Original subtitles

NARRATOR: \hThere is a place

in southern Africa

where some of the largest animals on Earth

live side by side.

Elephant,

giraffe,

buffalo,

hippo,

Nile crocodile,

all weighing in

at more than a ton.

But it’s the hottest and driest time of year.

Food and water are getting scarce.

How do these giants make it through the lean times?

(BUFFALO GRUNTING)

This is the story of amazing adaptations

and ingenious strategies,

that give these heavyweights the edge

in one of the hottest places in Africa.

(THEME MUSIC PLAYING)

(BIRDS CHIRPING)

The Luangwa,

one of the last great, untamed rivers in Africa.

It flows through a vast area of pristine wilderness.

A mosaic of habitats.

From plains and woodlands,

to verdant lagoons.

But every year, these disappear.

It’s October, the height of the dry season.

It hasn’t rained for six months.

The once fertile plains have turned to dust

and the lagoons are drying up fast.

The largest land animal on Earth

must overcome many challenges if it’s going to survive.

(ELEPHANTS SNORTING)

African elephants, weighing in at 6-1/2 tons,

need a guaranteed food supply, available 24/7.

But with the valley’s vegetation fading fast,

the grass on the plains is long past its best.

The woodlands provide a refuge.

But even here, they can’t be picky eaters.

The food is low in nutrients.

Everything goes in,

branches, seeds, roots and bark are all on the menu.

Their seven-foot trunk, made up of 40,000 muscles,

is the perfect tool for these bulk eaters,

grabbing everything they come across.

They spend 18 hours a day, every day,

feeding to meet their quota of 650 pounds of food.

But after all this work,

they digest less than half of what they eat.

And this means a lot of dung,

over 300 pounds every day.

For the resident troop of yellow baboons,

it’s irresistible.

They pick through this unusual delicacy

in search of undigested seeds.

While the elephants are shoveling in as much food as possible,

the tallest animal on Earth has a different strategy.

It’s a little more choosy about what it eats.

This male giraffe is sixteen feet tall,

and has the longest neck in the world.

He can reach delicacies others can’t,

and doesn’t need to feed on tough and tasteless vegetation.

An 18-inch tongue and dexterous, tough lips

mean he can tease out leafy treats

from the most hard to reach places.

(LEAVES RUSTLING)

Like elephants, giraffe also spend 18 hours a day feeding.

All this time with his tongue out,

means it needs protection from the sun.

A pigment called melanin makes his tongue dark blue,

an adaptation to prevent sunburn.

Pushing through the bushes in search of a meal

gives plenty of opportunities for parasites to latch on.

But a six-foot neck makes grooming a bit awkward.

Red-billed oxpeckers are here to lend a hand.

They keep him fit and healthy

by picking off disease-carrying ticks.

And in return, they get a free meal.

(OXPECKERS CHIRPING)

But giraffe aren’t the only giants

oxpeckers have a special relationship with.

(BUFFALOES GRUNTING)

Buffalo make their way towards the river.

They may be the smallest of Luangwa’s heavyweights,

just tipping the scale at one ton,

but unlike elephant and giraffe,

they have strength in numbers.

(BUFFALO GRUNTING)

Mega-herds of over 1,000 buffalo roam through the plains.

As food and water become scarce,

smaller herds join together,

a strategy which also protects them against predators.

Competition for food is higher.

But more eyes looking for danger,

means each buffalo can spend less time scanning

and more time feeding.

But it’s not always enough for the old and the weak.

This time of year is a struggle for these grazers.

(BUFFALO GRUNTING)

Each buffalo needs to scrape together over 30 pounds of food a day.

To find enough, they have to adapt,

expanding their diet from grasses to leaves.

But still, this scorched vegetation has little moisture.

It’s tough to break down.

To aid digestion and quench their thirst,

the herd heads to the river.

It’s one of the last remaining sources of water in this wilderness.

They drink as much as they can,

up to 18 gallons a day,

before making the long return journey to the plains.

The last of Luangwa’s heavyweight herbivores is the hippo.

(GRUNTING)

This male weighs over three tons.

He is the "beachmaster,"

the dominant bull.

During the day, he guards his territory

and a group of hippos known as a "pod."

At this time of year, several pods can be squeezed together

into the largest hippo congregations in the world,

over 300 strong.

(HIPPOS GRUNTING)

Bull hippos spend all day asserting their dominance over encroaching rivals.

(GRUNTING)

It’s exhausting.

But the setting sun

brings the hardworking beachmaster

some relief from the stresses of the day.

At night, like all hippos,

he leaves the river to graze on land.

A military-grade thermal camera,

which sees heat instead of light,

reveals his feeding habits in incredible detail.

Using tough, sharp-edged lips

he plucks grass instead of biting it with his teeth,

allowing him to graze shorter grass

than any other heavyweight.

He has to eat 90 pounds of vegetation.

When grass is in short supply,

and your table manners are this sloppy,

it can take all night.

In high concentrations, hippos can leave devastation in their wake.

The beachmaster would be a feast for these lions.

They’re the Nsefu pride, and they’re 14 strong.

But armor-like skin, over two inches thick,

and 20-inch tusks make him formidable prey.

It will take the whole pride to bring him down.

(DUNG SPLATTERING)

He splatters dung,

a rather unsubtle warning

for the lions to get out of the way.

(HIPPO GRUNTING)

(HIPPO GRUNTING) (LIONS GROWLING)

He’s too big and strong for the pride.

They will have to wait for smaller prey.

(ELEPHANT GROANING)

The elephant herd has even less to worry about than hippos.

After a day of feeding, it’s time for a quick nap.

Elephants sleep for four to five hours a day.

While lying down, the calf is at her most vulnerable,

but the herd will take it in turns

to listen out for any threats.

(BUFFALO GRUNTING)

For buffalo,

the dark is what nightmares are made of.

This is when the lions are most active.

As the lightest of the heavyweights,

a buffalo is a much easier target than a hippo

and one of the Nsefu pride’s favorite prey.

A big buffalo could feed them for up to three days.

The buffalo have poor eyesight and hearing.

At night,

they rely on their exceptional sense of smell,

letting them know when to stand and when to run.

(BUFFALO SNORTS)

(BUFFALO GRUNTING)

The herd tries to stay in a tight group.

Separation means being outnumbered,

and outgunned.

This buffalo has lost the safety of the herd.

(BUFFALO SNORTS)

(LION GROWLS)

He’s not defenseless.

Sharp horns curl around his head to form a bone shield,

known as a "boss."

One powerful strike could kill a lion.

(LIONS GROWLING)

But he can’t take them all on alone.

(BUFFALO BELLOWING)

He bellows to bring in reinforcements.

(BUFFALO BELLOWING)

A buffalo’s strength lies in group-defense.

Distress calls have been known to bring herds to the rescue.

(BUFFALO BELLOWING) (LIONS GROWLING)

The lions might be able to take one down,

but two together is just too much.

(LIONS GROWLING)

The Nsefu pride will have to go hungry, for now.

(LION EXHALES)

(BIRDS CHIRPING)

(HIPPO GRUNTING)

As the day dawns, and the hippos return to the safety of the river,

the rest of the bush’s inhabitants stir.

(BIRDS CHIRPING)

Tens of thousands of red-billed quelea take to the air.

They are the most numerous birds on Earth,

ten billion strong.

(CHIRPING CONTINUES)

At under an ounce each, they may not be heavyweights,

but the flock’s combined weight is more than a buffalo.

Having stretched their wings, they settle down to drink.

(WATER SPLASHING)

(SPLASHING CONTINUES)

Only a young crocodile would bother with such small prey.

It will be decades before this one grows

into the river’s apex predator.

This huge crocodile could live for 100 years

and will never stop growing.

He might end up more than twenty feet long.

And the Luangwa River is full of these giants.

Here, more are found than anywhere else in Zambia.

Nile crocodiles are the only predator in Africa to weigh more than a ton.

They are Luangwa’s final heavyweight.

These reptilian giants are so successful,

they have barely changed in over 200 million years.

There’s an uneasy truce between the river’s heavyweights.

This crocodile could easily take a newly born hippo.

But with its mother close by, it’s not worth the risk.

(GRUNTING)

A fully-grown hippo can bite a crocodile in half.

While hippos are struggling to find a meal,

the dry season can provide easy pickings for a crocodile.

Old and weak herbivores are struggling

to make it through this tough time of year.

All the crocodiles have to do is wait.

And they have plenty of time on their side.

After a big meal,

it will be two years before this dominant crocodile has to eat again,

so food is rarely an issue.

He faces a very different challenge to the other heavyweights.

Crocodiles are ectothermic,

their environment controls their body temperature.

In the cool morning air,

crocodiles are slow and sluggish.

It will take some time to raise their temperature

to an optimal 90 degrees Fahrenheit.

But their heavily armored skin hides a secret adaptation.

Each scale contains a rich network of capillaries.

As they bask, blood flows to the surface,

is heated by the sunlight,

and then returns to warm the body.

As these reptiles are heating up,

warm-blooded heavyweights are trying to cool down.

(BUFFALO GRUNTING)

Mud coats the buffalo’s skin

in a protective layer, like sunscreen

and also helps to remove parasites

and soothe insect bites.

But the lagoons are drying fast,

their mud becoming thick, sticky sludge.

(BUFFALOES SNORTING)

Every year, buffaloes run the risk of getting stuck.

(VULTURES CAWING)

Getting stuck means getting eaten.

(VULTURES CAWING)

For most, this lagoon still has enough water to be safe.

It acts like a beacon for all the valley’s warm-blooded residents.

Including the largest of the heavyweights.

(ELEPHANT TRUMPETING SOFTLY)

Temperatures in the Luangwa Valley

regularly hit 120 degrees Fahrenheit.

Staying cool is a constant problem for the elephants.

They’re so big and round,

they find it hard to lose heat from their inner core.

They don’t sweat,

water’s too precious to waste on thermoregulation.

So they have other ingenious adaptations to help them cool down.

Wrinkled skin means a larger surface area to radiate heat.

Unlike fur, the elephant’s sparse, bristly hair

lets air flow close to the body,

increasing heat loss by up to 20%.

But their most effective heat management adaptation

is their ears, the largest on Earth.

They are so large,

they increase an elephant’s total surface area

by up to 25%.

More space, from which they can lose heat.

A rich network of blood vessels

brings heat to the surface.

As elephants flap their giant ears,

air passes over the intricate web,

cooling the blood and lowering their temperature.

But when it’s 120 degrees Fahrenheit,

even these adaptations aren’t enough.

There’s only one thing left to do.

(TRUNK BLOWING)

Muddy water may help the herd cool down,

but it’s not the most thirst-quenching.

They prefer a cleaner drink.

(TRUMPETING SOFTLY)

They’re not the only thirsty animals heading to the river.

The Nsefu pride have beaten them to it.

Lions are a threat to the young calf.

(LIONS GROWLING) (ELEPHANT TRUMPETING)

The pride may have got here first,

but thirst drives the herd on.

(TRUMPETING)

The adult elephants keep the calf safely tucked between them,

while making it clear they’re not to be messed with.

(LION ROARING)

(TRUMPETING)

(TRUMPETING)

(GROWLING)

(ELEPHANT TRUMPETING) (GROWLING CONTINUES)

(TRUMPETING)

(GROWLING) (ELEPHANT TRUMPETING)

With their message delivered,

it’s safe for the herd to drink.

Their trunks make quick refreshment easy.

They don’t sip through it, like a straw.

They suck up more than 2-1/2 gallons with each giant sniff,

which they then squirt into their mouth.

They are thirstier than any other heavyweight,

and can down almost 60 gallons every day,

enough to fill a bathtub.

Mid-morning is when most of the valley’s wildlife comes out to drink.

But not all animals are lucky enough to have a trunk.

For a giraffe,

drinking is a little more complicated.

Reaching the water requires some expert maneuvering.

And simply lowering her head could be fatal.

While upright, a giraffe’s heart can beat up to 170 times a minute

to pump blood to the brain, six feet above.

This raises her blood pressure to twice that of any other mammal her size.

When she drinks, blood rushes down the neck

and floods towards the brain with gravity.

If unchecked,

the force would cause brain damage and certain death.

To stop this, her arteries have especially thick walls

keeping them from rupturing.

And extra one-way valves in her jugular vein prevent backflow.

When her head is lowered, the valves close,

stopping backflow blood from rushing into her brain.

As she tosses her head back,

they open, and blood flows back to the body.

She is perfectly adapted to the hellish heat of the dry season.

Slender legs and a long neck increase her surface area,

letting her lose heat much faster than an elephant.

In times of need, dark patches on her skin,

known as "thermal windows," are activated.

Blood vessels dilate under the patches,

increasing blood flow and releasing more heat.

The patches also have more and larger sweat glands,

which cools the blood flowing through the thermal window.

A difference of up to 50 degrees Fahrenheit

can be seen between these hot, radiating patches

and the spaces in between.

All these adaptations

mean a giraffe can go weeks without drinking at the cruelest time of year.

Even longer than a camel.

It’s the middle of the day.

Most animals have taken shelter from the sun’s blistering heat.

But the cold-blooded Nile crocodile

has only just warmed up.

It’s time to hunt.

As the water levels have fallen,

giant catfish have become concentrated in ever-shrinking pools,

making them easier to catch.

Sensory pits line a crocodile’s snout.

The pits allow it to detect movement,

rather than see in the murky water.

Lying still,

crocodiles wait for a fish to come too close.

And explode into action.

The giant catfish can be quite a mouthful,

but the crocodile’s 60 teeth are built to grip.

While the crocodiles relish the midday heat,

the beachmaster and his pod are struggling.

There’s no shade from the scorching midday sun.

(HIPPOS GRUNTING)

Their thick skin means they’re at risk from overheating.

The skin alone can weigh more than half a ton,

almost a fifth of a hippo’s weight.

(GRUNTING)

It secretes a thick, oily-red liquid,

a natural moisturizer and sunblock.

But the most effective strategy to avoid the sun,

is to stay submerged for much of the day,

in the protective muddy waters.

They seek out the deepest spots in the river

and sleep completely underwater.

Even though they’re asleep,

every now and again they come up for a breath of air.

(EXHALES)

(WATER BUBBLING)

But as the dry season takes hold,

the river keeps dropping.

If it gets too low,

much of the river will be too shallow to cover them.

The consequences for many hippos will be fatal.

The river is the main source of water left in the valley

and animals concentrate along its banks.

For the herbivorous heavyweights,

elephant, giraffe, hippo and buffalo,

competition within species, for resources and mates, becomes fierce.

(TRUMPETING)

Tempers flare.

Fights break out.

(GRUNTING)

For the beachmaster,

a spot in the deepest part of the river

is worth fighting for.

He may look docile,

but this heavyweight is one of the most aggressive animals on Earth.

(GRUNTING FIERCELY)

Scar covered and battle hardened,

he has to protect his 300-foot stretch of the river.

He’s in his prime.

His reign has lasted for almost four years,

but each dry season has been a relentless battle.

All along the river,

falling water levels are forcing hippos to search for a deeper spot.

The beachmaster’s kingdom

is under threat from rival males.

(HIPPOS GRUNTING)

Smaller, submissive males may be tolerated,

but fully grown bulls must be met head-on.

What a challenger may have in strength,

the beachmaster makes up for in experience.

Gaping his jaws 150 degrees wide,

he displays his arsenal.

Canines for slashing and incisors for stabbing.

The stakes are high.

Losing will force him out of the water

and expose him to the searing sun.

(LIPS SMACKING)

Lip smacking, the rival tries to intimidate him.

The beachmaster squares up,

hoping the rival will back down.

No such luck.

(BOTH GRUNTING)

(GRUNTING CONTINUES)

The beachmaster forces the challenger out of the river.

When evenly matched,

a serious fight is settled on land.

(BOTH GRUNTING)

They clash face-to-face,

protecting their flanks from each other’s slashing tusks.

Incisors inflict serious puncture wounds in the lower jaw.

The beachmaster, on the left, goes on the offensive.

Getting under his jaw, he forces his rival onto the back foot.

(BOTH GRUNTING)

Biting down with a force of almost a ton per square inch,

the beachmaster delivers a decisive blow.

(SNORTING)

Experience wins out.

The beachmaster retains his deep-water kingdom, for now.

(GRUNTING)

But it won’t be long until the next challenger comes along.

For the loser, severely weakened,

and with no deep water to rest in,

the consequences can prove fatal.

(HIPPO GROANS)

(WATER SPLASHING)

The reptilian heavyweights gather for the feast.

(HIPPO GROANS)

The biggest and strongest of the Nile crocodiles

open up the carcass for the others.

The less dominant just have to be patient.

Snapping down,

these heavyweights generate 2-1/2 tons of force per square inch,

the strongest bite on Earth.

They can’t chew,

instead they throw their weight around.

Latching on and spinning, their one-ton bodies

in a maneuver known as a "death roll,"

they rip chunks of flesh and swallow them whole.

They tolerate each other,

the most dominant feeding first.

But if there’s a dispute,

the biggest and strongest one always wins.

Nothing goes to waste.

Crocodiles have the strongest stomach acid in the world.

They will eat everything, from blubber to bones.

They also swallow stones, which stay in their bellies,

helping crush and break up food,

once it reaches their stomach.

By dawn, the carcass will be gone.

Nothing will remain.

The dry season is almost at an end.

Soon rains will quench the earth

and trigger an explosion of new growth.

Most of Luangwa’s heavyweights have made it through the hardest time of year.

The fact that these huge animals can survive in such an extreme land,

is a testament to their remarkable and impressive adaptations,

honed over millions of years.

From the giraffe’s tongue,

to the elephant’s ears,

these giants are perfectly equipped

to see out both feast and famine.

♪

♪