Predators

Predators across the planet.

Unmatched in strength...

...speed, strategy,

stealth...

...and teamwork.

But staying on top is never easy.

As the world around them changes,

they must adapt faster than ever before

to maintain their rule.

In Tanzania's Serengeti, a notorious brotherhood of cheetahs.

They command this vast hunting territory.

But their status is under attack.

Rivals are closing in.

The battle is no longer just to stay on top...

...but to stay alive,

as they try to cling on to their mighty alliance.

For the past six years,

male cheetahs Luka and Kovu

have held their territory here

in the southern plains of Africa's Serengeti.

Kovu, with his scarred nose,

is a cunning and meticulous hunter.

The brains of the operation.

While Luka, with his muscular frame,

is a creature of brute strength.

They're always at each other's side...

...but they're not brothers.

They were born 80 kilometres apart.

As young males, their paths crossed.

And through many years learning the rules of the savanna together,

their unbreakable bond was forged.

While females are solitary, male cheetahs band together.

But Luka's raw power, combined with Kovu's sharp mind,

has made them a double act like no other,

seeing off all rivals and dominating the largest prey.

Now eight years old,

the pair are fiercely territorial.

The hunting grounds they hold

are 50 square kilometres of rolling savannah.

There are rocky outcrops for cover...

pools to drink from...

and every year it floods with herds of zebra,

wildebeest, and gazelle.

They fiercely defend this territory from neighbouring males,

so any females that come here are theirs alone to mate with.

They are the epitome of an apex predator,

and the success of the entire population

relies on strong males like them

mating, and passing on their genes.

Luka and Kovu have become masters of this game.

But the rules of their world are changing.

It's August,

and the Serengeti's dry season is kicking into gear.

The sun scorches the grass,

herds are heading north to find water,

and the predators that remain are fighting over a shrinking supply of food.

But the twist of the knife

is that, for three years, the region has been plagued by drought.

The dry season months of June to October

have been getting hotter and hotter.

As Luka and Kovu's world becomes a hostile tinderbox,

guarding their patch is more crucial than ever.

So their rules are clear:

intruders keep out, or be killed.

But eight kilometres away...

...at their territory's western boundary...

...there's been a breach.

A gang of four powerful sons,

led by their imposing mum,

known as the Solaro family.

They have swagger and strength in numbers.

Even the hyenas seem to sense their power.

Watching Mum stalk gazelle,

the sons are fast learning the ways of the hunter.

For now, the four sons remain at Mum's side.

But any day now,

this band of brothers will leave as a coalition,

to stake their own territory.

There's no way Luka and Kovu can allow the Solaro sons

to share their patch.

In this drought, there won't be enough food to feed them all.

But against four males,

they'll be dangerously outnumbered.

The one thing that could help them

is far from here...

...160 kilometres to the north,

over rivers, and valleys...

...a mega-herd of 1.5 million wildebeest...

and zebra are on the move.

The pregnant females need to graze constantly to make milk.

When the rains return,

the plains in Luka and Kovu's territory

are where the sweetest grasses will grow,

so the herd must travel there.

When the herds arrive, there'll be enough zebra and wildebeest...

...to feed all the cheetahs across this region...

...and no need for the Solaro sons to encroach.

But it's not that easy.

Blocking the herd's path like a slick, black serpent...

...the Mara River.

Steep banks...

...deep water...

...no way round.

As the bankside swells with bodies,

their migration may have reached its limit.

If the herd can't reach the southern plains,

Luka and Kovu won't just go hungry,

they may face a turf war with the Solaro brothers.

But right now,

the boys have a bigger problem...

Smoke.

The drought has left the grass bone dry.

It ignites with terrifying ease.

Luka and Kovu have seen wildfires before.

They know they can spread with devastating speed.

As the heat rises,

they can only watch the inferno in disbelief.

There's nothing they can do.

They need to retreat to a safe haven.

As the fire blazes unchecked,

those who can't run, hide...

...while white storks descend

to make a quick meal of the insects escaping the blaze.

The flames tear through the heart of Luka and Kovu's hard-won territory.

Everything they have worked for may be about to slip away.

By morning, the fire's burned itself out,

and their entire territory is transformed.

Just scorched earth remains.

A hyena, singed and blistered by the fire,

slurps at a nest of baked ostrich eggs.

The mongoose emerge to an empty landscape.

The last of the gazelles have left.

Until the rains return,

this once-rich territory will remain barren.

The boys have no choice but to abandon it.

With no territory,

finding food will be a huge challenge.

And their ability to attract females is now near to none.

They must try to find a new ground,

but it's a crowded landscape.

If they head east,

they'll go beyond the boundary of the grasslands,

to where farmers kill cheetahs to protect their livestock.

So their only option is to head west,

deep into the Serengeti's heart.

A place ruled by hyenas,

lions and rival cheetahs,

all vying for the same food.

The duo's fate now rests more than ever

with the arrival of the wildebeest and zebra.

140 kilometres to the north,

the herd calculates its next move.

For their survival, they need to cross.

But a flotilla of crocodiles is lying in wait.

They are the apex predator of this water world,

and they've not eaten for months.

The elders who have run this gauntlet before know timing is everything.

There are no second chances.

The wet rocks become a perilous slick

that can snap legs and crack bones.

The walking wounded limp to safety.

Those too badly injured

are defenceless against the advancing crocodiles.

But while the crocodiles have their mouths full...

...hundreds of thousands more make it through.

With their noses to the wind, they push on south.

For Luka and Kovu, these herds can't arrive soon enough.

It's now September,

and the drought is tightening its grip.

Lions shelter from the midday sun...

marauding hyenas patrol the plains...

...and the Solaro Family are closing in,

now skirting past the scorched territory

once held by Luka and Kovu.

Oblivious to the threat trailing them,

the pair are now trying to adapt to life on the move,

as they continue searching for a new home.