Original subtitles

An African river.

For millions of years, the daily scene of a battle

between two uneven opponents:

swift antelopes, versus ferocious hunters.

(tense music)

In the water, the fearsome predators

usually have the upper hand.

But on land, the primordial beasts are more unwieldy.

And when it comes to raising young,

they show a surprisingly caring side,

protecting their nests ferociously.

This film gives a remarkable insight into one of

the most feared creatures on Earth,

and shatters the illusion of a vicious killer.

(dramatic music)

Africa's Serengeti, home to the Nile crocodile.

It will attack almost anything that crosses its path.

It is without doubt an unrivaled predator.

Yet, as a mother, the powerful hunter becomes the hunted.

And even more astonishingly, it has a surprising ally.

Serengeti National Park in Tanzania.

The Grumeti River winds its way through

the remote western corner of the park.

Its banks are lined by a forest rich in wildlife.

(soft music)

In June, the waters of the Grumeti run slowly.

Fish congregate in the rapids before

making their way further downstream.

The maribu, and the other billed storks

have rich pickings now.

And they're not the only ones.

Crocodiles, these ancient reptiles have outlived

the dinosaurs, and survived virtually unchanged,

for over 200 million years.

And during this time, they have perfected

their hunting strategies.

(foreboding music)

The Nile crocodile is found all over Africa,

and in most places, feeds mainly on fish.

This simple diet can sustain even the largest individuals,

which may weigh up to a ton.

This one has caught a large catfish in the river.

But in June, the waters of the river start to dry up.

(soft music)

All that is left are a few shallow pools.

For most animals, the lower water levels

make little difference.

Indeed for some, hunting becomes a little easier.

The deeper pools attract crocodiles.

When it gets too hot in the sun,

the cold-blooded reptiles gape,

and loose heat by evaporation from the moist inner surfaces,

or slip back into the water to cool off.

The large male will not tolerate a rival in his territory.

He is defending a favorite site along the river,

with a flat sandy beach,

where females like to lay their eggs.

Males with territories like these

have the best chance of mating.

Not surprisingly, he isn't willing to give it up.

These prehistoric reptiles have evolved a variety of

signals to prevent conflicts from escalating.

An upward-pointing snout is a submissive gesture,

which will quickly appease a rival.

Dominant males demonstrate their status

with impressive water displays.

The rippling of his flanks sends waves out into the water.

These are barely perceptible to the human ear.

But to other crocodiles, they are a clear message,

this male is ready to mate.

After weeks of fending off rivals, the males can

at last give their full attention to the females.

(soft music)

In the midst of all this activity,

an enormous army is approaching the river.

Over the next few weeks, the Grumeti River will be

invaded by hundreds of thousands of migrating wildebeest.

The animals are nervous of entering unfamiliar terrain.

But they are in desperate need of water.

Wildebeest need to drink every day.

Experienced animals know the dangers lurking in the water.

(tense music) (wildebeest bleating)

The herd moves on, guided by the older animals.

They steer clear of the deep pools

in which large reptiles can hide.

Instead, they head for the shallow waters further upstream.

The hunters are unable to follow,

separated by the drinking herds by a rocky barrier.

But some of the crocodiles are starving.

They have had no more than a few fish all year.

This male has decided to try and cross the barrier.

Climbing across the ridge between the two pools

takes nearly half an hour, and requires great effort.

The shallow waters, however,

offer little hope of going undetected.

Will the animal's efforts be in vain?

(tense music)

The resourceful hunter comes up with an ingenious solution.

It starts digging itself into the riverbed,

right under the watchful eyes of the drinking herds.

Deeper and deeper it sinks, until it is barely visible.

The wildebeest continue to arrive at the pool.

The hunter lies so low that no more than

the tip of its tail is visible.

The predator's strategy appears to have paid off.

The nervous wildebeest seem to sense the danger,

but can't see it.

(dramatic music)

After a few weeks, the shallow pools have dried up.

The marabou storks now gorge themselves

on the many stranded fish.

But for the wildebeest, this is bad news.

They have to move on to deeper pools.

The waters below are heaving with crocodiles.

The wrangling in the water has alarmed the wildebeest,

but after a few minutes, they're back.

They have no choice, and the hunters are waiting for them.

(wildebeest grunting)

They have taken a young calf.

(soft music)

A few kilometers upstream, the scene is a more peaceful one.

It hasn't rained for weeks, and large stretches

of the riverbed are bone-dry.

Away from the marauding males,

the female crocodiles are guarding their nests.

For nearly three months,

they will hardly move from this spot.

It is hot, gaping helps to cool down.

But today, this is not enough.

The female has to leave her nest,

and seek shelter in the shade.

From the bushes nearby, her every movement is being watched.

(tense music)

For a Nile monitor, crocodile eggs are

a highly-nutritious source of food.

The lizard is willing to risk being caught in the act.

After the effort of chasing off the egg thief,

the female needs to cool down.

A troupe of baboons have discovered something

right above the crocodile's nest...

Sweet, ripe figs.

Faced with such an abundance of fruit,

the greedy monkeys become choosy.

Discarded figs fall to the ground,

attracting impala, which now surround the crocodile's nest.

But that is not all, a herd of elephants have

descended on her nest site.

The female is besieged.

She has withdrawn into the bushes.

But the elephants are everywhere.

The heat of the day, and the invasion of her nest site

are too much for the attentive mother.

She has nowhere to turn.

The elephants have also occupied the water's edge,

blocking her path to the river.

She has no choice but to make do

with the little shade offered by the bushes.

But soon she is overheating.

Ignoring the elephant directly behind her,

she tries to get further into the shade.

In the meantime, the nest robber can pursue his

activity without disturbance.

The female lies motionless, in a dazed state.

She badly needs to cool down.

Nile monitors grow up to two meters long,

and are not fussy eaters.

But crocodile eggs are a particular treat.

The female lies listlessly in the shade.

Not until late afternoon, when it becomes a little cooler,

does she regain her energy.

(dramatic music)

But she is still slightly dazed.

Every movement seems to be an effort.

The baboons have discovered the open nest.

They're afraid of the large reptile,

but, getting no reaction from her,

they become more daring.

The female has now lost 20 of the eggs,

nearly half her brood.

(dramatic music)

But she has not given up yet.

By August, the land around the Grumeti is parched and dry.

The wildebeest now travel long distances between

the grazing sites and the remaining watering holes.

The crocodiles take full advantage of

the great congregations of animals.

The proficient hunters have tiny

pressure sensors on their heads,

which can detect the smallest movements in the water,

helping them to locate their quarry.

For just a few weeks, this bountiful supply of large prey

allows them to stock up in reserves

for the rest of the year.

(dramatic music)

But with so many animals jostling in the water,

the hunters' sensors are overpowered,

and they often miss their target.

The colossal beasts launch themselves

out of the water with astonishing speed.

But the heavily-built wildebeest are no

easy quarry to bring down.

Agile and fast, they pit all their skills

against the deadly predators.

The outcome is never certain.

(dramatic music)

Completely concealed underwater,

the powerful hunter suddenly propels itself out,

taking its victim by surprise.

Once the massive jaws lock,

the crocodile will try to drown its prey.

(wildebeest grunting)

By August, there is little left to eat

for the grazers in this part of the Serengeti.

Although the Grumeti River still has water,

the vast herds have to move on.

In September, water levels are so low,

that some of the crocodile eggs lie

nearly five meters above the river.

Every journey up to the nest is a huge effort

for the females, carrying 400 kilos of body weight

up the steep, sandy slopes.

Squabbles regularly break out at the nest sites.

The females are hungry and irritable.

Nile monitors continue to patrol the beach.

The crocodiles always have to be on their guard.

The egg thieves are on the lookout for unattended nests.

But some of the crocodile mothers have surprising allies.

A pair of thicknees.

The birds are also looking for a place to lay their eggs.

And it is no coincidence that they choose a spot

near the breeding crocodile.

The thicknee's brown plumage offers perfect camouflage,

crucial for a bird that makes its nest on the ground.

When it settles down on the sand,

it becomes virtually invisible.

The pair has agreed, the eggs are to be laid here.

The prowling monitor lizards are a danger

for the thicknees' eggs too.

But the birds will go to great lengths

to fend off the dangerous intruders.

(soft music)

By spreading its wings, the bird appears bigger,

and more imposing.

It seems to work, the lizard is unsure.

Since they have not yet laid their eggs,

both partners can join forces to ward off the hunter.

For two weeks, they attack the reptiles

the moment they make an appearance on the beach.

The message is clear:

this area is out of bounds for egg thieves.

At the end of September, the rains come at last.

(thunder rumbling)

The crocodile mothers now lie protectively

on top of their nests to keep them dry.

The Serengeti's hard, sun-baked earth can't absorb the rain.

The waters run off in torrents.

(soft, pensive music)

After a few days, the Grumeti River awakens again.

One pool after another fills up with water.

The forests burst into life.

(birds calling)

A mother cheetah is resting in the bushes with her young.

Although only two of her four cubs

have made it through the dry season,

the remaining youngsters are strong and healthy.

The young cub explores its surroundings.

Everything is investigated with a good chew.

The female takes a well-deserved break.

Cheetah mothers raise their cubs on their own,

and to feed her growing youngsters,

she is increasingly out hunting.

She needs to make a kill almost daily.

Out on the open plains, a herd of Thomson's gazelles,

with their young.

They are looking for the first fresh shoots after the rains.

The female cheetah sets off, following them at a distance.

Then she picks up speed.

(dramatic music)

The chase is on, over short distances,

she can easily outrun the gazelles,

reaching speeds of over 100 kilometers per hour.

But the gazelles have the advantage of greater agility.

She has brought down a young calf.

A good meal for her cubs.

(somber music)

All across the Serengeti, animals now thrive

on the lush, green grasslands,

transformed by the arrival of the rains.

The freshly-filled pools of the Grumeti River

have attracted a herd of hippopotamus.

They play boisterously,

reveling in the sudden abundance of water.

(hippos grunting)

The thicknees are not happy with the arrival

of the heavyweights on their beach.

The crocodiles are also not pleased.

But unlike the little waders,

they can stand up for themselves.

(crocodile growling)

She has made her point,

an angry crocodile mother is a formidable force.

Soon, there is a clearly visible exclusion zone

around her nest.

And those who don't read the signs,

have to learn the painful way.

(tense music)

After a few days, the rules are clear,

and both crocodiles and birds can

tend to their nests in peace again.

Thicknees have learned that by nesting near crocodiles,

they are safe from hippo trouble.

Now they can get down to the business of egg laying.

The birds continue to defend their neighbors

against the monitor lizards, and in return,

enjoy protection from unruly hippos,

a relationship that benefits both parties.

In contrast, a crocodile nesting on her own,

without help from birds or neighboring crocodiles,

has a far more difficult time.

The female under the fig tree is worn out

from continuous attacks by the monitor lizards.

Her nearest neighbor is too far away

to scare off the nest-raiders.

She has to fend for herself.

She is hot, and stressed,

and needs to cool down in the river.

The lizards are playing a gruesome game.

Relentlessly, they harass the poor mother,

not allowing her a moment's rest.

Whilst they can take turns cooling down in the shade,

the protective crocodile mother must stand guard

over her nest for as long as she can.

She is thin and gaunt from lack of food.

By the end of September, the midday sun is

directly overhead.

This is the hottest time of year,

the perfect temperature for the eggs.

But the female now can't stay in the sun

for longer than 10 minutes at a time.

There is little shade under the bushes,

and the monitor lizards still don't give a moment of peace.

(tense music)

(dramatic music)

The hunters circle her like a pack of hungry wolves.

In the mornings, she makes every effort

to stay close to her nest.

But during the midday heat,

she has to cool off in the water.

Increasingly, she avoids the strenuous journey down

to the river, and heads for the shade of the trees instead.

But from here, she cannot see her nest.

The protective mother is completely exhausted.

All her efforts of the last few months were in vain.

She falls into a state of torpor for hours at a time.

Every time she comes 'round, more eggs have gone.

Despite her dedication,

she will not raise any young this year.

Having too many neighbors, however,

can also be a hazard.

This perfect sunny beach has attracted

a number of breeding females.

There are repeated wrangles between neighbors.

A large, dominant female is particularly aggressive.

(crocodiles hissing)

The females will not tolerate strangers near their nests,

and with good reason.

The nests here are just a few meters apart,

and there is an uneasy truce between neighbors.

As the sun sets one October evening,

daytime animals retreat for the night.

(soft music)

In the cool darkness, others become active.

A leopard descends from a tree to patrol its territory.

But for the crocodiles on the Grumeti River,

this is a special night.

After more than three months assiduously

protecting their nests, the first eggs are hatching.

The mother answers their persistent calls

by helping to dig them free.

The powerful jaws gently pick up each hatchling

as it emerges.

Then she carries them down to the river.

The beach with the many breeding females

is witnessing the same special event.

The dominant female's hatchlings are the first to emerge.

She is running a little late, and as the sun rises,

is still busy carrying them to the water.

The thicknees have also had a new arrival.

Their chick has hatched just in time for them to be able

to leave the beach along with their crocodile neighbors.

But before they do so, they witness a tragic event.

A young female crocodile is sitting next to

the open nest of her neighbor.

A few hatchlings are still inside.

She is showing a more than curious

interest in the hatchlings.

She even dares to pick up some of the babies,

a dangerous and foolhardy act.

(tense music)

The angry mother restrains herself

to protect the delicate hatchlings.

(crocodile mother growling)

Despite the attacks from the older, dominant female,

the younger crocodile does not back down,

and refuses to move from the nest.

There appears to be a truce, and the older female

continues carrying hatchlings to the water.

Now the younger female also follows

with a mouthful of babies.

But the conflict has not been resolved.

Tensions rise again.

(tense music)

(crocodiles growling)

(crocodile hissing)

This extraordinary behavior of two females

fighting over the same hatchlings can only mean one thing.

The nest and babies actually belong to the younger female.

With so many nests side by side, the older animal

probably couldn't resist the calls of the hatchlings,

and dug them up, claiming them as her own.

The youngsters are all safely in the water.

Nile crocodile hatchlings are cared for by their mother

for up to two years.

Now both females are in the water,

and appear to join forces in maternal duties.

The young crocodiles will probably do well,

being cared for by two mothers.

They are more likely to survive the first

critical months of their lives.

But the eggs of the older female are still

buried in the stand.

Her young will presumably call for her in vain.

The tiny crocodiles are already able hunters,

snapping at everything that moves.

And one day, they too will become both caring parents,

and formidable predators.

(dramatic music)