Original subtitles

NARRATOR: Water and land,

prime habitat for two of Africa's deadliest species.

(grunting)

Crocs have 68 teeth...

and the strongest bite force on the planet.

Hippos have razor-sharp tusks that can chop you in half.

(snorts, growls)

Both have killer instinct.

Neither will relinquish their stronghold over the river.

And when nature throws a curve ball,

tolerance turns to violence.

Hippo versus croc.

Who is Africa's ultimate gladiator?

(Hippopotamuses growl, snort)

It's suicide month in the Luangwa Valley,

the season of extremes.

Paradise is about to turn into purgatory,

and this croc faces a battle she may not survive.

She's not alone.

Forget everything you thought

about hippos being cute and comical.

To share this river with crocodiles,

they need to be the meanest guys on the block.

(grunting)

Crocs are the most lethal freshwater predators on the planet.

They don't need to share,

but this is the beach master,

two and a half tons of testosterone-fueled rage.

He's possibly the most aggressive animal alive.

Put them in the ring together, and it is a clash of the titans.

(both growl)

They're about as different as any two animals can be,

but both are equipped to fight...

and kill.

And this battle will test them to the limits of their game.

Both have a shot at the title.

(growls)

Both have incredible adaptations

and chinks in their armor,

but they have the same goal,

to breed and survive.

The game is on,

and this lush environment is about to spiral

into a hotbed of feast and famine.

Many will succumb to the river's deadliest rival...

blistering heat.

Temperatures peak over 100 degrees Fahrenheit,

and their habitat is turning against them.

Six months without rain takes its toll.

For the crocs, it's time to focus on the next generation.

For others, it's a time to seek opportunities.

(eagle squawking)

(grunting)

- (snarls) - (growls)

For the beach master and his herd,

it's the start of deep unrest,

his territory is shrinking.

For both gladiators it's the beginning of a great march,

following the remaining water.

It's a time to adapt... or die.

(hippopotamus grunting)

Hippos eat roughly 80 pounds of grass per night,

and vegetation is dwindling.

The body count rises,

but it's tasty nutrition if you've got a stomach for it.

Crocs have the toughest digestive system in the animal kingdom.

They use and store almost every bite they eat

and can survive up to a year without a meal.

It's time to stock up.

Crocs can't chew,

their jaws and teeth are designed to grip and tear meat off the carcass.

The biggest and oldest crocs

get the first sitting and the choice cuts.

An 18-foot crocodile has a bite force

up to 5,000 pounds per square inch.

That's two and a half tons clamping down.

(growling)

(braying)

Powerful muscles hold the jaw shut

while 68 teeth pierce and hold on to the flesh.

Then he spins his body 360 degrees.

The muscular force of his body

combines with the sharpness of his teeth

and helps him tear flesh from the carcass.

It's known as the death roll.

He's got some of the strongest jaws on the planet

and a drought-defying metabolism.

The croc seems the odds-on favorite to win this match,

and the hippo, the wild card.

But to really get what makes each of our gladiators tick,

we need to dive deeper into their world.

Hippos and crocs need both land and water to thrive.

River frontage is prime real estate,

and for most of the year they live in a rich, watery wonderland.

With a skin that can weigh up to half a ton,

hippos spend up to 16 hours a day in water to keep hydrated.

It's not surprising

when you consider their closest relatives are whales.

Around 55 million years ago, hippos and whales split

from the same water-loving land mammal.

One branch took to the oceans and evolved into the whale.

(whale moans)

The other branch stayed topside

and became the amphibious, bulkier hippo we know today.

(grunts)

They can hold their breath for up to five minutes

and reach speeds of up to five miles an hour on the riverbed.

(grunting)

Crocs have been around much longer than hippos,

and they've hardly changed in over 70 million years.

You could say they hit the evolutionary jackpot.

Their adaptable design enabled them to outlive the dinosaurs

and become the most advanced reptiles...

(growls)

...on the planet.

He's a masterpiece of form and function.

His muscular tail makes up almost half his body length

and can propel him through the water

at speeds up to 20 miles per hour.

He has two sets of lungs,

which he uses like floats to sink and rise.

With this on board scuba tank,

he can stay underwater as long as two hours.

It's a dangerous neighborhood

for the beach master's newborn daughter.

(hippopotamuses clicking)

She also spends a lot of time underwater,

but right now she can only hold her breath for 40 seconds.

(clicking)

(low grunting)

She's submerged in a cocoon of sights and sounds.

(clicking)

Like whales, hippos communicate underwater

with clicks and whistles.

(whistles)

(clicking)

Mother and baby develop a strong bond which lasts several years.

And even the beach master plays a role,

he's her bodyguard.

(clicking)

For the first few weeks,

her safest bet is to fly under the radar.

She even suckles here,

folding her ears back and closing her nostrils

to keep the water out.

She'll nurse on milk for the next eight months,

so she'll need her mother to stay strong

through the tough times ahead.

As the pool gets more crowded,

food and water gets more scarce and energy is low.

(hippopotamuses groan)

(growls)

It's a dangerous time to share habitat with a super predator.

The Luangwa River is the lifeblood for hippos, crocs

and another age-old resident of the valley.

A shrinking river means their territories start to overlap.

Nearby villagers also rely on the river.

(honking)

(grunting)

But navigating these waters is a death-defying stunt.

This is hippo country.

They can bite a canoe in half,

but they don't eat their victims,

hippos kill to defend their territory.

(honks)

Fueled by high levels of testosterone,

male hippos are always running on angry.

The herd is already displaced,

and staying on the move is their best strategy.

Today they're getting the hell out of Dodge.

They'll find a new pool further downriver.

Hippos are social,

and nobody wants to be left behind.

At full throttle, this straggler

can reach speeds of up to 30 miles per hour.

That's faster than six-time Olympic champion Usain Bolt.

As they steadily march downstream,

the beach master and his herd run out of river.

The remaining pools bust at the seams.

As usual, testosterone runs high,

but that's not the only thing that makes hippos so deadly.

It's time to bring out the big guns.

(snarling)

The inside of his mouth is like an arsenal of weapons.

His four canines are thick and pointed.

Every time he closes his mouth they grind against each other

to keep the edges razor-sharp.

His lower canines can measure one and a half feet

and weigh up to 13 pounds.

The incisors are smaller but can still inflict damage.

The lower ones grow horizontally

and can reach a half a foot long.

They're there to stab his opponents like daggers.

Hippos don't need these teeth to eat grass,

their mouths are a purpose-built ivory arsenal.

With a hair-trigger temper...

and daggers for teeth,

hippos are the ultimate fighting machine.

They could snap a croc in half.

Bring it on.

(hippopotamus growls)

Like every true gladiator, crocodiles wear a suit of armor.

Their skin is a network of interconnected scales

made of keratin, the same as human fingernails.

Each scale has a tiny black sensor.

On his jaw, they're ten times as sensitive as a fingertip.

So, despite his scaly armor,

he can feel... every ripple around him.

He even has his own, unique mask,

complete with sealable nostrils.

The pattern is random, caused by cracks,

the same as you get when mud cools and dries out.

But it's not a shrinking process that causes the cracks.

As the embryo's skull expands,

the facial skin stretches until it cracks and tears,

leaving each crocodile

with a different arrangement of face scales.

Along his back, the scales are more defined

and reinforced with bone,

giving him extra armor plating to protect his inner organs.

Legends say his armor is bulletproof.

But now we'll find out if it's hippo-proof.

Suicide month is flying by,

and large parts of the valley have been deserted.

But these survival experts

are crossing over from the dark side.

It's mating season.

The dominant male ripples the water

to advertise he's ready to mate.

He rapidly contracts his trunk muscles just below the surface

to create an infrasound,

extremely low frequency signals which travel through the water.

His next move is to do what crocs do best,

be patient and wait.

Male crocs become sexually active

when they reach just over ten feet in length,

usually at about ten years old.

He's surprisingly gentle.

Thick-skinned gladiator turns to ardent suitor.

He circles her and rubs up against her,

patiently trying to ease her underwater.

It's all up to her.

When she's ready, a head lift.

Under the water he rotates her back legs and tail to one side,

to align his vent with hers.

The dominant male will fertilize hundreds of eggs this season

to secure the future of his species in this valley.

But there's no guarantee,

the river gives life,

but she also takes it away.

(honking, grunting)

The Luangwa Valley is home to roughly 25,000 hippos.

It's one of the greatest concentrations of hippos on the planet.

But 25,000 hippos take up a lot of space.

They're becoming bottlenecked in the shrinking river,

and hippo and croc are vying for the same territory.

Get off my lawn!

(hippopotamus snorting)

(growls)

A clash is inevitable.

(hippopotamus snorting)

Many of the crocs are moving to the riverbanks.

For these croc mothers,

it's time to hunker down and focus on the future.

The first egg emerges, covered in a thick layer of mucus,

which cushions its fall.

Over the next two and a half to three months,

her embryos develop inside their leathery shells.

Temperature plays a crucial role,

it determines the babies' gender.

Temperatures between 89 and 94 degrees Fahrenheit

produce males,

and temperatures below that dictate females.

She lays between 40 and 60 eggs...

and when she's done,

she tucks them into their darkened chamber

and hides them from the outside world.

She will guard this nest day and night,

but she can't guarantee their safety...

(eagle squawks)

...predators are on the prowl.

(eagle squawks)

The shrinking river is a predator's paradise,

and for the apex predator

the sweltering heat is an advantage.

The precious water lures prey like bees to a honey pot.

It's the perfect arena to stage an ambush.

Crocodiles are the leopards of the waterways,

their strategy is stealth and patience.

(wildebeest lowing)

(low growling)

(wildebeest lowing)

A cold, clinical execution,

the crocodile is the ultimate assassin,

a perfectly designed killing machine.

His torpedo-shaped body assigns minimal space to vital organs.

He is basically one big muscle,

a perfectly honed weapon of destruction.

It's the tail end of the dry season,

and the beach master is still holding his herd together.

(grunting)

But they're in deep muck.

On average, each hippo dumps three tons of waste

into this river per year.

Their journey has taken them from prime real estate

to Hell's Kitchen.

But one's misfortune is another's gain,

the crocs are cashing in on the hippos' demise.

The beach master's plucky little daughter

is learning some tough life lessons.

Among her herd, the odds are sinking.

But out on the banks, new life is emerging.

It's the start of a baby boom.

Ninety days have passed,

and the call to life is unmistakable.

(hatchlings squeaking)

Despite a million years of evolution

to prove his resilience,

this little super predator comes into the world

as fragile and vulnerable as any newborn baby.

(squeaking)

Their first challenge is survival,

and for this whole new generation of gladiators,

their battle is about to begin.

(eagle squawks)

Tension ripples through the gridlocked river.

(grunting)

The beach master battles to defend his territory

as newcomers trespass on his dwindling turf.

He scoops water in his mouth.

It means "back off."

(growling)

When feces starts flicking, it's the final warning.

His paddle-shaped tail

spreads testosterone-laced dung over maximum distance.

Get ready to rumble!

(growling)

The beach master controls breeding rights

to all the females in his territory.

(grunting)

(roaring)

He's been boss for ten years,

chasing off impostors is his specialty.

Weighing in at 5,500 pounds,

he's roughly the combined weight of two American football teams.

(low growling)

Come on, make my day.

The impostor turns tail,

he's no match for the beach master.

In the same neighborhood,

the crocs are staging their own siege,

but they're not wrangling territory,

they're in a feeding frenzy.

(hatchling squeaking)

The noisy hatchlings call their mother from the river.

(squeaking)

But others heard the same alarm,

and for them it's the dinner bell.

(hatchlings squeaking)

In a cold-blooded twist of nature,

her newborns are hunted down and devoured by their own kind.

(squeaking)

The mother tries to rescue the survivors.

Her super-sensitive skin

allows her to delicately carry them in her jaws...

the same jaws that can snap prey in half.

(hatchlings squeaking)

Four of her babies have made it this far,

but they're not out of the woods yet.

Only two percent of crocodile hatchlings make it to adulthood.

(hisses)

Other opportunists launch in on the action.

A bird's-eye view zones in on more babies downstream.

(squeaking)

The resident fish eagles

patrol this stretch of the river constantly.

Fish stocks are running low, and baby crocs are fast food.

(eagle squawking)

Of the 50 eggs the mother laid,

only one of her babies is likely to survive.

Perhaps crocs are not so bulletproof after all.

(grunting)

Nightfall brings relief from the heat,

but there's no relief from the cramped living space.

The crocs are muscling in, but the hippos stand their ground.

There's only one pool left.

For the beach master and his herd,

this is the last chance saloon...

and he'll defend it with his life.

(grunting)

The beach master has taken control

over the last decent pool in the valley,

and he'll take no prisoners.

But the crocs are muscling in on the same water.

This is point zero for both hippo and croc.

(growling)

The mother croc joins the throng,

her mission failed,

her four surviving offspring

lost to the greedy males of her own clan.

Tolerance has reached its tipping point.

(honks)

(grunting)

The beach master issues his warning,

but it's too late.

The thin skin of truce between croc and hippo

is starting to tear open.

The croc mother is set on a collision course,

right into the stronghold of the beach master's territory.

An army of hippos defending their pond,

the odds aren't good for a lone crocodile.

(grunting)

(honking)

(snorting)

The croc is banished.

The beach master held his ground...

but once more, the croc proves her knack at survival.

Perhaps her super sensors helped her escape the deadly tusks,

or her bony armor protected her.

Either way, she's lucky to be alive.

The dust settles, and the real tragedy unfolds.

In the chaos, one razor-sharp tusk hit a soft target.

The hippos' deadly defense

has cost them their most cherished member.

The tender calf is one more casualty on the list.

It may be two years before the mother nurses another baby.

As one life ebbs away, others gather strength,

each an evolutionary masterpiece,

hoping to defeat the odds and join the ranks of their elders.

Water and land...

prime habitat for two of Africa's most iconic species.

The hippo, a testosterone-fueled herbivore.

He'll defend the river with his life.

(snarls)

The croc...

cunning, cloaked in armor, but with a sensitive twist.

He's the most successful freshwater predator on the planet.

There are no winners in this contest,

both are champions in their own right.

For hippo and croc,

this ancient battle will continue.

Every year the dry season will pit them against each other

and weed out the weak and vulnerable.

It's not the strongest or the most intelligent who survive,

but those who best adapt to change.