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The grasslands of East Africa support more large animals than any other place on earth.
Hi, I'm George Page.
Here on the vast plains of the Maasai Mara, lush grasses provide food for more than a
million munching wildebeests, other grass eaters, and their predators.
And on the move, these vast herds seem to blanket the earth.
This profusion of life is here because of changes in the landscape which occurred millions
of years ago during the formation of Africa's great rift, the largest crack in the earth's
surface.
The plains are made of volcanic ash produced during the rifting process, resulting in good
soil for these nutritious grasses.
In essence, the grasslands and the life which thrives on them came out of the ashes.
The earth makes life.
Under nearly every contour and every physical condition, life is poured like plaster into
a mold or water into the shape of a lake, a lake in the great rift of Africa.
Life first occurred on earth about three and a half billion years ago when something, call
it a bolt of lightning, persuaded a molecule of primitive protein in a pond of chemicals
to make a copy of itself.
And then it made another and another.
Over unlimited time, life became organized into all the forms we now know.
But always, life was shaped by the shape of the earth.
Old Doinyo Lengai, the mountain of the Maasai god Engai.
Some parts of the earth are like factories of life because they are constantly changing
shape.
The plains and lakes of the great rift start in a place like this.
Most cultures explain the beginning of life with a god feeling lonely and deciding to
do something about it.
To the Maasai, the people of the East African plains, this volcano is Engai's laboratory.
His alchemy involves lava and water.
The lava rising up from a hole in the earth is very alkaline and very thin.
For years, it bubbles up into the mountaintop cauldron until one day the cauldron collapses
and the lava plunges back into the mountain, meets underground water and explodes.
The clash of temperatures instantly transforms the lava into a fountain of ash rising a mile
over the eastern rift valley where the winds from the Indian Ocean push it to the west.
The heaviest ash falls back on the mountain in caustic snowdrifts of pure sodium carbonate.
The lighter ash sweeps along in great dunes for up to 40 miles from the mountain's base.
Then where the dunes end and the ash from former dunes has mixed with water and settled
into a soil, life can begin.
The Serengeti.
Because the porous ash does not hold water, when there is no rain, there is very little
life.
But because the ash is rich in minerals, when the clouds do come, they bring one of the
greatest concentrations of life on earth.
Almost instantly, a desert becomes a luxuriant meadow.
Rainwater as it sinks through this ash pulls certain salts down with it and three feet
below the surface forms a calcium pavement harder than concrete.
Because deep roots cannot penetrate this barrier, there are no trees, only grasses, and the
creatures that live on grasses, and the creatures that eat the creatures that live on grasses.
There are woodlands on the edges of the Serengeti, and these are the permanent homes of the predators
and the browsers.
But the plain itself is the temporary home of the greatest herds of grazers on the planet.
Built of volcanic soil, the Serengeti forms the vast central plain of the Rift Valley.
And where there are no trees, there are instead animals.
In shaping the life of a place with too little room for roots, the earth has settled for
a forest of legs.
First comes the ash, then the rains, then the grass, then the grass eaters.
Not only can animals live without roots, they can move.
When the grass dies back, they move on.
When it grows again, they return.
First the zebras, then the wildebeests.
The main thing about being on the move is being on your feet.
One of the most precarious periods of a wildebeest life is the long three minutes after birth
before it can stand.
Almost all wildebeests are born at about the same time, a survival strategy based on the
principle of offering predators more than they can possibly take.
Once it is on its feet, a calf can run as fast as an adult, and yet one out of six are
still killed by lions, hyenas, wild dogs, or jackals.
While a calf is learning what its legs are for, it has another important job.
For the next year, it's going to have to follow its mother on some of the most turbulent and
crowded migrations undertaken by any animal.
First it has to work out that a wildebeest is what it is, and then which one of more
than a million other wildebeests it's going to follow.
Not this one.
By butting the calf, its neighbor is doing it a favor, directing it towards its mother.
A wealth of minerals explodes out of a mountain, becomes grass, becomes milk, becomes sturdy
wildebeest leg bone.
A caracal lynx, an eater of eaters of grass.
Not all grass eaters are wildebeests, though, and not all predators are after them.
However unsure of this, the wildebeest themselves might sometimes be.
The lynx lives on a different level from wildebeests and their predators.
Rodents also eat grass, and a time of plenty to this cat is a time when there's plenty
of them.
Somewhere here there are snakes eating lizards, mongooses eating insects, ground beetles eating
grubs.
Life flows into every crevice.
Wherever there's something to eat, there's something to eat it.
After the zebras and wildebeests come the Thompson's gazelles.
Few animals eat exactly the same thing in exactly the same way.
Gazelles like their grass short, so they take their time arriving, and when they do arrive,
the other grazers have already mown it for them.
Wild grass also enables them to use their principal defense, speed.
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For a pack of wild dogs, a gazelle fawn is barely a snack.
But by the time they return to their puffs, they will have taken several gazelles, eaten
their fill, and have plenty left over for the youngsters.
Cooperative living and hunting is common throughout the dog family.
It's an especially good strategy on the plains, where there's endless room for maneuver and
not many places for prey to hide.
In times of plenty, a predator's job is to get as much meat as possible for itself and
its cubs, whose births have been timed to coincide with the births of the grazing animals.
There is only one reason why more calves aren't killed.
The predators have had their fill.
There would be more predators if it weren't for one problem.
The poor could not survive the dry season.
Because the rift's volcanic ash is too porous to hold water, when the rain stops, life has
to make a massive move.
The lions, the wild dogs, and the hyenas retreat to the woodlands to eke out a living there,
while the zebras and then the wildebeests trek north, farther and farther away, where
the ash becomes finer and finer until it becomes ordinary soil.
When it is rich, the Serengeti is very rich, and when the animals it has nurtured depart,
it's the greatest annual shift of life on dry land.
The Maasai Mara in Kenya, north of the Serengeti.
It is surrounded by rift, but is relatively far from its direct influence.
It's less seasonal than the Serengeti, but like the Serengeti, it has its resident predators
waiting for their time of plenty.
The difference between cheetahs and lions is that lions can take almost any large animal,
but evolution has taken the cheetah down another path, specialization.
Lions can catch gazelles and not much else.
To fit into their particular contour of life, the key was speed, but in developing it, they
lost the strength to defend their kill from other predators.
It takes a lot of energy to catch a gazelle, and so a cheetah can't afford to lose its
prey too often, especially if there are cubs to feed.
Like all specialists, the fast cheetahs are fairly uncommon.
The strong lions, the generalists, are plentiful.
Lions are generalists too, and are even more successful.
Especially these humans, the Maasai.
In recent centuries, they have spread through many parts of the rift valley.
They are supreme practitioners of pastoralism, which is predation on an entirely new level.
Humans with their large brains, evolved while adapting to many different aspects of nature,
have discovered how to adapt nature to humans.
Their prey animals live with them.
The pastoralists take advantage of the animal's strong herd instincts.
They go where people want them to go, and are available at all times to be milked or
killed.
But the Maasai and their cattle are still part of the system dictated by the volcanic soil.
And when the rains change, and it's time for grazing animals to move, they move too.
The Maasai and their cattle have become as much a part of the plains as the zebras and
the wildebeests.
Now the predators of the Mara have to sit out their lean season.
October.
The Mara now is dry.
But in the south, the rains have returned to the Serengeti, and the wildebeests can
smell it.
They will go even though a lot of them won't survive the journey.
If ever a large animal could be said to move in swarms, this is it.
The maximum wildebeest lifespan is about 20 years, but wildebeests do not often get the
chance to die of old age.
Every mile of the way, dangers.
You can hear my shouts.
and possibly the greatest danger of all, the Mara River.
The Mara River is the largest river in the world.
One in six of all wildebeest dies in the rigors of migration, of drowning, trampling, broken bones,
or in the case of young animals being left behind.
This river is more than just an obstacle to wildebeests. It is one of the main sources of Lake Victoria.
Twenty-five years ago, the Mara River was the only river in the world that was left behind.
The Mara River was the only river in the world that was left behind.
The Mara River was the only river in the world that was left behind.
Twenty-five million years ago, there were no lakes in Africa.
But when the rift took the landscape and pushed it and pulled it and erupted on it and wrinkled it up,
it created many different kinds of places for water to flow into and settle.
Lake Baringo, one of the fresh, shallow, reedy lakes of the Eastern Rift.
It's at the extremely fertile end of a range of lakes that covers nearly every degree of depth,
salinity, and hospitality to life. Baringo is an easy lake to live on.
Whistling duck, jacana, fish eagle, yellow-billed stork, all are creatures of Africa's rivers.
Moving here required no special qualities. There's more water here than in a river, and it moves slower.
And there are rich reed beds and an undreamed-of expanse.
In fact, for a river creature, this lake is probably a better place to live than a river.
A Malachite kingfisher preens in the morning sun.
Another river bird, a hammer cop, prospecting for frogs.
A reed bed is essentially a grassland, but with a difference. There is no solid ground.
Some creatures wade. Otherwise, the grass itself becomes the living surface.
A red bishop is a weaver, a family that thrives in the Rift Valley's vast reed beds.
Where there's no ground, wings become more important than legs.
Even the mating display is performed in the air.
A northern masked weaver weaving. The nest is even lighter than the bird and hardly bends the long reed that it's attached to.
A goldenback weaver invites his female to use his aerial doorway.
This is the western rift's Akagera swamp, a vast region of lakes and floodplains where beds of papyrus have taken over the landscape.
A grazing mammal, a sitatunga.
It's a long-legged semi-aquatic bushbuck wading through unanchored islands of vegetation on a spongy mattress of roots.
The sitatunga's hooves are splayed to keep it from sinking through the matted roots, and when it steps, it raises its legs in the manner of a prancing horse, never making a splash.
And there are other water mammals, ones that have become such an integral part of their lake that they're practically islands in it.
Fish graze on the algae on their skin, and terrapins and small crocodiles have been known to haul up and bask on their backs. Various birds forage here, and occasionally an egret or a black crake will use one as a fishing perch.
But even so, the hippopotamus is not entirely aquatic. It still depends upon the rift's rich grasslands on shore for grazing at night.
Before the rift had created the grasslands by pulling the forests apart from each other, there were several species of hippo, but this is the only form that survived in the new world of lakes and savannas.
Its skin is smooth and thick, and water evaporates from it at a great rate, which is why it grazes at night and gets through the heat of the day more or less submerged.
It may not feed primarily in the lake, but it does everything else there. A male holds territory, for example. The fact that it's immersed in water doesn't prevent him from staking it out in the usual pungent way.
The famous yawn, too, is territorial display.
Some lakes are like rivers. Others, such as Lake Tanganyika in the southern part of the western rift, are like seas.
Lake Tanganyika is a long section of the rift which has simply filled up with water. Its walls are the walls of the rift.
It is clear and deep, 4,500 feet deep, so deep that no light penetrates to its bottom, a thousand feet below sea level.
Tanganyika is second only to Baikal in Siberia as the deepest lake on Earth. It was formed and filled 20 million years ago, and its fish have evolved in isolation.
The very sides of the rift itself shape the lake and its life. The rocks form the foundation for a rich growth of algae.
Snails, crabs, and prawns eat the algae and shelter in the crevices. Fish eat the algae, snails, crabs, prawns, and other fish.
There are sponges, jellyfish, plankton. It's almost an exact replica of a coral reef system, but built on stone. Corals cannot live here in freshwater.
Two-thirds of the fish are of the cichlid family, 139 species in all. But there are others too, catfish.
Eels, which look and behave like marine mores, but are no relation.
Completely unrelated creatures that live in similar places, like a deep sea and a deep lake, will grow to look and behave like each other.
This is known as convergent evolution. Life is sculpted by its surroundings.
But since no two places are exactly alike, everywhere there is always some kind of uniqueness.
This cichlid is not rooting in the sand for food. It's picking up the sand itself in order to do something that has never been observed in any ocean fish.
It's building a sand castle, a bowl of sand on a flat rock. The structure looks as though it might be a nest, but it's not.
Somewhere in the fish's distant past, the bowl probably was a nest, one that became increasingly useless as it became increasingly precarious.
Now it serves only as a mating couch, where the male entices a female down to mate.
But other species of cichlids do use and stand guard over bowl-shaped nests of thousands of vulnerable fry, fanning themselves with their tails to suck in oxygen.
Yet another protects her fry by keeping them in her mouth. The babies are allowed out as if to play, but at the first whiff of danger, they all streak home.
Since this protection is so effective, the mouth brooder doesn't need to spawn as many fry in the first place as the nest brooder does.
When these fry are a few days old, even though they're still vulnerable, still bite-sized to almost any fish around, they start to rise out of the nest.
At first, the parents corral them into a floating nest ball, but finally they let them join the rest of the potential food in the lake and put their trust in luck.
One place they won't go is the 85% of the lake below a depth of 600 feet. Lake Tanganyika may resemble a sea, but it's not one.
It's entirely enclosed and full of volcanic vapors, and the deep water does not circulate.
Here there's no dissolved oxygen. Nothing lives here, and when something dies in the upper layers and drifts down, its nutrients are lost forever.
Inside the lakes in the rift are infused with mineral salts. Lake Turkana is long and shallow and receives volcanic sediments from many parts of the valley, but it has plenty of oxygen, and it's full of life.
Here in the desolate land of the El Molo, which means the people who like to fish, its fertility is spectacular.
Fossils found around Lake Turkana suggest that it has been supporting Homo sapiens since the species first appeared on Earth.
As humans expanded across the flatlands, they often came to a halt at the shore of a lake. Lakes have water and food, and humans are so adaptable that those things are really all they need.
Some water, some food, and they can take it from there.
The distant lineage of the El Molo is unknown, but historical records and a look at their way of living and fishing suggest that they have been here a long time.
Before recent technology, the way humans responded to difficult problems was by developing great individual skills and then preserving them in their culture. It would take intensive teaching, patience, and practice to learn to fish this way.
Same lake, different people, another way of fishing. They are the lake's namesakes, the Turkana. There are 170,000 of them compared to only 250 El Molo.
They are cattle herders, not fishermen. But modern innovation such as life-saving medicine, restrictive tribal boundaries, and good veterinary care for their livestock has led to their land being overpopulated and overgrazed. And so some have taken up fishing.
It's not always been easy. Originally, they didn't like fish very much, didn't like venturing out in boats. In fact, some of the first boats they were given ended up as the roofs of houses. But they have now learned to use modern gill nets and to fish from the shore and the shallows.
They are developing a taste for fish, but they are also selling fish and buying meat. As well as using modern technology, they have joined the system of modern cash-based economics.
People can readjust their cultures to accommodate modern ways, but it's often those modern ways that force them to readjust in the first place. Still, the Turkana, with their technology, catch many more fish than the El Molo do.
The change is difficult, disorienting, perhaps even sad. But if any species can do it, humans can. With its wealth of landscapes, the rift created a species whose outstanding talent is its adaptability.
Turkana is a salty, alkaline lake, but other lakes in the eastern rift are so alkaline that they're caustic.
Fed by volcanic springs, super saturated with sodium carbonate, Lake Bogoria supports no life at all, almost. Life is such that even here, something has managed to break through and in abundance.
Another caustic lake, Magadi. The water comes from hot springs, but quickly cools as it flows and streams to the lake.
There, it evaporates, leaving behind its sodium salts. It looks as though nothing could survive here, but in fact, something does, algae.
The principle that where there's something to eat, there will always be something to eat it applies even here.
It's Tilapia, one of the cichlids, and it occupies a niche so narrow that you could actually point to its boundaries.
The algae can be found throughout the lake and the stream that feeds it. But in the stream, there is one short stretch where the fish can live without being burned by either the heat or caustic salts.
And not only do they eat the algae in their patch, when it runs out, they play a game of chicken in the hot water, dashing in, snatching mouthfuls, and darting back again before they cook.
Some lose the game, and of course, where there are fish, there are always fish eaters. A yellow-billed stork, feeding at the caustic end of the fish's range.
And even where the water is so caustic that it would burn a mammal's feet, there are those most anxious of birds, flamingos.
The greater flamingos feed on tiny crustaceans that can be found in many places.
But lesser flamingos here on Lake Bogoria are so specialized that they feed only at the salt lakes, sifting for the lowest organism found in almost any food chain, algae.
The flamingos are most at home in these steamy places. It's almost as if an advanced animal had returned in time to drink of the very beginnings of life, the primordial soup.
Lesser flamingos can eat the algae in the middle of the lakes, but they can't drink the water. To do that and to bathe, they have to find the same kind of not-too-hot, not-too-caustic places that the fish found.
But a flamingo's definition of not-too-hot is broader than a tilapia's and can extend up to 122 degrees. The birds can drink water that's even too hot for them to stand in.
And in these shallows, they brave something else, more dangerous than heat. Lake Bogoria has no fish, but curiously, the trees on its shores have a thriving population of fish eagles.
Wherever there is something to eat, there is something to eat it. The fish eagles of Bogoria live almost entirely on flamingos.
Courtship displayed. Lessers in the foreground, graders behind. Flamingos mate for life, and life is long. On average, about 50 years.
But to breed, flamingos fly down the Rift Valley 200 miles south, over the escarpments and volcanoes, all the great landscapes of the Rift.
They arrive at a lake whose salt-crusted shores are virtually without life, with water so caustic that it looks like cracked glass, so caustic that it ceases to be water at all and turns into a chemical sludge.
Lake Natron. Except for flamingos, there's only algae. Here, the flamingos, both lesser and greater, raise their young.
The lake is 40 by 20 miles, and the flamingos are in the middle of it. It was only recently that anyone seems to have known that the flamingos were here. No European explorers ever reported them, and they seemed to play no part in local folklore.
Graders are breeding here now, but when they have finished and the chicks have fledged, the lessers will move in and use the same nest platforms.
The lake's springs arise from the interior of the volcano that dominates it, Old Doño Lengay. The alkaline crust would burn the feet of any mammal or reptile that tried to reach the flamingo chicks.
The only predators that can reach the nests are the ones that fly here, but only Egyptian vultures seem to consider the trip worth the effort, and they don't try it very often.
The nest platforms raise the eggs and very young chicks to a level several vital degrees cooler than the searing heat of the rock surface. They also keep them clear of Natron's unpredictable floods.
The chicks leave the platforms less than three days after they hatch, all sizes and ages massing together and seeking out their parents so that they can drink their crop milk, which the adults manufacture in the process of desalting their own food.
As the chicks get older, they're herded by the adults into huge shifting lava-colored creches.
The throng poses the biggest danger of all to eggs still on the nest, as chicks of all ages recklessly mill back and forth.
Any young chick pushed off the nest mound quickly dies of heat exhaustion.
Lake Natron's flamingos are strangely missing from local folklore, but they may have been included in the mythology of a distant culture.
Africa's Rift Valley created the source of the Nile, and the Egyptians may have meant the flamingo when they referred to the bird brought out of the ashes by the god Osiris.
It was the symbol of resurrection, of life where no life is possible.
The Phoenix.
Nature is made possible by the financial support of viewers like you.
And by Siemens, engineering solutions in electronic components and medical systems, telecommunications, energy and automation, Siemens.
And by Canon, quality and innovation for the way we work and live.
And by the gas industry, helping provide cleaner air with clean gas energy.
Alleluia!
Alleluia!
Alleluia!
Alleluia!
This is PBS.