 > 0:02:26and this one has laid a couple of eggs
0:02:26 > 0:02:29down here in this gall on the tree.
0:02:29 > 0:02:32The perfect place for a nest, you might think.
0:02:34 > 0:02:38But this tiny lizard can only safely lay its eggs here
0:02:38 > 0:02:44thanks to one of Africa's largest, most iconic and bizarre animals,
0:02:44 > 0:02:46the giraffe.
0:03:02 > 0:03:08The story of why the gecko needs the giraffe is wonderful,
0:03:08 > 0:03:11and it will take us on a journey across the world,
0:03:11 > 0:03:15to some of our most breathtaking grasslands.
0:03:29 > 0:03:35They are habitats which occupy a quarter of the land surface of our planet.
0:03:51 > 0:03:56They support some of our most spectacular wildlife...
0:03:59 > 0:04:04and yet grasslands lack one of the basic ingredients for life...
0:04:08 > 0:04:11..a truly precious element.
0:04:13 > 0:04:15It's this -
0:04:17 > 0:04:19nitrogen,
0:04:19 > 0:04:21a colourless, tasteless gas.
0:04:22 > 0:04:28It's only when we chill it down to 196 degrees below zero
0:04:28 > 0:04:30that we can actually see it.
0:04:31 > 0:04:32I can tell you
0:04:32 > 0:04:37that almost everything that happens out here in this grassland ecosystem
0:04:37 > 0:04:42is governed by a craving for this rare resource.
0:04:42 > 0:04:46In fact, I'd go so far as to say that grasslands can only function
0:04:46 > 0:04:51because they can cope so ingeniously with so little of it.
0:04:51 > 0:04:55So, for once, perhaps this will make the ecologist's job a little easier,
0:04:55 > 0:04:59because to understand how grasslands work,
0:04:59 > 0:05:03all we need to do is follow the nitrogen.
0:05:15 > 0:05:17Australia.
0:05:31 > 0:05:37The grasslands here have some of the lowest levels of nitrogen on the planet,
0:05:37 > 0:05:44which makes the local wildlife perfect for demonstrating why it's so important.
0:05:47 > 0:05:51Nitrogen is the magic ingredient.
0:05:51 > 0:05:55When you add it to carbohydrate, you get protein.
0:05:55 > 0:05:59And protein is what you need to make living tissue.
0:05:59 > 0:06:05Protein is the building block for life, all life.
0:06:12 > 0:06:15A baby eastern grey kangaroo.
0:06:20 > 0:06:26When he was born, he weighed less than a one-pence piece.
0:06:34 > 0:06:39His dad, on the other hand, is one of the heaviest marsupials in the world.
0:06:41 > 0:06:45Which means that joey has a lot of growing up to do.
0:06:55 > 0:06:58In fact, from birth to adulthood,
0:06:58 > 0:07:03he'll increase his body size by 100,000 times.
0:07:07 > 0:07:11And all of that will be built with protein.
0:07:13 > 0:07:17And you can't make protein without nitrogen.
0:07:23 > 0:07:28Right now, he gets most of his protein from his mother,
0:07:28 > 0:07:33and she gets all of her protein from a diet of grass.
0:07:37 > 0:07:41At the moment, these kangaroos are just hanging out,
0:07:41 > 0:07:45and they look like a typical population of kangaroos,
0:07:45 > 0:07:48but I can assure you they're not.
0:07:50 > 0:07:54Because this is not your typical Australian grassland.
0:07:55 > 0:07:58It's Anglesea Golf Club near Melbourne.
0:08:07 > 0:08:13Kangaroos were here when the golf course was built 60 years ago,
0:08:13 > 0:08:16but since then, their population has boomed.
0:08:20 > 0:08:24At a recent count, there were 359 of them.
0:08:25 > 0:08:28That's nearly 20 for each hole.
0:08:32 > 0:08:38And the secret of their success is down to these immaculate fairways.
0:08:44 > 0:08:51This grass is so green and so lush because it's had something added to it.
0:08:51 > 0:08:53This.
0:08:53 > 0:08:55Nitrogen fertiliser.
0:08:56 > 0:08:59And I know it's a product of the industrial revolution
0:08:59 > 0:09:02that's therefore led to all of this lushness,
0:09:02 > 0:09:09but it certainly proves a point - the power of nitrogen in a grassland.
0:09:13 > 0:09:15It's added once a month.
0:09:15 > 0:09:19It seeps into the soil, is quickly taken up by the roots
0:09:19 > 0:09:27and then converted into proteins for stronger, healthier grass.
0:09:30 > 0:09:34Great for golf but perfect for the joey.
0:09:37 > 0:09:42The extra protein means that he can grow faster,
0:09:42 > 0:09:45become healthier and live longer
0:09:47 > 0:09:50and that's the power of nitrogen.
0:10:06 > 0:10:09On the plains of East Africa, there's an animal
0:10:09 > 0:10:14that you might think is the least likely to be affected
0:10:14 > 0:10:16by nitrogen levels in the grassland.
0:10:25 > 0:10:27SNARLING
0:10:27 > 0:10:30Nitrogen, or indeed the lack of it,
0:10:30 > 0:10:33plays a decisive role in any grassland ecosystem.
0:10:33 > 0:10:38It's even intrinsically entwined with the ecology of large predators
0:10:38 > 0:10:40like these lions.
0:10:42 > 0:10:44GROWLING
0:10:45 > 0:10:47This close, and I'm in no doubt
0:10:47 > 0:10:52that these animals are at the very top of their food chain.
0:10:55 > 0:10:58But to find out how nitrogen affects predators,
0:10:58 > 0:11:02I need to start at the bottom of the food chain...
0:11:10 > 0:11:13..and it all begins with a very special plant...
0:11:15 > 0:11:20..one of the great unsung heroes of our planet,
0:11:20 > 0:11:22grass.
0:11:26 > 0:11:29The really great thing about grass is that it's simple.
0:11:29 > 0:11:34Compared to other flowering plants, shrubs and trees,
0:11:34 > 0:11:36it requires minimal protein to build.
0:11:36 > 0:11:40So it can take all of the nitrogen from its roots
0:11:40 > 0:11:45and put it not into bulky structures but organise it efficiently, yet simply,
0:11:45 > 0:11:49to maximise photosynthesis to produce its food.
0:11:50 > 0:11:55So grass leaves have protein at much lower concentrations.
0:11:57 > 0:12:01But this gives grazing animals a real problem.
0:12:03 > 0:12:08Impala are one of Africa's commonest antelope,
0:12:08 > 0:12:10a favourite prey of big cats.
0:12:17 > 0:12:21But their biggest challenge is a much more basic one...
0:12:22 > 0:12:26..how to survive on nothing more than grass.
0:12:28 > 0:12:32The key is being very fussy about the sort of grass you eat,
0:12:32 > 0:12:37because some grass is richer in nitrogen than other grass.
0:12:37 > 0:12:41This impala is actually cherry-picking the leaves
0:12:41 > 0:12:44with the highest concentration of nitrogen.
0:12:47 > 0:12:51Even so, she'll have to work hard to extract it.
0:12:55 > 0:12:57Just watch her neck closely.
0:12:58 > 0:13:01Any moment now, she's going to regurgitate
0:13:01 > 0:13:04a ball of partially digested grass...
0:13:09 > 0:13:12..and she'll process it all over again.
0:13:16 > 0:13:19It's called chewing the cud.
0:13:19 > 0:13:23By digesting grass not once...
0:13:24 > 0:13:25..but twice,
0:13:25 > 0:13:30these animals can extract as much of the nitrogen as possible,
0:13:30 > 0:13:33but it still only works on the very best grass.
0:13:34 > 0:13:36Antelope, like these impala,
0:13:36 > 0:13:41can only survive on a diet of grass which is relatively high in nitrogen -
0:13:41 > 0:13:45grass like this. We call it sweet grass.
0:13:48 > 0:13:53This long grass, on the other hand, is known as sour grass,
0:13:53 > 0:13:58because the nitrogen in its leaves occurs at even lower concentrations.
0:14:02 > 0:14:05Antelope can't live here.
0:14:05 > 0:14:10They simply can't get enough nitrogen out of sour grass to survive.
0:14:24 > 0:14:27But there is an animal here that can change that...
0:14:28 > 0:14:31..a very rare one.
0:14:31 > 0:14:33This is what I've been looking for.
0:14:36 > 0:14:39The animal that has deposited this dung
0:14:39 > 0:14:43processes grass through its gut in a very different way than antelope,
0:14:43 > 0:14:45and I'm sure I can demonstrate that.
0:14:45 > 0:14:48Here is some antelope poo,
0:14:48 > 0:14:54and if I take just one of these and break it open here,
0:14:54 > 0:15:00you can see that what remains is pretty much nothing more than dust.
0:15:02 > 0:15:05Whereas this, on the other hand, is very different.
0:15:06 > 0:15:08If I break this one in half...
0:15:10 > 0:15:13..the grass is still very visible.
0:15:36 > 0:15:38RHINO SNORTS
0:15:45 > 0:15:47The white rhino.
0:15:47 > 0:15:49What an animal!
0:15:53 > 0:15:54Their sheer scale...
0:15:54 > 0:15:57I mean, they're the closest thing perhaps that we have on the planet
0:15:57 > 0:16:00to mammalian dinosaurs.
0:16:00 > 0:16:03And of course, they have a reputation for being pretty feisty,
0:16:03 > 0:16:09so I'm being very careful and not moving too quickly and keeping my voice down.
0:16:09 > 0:16:12In fact, this one's getting a little bit close,
0:16:12 > 0:16:16so I'm going to stop moving and talk...talking altogether.
0:16:19 > 0:16:25Their eyesight is poor, so if I'm still, they may not notice me.
0:16:31 > 0:16:34But they do have a great sense of smell.
0:16:40 > 0:16:43If the wind changes, they could charge.
0:17:04 > 0:17:07Absolutely fabulous things.
0:17:15 > 0:17:18Now, one of these animals has got no horns.
0:17:18 > 0:17:20It hasn't lost them in a scrap.
0:17:20 > 0:17:23They've been deliberately removed by the park rangers here,
0:17:23 > 0:17:26as these horns can have a tremendous value.
0:17:30 > 0:17:34Rhinos with horns are prized by poachers.
0:17:34 > 0:17:38The month before I arrived, they killed one in this very park.
0:17:40 > 0:17:44Cutting off her horn could save her life,
0:17:44 > 0:17:50and it's hoped that this practice will save the entire species.
0:17:52 > 0:17:54Losing a species like this
0:17:54 > 0:17:59would have a drastic impact on the entire grassland ecosystem.
0:18:02 > 0:18:08Her huge size allows her to live on grass where antelope just can't.
0:18:11 > 0:18:14Her body houses a massive gut, a fermentation chamber,
0:18:14 > 0:18:18so she can make up for the low quality of sour grass
0:18:18 > 0:18:21by digesting vast quantities of it.
0:18:27 > 0:18:32All of which means she produces a lot of dung...
0:18:37 > 0:18:42..which she drops in a very specific place -
0:18:42 > 0:18:44a midden.
0:18:44 > 0:18:48For rhinos, this is important. It's how they communicate.
0:18:54 > 0:18:57Rhinos come here from far and wide.
0:18:58 > 0:19:02By smelling the pile, they can tell who's around,
0:19:02 > 0:19:05how they're doing and who is ready to mate.
0:19:09 > 0:19:14It's a sort of faecal Facebook but with added value.
0:19:17 > 0:19:24It brings nitrogen-rich manure from all over the grassland to one place.
0:19:28 > 0:19:33So the grass growing here becomes increasingly sweeter
0:19:33 > 0:19:37until, as if by magic, rhinos have created
0:19:37 > 0:19:40a grazing lawn of sweet grass,
0:19:40 > 0:19:43perfect for fussy eaters like impala.
0:19:57 > 0:20:04Rhinos are ecosystem engineers upon which many other animals depend.
0:20:04 > 0:20:08That, surely, is their true value.
0:20:08 > 0:20:13That's why they're worth much more alive than dead.
0:20:21 > 0:20:22Right across the world,
0:20:22 > 0:20:27it's sweet grass that is crucial for most grassland grazers...
0:20:28 > 0:20:32..and it's this quest for sweet grass
0:20:32 > 0:20:36that drives one of the largest movements of animals on our planet.
0:20:47 > 0:20:53Every year, one and a half million wildebeest migrate 3,000 kilometres,
0:20:53 > 0:20:56all because of nitrogen.
0:20:58 > 0:21:02And this is when its impact reaches the top of the food chain.
0:21:19 > 0:21:22INSECTS BUZZING
0:21:47 > 0:21:50BONES CRUNCHING
0:21:52 > 0:21:56So, what has a lion kill got to do with nitrogen?
0:21:56 > 0:21:59Well, basically two things.
0:21:59 > 0:22:02You see, the lions here have identified
0:22:02 > 0:22:07the richest source of nitrogen available out here in the grassland -
0:22:07 > 0:22:09large herbivores.
0:22:09 > 0:22:13You see, their bodies are made up of principally proteins,
0:22:13 > 0:22:16and that protein is where the nitrogen is.
0:22:17 > 0:22:24Then it's the sweet grass which dictates where lions like to hunt.
0:22:26 > 0:22:28PURRS
0:22:30 > 0:22:36King of beasts they may be, but their lives are ruled by nitrogen.
0:22:37 > 0:22:40But how would a grassland predator survive
0:22:40 > 0:22:44if there were no sweet grass to hunt in?
0:23:05 > 0:23:10Depending on where you are in the world, the grassland always has a special name.
0:23:10 > 0:23:13In Africa, the savannah.
0:23:13 > 0:23:15In the US, it's the prairies.
0:23:15 > 0:23:18Here in South America, it's the cerrado.
0:23:23 > 0:23:25There's one animal that lives here that I'd love to show you.
0:23:25 > 0:23:28It's...it's really special.
0:23:28 > 0:23:29I've never seen one in the wild,
0:23:29 > 0:23:33but it's a truly fantastic animal by anyone's standards.
0:23:36 > 0:23:39This is Emas National Park.
0:23:42 > 0:23:46The name comes from the Brazilian for this bird...
0:23:47 > 0:23:49..the rhea.
0:23:53 > 0:23:55BIRDSONG
0:23:58 > 0:24:01But it's not a rhea that I'm after.
0:24:02 > 0:24:05What I'm after is a wolf.
0:24:09 > 0:24:13Maned wolves are one of the largest predators in South America,
0:24:13 > 0:24:17but their home ranges, their territories, are huge,
0:24:17 > 0:24:20so they're not easy to find or see.
0:24:35 > 0:24:38This wolf has a problem on her paws.
0:24:44 > 0:24:48You see, these grasslands are so low in nitrogen
0:24:48 > 0:24:52that they can't support herds of grazing animals,
0:24:52 > 0:24:54like impala or wildebeest.
0:25:01 > 0:25:04In fact, the wolf's survival here
0:25:04 > 0:25:07is all thanks to a relationship
0:25:07 > 0:25:10with one of the cerrado's smallest inhabitants.
0:25:12 > 0:25:14It's this, an ant.
0:25:15 > 0:25:20And the story of why the wolf needs the ant is an amazing one,
0:25:20 > 0:25:21and it's all down to the way
0:25:21 > 0:25:25that grassland ecosystems survive against the odds.
0:25:27 > 0:25:33Other species of canids - dogs, wolves - hunt in packs,
0:25:33 > 0:25:36but her life is a lonely one.
0:25:40 > 0:25:45There's just not enough nitrogen here for even two maned wolves,
0:25:45 > 0:25:47so one of them has to go.
0:26:17 > 0:26:23Hunting on her own means that even the odd deer is off the menu.
0:26:24 > 0:26:28Instead, she has to catch more modest prey.
0:27:23 > 0:27:28She may have walked miles just for that mouse...
0:27:30 > 0:27:34..and such meagre pickings won't sustain a wolf.
0:27:36 > 0:27:41So she has put herself on a bizarre dietary supplement.
0:27:50 > 0:27:55This is a lobeira fruit, from the word "lobo", which means wolf,
0:27:55 > 0:27:58and wolves love these things.
0:28:04 > 0:28:06They make the perfect midnight snack.
0:28:16 > 0:28:19Lobeira fruit make up about half of her diet.
0:28:21 > 0:28:23True, they don't have much nitrogen,
0:28:23 > 0:28:27but they are packed with vitamins and carbohydrates.
0:28:29 > 0:28:33So eating fruit means she needs to catch fewer mice.
0:28:33 > 0:28:34SNIFFING
0:28:34 > 0:28:37And that actually means that she can survive
0:28:37 > 0:28:40in this nitrogen-starved grassland.
0:28:46 > 0:28:49But it gets even better.
0:28:50 > 0:28:55The maned wolf is also helping the fruit.
0:28:56 > 0:29:00Wolves like to mark their territory, and maned wolves are no exception,
0:29:00 > 0:29:04and they like to choose high spots to do so.
0:29:04 > 0:29:07But, of course, here on the flat cerrado,
0:29:07 > 0:29:09such places are in short supply.
0:29:09 > 0:29:11So, the one they turn to is this,
0:29:11 > 0:29:16and this mound of soil here is the nest of leaf-cutter ants.
0:29:22 > 0:29:26When the wolf poos on the mound, it has an immediate effect.
0:29:37 > 0:29:41Soon most of the colony are out in force.
0:29:49 > 0:29:52The ants will salvage anything.
0:29:52 > 0:29:55They'll even try what's left of a mouse.
0:30:06 > 0:30:09But one of them has just found the real prize...
0:30:11 > 0:30:14..a seed from the lobeira fruit.
0:30:33 > 0:30:38The nutrient-rich coating from these seeds will be fed to the ant larvae.
0:30:57 > 0:31:03And, buried in the safety of the nest, those seeds will germinate.
0:31:03 > 0:31:05They've even got added fertiliser.
0:31:06 > 0:31:08So what we have here is an interaction
0:31:08 > 0:31:12between three totally disparate species -
0:31:12 > 0:31:15the ant, the fruit and the wolf.
0:31:16 > 0:31:19Now, the ants, they get food delivered straight to their door.
0:31:19 > 0:31:23The fruit has found something to disperse its seeds
0:31:23 > 0:31:26and something else to ensure that they germinate perfectly.
0:31:26 > 0:31:32And the wolves? Well, they're effectively farming their own food.
0:31:33 > 0:31:35What a story. What a story!
0:31:35 > 0:31:36It's stories like that
0:31:36 > 0:31:38that mean that you can always entertain
0:31:38 > 0:31:40a lifelong fascination with nature.
0:31:40 > 0:31:46And, you know, every single leaf-cutter ant nest out here on the cerrado
0:31:46 > 0:31:49has a lobeira fruit tree growing next to it.
0:31:50 > 0:31:51It works.
0:31:51 > 0:31:55And, you know, the most exciting thing for me
0:31:55 > 0:31:57is that none of the players in this system,
0:31:57 > 0:31:59the ant, the fruit or the wolf,
0:31:59 > 0:32:02has any knowledge or regard for what it's doing,
0:32:02 > 0:32:05and yet it works perfectly.
0:32:05 > 0:32:07Fantastic.
0:32:14 > 0:32:19These connections are not just important for the creatures concerned.
0:32:19 > 0:32:23Because of the way they move precious nitrogen around,
0:32:23 > 0:32:27they are crucial for the entire grassland ecosystem.
0:32:43 > 0:32:48Relationships between species evolve over millennia,
0:32:48 > 0:32:52but they can be destroyed in just a matter of years.
0:32:53 > 0:32:57And it's happened a lot in Australia's grasslands.
0:33:10 > 0:33:15This is Mount Rothwell Research Centre in Victoria.
0:33:16 > 0:33:20It's 400 hectares of high-security grassland.
0:33:26 > 0:33:30Scientists here are trying to restore animal relationships
0:33:30 > 0:33:33and thus mend a broken ecosystem.
0:33:39 > 0:33:42It's surrounded by 11 kilometres of fencing.
0:33:45 > 0:33:507,500 volts protect the perimeter...
0:33:56 > 0:33:58..and it's patrolled every day.
0:34:03 > 0:34:06I'm feeling a little imprisoned.
0:34:06 > 0:34:09But then, this fence is not designed to keep things in.
0:34:09 > 0:34:12It's actually designed to keep things out.
0:34:12 > 0:34:14You see, in here
0:34:14 > 0:34:19is the largest piece of native Australian grassland left in this region,
0:34:19 > 0:34:21and this fence is helping keep out
0:34:21 > 0:34:25a whole load of animals that they don't want in here.
0:34:25 > 0:34:27CAT MIAOWS
0:34:28 > 0:34:32This moggy is, or was, someone's pet,
0:34:32 > 0:34:37but she's also an alien predator that didn't evolve in this ecosystem.
0:34:39 > 0:34:41CAT MIAOWS
0:34:41 > 0:34:46You see, Australia has no native cats of any kind.
0:34:46 > 0:34:49Down under, she's an unstoppable killer
0:34:49 > 0:34:52along with feral dogs and foxes.
0:34:58 > 0:35:04These carnivores would do anything to get their jaws and claws on what's in here.
0:35:15 > 0:35:18This is a brush-tailed rock wallaby.
0:35:20 > 0:35:22And because of these introduced predators,
0:35:22 > 0:35:26he is now one of the rarest mammals in the world,
0:35:26 > 0:35:30and the extinction of just a few key creatures like him
0:35:30 > 0:35:32has had a catastrophic impact.
0:35:33 > 0:35:37Crucial ecological relationships are in tatters here,
0:35:37 > 0:35:40and as a result, this native grassland
0:35:40 > 0:35:45is now far more endangered than any tropical rainforest.
0:35:45 > 0:35:49The question is, if you remove all of the alien animals
0:35:49 > 0:35:52and reintroduce the key native ones,
0:35:52 > 0:35:57could Australia's grasslands be brought back to life?
0:35:57 > 0:35:58On the inside of this fence,
0:35:58 > 0:36:03a relatively small community of animals and plants has been saved,
0:36:03 > 0:36:07and I've got to say, some of them really are pretty odd,
0:36:07 > 0:36:09and to stand any chance of seeing them,
0:36:09 > 0:36:11I'm going to have to wait until after dark.
0:36:13 > 0:36:15INSECTS DRONE
0:36:32 > 0:36:36Welcome to the weird world of the native Aussie night.
0:36:58 > 0:37:02This is a southern brown bandicoot...
0:37:03 > 0:37:05..and I'm getting a superb view of it.
0:37:05 > 0:37:11I'm so close that I can actually see the saliva glistening in its mouth
0:37:11 > 0:37:13as it's chewing its food.
0:37:15 > 0:37:18It's one of about 20 different species of bandicoot,
0:37:18 > 0:37:23and they all come equipped with this long, pointed and sensitive snout.
0:37:25 > 0:37:29And they're principally insectivores, meat eaters,
0:37:29 > 0:37:32but they do play a very important role
0:37:32 > 0:37:37when it comes to maintaining the plant community in this ecosystem.
0:37:37 > 0:37:41He spends all of his time digging for food.
0:37:42 > 0:37:45By the end of the night, he'll have covered the grassland
0:37:45 > 0:37:48with lots of snout-shaped conical pits.
0:37:50 > 0:37:53Here's one of the pits, here.
0:37:53 > 0:37:57And when the wind blows, grass seeds are caught in here
0:37:57 > 0:38:02along with a lot of other detritus, all of which is rich in nitrogen.
0:38:02 > 0:38:07So they become a perfect place for germination.
0:38:27 > 0:38:32This is a bettong, otherwise known as a rat kangaroo.
0:38:32 > 0:38:34They're herbivores.
0:38:34 > 0:38:36At the moment, if you listen carefully,
0:38:36 > 0:38:40you can hear it munching on some roots or tubers that it's eating.
0:38:46 > 0:38:49All of these animals are so tame
0:38:49 > 0:38:55that's it's no wonder foreign cats and foxes have almost wiped them out.
0:38:57 > 0:39:02As it feeds, it effectively ploughs this hard soil,
0:39:02 > 0:39:05allowing air and water in,
0:39:05 > 0:39:07vital for the plants that live here.
0:39:12 > 0:39:16But so that the herbivores don't do too much damage,
0:39:16 > 0:39:20this miniature Serengeti also has its own mini lion.
0:39:21 > 0:39:23SNIFFING
0:39:43 > 0:39:45This is an eastern quoll...
0:39:46 > 0:39:49..a pocket-sized marsupial predator.
0:39:51 > 0:39:54Don't be fooled by his size.
0:39:54 > 0:39:58He can take prey much larger than himself.
0:39:58 > 0:40:01What's important is that unlike cats and foxes,
0:40:01 > 0:40:05quolls have co-evolved with their prey
0:40:05 > 0:40:08so they are a critical part of this ecosystem.
0:40:14 > 0:40:16The Rothwell experiment is working.
0:40:16 > 0:40:22Rare species of plants, birds and mammals, the entire grassland,
0:40:22 > 0:40:24is making a comeback here.
0:40:31 > 0:40:37The secret to healthy grasslands is having the right species in the right place...
0:40:39 > 0:40:45..and there's one animal that benefits grasslands more than any other on Earth.
0:40:55 > 0:40:59These monoliths dominate the cerrado in South America.
0:40:59 > 0:41:04There can be as many as 40,000 in one square kilometre.
0:41:08 > 0:41:13From the outside, these things appear entirely lifeless.
0:41:13 > 0:41:20In fact, you could sit down here alongside one and see nothing move all day.
0:41:20 > 0:41:22But living on the inside
0:41:22 > 0:41:27is perhaps the most important animal in this entire ecosystem.
0:41:31 > 0:41:36They are grasslands' secret weapon in the battle for nitrogen.
0:41:43 > 0:41:48Termites, half-blind distant cousins of cockroaches.
0:41:51 > 0:41:54There are so many millions living in this grassland
0:41:54 > 0:41:57that their combined weight is far greater
0:41:57 > 0:42:01than that of all of the mammals living here put together.
0:42:03 > 0:42:07And yet you would have no idea they were even here
0:42:07 > 0:42:10if they didn't build these huge mounds.
0:42:13 > 0:42:16They build them as cooling towers,
0:42:16 > 0:42:18to keep the temperature of the colony on the inside
0:42:18 > 0:42:21at an optimum 30 degrees centigrade,
0:42:21 > 0:42:24and they are remarkably efficient,
0:42:24 > 0:42:27normally accurate plus or minus a single degree.
0:42:28 > 0:42:32Not bad for a colony of primitive insects.
0:42:32 > 0:42:35But then, building these mounds all over the landscape
0:42:35 > 0:42:37is the least of their accomplishments.
0:42:37 > 0:42:39CAWING
0:42:42 > 0:42:44Because, one way or another,
0:42:44 > 0:42:50termites are fundamentally important to almost all life here.
0:42:58 > 0:43:03Especially the strangest of all, the giant anteater.
0:43:05 > 0:43:09These animals are related to armadillos and sloths.
0:43:09 > 0:43:14They're part of a group called edentates, which basically means "without teeth".
0:43:14 > 0:43:18But whilst armadillos and sloths do have rudimentary teeth,
0:43:18 > 0:43:22if you were to perform a dental examination on one of these guys,
0:43:22 > 0:43:24which would be difficult because their mouth is so small,
0:43:24 > 0:43:27you'd find no teeth at all.
0:43:28 > 0:43:32But it's not teeth he needs to unlock the termites' secret.
0:43:38 > 0:43:39If you look at its front feet,
0:43:39 > 0:43:43you can see it's got these two huge claws on each one of them,
0:43:43 > 0:43:46and they can break into just about any substrate.
0:43:46 > 0:43:49It also uses them for defence.
0:43:49 > 0:43:51It's said that if it's attacked by a larger predator,
0:43:51 > 0:43:56it will stand back on its tail and lash out with those claws.
0:44:00 > 0:44:05He uses his tongue, which is over 50cm long,
0:44:05 > 0:44:08flicking it in and out at around 150 times a minute.
0:44:16 > 0:44:21Giant anteaters eat 35,000 termites a day.
0:44:21 > 0:44:24Nevertheless, you could be forgiven for thinking
0:44:24 > 0:44:27that no matter how many they hoover up, or how quickly,
0:44:27 > 0:44:30they could never sustain an animal this size.
0:44:31 > 0:44:33But they do.
0:44:33 > 0:44:39By weight, termites are the most protein-rich food that you can find.
0:44:39 > 0:44:42There's more protein in these little insects
0:44:42 > 0:44:46than there is in beans, nuts, cheese, chicken, even roast beef.
0:44:46 > 0:44:52And what's interesting is that termites occur in ecosystems all over the world,
0:44:52 > 0:44:55and wherever they do, there are creatures like this
0:44:55 > 0:45:00that have evolved to feed exclusively on termites.
0:45:09 > 0:45:12The reason termites are so rich in protein
0:45:12 > 0:45:17is all down to some very intimate relationships.
0:45:18 > 0:45:21The first is with a fungus.
0:45:21 > 0:45:23Deep within the mound,
0:45:23 > 0:45:28the fungus breaks down dead grass so the termites can digest it.
0:45:28 > 0:45:32Not much else could eke a living out of this stuff.
0:45:41 > 0:45:44The second is more remarkable still.
0:45:44 > 0:45:49You see, termites can obtain nitrogen
0:45:49 > 0:45:51directly from the air.
0:45:54 > 0:45:56And they achieve this through another symbiotic relationship,
0:45:56 > 0:45:59an even more intimate one.
0:45:59 > 0:46:02Because living inside their digestive systems
0:46:02 > 0:46:05are amazing nitrogen-trapping bacteria,
0:46:05 > 0:46:10and it's this that gives termites their special powers.
0:46:10 > 0:46:13So using the nitrogen they get from that bacteria,
0:46:13 > 0:46:15the nutrients they get from the fungus,
0:46:15 > 0:46:16they're able to turn
0:46:17 > 0:46:23this dead, woody material into a productive food source.
0:46:23 > 0:46:28This stuff, which is so low in nitrogen, so low in protein,
0:46:28 > 0:46:30they can turn into edible protein,
0:46:30 > 0:46:35and that's how they can form these vast colonies.
0:46:37 > 0:46:41The termite mound becomes a nitrogen hot spot.
0:46:41 > 0:46:44That's good for anteaters
0:46:44 > 0:46:50but also for all the surrounding plants and for all the other animals living here.
0:47:02 > 0:47:08The incredible actions of termites nurture grasslands all over the world...
0:47:11 > 0:47:14..including Kenya's whistling acacia savannah.
0:47:31 > 0:47:35Here, the impact of termites goes right to the top...
0:47:37 > 0:47:41..all the way to the world's tallest land animal.
0:48:06 > 0:48:10When I was a child, we thought there was just one type of giraffe,
0:48:10 > 0:48:13but now we know there are six different species.
0:48:15 > 0:48:18This one's a reticulated giraffe.
0:48:30 > 0:48:32He can reach anything,
0:48:32 > 0:48:38but of all the plants here, he's chosen to eat the whistling acacia tree.
0:48:43 > 0:48:44But just look at it.
0:48:44 > 0:48:47It's one of the best-defended plants in the whole of Africa.
0:49:06 > 0:49:10But why are these trees so well armed
0:49:10 > 0:49:14against browsing animals like these giraffes?
0:49:14 > 0:49:19Well, the answer, you won't be surprised, comes down to nitrogen.
0:49:19 > 0:49:25You see, these trees' leaves are absolutely packed with nitrogen.
0:49:26 > 0:49:30That's why they are the botanical equivalent of Fort Knox.
0:49:32 > 0:49:36At the base of many of these acacias are colonies of African termites.
0:49:38 > 0:49:40The acacias' roots are boring under the mounds,
0:49:40 > 0:49:44tapping into a rich well of nitrogen.
0:49:44 > 0:49:49As a result, these acacias become an oasis in a nitrogen desert.
0:49:51 > 0:49:53So it's really no wonder
0:49:53 > 0:49:57that the thorns alone don't deter giraffes from tucking in.
0:49:59 > 0:50:04So, not to be beaten, the tree employs another line of defence,
0:50:04 > 0:50:07its own private army.
0:50:09 > 0:50:10Now, just watch this.
0:50:10 > 0:50:15I'm going to pretend to be a giraffe browsing on this branch here.
0:50:15 > 0:50:19So I'm going to pull at the leaves, shake it about a bit,
0:50:19 > 0:50:24try and not get jabbed by the thorns here.
0:50:24 > 0:50:25But just look at this.
0:50:25 > 0:50:27Very quickly,
0:50:27 > 0:50:34a whole mass of these Crematogaster ants swarms out and covers my hand.
0:50:34 > 0:50:37And I can tell you that, if you were a giraffe browsing on this,
0:50:37 > 0:50:41you wouldn't want these things all over your tongue.
0:50:42 > 0:50:45Each ant is armed with a chemical weapon.
0:50:45 > 0:50:48It's capable of squirting venom.
0:50:50 > 0:50:54Each gall houses a separate colony of ants,
0:50:54 > 0:50:58and each branch might have a dozen or more of these galls.
0:51:07 > 0:51:11So the only way a giraffe can get an ant-free meal
0:51:11 > 0:51:14is to grab a quick snack and then move on.
0:51:32 > 0:51:35The tree has evolved to produce these hollow thorns,
0:51:35 > 0:51:41and they are the perfect structures for the ants to make their colonies inside.
0:51:41 > 0:51:44And in return for the plant's investment,
0:51:44 > 0:51:48it gets these insects as vigorous defenders.
0:51:57 > 0:52:03But this is just the beginning of a truly amazing web of relationships.
0:52:12 > 0:52:15These are patas monkeys.
0:52:23 > 0:52:29As grassland specialists, they're the fastest-running primates in the world.
0:52:29 > 0:52:34In the 100-metre sprint, they'd beat any Olympian by three seconds.
0:52:45 > 0:52:48To fuel their energetic lifestyles,
0:52:48 > 0:52:53their favourite food is Crematogaster ants and their larvae.
0:52:59 > 0:53:03The trick is finding them in just the right position.
0:53:07 > 0:53:10He could easily have his eye out on those thorns.
0:53:52 > 0:53:55Once ripped open, the ants abandon the gall,
0:53:55 > 0:54:02but this act of primate vandalism only serves to enrich this mini ecosystem.
0:54:04 > 0:54:09You see, a short while later, a new occupant has moved in.
0:54:16 > 0:54:19Here, protected from predators and the harsh sun,
0:54:19 > 0:54:23a dwarf gecko has laid two eggs.
0:54:33 > 0:54:38Because she isn't a threat to either them or the acacia, the ants mostly ignore her.
0:54:46 > 0:54:51After four months, a perfect miniature gecko hatches out.
0:55:03 > 0:55:05It's completely defenceless,
0:55:05 > 0:55:11but luckily, it's found itself in the perfect nest.
0:55:16 > 0:55:22It couldn't possibly appreciate all of the creatures here on the grassland
0:55:22 > 0:55:26that have come together to put a safe roof over its head.
0:55:34 > 0:55:36The giraffe eats the acacia tree,
0:55:36 > 0:55:41so it continually produces those galls which form the geckos' home.
0:55:41 > 0:55:45The acacia tree needs the ants to protect its leaves and keep it healthy,
0:55:45 > 0:55:51and in turn, the patas monkey needs those ants and their larvae as food.
0:55:51 > 0:55:54And all of this can only happen
0:55:54 > 0:55:57because the tree has managed to accumulate nitrogen
0:55:57 > 0:56:01from a grassland that's evolved to prosper
0:56:01 > 0:56:06despite the fact that this element is always in short supply.
0:56:12 > 0:56:19It's often said that you can only tell who your real friends are in times of need.
0:56:21 > 0:56:23This is also true in nature.
0:56:26 > 0:56:32You might ask if it really matters if an animal becomes extinct.
0:56:34 > 0:56:39Well, so intricate are the connections in the natural world
0:56:39 > 0:56:43that there's no way to predict the impact of adding or removing species
0:56:43 > 0:56:45until it's too late.
0:56:54 > 0:56:58Who would have thought that a bettong would need a bandicoot,
0:56:58 > 0:57:02that a leaf-cutter ant would need a maned wolf,
0:57:02 > 0:57:06or, indeed, that a gecko would need a giraffe?
0:57:06 > 0:57:12Now, the complex web of relationships that we've seen
0:57:12 > 0:57:14have evolved over millions of years,
0:57:14 > 0:57:18but we've only scratched the surface of a myriad of stories
0:57:18 > 0:57:24that, when they come together, make these grasslands functional ecosystems,
0:57:24 > 0:57:30and it's here that I've learned to see the real beauty in nature.
0:57:30 > 0:57:34You see, for me, it's not in the minute detail.
0:57:34 > 0:57:37It's in the bigger picture.
0:57:37 > 0:57:43Because this works perfectly, and that is beautiful.
0:58:01 > 0:58:05If you'd like to know more about the fascinating web of links between species,
0:58:05 > 0:58:11the Open University has produced some material both to inform and inspire you.
0:58:11 > 0:58:13For your free copy,
0:58:13 > 0:58:16or to find out more about Open University programmes, ring:
0:58:21 > 0:58:22Or go to the website:
0:58:26 > 0:58:28And then follow the links to Open University.
0:58:29 > 0:58:32And join me next time,
0:58:32 > 0:58:36when I'll be travelling to the world's greatest seasonal forest.