Nature's Epic Journeys (2016–…): Season 1, Episode 3 - Zebras - full transcript

We're about to follow
the world's greatest migrations,

and reveal their secrets in a way
that's never been done before.

All over the world,
animals are on the move...

embarking on vast journeys that
they depend upon for survival -

to find food, to give birth,
or to escape danger.

Travelling hundreds of miles

through some of the world's
most breathtaking wildernesses...

...that can turn against them
at any moment.

That rapid's really picking up.

They're just disappearing
under the water.

Ground-breaking technology
allows our team



to follow these migrations
more closely than ever before,

and understand them
in unprecedented detail.

We can track this ele's movement
in real-time.

Using the latest
satellite tracking technology,

we can monitor individual animals

and witness first-hand
their struggles for survival.

We've got a drama down here.

We've got it. We've got the wolf.
We've got the wolf.

This time, we'll follow
thousands of zebra

as they undergo their gruelling
annual migration in search of food.

They must reach
their grazing grounds

just as the rainy season begins.

Arriving too early or too late
could spell disaster.

For the first time,
satellite tracking allows us



to stay with individual mothers,
foals and dominant males

as they brave drought,
hunger and ferocious predators.

Below me, this wilderness
has kept hidden

a journey that's never
been followed before,

and about which
virtually nothing is known.

It's the longest land migration
in all of Africa.

This is the untold story
of the great zebra migration.

Northern Botswana -

a vast, parched wilderness

the size of the United Kingdom.

At the end of Botswana's
brutal dry season,

thousands of zebra gather
on the Chobe floodplain

as they prepare to
travel 250km south

to Nxai Pan National Park.

The journey takes them through
one of the most punishing landscapes

in southern Africa.

Travelling in family groups,

many of the females are heavily
pregnant or supporting young foals.

Each year, their goal is the same -

to reach Nxai Pan's fertile plains

just as the rains produce the first
flush of nutrient-rich vegetation.

The timing of this journey
is crucial.

Leave too early and they risk
arriving at Nxai Pan

before the lush grass appears.

Leave too late and they'll miss out
on the best food on arrival.

Our first camp is on the edge
of the Chobe River,

the starting line for the migration.

Yeah, I've been looking at her data
over the last...

'I've joined a team of specialist
biologists and cameramen'

to attempt something
that's never been done before.

We plan to travel with the zebra
on the ground,

following their every move.

Around 2,000 zebra are gathering

across the vast Chobe River
floodplain,

dotted across the landscape in
family groups of up to 20 animals.

They won't be travelling en masse.

Instead, each individual family
will make its own decisions

during the migration.

'I'm joining the scientists
who are collaring the zebra,

'so that the team can track them.'

OK, Mike,
Larry's getting ready to dart.

Great shot.

I wouldn't even recognise
which one he was focusing on.

Next minute - boof, done.

The dart contains a sedative

that immobilises the zebra
within five to ten minutes.

Once the zebra goes down,

the team have to act
as quickly as possible.

You tell me when it's OK to get out.

You can get out. Yeah?

'A towel is put over the animals
eyes to help keep it calm.'

Well done.

Just check it. Is that all right?

It's really thanks
to this technology

that we'll be able
to stick with these zebra,

getting readings every hour.

And that means, for the first time,
we'll be able to follow them.

That's not only going to give us
insights into where they go when,

but also into their behaviour,
their decision-making process.

That's bound to reveal some unknowns
into the lives of these zebra.

'The collaring data will not only
help us to keep up with them,

'but we'll see for ourselves
just how tough they need to be

'to take on this migration.'

It's only when you get really close
to these animals

that you realise just how sturdy
they are, how hardy.

You know, they need to be -

they're about to embark on what is

the longest land migration
in Africa.

'The hourly updates
from the satellite collars

'will allow us to follow
a number of different families,

'each with a collared animal in it.'

Awesome. That was hugely satisfying.

One of the zebra collared

is a very special
nine-year-old female called Janet.

She was the first zebra
in this population to be collared,

way back in 2012.

We first discovered
this migration in 2012.

Up until that point, people
didn't know where the zebra move.

So, in the dry season,
you had zebra up here,

and then, in the rainy season,
they disappeared...

Exactly.
So, 2012 the first collars went up.

OK. And, Janet, she was collared
just up here on the floodplains.

It was very exciting -

we didn't know where she was going
to go, or what she was going to do.

She moved 250km all the way down
to Nxai Pan,

down here, in the south.

This is the longest mammal migration
in the whole of Africa,

which is amazing.

The average round trip distance
is about 955km,

which beats the wildebeest migration
in East Africa.

The first year she was collared,

Janet's data completely changed our
understanding of zebra migrations.

It was assumed that the zebra
travelled just 60km or so

to the grassy plains
of Saruti Marsh or Seloko.

But Janet's collar revealed

fascinating new information
to scientists.

She was travelling much further,

all the way to Nxai Pan.

That year, Janet became
the official record holder

for the longest land migration
in Africa.

But this huge journey
takes the zebra

through an area
with virtually no food or water,

and plenty of cover for predators.

'So why do they leave Chobe at all?'

Chobe can sustain wildlife
all year round.

The rains obviously hit Chobe
as well, the grasses get better.

Why would zebra leave Chobe
in the first place?

The zebra there have competition
with other animals,

so they need a new resource,

and the vegetation that comes up
in Nxai Pan is very nutritious,

the soils are very fertile, and so
the grasses are so much better.

For the zebra, the potential rewards
seem to outweigh the risks.

But how exactly do they survive
this immense journey?

How do they navigate through
a featureless landscape?

How does it all even begin?

We're down on the floodplains.

We've been looking for Janet
this morning.

Cameraman Max Hug Williams' mission

will be to follow the frontrunners
all the way to Nxai Pan,

250km to the south.

Our other cameraman, Bob Poole,

will hang back following
the families that are last to leave.

Making the journey
are heavily pregnant females...

...as well as mothers
with young foals.

For them, the 250km migration

will be particularly dangerous.

Filming the zebra
as they gather on the plain

gives Bob the chance
to familiarise himself

with the collared individuals.

If you look at these zebra,

each one of them has totally
different patterns in their stripes.

And she has got some pretty
distinguishing markings on her.

She's got a beautiful sort of W
on her left shoulder,

and so we've called her Winnie.

She's got a foal -

it hangs right next to its mother
almost all the time,

and they seem
quite affectionate together.

At six years old, Winnie may have
already had three other foals

and carried out six migrations.

Although zebra foals can stand
at less than an hour old,

these babies won't have walked
more than a few kilometres a day.

You can see these little things
can run.

And I suppose all this behaviour
is really important,

because they're going to have to
move all the way south.

These zebra are about to move
in a mass exodus

towards the south of Botswana,

and one of the biggest mysteries
is just what triggers this.

One theory is that
the start of the rainy season

sets off an irresistible urge
to migrate.

Luckily, the team don't have to
wait long before the first downpour.

THUNDER RUMBLES

With the rains, everything changes.

Very excited right now.

I mean, we've been waiting
for the rains, and here they are.

Poola.

"Poola" they call it
here in Botswana.

And that's the same word they use
for money.

In Africa, just add water,

and everything works.

And it's not just Bob who's reacting
to the change in the weather.

Our satellite data shows that
in the last few hours,

all the zebra have crossed
the Chobe River

and have started to move south.

The migration has started.

250km to go.

There's absolutely nothing
on these plains any more.

There's just the last pocket
of five or six,

but, otherwise,
this plain is absolutely empty.

Now the migration is under way,

we'll have to keep up with them
every step of this journey.

The open floodplain offered
some safety from predators,

but now they face thick forest...

...and their first big challenge -

a pack of African wild dogs,

the continent's
most relentless predators.

Surrounded by trees,
the zebra won't see them coming.

Even without cover,
wild dogs are a real threat.

They may not be the biggest
of Africa's predators,

but their highly efficient method
of hunting as a pack

certainly makes them
one of the most effective.

During a hunt, each dog has a role.

A leader drives the prey forward...

...while others act as flankers,

corralling the prey
towards the rest of the pack.

The ultimate endurance hunters,

their ability to run up to 70kph
and use sophisticated teamwork

allows them to take down animals
far larger than themselves.

Meticulous coordination
results in a kill

Meticulous coordination
results in a kill

more often than any other predator.

In the forest, the wild dogs
have already left Max far behind.

You can see, actually,
there's dog tracks everywhere.

They split out. There's one here...

Look at that.
That's a leopard track.

I mean, on the plains
they can see what's around,

and when one gets a sense
of some danger, they all bolt.

But in here, this is where leopards,
wild dogs,

have a chance of actually taking...
Especially the foals.

I mean, some of them
were even struggling

to cross the river this morning,

and you think, "How are they going
to make this epic journey of 250km?"

I have absolutely no idea.

With so many predators about,

Max needs to catch up with the zebra

to see
if they've managed to stay safe.

'Max, Max, Max.
This is Rob, at base camp.'

Just got some updated coordinates
for you.

So, 1791 has moved south...

In the forest just south
of the wild dog tracks,

the satellite data leads Max
to his first collared zebra,

who still has 230km to go.

She looks heavily pregnant.

You can see.

A zebra with so few stripes
on her front legs...

I mean, it looks like someone's
got an eraser and rubbed them out.

It's like she's got a pair of tights
on or something.

She's very relaxed, though.
That's great.

What are we going to call her, then?

Because we've got Winnie -

she's really easy to identify
with the W.

And we've got to come up with
something with...

She's definitely got a pair
of socks on or something.

Socks. Socks, OK.

Socks it is.

At only four years old,

Socks is a young
and inexperienced mother.

This may even be
her first pregnancy.

She's in a small family
of just seven animals.

But these families, or harems,
can be up to 20 animals strong,

and are usually made up of
unrelated females and their young,

led by a single dominant male.

The more experienced and powerful
the stallion, the bigger the harem.

Look at this male.

He's got really obvious
thick, black bands on his neck,

and also on his right flank
there's a marking

which almost looks like a wishbone.

We'll have to call him Wishbone.

Wishbone's job is crucial.

He must protect Socks
and the others from predators,

particularly now as they travel
through this dense forest.

Wishbone, Socks
and the rest of the family

are ahead of the other zebra...

...closely followed by Max.

Bringing up the rear is Bob.

He now has the chance
to see how Winnie

and the other herds at the back
deal with the dangers of the forest.

This is pretty exciting.

There's a lot of zebra now,
packed together,

and they all seem to be
on the move south.

Winnie's in the middle, there,

and she's travelling along with
her foal and the rest of her family.

But, you know, for the first time,
there's so many zebra.

Amongst the large group at the rear
are two other collared females -

a pregnant mare called Spirit

and a ten-year-old called Jewel.

Travelling together for safety
is a good idea.

Just a few kilometres to the west,

Max has found a young family
who haven't been so wise...

...as the wild dogs are well aware.

Believe you me, when they get going,

if they want
to run something down,

there's pretty much nothing
that they can't take.

But, luckily for the zebra,
it looks like these guys have fed

and they're just relaxing
in the shade.

When the dogs' hunger returns,

the pregnant females
or those with foals

will be particularly vulnerable
to attack.

If Socks gave birth,

she's not a million miles away
from here.

I mean, that would be
an easy prey for them.

Meanwhile,
there's been some worrying news

about another collared animal.

The satellite data
shows that one zebra

didn't travel far
from the Chobe floodplain,

and it hasn't moved
for the last two days.

We've got a signal, Max.

Is it strong? Are you
getting something close by?

Yeah, it's a strong signal.

It's certainly around here
somewhere.

The team will have to home in

using the VHF radio signal
emitted by the collar.

Numan Chuma, tracker
and wildlife guide, leads us in.

But if the zebra is dead,

there may still be predators
feeding on the carcass.

If it is a lion on a kill,

I mean, we've got to be pretty
careful here, haven't we? Yeah.

You need to spot the animal before
the animal sees you. Sees you.

As they get closer, clues emerge
as to what might have happened.

You know, I can see
quite a few tracks - a hyena...

Something dragging it this way.

That way.

Oh. I can see something.

Here's the carcass, so...

It looks like this zebra
may have fallen prey

to one of the forest's
many predators.

Collar there. Uh-huh.

Look how many maggots
there are already. It's only...

Yeah... two days old.

Nothing lasts very long out here.
Mm-mmm. So you can see this...

It looks like a puncture wound.
They're claw marks...

It's difficult
to know exactly how it died,

but this zebra's collar
is fitted with a camera.

It still looks intact, doesn't it?

It does, yeah.

OK, let's take this off.

Once the footage is downloaded,
it may reveal exactly what happened.

So, that's the last shot
from the morning...

So...

Oh, look. Is that you?

That's me, yeah.

This is when the animal
was collared, on 20th November.

'The camera recorded in short bursts
to extend its battery life.

'For the first few days,
the zebra behaved normally,

'grazing and moving around
the floodplain like Socks,

'Janet and the others.

'Then, four days later,
it crossed the Chobe River again.'

All right, so it's back
on the Botswanan side.

Looks like it's moving a bit faster
there.

Haven't seen many zebra
around him, do you?

Oh, you can see his shadow.

Yeah. So he's swinging his tail...

And now... Now he's lying down.

Looks like he's on the ground.

Zebra tend not to lie down,

especially when
they're by themselves.

Yeah. That makes sense.

It's not particularly safe
to lie down like that. Well, yeah.

The zebra stayed here
for around 36 hours,

moving about a little,
but never leaving this location.

Something was clearly wrong.

BUZZING

Yeah, lots of flies.

Yeah. And he's doing something with
his mouth, but he's not grazing.

We can't see if there's any blood
or any sort of...

foam coming from the mouth,

so we're not sure
what's happening there.

With no clear evidence of predation,

our team thinks
he may have been bitten

by one of Botswana's
poisonous snakes.

He's down again, look.

We don't know how long
he stayed down for.

Between the... Yeah.
How long, during the day...

'Before long,
vultures begin to gather.'

And just a few hours later,
the zebra is dead.

Oh...

That's it. That's it. Game over.

Despite not being able to determine
the exact cause of death,

the collar data shows just how
dangerous it can be out here.

Our latest satellite data shows

that many of the zebra
are making steady progress south.

But Socks, the four-year-old female
that Max spotted in the forest,

is pushing ahead of Winnie,
Janet and the others,

with her family in tow.

I guess she's just a lot slinkier
than we are.

Helping Max get as close to them
as possible is Duncan Rowles,

an experienced tracker
and safari guide.

Max, Max, Max.
This is Rob, at base camp.

Max has Socks'
latest satellite position

and is trying desperately
to catch up with her and her family.

And you can just see
how far Socks has come.

30km just yesterday.

Now she's still in
this really thick bush here.

The only way for us to have a chance
of even getting a glimpse of her

is carry on... on this, which is as
good as a road as you'll ever get,

travel all the way round,

and then hope that she pops out
somewhere near here.

It's not clear why Socks' family
has broken away from the others,

but since she's heavily pregnant,

she might be trying to reach
Nxai Pan before giving birth.

Her incredible pace means that
the hourly satellite data

is not accurate enough
to locate her precisely.

So the team have to resort to
another system.

These collars allow scientists
to track animal movements

in two different ways.

The first part
uses a network of satellites

to calculate its location,

in the same way as your phones
and your cars

use their navigation systems.

But for real-time,
on-the-ground tracking,

the collar also emits a VHF signal

that can be picked up
with radio telemetry equipment,

and every single animal
will have its own unique frequency.

With Socks fast disappearing
into this vast landscape,

it's the VHF radio signal
that will give Max his best chance

of catching up with her
to see if she's OK.

But in forest this thick, he might
get close and still not see her.

She's very close.

We know that.

The best chance
is to just get the telemetry up

and just see
where that ping's coming from.

She's super close now.

She's... She's just in these bushes.

A really strong signal from here.

That is zebra tracks. Oh, man...

And that's completely fresh.
That's a split second.

She must have just crossed
before we came round that corner.

Having so narrowly missed
Socks and her family,

Max now has very little chance
of spotting them

as they head
into the ever-thickening forest.

And how are we supposed
to follow that?

I can't even see you from here.

Socks has covered an amazing 50km
in the last day and a half,

but still has 200km to go.

'This migration
is so new to science

'that every bit of data we gather
helps scientists to understand

'the nature
of this extraordinary journey.'

We need more data
to really build up that picture.

Then the satellite data
shows something

that stops us in our tracks.

Within hours of each other,

almost all the other zebra
have made a U-turn

and are heading right back
to their starting point

on the Chobe floodplain.

Do you have a signal?
Yes, I've got a signal.

Let me just turn it up for you.

Bob tries to intercept the zebra
families as they return north,

hoping to see them
cross the only tarmac road in Chobe.

The radio telemetry shows
that Winnie's family

are just about to cross.

Where's Winnie? Where's Winnie?
Where's Winnie?

Shoot. There she is.

Winnie and her herd
are an experienced family,

so what could possibly
have made them turn back?

Has some other cue
in the environment

told them they've left too soon?

Or could the number of predators
in the forest have driven them back?

It seems like confusing times
for these zebra.

It's almost like
they can't make up their mind.

Are they going to go on
this migration or not?

They might not be comfortable yet

with the amount of rain that's
fallen to make the commitment.

So they have to be very confident

that there's enough water
down there.

Zebra need to drink
pretty much every day,

and normally stay within
10 to 15km of water.

Perhaps a lack of water further
south has influenced their return.

So there's a lot of fascinating
behaviour going on. Not only...

'Revealing as it is,

'the satellite data
can only tell us so much.'

These are complex animals,
aren't they?

They certainly are, and it's not
a straightforward migration.

No. It's not.
It's not like wildebeest just,

"Right, go, all together!"

Exactly. They make
very different decisions.

Exactly. Now, that's what
we've observed so far -

different family groups
will make different decisions

and some groups will leave earlier,

some groups will hang back
and then move later.

Combining the satellite data
that's coming in

with the information we're getting
from the teams on the ground,

that's going to build a much,
much bigger and better picture.

Whatever the reason,

the majority of families
have decided to head back

to the food and water
of the Chobe floodplain.

With an entire 250km
still to go,

Bob finds that Janet, Winnie,
Spirit and Jewel

are showing no signs
of restarting any time soon.

So Bob will wait with them
until they're ready

to start the journey again.

So there's Winnie, coming down.

God... That is great.

Getting a nice drink.

It must be hard for them
to make the decision to move south,

like Socks has now.

Why in the world would you want
to leave this amazing paradise?

But this paradise
won't last forever.

If too many zebra stay here,
the food will run out.

And they'll miss out on the more
nutritious vegetation at Nxai Pan.

If our female zebra
want to give their foals

the best possible start in life,

they'll have to leave here
very soon.

Socks and her family, however,

are well on their way to having
Nxai Pan all to themselves.

She's actually moved
quite far south now.

'24.9818.'

Socks is motoring 8k an hour.

That's unbelievable. There's no way
we can keep up with that.

It's taken us an hour to do 1.5km!

Not only is Socks' family
now well ahead of the others,

they travel in a direct
line to Nxai Pan.

In the flat wilderness of Botswana,

the zebra
somehow navigate perfectly,

with no hills or landmarks
for reference.

Scientists still don't fully
understand exactly how they do this.

Until very recently, it was assumed
these routes were learned

and then passed down
from generation to generation.

But I'm travelling
to meet a scientist

who made a ground-breaking discovery
that turned this theory on its head.

In the 1950s and '60s, thousands
of miles of fences were erected

in an attempt to stop diseases
being transmitted

from wildlife to domestic livestock.

But these fences stopped
many animals

from carrying out
their annual movements.

A few years ago, when some of
these fences were removed,

an ancient migration
was seen to start up once more,

following its exact same route.

Dr Hattie Bartlam-Brooks
of the Royal Veterinary College

made this discovery.

So if the fence was up for 36 years

and zebra live to about 15 years
in the wild,

so there was no zebra
that knew about this route

that was alive
when this fence went down.

I think that's the most exciting
part about the story.

Everyone presumes that
terrestrial migrations are taught.

But in this case, it can't.

The mothers
couldn't have taught the foals.

So I think there's a genetic urge
to make the move.

Something in the zebra's
genetic code drives them to migrate,

but what's even more fascinating
about Hattie's discovery

is that it seems their genes
also tells them where to go -

something that zebra scientists
didn't think possible.

I think it just shows
how complex they are.

We take it for granted
that it's just a zebra,

it walks around, it eats grass,
when it gets hungry,

it walks to some more grass,
but it's not like that.

There's a huge complex interplay
of things going on.

They're not just a stripy donkey.

For the zebras still in Chobe,

something else
is telling them to stay put.

Hopefully we can get you out there.
Great. OK, good luck.

But they have moved off
the floodplain

to an area
just south of the main road.

Bob is catching up with them to try
to understand what's going on.

He finds them 240km from Nxai Pan,

in an area recently razed
to the ground by a forest fire.

Sam, look at this, eh?

All the ash on the ground
is giving it nutrients.

The result is amazing, isn't it?

Suddenly, you get this beautiful
green grass coming up,

and that's what they're eating
right now, and they're loving it.

Ash is an excellent source
of trace elements

that new vegetation thrives in.

Seeing exactly what the zebra
are doing on the ground

allows a deeper insight
into the movement data.

So we know that our zebra
haven't moved south yet,

and that there's a burnt area
here now.

How does it affect the migration,
the timing of it?

This could delay it,

especially if there's not enough
water or vegetation further south.

They're going to stay in this area

and take full advantage
of this new growth of grass.

So this is doing the zebra
quite a big favour,

giving them an extra source of food,
as they need to wait, anyway.

Next rains,
you're ready to move down.

Janet, Winnie, Spirit and Jewel are
staying put for a very good reason.

150km south,
Socks and her family

have stopped for
the first time in six days.

Socks is past the halfway point
of the migration

and now she's stopped in an area
for over 24 hours,

so does this mean that even though
she left really early,

possibly to have her foal
in the Nxai Pan area,

that she gave birth to the foal
over the past 24 hours?

It would be very, very good

if Max could catch up with her
and see for himself.

The problem is, it's still extremely
tough terrain to get through.

Oh, she's so close.

She's literally
straight in front of us,

and that's as strong a signal
as you get.

I'm just worried that this is
a really bad place on the journey

to have a youngster,
because she'll be feeling weak,

there's very little water,
next to no food,

and she's still got a third
of this journey to make.

As if that wasn't enough,
it still hasn't rained.

Scattered across
this hostile wilderness

are depressions on the landscape
called pans.

As long as there is rain,

the water in these pans
offers a lifeline for wildlife.

Using data from the last 24 hours,
Max searches the landscape.

He finds a pan, but it's certainly
not the oasis Socks needs.

There's nothing to drink here.

You can see they've been trying,
because these are zebra tracks here.

Oh, they're zebs, yeah. And they've
actually been into the mud,

obviously just trying to suck
whatever they can off the top.

That's definitely got to be Socks.

She's come here, and trying
to get water from this mud wallow,

I mean, she must be desperate.

This elephant's come into drink,
there's nothing even for him.

He's not even trying.

Again.

With the light fading,

there's little chance
of finding Socks today.

It's too dangerous for Max
and Duncan to drive at night,

but Socks could keep pushing south
and leave them behind again.

But there's nothing Max and Duncan
can do till morning.

Back at base camp,
it's time to take stock

of what we've discovered so far.

As of today, here's what we know
about our collared zebra.

The majority of them
are back in the floodplain.

They've been moving between
the burnt area and the floodplain.

We've had a few showers,

but it indicates
that it's not quite the trigger,

the environmental cue,

that these zebras need
to actually embark on the migration.

So why has Socks
dashed towards Nxai Pan?

Is it that she simply
misread the cues?

It's becoming clear
that their decision-making process

is much more complex
than we first thought.

The following morning, Max might
finally be in for a lucky break.

Firebreaks are swathes cut in
the forest to stop fires spreading.

It looks like Socks' path

might take her directly across one.

Our best chance
of catching her in the open

and seeing what condition she's in

is to try and intercept her
as she crosses.

With the data coming in every hour,

they need to get into position
before she arrives.

We don't know
what kind of state she's in

or even if she's had her foal.

Ready. This is five minutes old.

19.2425.

You know, it's vital that
we actually set eyes on her,

because we're starting
to really worry.

SOFT WHISTLE Right here.

She's crossing. It's her, it's her.

There's only three of them,
which is strange.

I didn't see Wishbone, the stallion.

It's only the briefest of glimpses,
and of only three of them,

but 90km from her destination,
Socks is alive and well.

We'll have to look
at this footage again.

The footage suggests that
she hasn't had her foal yet,

which is good news, and information
we'd never have gleaned

from the satellite data alone.

But the absence of Wishbone,
the stallion, is a real concern.

He should be protecting the herd
from predators

during this last push to Nxai Pan.

Then, out of the blue,
Socks' satellite collar

stops sending location updates.

Without this essential data,
we have no way of finding Socks

in this vast wilderness.

Her last known position
is 40km from Nxai Pan.

Max's only option now
is to continue south

and hope that he can spot her
emerging onto the open pan.

Back in Chobe,
Winnie, Janet, Spirit and Jewel

have at last started to move south.

This time,
they don't stop at the burnt area,

they keep going, and now
they have 180km to go.

At last, the main migration
has started in earnest.

It's time for the rest of the team
to break camp

and head south to Nxai Pan.

Around 10,000 years ago,
Nxai Pan was an enormous lake.

Now dried up, its soil is packed

with potassium, calcium
and magnesium.

During the rainy season,

these minerals produce lush
and highly nutritious grass.

But when Max arrives,
things are not as he'd hoped.

We've arrived expecting to see
a flush of green grass,

which is why the zebra
come this way,

but the rains have not hit here yet.

Even if the zebra
make it through the forest,

there'll be nothing for them to eat
at the end of it.

And that's not their only threat.

A pride of 14 hungry lions
are lying in wait

for the exhausted zebra
as they arrive.

Lions are the largest predators
in Africa.

They have explosive speed and power.

Unlike African wild dogs,

a single lion
can take down a fully grown zebra.

When there are lots of zebra around,
the lions will kill frequently,

feeding on the most nutritious parts

and leaving the leftovers
for scavengers.

But the harsh dry season has taken
its toll on the Nxai Pan lions.

These lions
will have had a tough time.

You can see they're quite skinny.

But they've got through
the dry season

and they know that
all the grazing animals are coming,

and their number one food choice
will be zebra,

and all of our collared animals in
a week or so are going to be here.

Not only will the zebra
find hungry lions waiting for them,

they may also find themselves facing
a complete lack of food

if they arrive here
before the rains.

The changing of the seasons in
Botswana could not be more dramatic.

At the end of the dry season,

temperatures soar as high
as an unbearable 45 degrees C.

The land is scorched and cracked
until, on the horizon,

a lightning bolt announces
the beginning of the rains,

and everything changes.

As the heat soars,
moisture builds in the atmosphere

and enormous clouds appear,
looming across the skies.

THUNDER RUMBLES

For a while,
the showers are localised,

but then the heavens open.

THUNDER CRASHES

Here, as much as 12cm of rain
can fall in a single downpour.

This is what the zebra
have been waiting for.

Several weeks late
but, finally, the rains have come,

and soon, this dry, parched saltpan

is going to transform
into a lush, green field,

full of protein and mineral-rich
grass that the zebra rely on,

especially now that they're foaling.

The satellite data shows

that all our collared zebra
are now just north of Nxai Pan,

having averaged 30km a day
for over a week.

Somehow, they knew that
all of this was about to happen.

They have timed this to perfection.

Now the rains have truly arrived,

the nutritious grasses of Nxai Pan
will start growing.

But the lions will be waiting.

We've established our new base camp
at the northern end of Nxai Pan,

to catch the zebra as they come out
of the forests and onto the plains.

The morning after the rains,

the satellite data
reveals some great news.

Janet! It's Janet. In the open.

She's been giving us the run-around,

but now we're going to finally
clock eyes on her,

see what condition she's in.

She can't be very far.
It's just about 3k from camp.

We know she's here, but
the data point is now an hour old.

In this flat and open pan,
radio telemetry should work well.

Strongest signal's from this...
This group here.

Have a look. See, I think
the second one's got a collar. OK.

That's her.
Fantastic. Amazing.

Look, she's coming right through
the middle of these springbok.

And this zebra,
she was the first one documented

making this huge migration
down here,

and we're meeting up with her again,
she's done it again.

Amazing.

In Chobe,
Janet was part of a family of 15.

But now there are only five of them.

Hopefully, the rest of her herd
are also here somewhere

and haven't succumbed
to exhaustion or predation.

Thankfully, the data shows

that all the other families
are also pouring into the park.

Max, Max, it's Liz. Do you copy?

'Hey, Liz, how are you doing?'

'Well, 14km away from camp

'is Spirit.'

But when Max catches up with Spirit,
he finds that all is not well.

That's Spirit.

Spirit was pregnant.

We can't be sure
what happened to her foal,

but it looks like her family have
had a recent run-in with the lions.

Fresh wounds on three of the zebra
in this group.

I mean, it's the unmistakable marks
left by a lion.

There's a small foal,

and you can see his whole hind
has been ripped open.

That must have happened last night.

The lions were around,
we heard them roaring.

It's bumper season for them
now that the zebra are here.

We need to find out
if Socks is still alive.

Even though her collar's GPS
has failed,

it may still have a VHF signal.

On the ground,
the range is just a few kilometres,

but from the air, it's closer to 40.

It's only when you get up here

that you really realise
the vast expanse of this place.

I mean, where could she be

and how far do we have to look
in every direction?

She could be anywhere in an area
up to 15,000 square kilometres.

That is absolutely huge,
so it's needle in a haystack stuff.

We absolutely had no hope
on the ground. What are our chances?

If the telemetry transmitter
is still working,

we've got a very good chance
of finding her.

So, Liz, we've got a little bit
of altitude now,

and I'm going to put
this receiver on.

You'll hear some static
start to come through.

This is set on Socks' frequency.

We'll just listen
through a lot of noise initially,

cos all you can hear is static,

and then you're just listening
for a tiny, tiny little beep.

Beep. And when we hear that,

we start honing in and trying to
zone in on where she is.

OK. You keep your ears peeled.
I am going to do my best for you.

STATIC

But finding a signal in an area
this size seems next to impossible,

even from the air.

Max is standing by,
ready to go in on the ground,

should we find anything.

STATIC

FAINT BEEP

You hear that?

There was the faintest, tiniest
little beep through this static.

I'm just hearing the static.
Yeah, yeah, so listen really...

Can you hear a beep?
Yeah, yeah, but it's tiny.

It really is very subtle.
FAINT BEEP

BEEPING

It's Socks!

BOTH LAUGH

Oh, my gosh, that's brilliant!

That is definitely the unmistakable
beep of a VHF collar.

Socks is here, she's in Nxai Pan.

Now that we've picked up a signal,
we have to fly in a search pattern

until we pinpoint
its exact location.

BEEPING

It's her, it's her. It's this group
of zebra there. It has to be. Yeah.

'Max, Max, it's Liz. I've got
some fantastic news for you.'

We've just located Socks.

That's amazing news.

She's in a group of ten zebra.

Now, we couldn't get a visual
on Socks herself, but...

'If we're to see how Socks
and her family are doing,

'Max will have to catch up with them
on the ground.'

We'll head that way
and let you know how we get on.

Oh, I'm so happy about this.
Good luck with it all.

Last time we saw Socks,
she was travelling

without the protection of Wishbone,
the stallion.

We need to know how she's doing,
and if she's had her foal.

We're not far off now.

We're almost parallel with them,
so if you start scanning a bit.

It looks like
there's some animals just...

Oh, look. Amazing, amazing.

Look. That's Socks.

She's got her unmistakable
white socks on.

She's with the stallion.

It looks like they're all there.

Then Max spots something moving
in the long grass.

It's her foal.

He's absolutely tiny.

She must have dropped this foal
in the last couple of days.

How cool is that?!

When you look at Socks now and see
what fantastic condition she's in...

She made this journey
really early on,

but that's given her time
to recuperate

and now she's given birth
in the best possible place.

She's found
this little Garden of Eden here

where there's more grass
than we've seen anywhere else,

so she's given this little fella
the best possible start in life.

The funny thing is,
her foal has stripes on its legs.

He's taken after Dad.

As more and more zebra families
pour into Nxai Pan

at the end of a gruelling migration,
the plains come to life.

The first green shoots
are pushing up,

and the time to rest, give birth
and feed on the bounty has arrived.

This little foal is only hours old

and it's still so unsure
on its feet.

I mean, it is just
the most beautiful scene,

and the stallion
is just standing by,

being extremely protective
of his mare and his new foal.

And we know so little
about these interactions,

there's still so much to understand,

but just seeing this scene today

really does paint
a wonderful picture.

And as much as I couldn't help
but question

why on earth an animal
would decide to make

such a ridiculously long
and arduous journey...

...watching this now,
it all makes sense.

It's worth the journey, it's worth
the trial and tribulations,

because as a mother,

you have every instinct telling you,
we need to make it down here,

this is going to make
our family stronger,

our foals will be stronger.

Ultimately,
that's what survival is all about.

During our time in Botswana,
we've had a privileged insight

into Africa's longest and most
recently discovered land migration.

We've discovered the importance

of each family making the right
decision at the right time.

And we've revealed that
part of their ability to navigate

is written in their genes.

The discovery of this
zebra migration is so important.

It represents
what ground-breaking science

can reveal about the natural world

in a way that
simply wasn't possible before.

What surprised me the most is just
how complex these animals are.

A strong biological instinct,
a drive to explore and to navigate,

a constant adjustment
to a changing environment.

They're all at play here.

As difficult as this migration is,
these zebra achieve it perfectly.

There is still
so much to understand,

but ultimately,
this research will help scientists

to preserve
this precious migratory route,

but it will also provide
invaluable insights

that could help to save species and
their habitats across the world.