♪♪ NARRATOR: Hidden in the heart of Africa lies a place of wonder.

♪♪ This bountiful terrain draws migrants in their thousands.

But not all can make such journeys, and so this rugged land is the permanent home of three tribes.

[ Hippos grunting ] Hippos... crocodiles... ...and lions.

Each wary of the other... [ Crocodile hisses ] ...their stories unfold in parallel.

[ Thunder rumbles ] They live in harmony -- more or less -- until a fierce climatic cycle turns their world upside down.

♪♪ Relentless drought turn tussles over territory... [ Elephant grunting ] ...into battles for survival.

[ Thunder crashes ] What should be life-giving rain delivers floods of biblical proportion.

These age-old floodplains are no longer ruled by vagabond lions... [ Lion growls ] ...but by a greater power.

This is Katavi.

♪♪ ♪♪ NARRATOR: At the heart of Africa's Great Rift Valley in western Tanzania lies an ancient ribbon of land, remote and inaccessible.

Katavi is almost 2,000 square miles of unspoiled wilderness.

♪♪ ♪♪ The black wings of open-billed storks fill Katavi's skies.

The low water levels for this time of year draw them here unusually early and in unprecedented numbers.

A sign of rare, once-in-a-lifetime climate phenomenon gripping the land.

[ Storks chittering ] [ Lioness growls ] And under this foreshadow of disaster, new life is beginning.

A young lioness has given birth.

She is Mwezi, a member of the pride that lives along the banks of the Katuma River.

♪♪ This is her first litter.

[ Cubs mewling ] Four healthy lion cubs, just a few hours old and only just beginning to open their eyes.

♪♪ A month ago, she separated from the pride to find a secluded place to bring her cubs into the world.

But it will soon be time to introduce these little ones to the rest of the family.

♪♪ Motherhood is exhausting.

♪♪ As her cubs get bigger, she'll need the support of her own mother and aunts.

And the protection of their father, Arthur.

♪♪ But weeks ago, Arthur followed the buffalo herds into the forest and has still not returned.

♪♪ ♪♪ Unbeknown to this first-time mother, he was wounded in battle... [ Lion growls ] [ Lion growls, buffalo grunts ] [ Lion roars ] ...immobilized and left for dead.

♪♪ Their cubs have been born at a precarious moment in time.

♪♪ For this time of year, rainfall is extremely low.

Less grazing means prey is scarce in what would usually be a time of plenty.

But for the open-billed storks, the shallow river provides a feeding opportunity not to be missed.

♪♪ Their early arrival warns of an extreme drought.

♪♪ ♪♪ [ Lioness mewling ] ♪♪ Mwezi's calls for her family's support go unanswered.

But not unnoticed.

A rogue male who arrived with the buffalo weeks ago has been biding his time.

♪♪ Over the next few weeks, there's still no rain.

The once mighty Katuma River is little more than a stream.

[ Elephants trumpet, grunt ] [ Elephant trumpets ] Reunited with the sisterhood, Mwezi does her best to conserve energy.

The pride is growing.

Mwezi's mother, Patch, has new cubs, too -- her fifth litter.

[ Hippos grunting ] An experienced mother, she's well aware of how many dangers the cubs face.

♪♪ ♪♪ ♪♪ ♪♪ They share the dwindling river with elephants and hippos.

As herbivores, they're no direct threat to the cubs.

But Patch is jumpy.

♪♪ The water's edge is not a safe place to be.

Hippos can be unpredictable.

And crocodiles could be lurking just under the surface.

The cubs must get to know their neighbors.

[ Elephants grumbling ] And learn to respect their boundaries.

♪♪ Katavi is a tough place for lions.

Few cubs survive their first year here at the best of times.

♪♪ ♪♪ ♪♪ With scant resources and a missing father, this family is facing the worst of times.

But there is one positive.

The rest of the pride is together.

Patch and Mwezi can share the task of raising the eight cubs they have between them.

♪♪ Set back from the river, this grove of trees is the ideal base for the pride.

Nooks and crannies provide places to escape the heat... ...and hide, if necessary.

While the grown-ups use the higher levels as a vantage point for spotting prey and potential threats to the cubs.

In the cool of the morning, Patch usually leads the pride on patrol.

She's hungry and running out of milk.

[ Cubs mewling ] ♪♪ Despite this, she doesn't join the pride today.

♪♪ Mwezi remains behind on mothering duty, too.

Adult lions can survive without food for almost two weeks.

The cubs cannot.

The rest of the pride sets off along the banks of the Katuma where they can stay close to shade and water in the rising heat.

♪♪ With so little rain this year, only the largest bends in the river are deep enough for hippos to wallow.

Space is at a premium, so securing a place in the water means taking extraordinary measures.

Displaced by low water levels upstream, these two males are challenging the dominant resident bull.

[ Hippos grunting ] This is extremely unusual, even for this experienced alpha male.

♪♪ It's unnerving for a female and her vulnerable calf.

[ Hippos grunting ] ♪♪ The resident alpha male faces up to one of the challengers... ♪♪ ...who seems to back down... ♪♪ [ Hippo grunting ] ...but then proceeds to enter the bull's territory... ...much to the dismay of the resident females.

The alpha is not sure what to do.

Try to displace the guy in the water... [ Hippo bellows ] ...or take on the one bellowing at him on land?

[ Hippos grunting ] ♪♪ He's never encountered a situation like this before.

♪♪ Opening his jaws as wide as he can might warn off his attacker.

No such luck.

[ Hippos bellow ] And his threat display has backfired.

His nose is now well and truly pierced.

[ Hippos grunting ] The other challenger seizes the opportunity... [ Hippos grunting ] ...and joins in the fight.

The poor old alpha is in dire straits.

[ Hippo growling ] Attack from two cooperating males is incredibly rare.

They have a combined weight of over 10,000 pounds.

And the strongest bite force of any land animal.

They push and pull him into deeper water.

♪♪ Even at rest, a hippo can only hold its breath for five minutes.

[ Hippos grunting ] The challengers seem to know that holding him under will drown him.

♪♪ ♪♪ If the alpha dies, this baby hippo is likely to be killed by his successors.

♪♪ So, as the old bull takes his final breaths, the mother quietly slips away with her calf.

[ Hippos grunting ] A coup by two hippo bulls is out of the ordinary.

But this is no ordinary year.

A deepening drought brought about by a once-in-a-lifetime weather shift is altering animal behaviors across Katavi.

As a new day dawns on a radically changed hippo colony... ♪♪ ♪♪ ...the old bull who was once their protector, the father of their young, lies dead in one of the last remaining water channels.

One by one, the clan approach and begin gently nuzzling him.

It's not clear what is happening here.

♪♪ As more gather around his body, it's hard not to interpret this behavior as mourning.

[ Hippo bellows ] Or at least as a way of coming to terms with their loss.

♪♪ [ Hippo bellows ] ♪♪ This type of procession has been observed with elephants but is extremely rare amongst hippos.

[ Hippos grunting ] ♪♪ [ Elephants grunting ] ♪♪ These sweltering temperatures, without relief from rain, have not been experienced for almost a hundred years.

Shady branches provide respite from the oppressive heat.

One reason why tree climbing is a vital skill for Katavi's lions.

♪♪ Mwezi would never have spotted the warthogs from ground level.

♪♪ She'll need to be quick.

♪♪ ♪♪ And sneaky.

Using the gullies as cover, she might be able to get close enough to launch an attack.

♪♪ ♪♪ [ Warthog squeals ] ♪♪ Sprinting for long enough to catch a warthog in this heat is impossible.

But something else catches her eye.

[ Vultures squawking ] Vultures are always worth investigating.

They can spot prey from 4 miles away.

But a feast this size won't stay secret for long.

The death of the hippo is a bounty for the crocodiles.

If they can get into it.

The largest and wisest croc knows the technique.

Grip...and twist.

These ancients are perfectly adapted to a feast-and-famine existence.

♪♪ This meal will keep the whole float going for months.

♪♪ Alone with the cubs, Patch is weakening and desperate for a meal.

[ Elephant trumpets ] Mwezi has not returned.

♪♪ Patch knows that vultures are a sure sign of food, too.

It's a lesson all lions learn early.

♪♪ A potential meal right on her doorstep is too tempting to pass up.

♪♪ Patch knows leaving the cubs is risky.

But she's losing condition.

She's no milk left.

And if she can't feed the little ones, they'll die.

♪♪ The cubs have never been left completely alone before.

Camouflage is their only protection.

But on the other side of the river, the rogue male is poised to take advantage of any opportunity.

Camouflage may not be enough.

♪♪ In her weakened state, walking just one mile along the riverbank is an effort.

♪♪ But the scent of flesh in the air drives Patch on.

And at last, she recognizes Mwezi.

♪♪ Stepping into the water with crocodiles is nerve-racking.

♪♪ Patch knows well that getting too close to those teeth can be hazardous.

[ Lioness growls ] ♪♪ ♪♪ If a croc grabs her, she'll never escape.

But with her own teeth wearing down, the soft hippo flesh is just the meal she so desperately needs.

♪♪ ♪♪ ♪♪ Starvation emboldens her.

[ Lioness growling ] ♪♪ But with every bite, she's dancing with death.

[ Lioness growling ] ♪♪ ♪♪ Not a moment too soon, reinforcements arrive.

The rest of the pride on patrol have also followed the vultures to the hippo carcass.

♪♪ ♪♪ ♪♪ The balance of power shifts.

♪♪ And reluctantly, the crocodiles relinquish their prize.

[ Lioness growls ] ♪♪ At last, the pride can feed properly.

♪♪ Each will eat their fill, up to a quarter of their own body weight.

♪♪ ♪♪ But with the whole pride absent from the den, they could pay the ultimate price for their meal.

Less than a mile downriver, the rogue male is crossing into the pride's territory.

♪♪ ♪♪ He's been watching and waiting.

♪♪ There's been no sign of Arthur, the pride male, for weeks.

♪♪ The time is ripe for a takeover.

♪♪ All that stands in his way are the cubs.

If he's to father his own, he needs the females to come back into estrus.

And they won't do that while their infants are nursing.

♪♪ [ Birds chittering ] Spur-fowl alarm calls prompt the cubs into hiding.

The rogue can smell them now.

He's close.

He spotted movement among the branches.

If the cubs stay hidden, they might be safe.

♪♪ ♪♪ But the arrival of a stranger arouses the curiosity of one.

♪♪ It's a terrible mistake.

[ Lion growls, cub yelps ] ♪♪ Confused and frightened, the cubs can do nothing but wait for the rogue's next move.

With tree climbing in his blood, one cub follows his instinct to move higher.

But he's not strong enough to get up very far.

[ Insects buzzing ] There's nothing for it now but to sit still and hope he goes unnoticed.

[ Heart beating ] ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ ♪♪ [ Branches snapping ] [ Lions growls ] [ Cub yelps ] [ Lion growls ] ♪♪ ♪♪ A mile away, Patch cannot have heard her cubs' cries.

But perhaps she senses something is wrong.

♪♪ The rogue's brutal mission isn't over.

He won't stop till all the cubs are dead.

♪♪ With stuffed bellies, the pride head back to the den.

♪♪ ♪♪ ♪♪ ♪♪ [ Lioness mewls ] Patch calls for her cubs.

♪♪ Normally, they'd come running.

[ Lioness mewls ] Mwezi realizes something is wrong.

♪♪ [ Lioness mewls ] The rogue flees before he and his crime are discovered.

♪♪ [ Lioness mewls ] ♪♪ Still no reply to her calls.

Until...

He's terrified but alive.

Another... [ Lioness mewls ] ♪♪ ♪♪ Soft moans reassure their traumatized cubs.

[ Lioness mewls ] And one by one, more emerge from their hiding places.

♪♪ [ Lioness mewls ] ♪♪ The family reunites.

In all, there are six survivors.

Patch and Mwezi have lost one cub each.

♪♪ [ Lioness mewls ] But the outcome could have been so much worse.

The pride will have to move.

Their den is no longer safe.

The rogue didn't finish the job.

The weeks wear on and conditions in Katavi deteriorate.

♪♪ Distant storms bring not rain but fire, sparked by lightning.

♪♪ Hot winds whip ash into dust devils that haunt the land like malevolent spirits.

♪♪ ♪♪ It's hell on Earth.

♪♪ Corralled by swathes of charred, inedible grassland, the buffalo are forced to return to the plains.

♪♪ ♪♪ Only the hardiest can survive here on the dry, meager forage and last remnants of water.

♪♪ ♪♪ Arthur has survived against all odds.

Two months ago, he abandoned the pride to follow the buffalo herds.

♪♪ [ Buffalo lows ] Emaciated and injured, his journey with them has taken its toll.

♪♪ ♪♪ ♪♪ He cannot tolerate the heat of these open plains.

♪♪ So he returns to his pride's territory... ♪♪ [ Lion mewls ] ...in search of solace from his family.

[ Mewling continues ] ♪♪ [ Mewling continues ] But his calls to the pride go unanswered.

Arthur is not the only male searching for the pride.

The cub killer is on the prowl, too.

♪♪ [ Birds squawking ] More than 10 miles south, Patch and Mwezi are beyond the reach of Arthur's roars.

In these lean times, hungry hunters have no choice but to cash in on the success of others.

♪♪ [ Lioness growls, crocodile hisses ] But these stolen meals never last long.

♪♪ [ Hyenas yipping ] ♪♪ And the lions move on.

♪♪ ♪♪ Night offers the only relief from the crushing heat.

[ Insects chirping ] And it's just cool enough for crocodiles to set out in search of water.

The largest might weigh over 900 kilograms.

♪♪ ♪♪ They can only manage a few steps before needing to rest.

♪♪ ♪♪ The hippo mother and baby also use the cool of the night to travel.

♪♪ ♪♪ As water vanishes from Katavi's lands, so too do the hippo mother's choices.

[ Hippos grunting ] ♪♪ Gone is the safety of her pod and the nursery herds.

[ Hippos grunting ] ♪♪ Now her only option is one of the overcrowded mud wallows.

[ Hippos bellowing ] Hardly a safe place for a baby.

♪♪ [ Hippos bellowing ] ♪♪ But she's not safe out of the pool, either.

♪♪ Hippos outweigh lions 10 to 1 and are rarely targeted as prey.

♪♪ But everyone is fractious.

♪♪ And hungry lions can do crazy things.

♪♪ ♪♪ The mother makes her choice.

Better the melee than the mouth of a predator.

She's chosen her spot wisely.

And old grandfather hippo has no objections to their company.

[ Hippos grunting ] ♪♪ ♪♪ And his presence is enough to dissuade the lions from attacking.

♪♪ They need to look for other opportunities.

♪♪ [ Hippos grunting ] A mother with twins, almost unheard of in hippos.

♪♪ ♪♪ If they stay close to her, she'll be able to protect them.

But it's hard not to panic when you're being stalked by a lion.

♪♪ ♪♪ Their mother is powerless.

♪♪ If she helps her stricken calf, she'll leave the other one exposed.

♪♪ They can only leave him to his fate.

♪♪ A small hippo can't feed the entire pride.

♪♪ As the weather cycle tightens its grip on the region, many are drawn to the dwindling Katuma River's last resources.

When your stomach's rumbling, everything starts to look like prey.

♪♪ ♪♪ ♪♪ ♪♪ A 3-foot croc seems doable.

♪♪ [ Crocodile hisses ] [ Lioness growls ] ♪♪ [ Crocodile hisses, lioness grunts ] ♪♪ Grandma is a lot more intimidating.

Pick on someone your own size.

♪♪ ♪♪ Maybe something with fewer teeth?

♪♪ ♪♪ ♪♪ Bellies full of fish, pelicans are slow to get airborne.

[ Pelican screeches ] ♪♪ ♪♪ The young lion has found herself a bonanza.

Juvenile birds, unaware of the consequences of overfeeding, are the target.

♪♪ [ Pelican squawks ] ♪♪ The frenzied lioness is creating a stockpile.

She selects her next victim, grounded by a cargo of excess catfish.

Target locked.

[ Pelican squawks ] But this pelican's not giving up without a fight.

[ Pelican hissing ] [ Pelican hissing ] [ Pelican hissing ] Time to call it a day and go back to the birds she caught earlier.

If she can remember where she left them.

But her stash has been discovered.

Lions aren't the only opportunists here.

The crocs aren't killing the pelicans, but they've got no qualms about scavenging the dead.

♪♪ A harsh lesson for the hungry lioness.

♪♪ The mud pools are becoming totally overpopulated.

[ Pelicans squawking ] ♪♪ ♪♪ And under cover of sunset, the hippo mother and her calf once more slip away, to take their chances elsewhere.

♪♪ ♪♪ [ Thunder crashes ] Next time in Katavi, at long last, the rains return.

Relief among all the resident tribes is palpable.

♪♪ Even the crocodiles, ancient survivors, were at breaking point.

♪♪ ♪♪ The water's return brings the promise of space to spread out.

♪♪ ♪♪ [ Thunder rumbles ] ♪♪ And the return of prey.

[ Zebra braying, lioness growling ] [ Thunder crashes ] But as the waters keep rising, relief gives way to trepidation.

Lion cubs are growing up in a flooded Katavi landscape that's never been seen before.

♪♪ ♪♪ ♪♪ ♪♪ ♪♪ To learn more about what you've seen on this "Nature" program, visit pbs.org.

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