Original subtitles

In the north of Tanzania,

towering mountains line a dramatic valley.

Its walls carved by shifts in the earth's surface

long ago . . .

Enriched by ancient volcanoes,

its slopes provide a variety of habitats

for life to thrive.

And its great centerpiece

holds water through even the driest of times.

This is Lake Manyara National Park.

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East Africa's landscape

is defined by a geological phenomenon

unlike any other on earth.

Thirty million years ago,

an upwelling of molten rock beneath the earth's crust

caused the planet's surface to begin to shift,

tearing continental Africa apart.

Over the eons as the tectonic plates split,

the land has fractured along two fault zones

to form towering mountains

and sunken valleys

that stretch over 3,700 miles.

Known as the Great Rift Valley,

this geological scar is so immense

it can be seen from space.

Molten lava once burst to the surface of this rift

through volcanoes lining the fault zones.

And the rift is still active.

Where the earth erupts, a caustic environment

supports only the most specialized of species.

But where eruptions have long since ceased,

ash that once spewed across the land

now provides some of the continent's most fertile soils.

This rich earth

lines the slopes of Lake Manyara National Park.

Water collects in the rift mountains,

flowing down into the valley below.

On its descent it nurtures diverse habitats;

From forest and woodland savanna,

to grasslands

and marshes.

Eventually it flows into a great lake in the valley floor.

This lake is a haven to a multitude of species

that depend on it throughout the dry season.

Beyond its banks, the valley provides for life as well.

Rooted in nourishing soils,

the park's varied environments

are the living legacy of ancient volcanic activity.

They provide homes for many species;

Some specialized to a particular niche.

While others know how to take advantage

of all that's on offer.

For them the park's variety presents a banquet

fit for a huge family.

It's morning in Lake Manyara National Park.

A troop of olive baboons gathers in the valley's foothills

before embarking on its daily journey.

They spend the night in the safety of the high cliffs,

and travel by day to the sweet grasslands

of the valley floor.

The troop numbers sixty strong,

and it's growing.

The newest baby's pink face

means she's younger than four months.

And she's already developed

the strength and coordination to climb.

For her and her older cousins,

life is simple.

While they play,

their seniors engage in their favorite pastime.

Grooming.

Soon it's time to begin their journey.

Babies cling to their mothers' bellies for at least six weeks.

By twelve weeks old they ride jockey style,

saving their energy

for the next play break.

There's time to steal a quick drink.

This water flows down from the mountains,

which rise up to 2,000 feet above the valley floor.

Now in the height of the dry season

it's crucial to life in the park,

fuelling growth through the toughest times.

In places it runs as streams.

In others it seeps through the earth as groundwater,

accessed by the deep roots of trees.

Eventually it spills into lake Manyara itself.

The foothills are the first to receive the mountain runoff;

And here vegetation grows green and dense.

For this Blue monkey,

the forest is a permanent home.

When he's old enough,

he'll challenge for control of a harem of females.

For now he lives alone,

moving between the territories of other Blue monkeys.

Manyara's dense vegetation

is crucial to him and his kind.

Blue monkeys can't cope with long exposure

to the park's tropical sunshine.

Luckily for him, the forests offer plenty of shade.

And food too.

He gets almost two thirds of his forage

from only ten plant species,

all of which are provided in a small home range

in the dense forest.

For the baboons,

things are very different.

They have incredibly varied diets,

eating virtually all the edible plants in their travels

through Manyara's different habitats.

And they've found one of their favorite foods.

The appropriately named

Sausage tree grows enormous fruit.

They're a mouthful,

even for a male with 2 inch long canines.

These razor sharp teeth

also play a crucial role in battles for power,

and provide important defense against the baboons' predators.

As do the troop's numbers.

The troop moves with a strong contingent of big males.

They band together to protect their kin.

This means that unlike most of Africa's primates

the troop can venture onto more open ground,

far from the safety of trees.

But the baboons must be wary at all times.

There are leopards about.

This big male's territory

covers the border between Manyara's forest and savanna.

He lives a completely solitary life.

But his range overlaps with those of numerous females.

From his vantage point

he advertises his position to both potential mates

and competitors.

For him the tree is a resting place,

lookout point

and stage for making his presence known.

But for many of the park's other creatures,

the huge trees that thrive in the rich soils

have a simpler importance.

Figs are a favorite of Silvery-cheeked hornbills.

This male and female pair

wanders the treetops together in search of fruit.

Unable to chew,

the hornbill must position the fig perfectly

for swallowing whole.

And it's easier said than done.

But figs aren't the only food available.

Like many birds, the hornbills will eat insects.

And these are abundant in Lake Manyara National Park.

These bees are preparing to move to a new home.

They've left their hive with their queen

and cluster in a nearby acacia tree,

awaiting the return of scouts.

When a suitable new home has been found,

the scouts will give the colony directions

in the form of an intricate dance.

In their old home

worker bees left behind will raise a new queen,

allowing reproduction to happen in the old hive

while a new one is created.

Acacia trees like this

grow abundantly in the savanna woodlands

between the forests of the foothills

and the grasslands in the valley floor.

Here, away from the lake, surface water is sparse,

especially now in the height of the dry season.

But the acacias' deep roots give them access to groundwater.

These trees are a favorite of another of the park's primates.

Vervet monkeys.

These youngsters are remarkably adept

at avoiding injury amongst the thorns.

But the acacias are more than just props for play.

They produce new leaves and flowers during the dry season -

fodder for the monkeys.

Like the baboons, Vervets are opportunistic omnivores

and they eat a range of foods.

Remarkably this includes the seemingly least appetizing part

of an acacia tree . . .

Its thorns.

By breaking these off and eating their nutritious base,

the monkeys turn the tree's only defense mechanism

into a source of food.

The troop's youngest baby

will rely entirely on its mother for comfort and protection

until it's three months old.

But it takes any opportunity to explore.

By six months old it will be largely independent.

For now,

mum's not letting it out of reach.

Its older cousins engage in some roughhousing in the open.

Unlike the baboons,

the Vervets are defenseless against big predators,

and can't stray too far from the safety of trees.

They keep many eyes on the lookout.

Vervets have at least five different warning calls,

for various threats.

And they've learnt to respond to similar cues

from another species.

A Superb starling gives different calls

for terrestrial and air predators,

to warn its own species.

By learning to respond to the bird's calls,

the monkeys gain extra sentries.

With a much bigger family than the monkeys,

the baboons have plenty of lookouts.

Deep into the savanna,

the troop is more than halfway on its journey.

They too take full advantage of all the acacias have to offer.

The youngsters devour pods, leaves and flowers alike.

Their opposable thumbs allow them to handle their fodder

with remarkable dexterity.

But some pods fall through the gaps.

Their inclusive diet means the baboons have plenty of options

for a satisfying snack.

Roots offer both food and moisture.

And experience has taught the adults

which part of each plant

offers most in the way of sustenance.

This ability to select specific parts of different plants

sets baboons apart from many of the savanna's animals.

While the troop feeds,

there is time for a midday grooming session.

Females will often form relationships

with particular males,

relying on them for defense against aggression from others.

Grooming is an important part of cementing these relationships.

But sitting around is boring for the young pink-faced baby.

She is intent on exploring her world.

Eventually the troop moves off on the final leg of its journey.

When the baboons are gone,

a family of elephants

carefully gathers the pods they've left behind.

At this dry time of year,

Manyara's elephants separate into small groups

to make the most of available resources.

Nursing mothers are especially pressed

to find enough nutrition.

The newest baby

drinks more than two and a half gallons of milk a day.

Her mother must add

to the hundreds of pounds she already eats

to account for the burden of nursing.

Like the baboons, elephants have incredibly varied diets

and the young mother will chomp through everything on offer.

A savanna's combination of dry grass and woody vegetation

provides the browsing elephants with lots of options.

But for the park's grazers,

the flatlands surrounding the lake

provide better feeding.

Here, large swathes remain green

despite the long months since it last rained in the valley.

The lushest of all are broad marshlands at the lakes edge,

where groundwater bubbles to the surface in springs.

Here it fuels the growth of Smooth flatsedge.

In the dry season this sedge

can form 60 percent of the diet of buffalos.

The old bulls in this group have been ejected from their herds,

unable to compete for dominance with younger males.

They now wander the marshes with only each other

and some Cattle egrets for company.

The birds take full advantage of the buffalos' presence.

They snap up insects disturbed by the hefty herbivores.

And use them as perches with better vantage points.

The water seeping into this marsh

is reaching the final stage of its journey from the hills.

What isn't absorbed by the sedge

will run into lake Manyara itself,

the park's centerpiece,

and huge epicenter of life.

It's home to many of the 400 species of bird

found in the park.

They flock to Manyara from far and wide to feed . . .

and to breed.

Many large waterbirds frequent the lake,

but among these the two species dominate.

At 24 pounds,

the Great white pelican is the biggest of the lake's birds.

To lift their bulk,

these huge birds have wingspans of more than eleven feet.

They spend as much as a quarter of the day foraging,

scooping fish from the water in their pouches.

These birds are known for their cooperation,

working together to herd fish into the shallows

for easy pickings.

The pelicans share the lake with another imposing species . . .

the Yellow-billed stork.

Flocks roost on the grassy shore.

At only a fifth of the pelicans' weight

they can spend much less time foraging, and more time resting.

As they stride through the shallows,

the storks stir the mud of the lake bed, disturbing their prey.

Intensely tactile bills snap shut

as soon as they feel anything edible.

They feed on a variety of aquatic life

including fish, frogs and crustaceans.

There's enough food in the lake

to support flocks hundreds strong.

The lake's abundance is only truly appreciated

when compared with a very different scene,

just 60 miles to the north.

Lake Natron.

Here, the water supports very little.

Like lake Manyara,

the water flows into Natron from the surrounding highlands.

But one looming peak

makes this lake a very different environment.

Ol Doinyo Lengai.

Towering over 7,200 feet above the plains,

this active volcano is known to the local Maasai people

as 'the mountain of the gods'.

In the last hundred years, it has erupted 15 times,

spreading volcanic chemicals over the surrounding soils.

Water flowing both above and below ground

carries these chemicals into the lake.

High evaporation rates

leave behind such high concentrations of salts

that the lake's water can corrode flesh.

Now in the height of the dry season,

broad, barren mud flats

surround the receding caustic waters of lake Natron.

Very little lives in this extreme and unforgiving land.

With a fantastic exception.

Flamingos.

There are between 1,5 and 2,5 million of these birds

in east Africa.

And most of them hatch on the mud islands of lake Natron.

Terrestrial predators can't wade through the corrosive water

to reach the flamingos' nests

but the elegant birds have adapted to thrive here.

Their legs have tough outer coverings to protect them.

Flamingos feed on microscopic algae,

filtering it from the water.

The upside-down curve to their beaks

allows for maximum intake

when reaching from their height of more than 3 feet.

In places, the lake's corrosive water

bubbles up from beneath the earth

at extremely high temperatures.

And the flamingos must shift from foot to foot

to withstand the heat.

The huge flock will feed for up to

twelve and a half hours in a day to get all it needs.

The flamingos aren't the only specialists living here.

In streams feeding the lake,

a school of Alkaline tilapia makes its home.

They are specially adapted to survive in the oxygen deprived,

caustic waters.

Like the flamingos, they feed largely on the lake's algae,

grazing the surface of stones.

These two very different creatures

thrive where few others can survive,

succeeding through their specialization.

At Natron's neighbor to the south,

the allures of the more forgiving lake Manyara

are lost on the baboons.

They've been on the move all morning,

and they're reaching their destination.

For them the valley floor's main attraction

is these green grasslands.

Despite their varied diets,

grass can make up more than half of their food.

And these long blades hold a remarkable treat for the troop.

Spider webs.

There is no definite explanation for this choice of food.

The baboons could be relishing anything caught in the webs,

rather than the silk itself.

While they settle in to feed,

there is plenty of time for troop life to play out.

And of course, this involves some grooming.

But not all is completely peaceful.

A show of aggression helps reinforce rank between males.

Might is right in baboon society.

While the males fight for dominance,

the young female baby inherits her mother's rank,

which she will keep for life.

As always,

the troop keeps a vigilant watch for predators

and others are quick to take advantage.

With more eyes on the lookout,

the wildebeest and zebra join the baboons.

The primates know how to get exactly what they want

from the grass.

The zebra make up for their lack of opposable thumbs

with delicate lips

that efficiently pluck even the shortest blades.

Zebra are adapted to subsist on a variety of grass types.

Whereas the wildebeest rely on short, tender growth.

Both of these grazers

take advantage of the baboons' company while it lasts.

Come nightfall, the troop will be vulnerable here.

Once they've eaten their fill,

they begin their return journey to the safe high ground

of the valley's steep walls.

Tomorrow they will repeat the journey,

taking all they need from the varied environment

of lake Manyara National Park.

Lake Manyara's lush valley

is the living legacy of past violent upheavals.

Rich soils combine with flowing water

to fuel growth in abundance.

The many creatures that live here

find food . . .

and shelter in plenty.

From generation to generation

they make use of Manyara's resources

as best they know how.

Filling each niche

from its foothill forests

to the watery haven

of its great lake.

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