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We're about to follow the world's greatest migrations, | 0:00:03 | 0:00:07 | |
and reveal their secrets in a way that's never been done before. | 0:00:07 | 0:00:11 | |
All over the world, animals are on the move... | 0:00:13 | 0:00:17 | |
embarking on vast journeys that they depend upon for survival - | 0:00:17 | 0:00:22 | |
to find food, to give birth, or to escape danger. | 0:00:22 | 0:00:27 | |
Travelling hundreds of miles | 0:00:29 | 0:00:31 | |
through some of the world's most breathtaking wildernesses... | 0:00:31 | 0:00:34 | |
..that can turn against them at any moment. | 0:00:36 | 0:00:39 | |
That rapid's really picking up. | 0:00:39 | 0:00:41 | |
They're just disappearing under the water. | 0:00:41 | 0:00:43 | |
Ground-breaking technology allows our team | 0:00:43 | 0:00:46 | |
to follow these migrations more closely than ever before, | 0:00:46 | 0:00:50 | |
and understand them in unprecedented detail. | 0:00:50 | 0:00:53 | |
We can track this ele's movement in real-time. | 0:00:55 | 0:00:59 | |
Using the latest satellite tracking technology, | 0:00:59 | 0:01:02 | |
we can monitor individual animals | 0:01:02 | 0:01:05 | |
and witness first-hand their struggles for survival. | 0:01:05 | 0:01:08 | |
We've got a drama down here. | 0:01:08 | 0:01:10 | |
We've got it. We've got the wolf. We've got the wolf. | 0:01:10 | 0:01:14 | |
This time, we'll follow thousands of zebra | 0:01:14 | 0:01:17 | |
as they undergo their gruelling annual migration in search of food. | 0:01:17 | 0:01:21 | |
They must reach their grazing grounds | 0:01:24 | 0:01:26 | |
just as the rainy season begins. | 0:01:26 | 0:01:29 | |
Arriving too early or too late could spell disaster. | 0:01:29 | 0:01:33 | |
For the first time, satellite tracking allows us | 0:01:35 | 0:01:39 | |
to stay with individual mothers, foals and dominant males | 0:01:39 | 0:01:43 | |
as they brave drought, hunger and ferocious predators. | 0:01:43 | 0:01:47 | |
Below me, this wilderness has kept hidden | 0:01:49 | 0:01:52 | |
a journey that's never been followed before, | 0:01:52 | 0:01:55 | |
and about which virtually nothing is known. | 0:01:55 | 0:01:58 | |
It's the longest land migration in all of Africa. | 0:01:58 | 0:02:03 | |
This is the untold story of the great zebra migration. | 0:02:03 | 0:02:07 | |
Northern Botswana - | 0:02:21 | 0:02:23 | |
a vast, parched wilderness | 0:02:23 | 0:02:26 | |
the size of the United Kingdom. | 0:02:26 | 0:02:27 | |
At the end of Botswana's brutal dry season, | 0:02:29 | 0:02:32 | |
thousands of zebra gather on the Chobe floodplain | 0:02:32 | 0:02:35 | |
as they prepare to travel 250km south | 0:02:35 | 0:02:39 | |
to Nxai Pan National Park. | 0:02:39 | 0:02:41 | |
The journey takes them through one of the most punishing landscapes | 0:02:47 | 0:02:51 | |
in southern Africa. | 0:02:51 | 0:02:53 | |
Travelling in family groups, | 0:02:55 | 0:02:57 | |
many of the females are heavily pregnant or supporting young foals. | 0:02:57 | 0:03:02 | |
Each year, their goal is the same - | 0:03:03 | 0:03:06 | |
to reach Nxai Pan's fertile plains | 0:03:06 | 0:03:08 | |
just as the rains produce the first flush of nutrient-rich vegetation. | 0:03:08 | 0:03:13 | |
The timing of this journey is crucial. | 0:03:13 | 0:03:17 | |
Leave too early and they risk arriving at Nxai Pan | 0:03:17 | 0:03:20 | |
before the lush grass appears. | 0:03:20 | 0:03:22 | |
Leave too late and they'll miss out on the best food on arrival. | 0:03:22 | 0:03:26 | |
Our first camp is on the edge of the Chobe River, | 0:03:32 | 0:03:35 | |
the starting line for the migration. | 0:03:35 | 0:03:37 | |
Yeah, I've been looking at her data over the last... | 0:03:37 | 0:03:41 | |
'I've joined a team of specialist biologists and cameramen' | 0:03:41 | 0:03:44 | |
to attempt something that's never been done before. | 0:03:44 | 0:03:47 | |
We plan to travel with the zebra on the ground, | 0:03:50 | 0:03:53 | |
following their every move. | 0:03:53 | 0:03:55 | |
Around 2,000 zebra are gathering | 0:04:05 | 0:04:08 | |
across the vast Chobe River floodplain, | 0:04:08 | 0:04:10 | |
dotted across the landscape in family groups of up to 20 animals. | 0:04:10 | 0:04:15 | |
They won't be travelling en masse. | 0:04:15 | 0:04:18 | |
Instead, each individual family will make its own decisions | 0:04:18 | 0:04:21 | |
during the migration. | 0:04:21 | 0:04:23 | |
'I'm joining the scientists who are collaring the zebra, | 0:04:25 | 0:04:28 | |
'so that the team can track them.' | 0:04:28 | 0:04:30 | |
OK, Mike, Larry's getting ready to dart. | 0:04:40 | 0:04:42 | |
Great shot. | 0:04:44 | 0:04:45 | |
I wouldn't even recognise which one he was focusing on. | 0:04:45 | 0:04:48 | |
Next minute - boof, done. | 0:04:48 | 0:04:50 | |
The dart contains a sedative | 0:04:50 | 0:04:51 | |
that immobilises the zebra within five to ten minutes. | 0:04:51 | 0:04:55 | |
Once the zebra goes down, | 0:05:03 | 0:05:05 | |
the team have to act as quickly as possible. | 0:05:05 | 0:05:08 | |
You tell me when it's OK to get out. | 0:05:08 | 0:05:09 | |
-You can get out. -Yeah? | 0:05:09 | 0:05:11 | |
'A towel is put over the animals eyes to help keep it calm.' | 0:05:16 | 0:05:20 | |
Well done. | 0:05:21 | 0:05:22 | |
Just check it. Is that all right? | 0:05:25 | 0:05:27 | |
It's really thanks to this technology | 0:05:27 | 0:05:30 | |
that we'll be able to stick with these zebra, | 0:05:30 | 0:05:34 | |
getting readings every hour. | 0:05:34 | 0:05:36 | |
And that means, for the first time, we'll be able to follow them. | 0:05:36 | 0:05:40 | |
That's not only going to give us insights into where they go when, | 0:05:40 | 0:05:43 | |
but also into their behaviour, their decision-making process. | 0:05:43 | 0:05:47 | |
That's bound to reveal some unknowns into the lives of these zebra. | 0:05:47 | 0:05:53 | |
'The collaring data will not only help us to keep up with them, | 0:05:53 | 0:05:57 | |
'but we'll see for ourselves just how tough they need to be | 0:05:57 | 0:05:59 | |
'to take on this migration.' | 0:05:59 | 0:06:02 | |
It's only when you get really close to these animals | 0:06:02 | 0:06:04 | |
that you realise just how sturdy they are, how hardy. | 0:06:04 | 0:06:07 | |
You know, they need to be - | 0:06:09 | 0:06:11 | |
they're about to embark on what is | 0:06:11 | 0:06:12 | |
the longest land migration in Africa. | 0:06:12 | 0:06:16 | |
'The hourly updates from the satellite collars | 0:06:16 | 0:06:18 | |
'will allow us to follow a number of different families, | 0:06:18 | 0:06:21 | |
'each with a collared animal in it.' | 0:06:21 | 0:06:24 | |
Awesome. That was hugely satisfying. | 0:06:25 | 0:06:27 | |
One of the zebra collared | 0:06:31 | 0:06:32 | |
is a very special nine-year-old female called Janet. | 0:06:32 | 0:06:37 | |
She was the first zebra in this population to be collared, | 0:06:37 | 0:06:41 | |
way back in 2012. | 0:06:41 | 0:06:43 | |
We first discovered this migration in 2012. | 0:06:45 | 0:06:49 | |
Up until that point, people didn't know where the zebra move. | 0:06:49 | 0:06:52 | |
So, in the dry season, you had zebra up here, | 0:06:52 | 0:06:55 | |
and then, in the rainy season, they disappeared... | 0:06:55 | 0:06:58 | |
Exactly. So, 2012 the first collars went up. | 0:06:58 | 0:07:00 | |
-OK. -And, Janet, she was collared just up here on the floodplains. | 0:07:00 | 0:07:04 | |
It was very exciting - | 0:07:04 | 0:07:05 | |
we didn't know where she was going to go, or what she was going to do. | 0:07:05 | 0:07:08 | |
She moved 250km all the way down to Nxai Pan, | 0:07:08 | 0:07:13 | |
down here, in the south. | 0:07:13 | 0:07:14 | |
This is the longest mammal migration in the whole of Africa, | 0:07:14 | 0:07:18 | |
which is amazing. | 0:07:18 | 0:07:19 | |
The average round trip distance is about 955km, | 0:07:19 | 0:07:23 | |
which beats the wildebeest migration in East Africa. | 0:07:23 | 0:07:26 | |
The first year she was collared, | 0:07:27 | 0:07:29 | |
Janet's data completely changed our understanding of zebra migrations. | 0:07:29 | 0:07:35 | |
It was assumed that the zebra travelled just 60km or so | 0:07:35 | 0:07:39 | |
to the grassy plains of Saruti Marsh or Seloko. | 0:07:39 | 0:07:43 | |
But Janet's collar revealed | 0:07:43 | 0:07:44 | |
fascinating new information to scientists. | 0:07:44 | 0:07:46 | |
She was travelling much further, | 0:07:48 | 0:07:50 | |
all the way to Nxai Pan. | 0:07:50 | 0:07:54 | |
That year, Janet became the official record holder | 0:07:54 | 0:07:57 | |
for the longest land migration in Africa. | 0:07:57 | 0:08:00 | |
But this huge journey takes the zebra | 0:08:01 | 0:08:04 | |
through an area with virtually no food or water, | 0:08:04 | 0:08:07 | |
and plenty of cover for predators. | 0:08:07 | 0:08:09 | |
'So why do they leave Chobe at all?' | 0:08:13 | 0:08:15 | |
Chobe can sustain wildlife all year round. | 0:08:16 | 0:08:20 | |
The rains obviously hit Chobe as well, the grasses get better. | 0:08:20 | 0:08:23 | |
Why would zebra leave Chobe in the first place? | 0:08:23 | 0:08:26 | |
The zebra there have competition with other animals, | 0:08:26 | 0:08:29 | |
so they need a new resource, | 0:08:29 | 0:08:31 | |
and the vegetation that comes up in Nxai Pan is very nutritious, | 0:08:31 | 0:08:35 | |
the soils are very fertile, and so the grasses are so much better. | 0:08:35 | 0:08:39 | |
For the zebra, the potential rewards seem to outweigh the risks. | 0:08:39 | 0:08:44 | |
But how exactly do they survive this immense journey? | 0:08:44 | 0:08:47 | |
How do they navigate through a featureless landscape? | 0:08:48 | 0:08:52 | |
How does it all even begin? | 0:08:52 | 0:08:54 | |
We're down on the floodplains. | 0:08:55 | 0:08:57 | |
We've been looking for Janet this morning. | 0:08:57 | 0:08:58 | |
Cameraman Max Hug Williams' mission | 0:08:58 | 0:09:00 | |
will be to follow the frontrunners all the way to Nxai Pan, | 0:09:00 | 0:09:04 | |
250km to the south. | 0:09:04 | 0:09:06 | |
Our other cameraman, Bob Poole, | 0:09:08 | 0:09:10 | |
will hang back following the families that are last to leave. | 0:09:10 | 0:09:14 | |
Making the journey are heavily pregnant females... | 0:09:24 | 0:09:28 | |
..as well as mothers with young foals. | 0:09:29 | 0:09:32 | |
For them, the 250km migration | 0:09:36 | 0:09:38 | |
will be particularly dangerous. | 0:09:38 | 0:09:41 | |
Filming the zebra as they gather on the plain | 0:09:45 | 0:09:48 | |
gives Bob the chance to familiarise himself | 0:09:48 | 0:09:50 | |
with the collared individuals. | 0:09:50 | 0:09:53 | |
If you look at these zebra, | 0:09:53 | 0:09:55 | |
each one of them has totally different patterns in their stripes. | 0:09:55 | 0:09:59 | |
And she has got some pretty distinguishing markings on her. | 0:09:59 | 0:10:03 | |
She's got a beautiful sort of W on her left shoulder, | 0:10:03 | 0:10:08 | |
and so we've called her Winnie. | 0:10:08 | 0:10:10 | |
She's got a foal - | 0:10:10 | 0:10:12 | |
it hangs right next to its mother almost all the time, | 0:10:12 | 0:10:15 | |
and they seem quite affectionate together. | 0:10:15 | 0:10:17 | |
At six years old, Winnie may have already had three other foals | 0:10:24 | 0:10:28 | |
and carried out six migrations. | 0:10:28 | 0:10:30 | |
Although zebra foals can stand at less than an hour old, | 0:10:32 | 0:10:36 | |
these babies won't have walked more than a few kilometres a day. | 0:10:36 | 0:10:41 | |
You can see these little things can run. | 0:10:41 | 0:10:45 | |
And I suppose all this behaviour is really important, | 0:10:45 | 0:10:47 | |
because they're going to have to move all the way south. | 0:10:47 | 0:10:51 | |
These zebra are about to move in a mass exodus | 0:10:56 | 0:11:00 | |
towards the south of Botswana, | 0:11:00 | 0:11:03 | |
and one of the biggest mysteries is just what triggers this. | 0:11:03 | 0:11:06 | |
One theory is that the start of the rainy season | 0:11:06 | 0:11:10 | |
sets off an irresistible urge to migrate. | 0:11:10 | 0:11:13 | |
Luckily, the team don't have to wait long before the first downpour. | 0:11:14 | 0:11:18 | |
THUNDER RUMBLES | 0:11:19 | 0:11:21 | |
With the rains, everything changes. | 0:11:40 | 0:11:43 | |
Very excited right now. | 0:11:47 | 0:11:50 | |
I mean, we've been waiting for the rains, and here they are. | 0:11:50 | 0:11:53 | |
Poola. | 0:11:53 | 0:11:55 | |
"Poola" they call it here in Botswana. | 0:11:55 | 0:11:57 | |
And that's the same word they use for money. | 0:11:57 | 0:12:00 | |
In Africa, just add water, | 0:12:00 | 0:12:01 | |
and everything works. | 0:12:01 | 0:12:03 | |
And it's not just Bob who's reacting to the change in the weather. | 0:12:05 | 0:12:09 | |
Our satellite data shows that in the last few hours, | 0:12:12 | 0:12:16 | |
all the zebra have crossed the Chobe River | 0:12:16 | 0:12:18 | |
and have started to move south. | 0:12:18 | 0:12:21 | |
The migration has started. | 0:12:25 | 0:12:27 | |
250km to go. | 0:12:30 | 0:12:33 | |
There's absolutely nothing on these plains any more. | 0:12:36 | 0:12:40 | |
There's just the last pocket of five or six, | 0:12:40 | 0:12:44 | |
but, otherwise, this plain is absolutely empty. | 0:12:44 | 0:12:47 | |
Now the migration is under way, | 0:12:47 | 0:12:49 | |
we'll have to keep up with them every step of this journey. | 0:12:49 | 0:12:53 | |
The open floodplain offered some safety from predators, | 0:12:55 | 0:12:59 | |
but now they face thick forest... | 0:12:59 | 0:13:01 | |
..and their first big challenge - | 0:13:03 | 0:13:07 | |
a pack of African wild dogs, | 0:13:07 | 0:13:09 | |
the continent's most relentless predators. | 0:13:09 | 0:13:12 | |
Surrounded by trees, the zebra won't see them coming. | 0:13:15 | 0:13:19 | |
Even without cover, wild dogs are a real threat. | 0:13:23 | 0:13:27 | |
They may not be the biggest of Africa's predators, | 0:13:27 | 0:13:30 | |
but their highly efficient method of hunting as a pack | 0:13:30 | 0:13:33 | |
certainly makes them one of the most effective. | 0:13:33 | 0:13:36 | |
During a hunt, each dog has a role. | 0:13:38 | 0:13:41 | |
A leader drives the prey forward... | 0:13:45 | 0:13:47 | |
..while others act as flankers, | 0:13:49 | 0:13:52 | |
corralling the prey towards the rest of the pack. | 0:13:52 | 0:13:55 | |
The ultimate endurance hunters, | 0:13:56 | 0:14:00 | |
their ability to run up to 70kph and use sophisticated teamwork | 0:14:00 | 0:14:05 | |
allows them to take down animals far larger than themselves. | 0:14:05 | 0:14:09 | |
Meticulous coordination results in a kill | 0:14:12 | 0:14:14 | |
more often than any other predator. | 0:14:14 | 0:14:17 | |
In the forest, the wild dogs have already left Max far behind. | 0:14:19 | 0:14:24 | |
You can see, actually, there's dog tracks everywhere. | 0:14:27 | 0:14:30 | |
They split out. There's one here... | 0:14:30 | 0:14:33 | |
Look at that. That's a leopard track. | 0:14:36 | 0:14:38 | |
I mean, on the plains they can see what's around, | 0:14:38 | 0:14:41 | |
and when one gets a sense of some danger, they all bolt. | 0:14:41 | 0:14:44 | |
But in here, this is where leopards, wild dogs, | 0:14:44 | 0:14:48 | |
have a chance of actually taking... Especially the foals. | 0:14:48 | 0:14:51 | |
I mean, some of them were even struggling | 0:14:51 | 0:14:53 | |
to cross the river this morning, | 0:14:53 | 0:14:54 | |
and you think, "How are they going to make this epic journey of 250km?" | 0:14:54 | 0:14:58 | |
I have absolutely no idea. | 0:14:58 | 0:15:00 | |
With so many predators about, | 0:15:00 | 0:15:02 | |
Max needs to catch up with the zebra | 0:15:02 | 0:15:04 | |
to see if they've managed to stay safe. | 0:15:04 | 0:15:07 | |
'Max, Max, Max. This is Rob, at base camp.' | 0:15:07 | 0:15:10 | |
Just got some updated coordinates for you. | 0:15:10 | 0:15:12 | |
So, 1791 has moved south... | 0:15:12 | 0:15:16 | |
In the forest just south of the wild dog tracks, | 0:15:16 | 0:15:20 | |
the satellite data leads Max to his first collared zebra, | 0:15:20 | 0:15:23 | |
who still has 230km to go. | 0:15:23 | 0:15:27 | |
She looks heavily pregnant. | 0:15:27 | 0:15:29 | |
You can see. | 0:15:29 | 0:15:30 | |
A zebra with so few stripes on her front legs... | 0:15:33 | 0:15:36 | |
I mean, it looks like someone's got an eraser and rubbed them out. | 0:15:36 | 0:15:39 | |
It's like she's got a pair of tights on or something. | 0:15:39 | 0:15:42 | |
She's very relaxed, though. That's great. | 0:15:42 | 0:15:45 | |
What are we going to call her, then? | 0:15:45 | 0:15:46 | |
Because we've got Winnie - | 0:15:46 | 0:15:48 | |
she's really easy to identify with the W. | 0:15:48 | 0:15:51 | |
And we've got to come up with something with... | 0:15:51 | 0:15:54 | |
She's definitely got a pair of socks on or something. | 0:15:54 | 0:15:56 | |
-Socks. -Socks, OK. | 0:15:56 | 0:15:58 | |
Socks it is. | 0:15:58 | 0:16:00 | |
At only four years old, | 0:16:02 | 0:16:04 | |
Socks is a young and inexperienced mother. | 0:16:04 | 0:16:07 | |
This may even be her first pregnancy. | 0:16:07 | 0:16:10 | |
She's in a small family of just seven animals. | 0:16:12 | 0:16:15 | |
But these families, or harems, can be up to 20 animals strong, | 0:16:15 | 0:16:20 | |
and are usually made up of unrelated females and their young, | 0:16:20 | 0:16:23 | |
led by a single dominant male. | 0:16:23 | 0:16:26 | |
The more experienced and powerful the stallion, the bigger the harem. | 0:16:26 | 0:16:31 | |
Look at this male. | 0:16:31 | 0:16:33 | |
He's got really obvious thick, black bands on his neck, | 0:16:33 | 0:16:35 | |
and also on his right flank there's a marking | 0:16:35 | 0:16:38 | |
which almost looks like a wishbone. | 0:16:38 | 0:16:40 | |
We'll have to call him Wishbone. | 0:16:42 | 0:16:44 | |
Wishbone's job is crucial. | 0:16:46 | 0:16:48 | |
He must protect Socks and the others from predators, | 0:16:48 | 0:16:51 | |
particularly now as they travel through this dense forest. | 0:16:51 | 0:16:55 | |
Wishbone, Socks and the rest of the family | 0:17:02 | 0:17:05 | |
are ahead of the other zebra... | 0:17:05 | 0:17:06 | |
..closely followed by Max. | 0:17:08 | 0:17:10 | |
Bringing up the rear is Bob. | 0:17:11 | 0:17:14 | |
He now has the chance to see how Winnie | 0:17:14 | 0:17:16 | |
and the other herds at the back deal with the dangers of the forest. | 0:17:16 | 0:17:20 | |
This is pretty exciting. | 0:17:20 | 0:17:22 | |
There's a lot of zebra now, packed together, | 0:17:22 | 0:17:24 | |
and they all seem to be on the move south. | 0:17:24 | 0:17:26 | |
Winnie's in the middle, there, | 0:17:28 | 0:17:29 | |
and she's travelling along with her foal and the rest of her family. | 0:17:29 | 0:17:33 | |
But, you know, for the first time, there's so many zebra. | 0:17:33 | 0:17:36 | |
Amongst the large group at the rear are two other collared females - | 0:17:42 | 0:17:47 | |
a pregnant mare called Spirit | 0:17:47 | 0:17:50 | |
and a ten-year-old called Jewel. | 0:17:50 | 0:17:52 | |
Travelling together for safety is a good idea. | 0:17:57 | 0:18:01 | |
Just a few kilometres to the west, | 0:18:02 | 0:18:04 | |
Max has found a young family who haven't been so wise... | 0:18:04 | 0:18:08 | |
..as the wild dogs are well aware. | 0:18:11 | 0:18:14 | |
Believe you me, when they get going, | 0:18:26 | 0:18:28 | |
if they want to run something down, | 0:18:28 | 0:18:29 | |
there's pretty much nothing that they can't take. | 0:18:29 | 0:18:32 | |
But, luckily for the zebra, it looks like these guys have fed | 0:18:32 | 0:18:35 | |
and they're just relaxing in the shade. | 0:18:35 | 0:18:38 | |
When the dogs' hunger returns, | 0:18:48 | 0:18:50 | |
the pregnant females or those with foals | 0:18:50 | 0:18:52 | |
will be particularly vulnerable to attack. | 0:18:52 | 0:18:55 | |
If Socks gave birth, | 0:18:57 | 0:19:00 | |
she's not a million miles away from here. | 0:19:00 | 0:19:02 | |
I mean, that would be an easy prey for them. | 0:19:02 | 0:19:05 | |
Meanwhile, there's been some worrying news | 0:19:11 | 0:19:14 | |
about another collared animal. | 0:19:14 | 0:19:16 | |
The satellite data shows that one zebra | 0:19:18 | 0:19:21 | |
didn't travel far from the Chobe floodplain, | 0:19:21 | 0:19:24 | |
and it hasn't moved for the last two days. | 0:19:24 | 0:19:27 | |
We've got a signal, Max. | 0:19:31 | 0:19:32 | |
Is it strong? Are you getting something close by? | 0:19:32 | 0:19:34 | |
Yeah, it's a strong signal. | 0:19:34 | 0:19:36 | |
It's certainly around here somewhere. | 0:19:36 | 0:19:37 | |
The team will have to home in | 0:19:37 | 0:19:39 | |
using the VHF radio signal emitted by the collar. | 0:19:39 | 0:19:43 | |
Numan Chuma, tracker and wildlife guide, leads us in. | 0:19:43 | 0:19:46 | |
But if the zebra is dead, | 0:19:49 | 0:19:50 | |
there may still be predators feeding on the carcass. | 0:19:50 | 0:19:53 | |
If it is a lion on a kill, | 0:19:53 | 0:19:55 | |
-I mean, we've got to be pretty careful here, haven't we? -Yeah. | 0:19:55 | 0:19:58 | |
-You need to spot the animal before the animal sees you. -Sees you. | 0:19:58 | 0:20:01 | |
As they get closer, clues emerge as to what might have happened. | 0:20:01 | 0:20:05 | |
You know, I can see quite a few tracks - a hyena... | 0:20:05 | 0:20:08 | |
Something dragging it this way. | 0:20:08 | 0:20:10 | |
That way. | 0:20:10 | 0:20:11 | |
-Oh. -I can see something. | 0:20:11 | 0:20:13 | |
Here's the carcass, so... | 0:20:13 | 0:20:14 | |
It looks like this zebra may have fallen prey | 0:20:16 | 0:20:18 | |
to one of the forest's many predators. | 0:20:18 | 0:20:21 | |
-Collar there. -Uh-huh. | 0:20:21 | 0:20:22 | |
Look how many maggots there are already. It's only... | 0:20:26 | 0:20:28 | |
-Yeah. -..two days old. | 0:20:28 | 0:20:29 | |
-Nothing lasts very long out here. -Mm-mmm. -So you can see this... | 0:20:29 | 0:20:32 | |
-It looks like a puncture wound. -They're claw marks... | 0:20:32 | 0:20:35 | |
It's difficult to know exactly how it died, | 0:20:35 | 0:20:38 | |
but this zebra's collar is fitted with a camera. | 0:20:38 | 0:20:41 | |
It still looks intact, doesn't it? | 0:20:41 | 0:20:43 | |
It does, yeah. | 0:20:43 | 0:20:44 | |
OK, let's take this off. | 0:20:44 | 0:20:46 | |
Once the footage is downloaded, it may reveal exactly what happened. | 0:20:46 | 0:20:51 | |
So, that's the last shot from the morning... | 0:20:51 | 0:20:54 | |
So... | 0:20:54 | 0:20:56 | |
-Oh, look. -Is that you? | 0:20:56 | 0:20:57 | |
That's me, yeah. | 0:20:57 | 0:20:58 | |
This is when the animal was collared, on 20th November. | 0:20:58 | 0:21:02 | |
'The camera recorded in short bursts to extend its battery life. | 0:21:02 | 0:21:05 | |
'For the first few days, the zebra behaved normally, | 0:21:10 | 0:21:13 | |
'grazing and moving around the floodplain like Socks, | 0:21:13 | 0:21:15 | |
'Janet and the others. | 0:21:15 | 0:21:17 | |
'Then, four days later, it crossed the Chobe River again.' | 0:21:17 | 0:21:21 | |
All right, so it's back on the Botswanan side. | 0:21:21 | 0:21:24 | |
Looks like it's moving a bit faster there. | 0:21:24 | 0:21:27 | |
Haven't seen many zebra around him, do you? | 0:21:27 | 0:21:30 | |
Oh, you can see his shadow. | 0:21:30 | 0:21:31 | |
-Yeah. -So he's swinging his tail... | 0:21:31 | 0:21:34 | |
-And now... -Now he's lying down. | 0:21:34 | 0:21:36 | |
Looks like he's on the ground. | 0:21:36 | 0:21:38 | |
Zebra tend not to lie down, | 0:21:38 | 0:21:39 | |
especially when they're by themselves. | 0:21:39 | 0:21:42 | |
Yeah. That makes sense. | 0:21:42 | 0:21:43 | |
-It's not particularly safe to lie down like that. -Well, yeah. | 0:21:43 | 0:21:46 | |
The zebra stayed here for around 36 hours, | 0:21:50 | 0:21:54 | |
moving about a little, but never leaving this location. | 0:21:54 | 0:21:58 | |
Something was clearly wrong. | 0:21:58 | 0:22:00 | |
BUZZING | 0:22:04 | 0:22:07 | |
Yeah, lots of flies. | 0:22:07 | 0:22:08 | |
-Yeah. -And he's doing something with his mouth, but he's not grazing. | 0:22:08 | 0:22:12 | |
We can't see if there's any blood or any sort of... | 0:22:12 | 0:22:15 | |
foam coming from the mouth, | 0:22:15 | 0:22:16 | |
so we're not sure what's happening there. | 0:22:16 | 0:22:19 | |
With no clear evidence of predation, | 0:22:20 | 0:22:23 | |
our team thinks he may have been bitten | 0:22:23 | 0:22:25 | |
by one of Botswana's poisonous snakes. | 0:22:25 | 0:22:28 | |
He's down again, look. | 0:22:33 | 0:22:34 | |
We don't know how long he stayed down for. | 0:22:34 | 0:22:36 | |
Between the... Yeah. How long, during the day... | 0:22:36 | 0:22:38 | |
'Before long, vultures begin to gather.' | 0:22:38 | 0:22:41 | |
And just a few hours later, the zebra is dead. | 0:22:43 | 0:22:46 | |
Oh... | 0:22:48 | 0:22:49 | |
-That's it. -That's it. Game over. | 0:22:50 | 0:22:52 | |
Despite not being able to determine the exact cause of death, | 0:22:56 | 0:23:00 | |
the collar data shows just how dangerous it can be out here. | 0:23:00 | 0:23:03 | |
Our latest satellite data shows | 0:23:11 | 0:23:13 | |
that many of the zebra are making steady progress south. | 0:23:13 | 0:23:17 | |
But Socks, the four-year-old female that Max spotted in the forest, | 0:23:18 | 0:23:22 | |
is pushing ahead of Winnie, Janet and the others, | 0:23:22 | 0:23:25 | |
with her family in tow. | 0:23:25 | 0:23:27 | |
I guess she's just a lot slinkier than we are. | 0:23:27 | 0:23:29 | |
Helping Max get as close to them as possible is Duncan Rowles, | 0:23:29 | 0:23:33 | |
an experienced tracker and safari guide. | 0:23:33 | 0:23:36 | |
Max, Max, Max. This is Rob, at base camp. | 0:23:37 | 0:23:40 | |
Max has Socks' latest satellite position | 0:23:40 | 0:23:43 | |
and is trying desperately to catch up with her and her family. | 0:23:43 | 0:23:47 | |
And you can just see how far Socks has come. | 0:23:49 | 0:23:52 | |
30km just yesterday. | 0:23:52 | 0:23:54 | |
Now she's still in this really thick bush here. | 0:23:54 | 0:23:58 | |
The only way for us to have a chance of even getting a glimpse of her | 0:23:58 | 0:24:02 | |
is carry on...on this, which is as good as a road as you'll ever get, | 0:24:02 | 0:24:08 | |
travel all the way round, | 0:24:08 | 0:24:10 | |
and then hope that she pops out somewhere near here. | 0:24:10 | 0:24:14 | |
It's not clear why Socks' family has broken away from the others, | 0:24:17 | 0:24:21 | |
but since she's heavily pregnant, | 0:24:21 | 0:24:23 | |
she might be trying to reach Nxai Pan before giving birth. | 0:24:23 | 0:24:26 | |
Her incredible pace means that the hourly satellite data | 0:24:29 | 0:24:33 | |
is not accurate enough to locate her precisely. | 0:24:33 | 0:24:36 | |
So the team have to resort to another system. | 0:24:40 | 0:24:43 | |
These collars allow scientists to track animal movements | 0:24:45 | 0:24:48 | |
in two different ways. | 0:24:48 | 0:24:49 | |
The first part uses a network of satellites | 0:24:49 | 0:24:52 | |
to calculate its location, | 0:24:52 | 0:24:53 | |
in the same way as your phones and your cars | 0:24:53 | 0:24:56 | |
use their navigation systems. | 0:24:56 | 0:24:57 | |
But for real-time, on-the-ground tracking, | 0:24:57 | 0:25:00 | |
the collar also emits a VHF signal | 0:25:00 | 0:25:03 | |
that can be picked up with radio telemetry equipment, | 0:25:03 | 0:25:06 | |
and every single animal will have its own unique frequency. | 0:25:06 | 0:25:09 | |
With Socks fast disappearing into this vast landscape, | 0:25:13 | 0:25:17 | |
it's the VHF radio signal that will give Max his best chance | 0:25:17 | 0:25:21 | |
of catching up with her to see if she's OK. | 0:25:21 | 0:25:24 | |
But in forest this thick, he might get close and still not see her. | 0:25:29 | 0:25:34 | |
She's very close. | 0:25:34 | 0:25:36 | |
We know that. | 0:25:36 | 0:25:37 | |
The best chance is to just get the telemetry up | 0:25:37 | 0:25:39 | |
and just see where that ping's coming from. | 0:25:39 | 0:25:41 | |
She's super close now. | 0:25:44 | 0:25:45 | |
She's... She's just in these bushes. | 0:25:45 | 0:25:47 | |
A really strong signal from here. | 0:25:47 | 0:25:49 | |
-That is zebra tracks. -Oh, man... | 0:25:52 | 0:25:56 | |
And that's completely fresh. That's a split second. | 0:25:56 | 0:25:59 | |
She must have just crossed before we came round that corner. | 0:25:59 | 0:26:03 | |
Having so narrowly missed Socks and her family, | 0:26:03 | 0:26:06 | |
Max now has very little chance of spotting them | 0:26:06 | 0:26:09 | |
as they head into the ever-thickening forest. | 0:26:09 | 0:26:12 | |
And how are we supposed to follow that? | 0:26:12 | 0:26:14 | |
I can't even see you from here. | 0:26:14 | 0:26:16 | |
Socks has covered an amazing 50km in the last day and a half, | 0:26:17 | 0:26:22 | |
but still has 200km to go. | 0:26:22 | 0:26:25 | |
'This migration is so new to science | 0:26:28 | 0:26:30 | |
'that every bit of data we gather helps scientists to understand | 0:26:30 | 0:26:34 | |
'the nature of this extraordinary journey.' | 0:26:34 | 0:26:37 | |
We need more data to really build up that picture. | 0:26:37 | 0:26:39 | |
Then the satellite data shows something | 0:26:41 | 0:26:43 | |
that stops us in our tracks. | 0:26:43 | 0:26:45 | |
Within hours of each other, | 0:26:45 | 0:26:47 | |
almost all the other zebra have made a U-turn | 0:26:47 | 0:26:50 | |
and are heading right back to their starting point | 0:26:50 | 0:26:53 | |
on the Chobe floodplain. | 0:26:53 | 0:26:55 | |
-Do you have a signal? -Yes, I've got a signal. | 0:27:01 | 0:27:03 | |
Let me just turn it up for you. | 0:27:03 | 0:27:05 | |
Bob tries to intercept the zebra families as they return north, | 0:27:05 | 0:27:08 | |
hoping to see them cross the only tarmac road in Chobe. | 0:27:08 | 0:27:12 | |
The radio telemetry shows that Winnie's family | 0:27:12 | 0:27:15 | |
are just about to cross. | 0:27:15 | 0:27:17 | |
Where's Winnie? Where's Winnie? Where's Winnie? | 0:27:19 | 0:27:22 | |
Shoot. There she is. | 0:27:22 | 0:27:25 | |
Winnie and her herd are an experienced family, | 0:27:25 | 0:27:28 | |
so what could possibly have made them turn back? | 0:27:28 | 0:27:32 | |
Has some other cue in the environment | 0:27:32 | 0:27:34 | |
told them they've left too soon? | 0:27:34 | 0:27:36 | |
Or could the number of predators in the forest have driven them back? | 0:27:36 | 0:27:40 | |
It seems like confusing times for these zebra. | 0:27:42 | 0:27:46 | |
It's almost like they can't make up their mind. | 0:27:46 | 0:27:49 | |
Are they going to go on this migration or not? | 0:27:49 | 0:27:51 | |
They might not be comfortable yet | 0:27:53 | 0:27:55 | |
with the amount of rain that's fallen to make the commitment. | 0:27:55 | 0:27:59 | |
So they have to be very confident | 0:27:59 | 0:28:01 | |
that there's enough water down there. | 0:28:01 | 0:28:03 | |
Zebra need to drink pretty much every day, | 0:28:05 | 0:28:07 | |
and normally stay within 10 to 15km of water. | 0:28:07 | 0:28:11 | |
Perhaps a lack of water further south has influenced their return. | 0:28:11 | 0:28:15 | |
So there's a lot of fascinating behaviour going on. Not only... | 0:28:15 | 0:28:19 | |
'Revealing as it is, | 0:28:19 | 0:28:20 | |
'the satellite data can only tell us so much.' | 0:28:20 | 0:28:23 | |
These are complex animals, aren't they? | 0:28:23 | 0:28:25 | |
They certainly are, and it's not a straightforward migration. | 0:28:25 | 0:28:28 | |
No. It's not. It's not like wildebeest just, | 0:28:28 | 0:28:30 | |
"Right, go, all together!" | 0:28:30 | 0:28:31 | |
-Exactly. -They make very different decisions. | 0:28:31 | 0:28:34 | |
Exactly. Now, that's what we've observed so far - | 0:28:34 | 0:28:36 | |
different family groups will make different decisions | 0:28:36 | 0:28:39 | |
and some groups will leave earlier, | 0:28:39 | 0:28:40 | |
some groups will hang back and then move later. | 0:28:40 | 0:28:43 | |
Combining the satellite data that's coming in | 0:28:43 | 0:28:45 | |
with the information we're getting from the teams on the ground, | 0:28:45 | 0:28:47 | |
that's going to build a much, much bigger and better picture. | 0:28:47 | 0:28:50 | |
Whatever the reason, | 0:28:53 | 0:28:55 | |
the majority of families have decided to head back | 0:28:55 | 0:28:57 | |
to the food and water of the Chobe floodplain. | 0:28:57 | 0:29:01 | |
With an entire 250km still to go, | 0:29:12 | 0:29:17 | |
Bob finds that Janet, Winnie, Spirit and Jewel | 0:29:17 | 0:29:20 | |
are showing no signs of restarting any time soon. | 0:29:20 | 0:29:24 | |
So Bob will wait with them until they're ready | 0:29:26 | 0:29:28 | |
to start the journey again. | 0:29:28 | 0:29:30 | |
So there's Winnie, coming down. | 0:29:32 | 0:29:35 | |
God... That is great. | 0:29:35 | 0:29:37 | |
Getting a nice drink. | 0:29:39 | 0:29:41 | |
It must be hard for them to make the decision to move south, | 0:29:42 | 0:29:47 | |
like Socks has now. | 0:29:47 | 0:29:48 | |
Why in the world would you want to leave this amazing paradise? | 0:29:48 | 0:29:52 | |
But this paradise won't last forever. | 0:29:52 | 0:29:56 | |
If too many zebra stay here, the food will run out. | 0:29:56 | 0:30:00 | |
And they'll miss out on the more nutritious vegetation at Nxai Pan. | 0:30:01 | 0:30:05 | |
If our female zebra want to give their foals | 0:30:10 | 0:30:12 | |
the best possible start in life, | 0:30:12 | 0:30:14 | |
they'll have to leave here very soon. | 0:30:14 | 0:30:17 | |
Socks and her family, however, | 0:30:19 | 0:30:21 | |
are well on their way to having Nxai Pan all to themselves. | 0:30:21 | 0:30:25 | |
She's actually moved quite far south now. | 0:30:25 | 0:30:28 | |
'24.9818.' | 0:30:28 | 0:30:31 | |
Socks is motoring 8k an hour. | 0:30:31 | 0:30:34 | |
That's unbelievable. There's no way we can keep up with that. | 0:30:34 | 0:30:37 | |
It's taken us an hour to do 1.5km! | 0:30:37 | 0:30:41 | |
Not only is Socks' family now well ahead of the others, | 0:30:48 | 0:30:51 | |
they travel in a direct line to Nxai Pan. | 0:30:51 | 0:30:55 | |
In the flat wilderness of Botswana, | 0:31:03 | 0:31:05 | |
the zebra somehow navigate perfectly, | 0:31:05 | 0:31:08 | |
with no hills or landmarks for reference. | 0:31:08 | 0:31:10 | |
Scientists still don't fully understand exactly how they do this. | 0:31:11 | 0:31:16 | |
Until very recently, it was assumed these routes were learned | 0:31:17 | 0:31:20 | |
and then passed down from generation to generation. | 0:31:20 | 0:31:24 | |
But I'm travelling to meet a scientist | 0:31:26 | 0:31:28 | |
who made a ground-breaking discovery that turned this theory on its head. | 0:31:28 | 0:31:32 | |
In the 1950s and '60s, thousands of miles of fences were erected | 0:31:33 | 0:31:38 | |
in an attempt to stop diseases being transmitted | 0:31:38 | 0:31:41 | |
from wildlife to domestic livestock. | 0:31:41 | 0:31:43 | |
But these fences stopped many animals | 0:31:43 | 0:31:45 | |
from carrying out their annual movements. | 0:31:45 | 0:31:49 | |
A few years ago, when some of these fences were removed, | 0:31:49 | 0:31:52 | |
an ancient migration was seen to start up once more, | 0:31:52 | 0:31:56 | |
following its exact same route. | 0:31:56 | 0:31:58 | |
Dr Hattie Bartlam-Brooks of the Royal Veterinary College | 0:32:01 | 0:32:04 | |
made this discovery. | 0:32:04 | 0:32:06 | |
So if the fence was up for 36 years | 0:32:06 | 0:32:08 | |
and zebra live to about 15 years in the wild, | 0:32:08 | 0:32:11 | |
so there was no zebra that knew about this route | 0:32:11 | 0:32:14 | |
that was alive when this fence went down. | 0:32:14 | 0:32:16 | |
I think that's the most exciting part about the story. | 0:32:16 | 0:32:18 | |
Everyone presumes that terrestrial migrations are taught. | 0:32:18 | 0:32:21 | |
But in this case, it can't. | 0:32:21 | 0:32:22 | |
The mothers couldn't have taught the foals. | 0:32:22 | 0:32:25 | |
So I think there's a genetic urge to make the move. | 0:32:25 | 0:32:28 | |
Something in the zebra's genetic code drives them to migrate, | 0:32:28 | 0:32:32 | |
but what's even more fascinating about Hattie's discovery | 0:32:32 | 0:32:35 | |
is that it seems their genes also tells them where to go - | 0:32:35 | 0:32:39 | |
something that zebra scientists didn't think possible. | 0:32:39 | 0:32:43 | |
I think it just shows how complex they are. | 0:32:43 | 0:32:45 | |
We take it for granted that it's just a zebra, | 0:32:45 | 0:32:47 | |
it walks around, it eats grass, when it gets hungry, | 0:32:47 | 0:32:50 | |
it walks to some more grass, but it's not like that. | 0:32:50 | 0:32:52 | |
There's a huge complex interplay of things going on. | 0:32:52 | 0:32:55 | |
They're not just a stripy donkey. | 0:32:55 | 0:32:56 | |
For the zebras still in Chobe, | 0:33:01 | 0:33:03 | |
something else is telling them to stay put. | 0:33:03 | 0:33:06 | |
-Hopefully we can get you out there. -Great. -OK, good luck. | 0:33:06 | 0:33:09 | |
But they have moved off the floodplain | 0:33:09 | 0:33:12 | |
to an area just south of the main road. | 0:33:12 | 0:33:14 | |
Bob is catching up with them to try to understand what's going on. | 0:33:18 | 0:33:21 | |
He finds them 240km from Nxai Pan, | 0:33:23 | 0:33:27 | |
in an area recently razed to the ground by a forest fire. | 0:33:27 | 0:33:30 | |
Sam, look at this, eh? | 0:33:36 | 0:33:37 | |
All the ash on the ground is giving it nutrients. | 0:33:37 | 0:33:41 | |
The result is amazing, isn't it? | 0:33:41 | 0:33:43 | |
Suddenly, you get this beautiful green grass coming up, | 0:33:43 | 0:33:47 | |
and that's what they're eating right now, and they're loving it. | 0:33:47 | 0:33:50 | |
Ash is an excellent source of trace elements | 0:33:50 | 0:33:53 | |
that new vegetation thrives in. | 0:33:53 | 0:33:56 | |
Seeing exactly what the zebra are doing on the ground | 0:33:56 | 0:33:59 | |
allows a deeper insight into the movement data. | 0:33:59 | 0:34:02 | |
So we know that our zebra haven't moved south yet, | 0:34:02 | 0:34:05 | |
and that there's a burnt area here now. | 0:34:05 | 0:34:09 | |
How does it affect the migration, the timing of it? | 0:34:09 | 0:34:12 | |
This could delay it, | 0:34:12 | 0:34:13 | |
especially if there's not enough water or vegetation further south. | 0:34:13 | 0:34:16 | |
They're going to stay in this area | 0:34:16 | 0:34:18 | |
and take full advantage of this new growth of grass. | 0:34:18 | 0:34:21 | |
So this is doing the zebra quite a big favour, | 0:34:21 | 0:34:24 | |
giving them an extra source of food, as they need to wait, anyway. | 0:34:24 | 0:34:27 | |
Next rains, you're ready to move down. | 0:34:27 | 0:34:29 | |
Janet, Winnie, Spirit and Jewel are staying put for a very good reason. | 0:34:32 | 0:34:37 | |
150km south, Socks and her family | 0:34:41 | 0:34:45 | |
have stopped for the first time in six days. | 0:34:45 | 0:34:48 | |
Socks is past the halfway point of the migration | 0:34:51 | 0:34:54 | |
and now she's stopped in an area for over 24 hours, | 0:34:54 | 0:35:00 | |
so does this mean that even though she left really early, | 0:35:00 | 0:35:04 | |
possibly to have her foal in the Nxai Pan area, | 0:35:04 | 0:35:08 | |
that she gave birth to the foal over the past 24 hours? | 0:35:08 | 0:35:11 | |
It would be very, very good | 0:35:11 | 0:35:13 | |
if Max could catch up with her and see for himself. | 0:35:13 | 0:35:16 | |
The problem is, it's still extremely tough terrain to get through. | 0:35:16 | 0:35:20 | |
Oh, she's so close. | 0:35:33 | 0:35:35 | |
She's literally straight in front of us, | 0:35:35 | 0:35:38 | |
and that's as strong a signal as you get. | 0:35:38 | 0:35:40 | |
I'm just worried that this is a really bad place on the journey | 0:35:40 | 0:35:45 | |
to have a youngster, because she'll be feeling weak, | 0:35:45 | 0:35:50 | |
there's very little water, next to no food, | 0:35:50 | 0:35:53 | |
and she's still got a third of this journey to make. | 0:35:53 | 0:35:56 | |
As if that wasn't enough, it still hasn't rained. | 0:35:59 | 0:36:02 | |
Scattered across this hostile wilderness | 0:36:11 | 0:36:13 | |
are depressions on the landscape called pans. | 0:36:13 | 0:36:17 | |
As long as there is rain, | 0:36:17 | 0:36:19 | |
the water in these pans offers a lifeline for wildlife. | 0:36:19 | 0:36:22 | |
Using data from the last 24 hours, Max searches the landscape. | 0:36:23 | 0:36:27 | |
He finds a pan, but it's certainly not the oasis Socks needs. | 0:36:30 | 0:36:34 | |
There's nothing to drink here. | 0:36:34 | 0:36:37 | |
You can see they've been trying, because these are zebra tracks here. | 0:36:37 | 0:36:40 | |
-Oh, they're zebs, yeah. -And they've actually been into the mud, | 0:36:40 | 0:36:43 | |
obviously just trying to suck whatever they can off the top. | 0:36:43 | 0:36:46 | |
That's definitely got to be Socks. | 0:36:46 | 0:36:48 | |
She's come here, and trying to get water from this mud wallow, | 0:36:48 | 0:36:52 | |
I mean, she must be desperate. | 0:36:52 | 0:36:54 | |
This elephant's come into drink, there's nothing even for him. | 0:36:54 | 0:36:57 | |
He's not even trying. | 0:36:57 | 0:36:58 | |
Again. | 0:37:02 | 0:37:04 | |
With the light fading, | 0:37:04 | 0:37:05 | |
there's little chance of finding Socks today. | 0:37:05 | 0:37:08 | |
It's too dangerous for Max and Duncan to drive at night, | 0:37:11 | 0:37:15 | |
but Socks could keep pushing south and leave them behind again. | 0:37:15 | 0:37:19 | |
But there's nothing Max and Duncan can do till morning. | 0:37:23 | 0:37:26 | |
Back at base camp, it's time to take stock | 0:37:37 | 0:37:40 | |
of what we've discovered so far. | 0:37:40 | 0:37:42 | |
As of today, here's what we know about our collared zebra. | 0:37:42 | 0:37:46 | |
The majority of them are back in the floodplain. | 0:37:46 | 0:37:49 | |
They've been moving between the burnt area and the floodplain. | 0:37:49 | 0:37:52 | |
We've had a few showers, | 0:37:52 | 0:37:54 | |
but it indicates that it's not quite the trigger, | 0:37:54 | 0:37:57 | |
the environmental cue, | 0:37:57 | 0:37:59 | |
that these zebras need to actually embark on the migration. | 0:37:59 | 0:38:02 | |
So why has Socks dashed towards Nxai Pan? | 0:38:02 | 0:38:07 | |
Is it that she simply misread the cues? | 0:38:07 | 0:38:10 | |
It's becoming clear that their decision-making process | 0:38:12 | 0:38:15 | |
is much more complex than we first thought. | 0:38:15 | 0:38:18 | |
The following morning, Max might finally be in for a lucky break. | 0:38:20 | 0:38:24 | |
Firebreaks are swathes cut in the forest to stop fires spreading. | 0:38:26 | 0:38:31 | |
It looks like Socks' path | 0:38:31 | 0:38:33 | |
might take her directly across one. | 0:38:33 | 0:38:35 | |
Our best chance of catching her in the open | 0:38:38 | 0:38:40 | |
and seeing what condition she's in | 0:38:40 | 0:38:42 | |
is to try and intercept her as she crosses. | 0:38:42 | 0:38:45 | |
With the data coming in every hour, | 0:38:47 | 0:38:49 | |
they need to get into position before she arrives. | 0:38:49 | 0:38:52 | |
We don't know what kind of state she's in | 0:38:52 | 0:38:54 | |
or even if she's had her foal. | 0:38:54 | 0:38:56 | |
-Ready. -This is five minutes old. | 0:38:56 | 0:38:59 | |
19.2425. | 0:38:59 | 0:39:00 | |
You know, it's vital that we actually set eyes on her, | 0:39:08 | 0:39:12 | |
because we're starting to really worry. | 0:39:12 | 0:39:14 | |
-SOFT WHISTLE -Right here. | 0:39:16 | 0:39:18 | |
She's crossing. It's her, it's her. | 0:39:18 | 0:39:20 | |
There's only three of them, which is strange. | 0:39:24 | 0:39:26 | |
I didn't see Wishbone, the stallion. | 0:39:26 | 0:39:29 | |
It's only the briefest of glimpses, and of only three of them, | 0:39:30 | 0:39:34 | |
but 90km from her destination, Socks is alive and well. | 0:39:34 | 0:39:38 | |
We'll have to look at this footage again. | 0:39:38 | 0:39:40 | |
The footage suggests that she hasn't had her foal yet, | 0:39:43 | 0:39:46 | |
which is good news, and information we'd never have gleaned | 0:39:46 | 0:39:50 | |
from the satellite data alone. | 0:39:50 | 0:39:52 | |
But the absence of Wishbone, the stallion, is a real concern. | 0:39:52 | 0:39:56 | |
He should be protecting the herd from predators | 0:39:56 | 0:39:59 | |
during this last push to Nxai Pan. | 0:39:59 | 0:40:01 | |
Then, out of the blue, Socks' satellite collar | 0:40:09 | 0:40:12 | |
stops sending location updates. | 0:40:12 | 0:40:15 | |
Without this essential data, we have no way of finding Socks | 0:40:15 | 0:40:18 | |
in this vast wilderness. | 0:40:18 | 0:40:21 | |
Her last known position is 40km from Nxai Pan. | 0:40:21 | 0:40:25 | |
Max's only option now is to continue south | 0:40:30 | 0:40:33 | |
and hope that he can spot her emerging onto the open pan. | 0:40:33 | 0:40:37 | |
Back in Chobe, Winnie, Janet, Spirit and Jewel | 0:40:43 | 0:40:46 | |
have at last started to move south. | 0:40:46 | 0:40:49 | |
This time, they don't stop at the burnt area, | 0:40:55 | 0:40:58 | |
they keep going, and now they have 180km to go. | 0:40:58 | 0:41:02 | |
At last, the main migration has started in earnest. | 0:41:07 | 0:41:11 | |
It's time for the rest of the team to break camp | 0:41:13 | 0:41:16 | |
and head south to Nxai Pan. | 0:41:16 | 0:41:18 | |
Around 10,000 years ago, Nxai Pan was an enormous lake. | 0:41:43 | 0:41:47 | |
Now dried up, its soil is packed | 0:41:47 | 0:41:50 | |
with potassium, calcium and magnesium. | 0:41:50 | 0:41:53 | |
During the rainy season, | 0:41:54 | 0:41:56 | |
these minerals produce lush and highly nutritious grass. | 0:41:56 | 0:41:59 | |
But when Max arrives, things are not as he'd hoped. | 0:42:01 | 0:42:04 | |
We've arrived expecting to see a flush of green grass, | 0:42:07 | 0:42:11 | |
which is why the zebra come this way, | 0:42:11 | 0:42:13 | |
but the rains have not hit here yet. | 0:42:13 | 0:42:15 | |
Even if the zebra make it through the forest, | 0:42:27 | 0:42:30 | |
there'll be nothing for them to eat at the end of it. | 0:42:30 | 0:42:32 | |
And that's not their only threat. | 0:42:34 | 0:42:36 | |
A pride of 14 hungry lions are lying in wait | 0:42:41 | 0:42:44 | |
for the exhausted zebra as they arrive. | 0:42:44 | 0:42:47 | |
Lions are the largest predators in Africa. | 0:42:52 | 0:42:56 | |
They have explosive speed and power. | 0:42:56 | 0:42:58 | |
Unlike African wild dogs, | 0:42:59 | 0:43:01 | |
a single lion can take down a fully grown zebra. | 0:43:01 | 0:43:04 | |
When there are lots of zebra around, the lions will kill frequently, | 0:43:12 | 0:43:16 | |
feeding on the most nutritious parts | 0:43:16 | 0:43:18 | |
and leaving the leftovers for scavengers. | 0:43:18 | 0:43:20 | |
But the harsh dry season has taken its toll on the Nxai Pan lions. | 0:43:22 | 0:43:26 | |
These lions will have had a tough time. | 0:43:29 | 0:43:31 | |
You can see they're quite skinny. | 0:43:31 | 0:43:33 | |
But they've got through the dry season | 0:43:33 | 0:43:35 | |
and they know that all the grazing animals are coming, | 0:43:35 | 0:43:38 | |
and their number one food choice will be zebra, | 0:43:38 | 0:43:41 | |
and all of our collared animals in a week or so are going to be here. | 0:43:41 | 0:43:45 | |
Not only will the zebra find hungry lions waiting for them, | 0:43:48 | 0:43:53 | |
they may also find themselves facing a complete lack of food | 0:43:53 | 0:43:56 | |
if they arrive here before the rains. | 0:43:56 | 0:43:59 | |
The changing of the seasons in Botswana could not be more dramatic. | 0:44:06 | 0:44:11 | |
At the end of the dry season, | 0:44:11 | 0:44:13 | |
temperatures soar as high as an unbearable 45 degrees C. | 0:44:13 | 0:44:17 | |
The land is scorched and cracked until, on the horizon, | 0:44:17 | 0:44:22 | |
a lightning bolt announces the beginning of the rains, | 0:44:22 | 0:44:26 | |
and everything changes. | 0:44:26 | 0:44:27 | |
As the heat soars, moisture builds in the atmosphere | 0:44:30 | 0:44:35 | |
and enormous clouds appear, looming across the skies. | 0:44:35 | 0:44:39 | |
THUNDER RUMBLES | 0:44:39 | 0:44:41 | |
For a while, the showers are localised, | 0:44:47 | 0:44:51 | |
but then the heavens open. | 0:44:51 | 0:44:53 | |
THUNDER CRASHES | 0:44:53 | 0:44:55 | |
Here, as much as 12cm of rain can fall in a single downpour. | 0:45:13 | 0:45:18 | |
This is what the zebra have been waiting for. | 0:45:24 | 0:45:27 | |
Several weeks late but, finally, the rains have come, | 0:45:27 | 0:45:31 | |
and soon, this dry, parched saltpan | 0:45:31 | 0:45:34 | |
is going to transform into a lush, green field, | 0:45:34 | 0:45:37 | |
full of protein and mineral-rich grass that the zebra rely on, | 0:45:37 | 0:45:43 | |
especially now that they're foaling. | 0:45:43 | 0:45:45 | |
The satellite data shows | 0:45:49 | 0:45:51 | |
that all our collared zebra are now just north of Nxai Pan, | 0:45:51 | 0:45:55 | |
having averaged 30km a day for over a week. | 0:45:55 | 0:45:58 | |
Somehow, they knew that all of this was about to happen. | 0:46:00 | 0:46:03 | |
They have timed this to perfection. | 0:46:03 | 0:46:06 | |
Now the rains have truly arrived, | 0:46:11 | 0:46:13 | |
the nutritious grasses of Nxai Pan will start growing. | 0:46:13 | 0:46:17 | |
But the lions will be waiting. | 0:46:18 | 0:46:20 | |
We've established our new base camp at the northern end of Nxai Pan, | 0:46:26 | 0:46:30 | |
to catch the zebra as they come out of the forests and onto the plains. | 0:46:30 | 0:46:34 | |
The morning after the rains, | 0:46:37 | 0:46:39 | |
the satellite data reveals some great news. | 0:46:39 | 0:46:42 | |
-Janet! -It's Janet. -In the open. | 0:46:42 | 0:46:43 | |
She's been giving us the run-around, | 0:46:43 | 0:46:45 | |
but now we're going to finally clock eyes on her, | 0:46:45 | 0:46:47 | |
see what condition she's in. | 0:46:47 | 0:46:49 | |
-She can't be very far. -It's just about 3k from camp. | 0:46:49 | 0:46:52 | |
We know she's here, but the data point is now an hour old. | 0:46:54 | 0:46:58 | |
In this flat and open pan, radio telemetry should work well. | 0:46:59 | 0:47:04 | |
-Strongest signal's from this... -This group here. | 0:47:09 | 0:47:11 | |
-Have a look. See, I think the second one's got a collar. -OK. | 0:47:18 | 0:47:21 | |
-That's her. -Fantastic. -Amazing. | 0:47:24 | 0:47:27 | |
Look, she's coming right through the middle of these springbok. | 0:47:27 | 0:47:30 | |
And this zebra, she was the first one documented | 0:47:30 | 0:47:34 | |
making this huge migration down here, | 0:47:34 | 0:47:36 | |
and we're meeting up with her again, she's done it again. | 0:47:36 | 0:47:39 | |
Amazing. | 0:47:39 | 0:47:42 | |
In Chobe, Janet was part of a family of 15. | 0:47:42 | 0:47:45 | |
But now there are only five of them. | 0:47:46 | 0:47:49 | |
Hopefully, the rest of her herd are also here somewhere | 0:47:50 | 0:47:54 | |
and haven't succumbed to exhaustion or predation. | 0:47:54 | 0:47:57 | |
Thankfully, the data shows | 0:48:03 | 0:48:05 | |
that all the other families are also pouring into the park. | 0:48:05 | 0:48:08 | |
Max, Max, it's Liz. Do you copy? | 0:48:08 | 0:48:10 | |
'Hey, Liz, how are you doing?' | 0:48:10 | 0:48:12 | |
'Well, 14km away from camp | 0:48:12 | 0:48:14 | |
'is Spirit.' | 0:48:14 | 0:48:16 | |
But when Max catches up with Spirit, he finds that all is not well. | 0:48:17 | 0:48:22 | |
That's Spirit. | 0:48:25 | 0:48:27 | |
Spirit was pregnant. | 0:48:28 | 0:48:30 | |
We can't be sure what happened to her foal, | 0:48:32 | 0:48:35 | |
but it looks like her family have had a recent run-in with the lions. | 0:48:35 | 0:48:38 | |
Fresh wounds on three of the zebra in this group. | 0:48:44 | 0:48:47 | |
I mean, it's the unmistakable marks left by a lion. | 0:48:47 | 0:48:51 | |
There's a small foal, | 0:48:52 | 0:48:54 | |
and you can see his whole hind has been ripped open. | 0:48:54 | 0:48:58 | |
That must have happened last night. | 0:48:58 | 0:49:00 | |
The lions were around, we heard them roaring. | 0:49:00 | 0:49:03 | |
It's bumper season for them now that the zebra are here. | 0:49:03 | 0:49:07 | |
We need to find out if Socks is still alive. | 0:49:13 | 0:49:15 | |
Even though her collar's GPS has failed, | 0:49:18 | 0:49:21 | |
it may still have a VHF signal. | 0:49:21 | 0:49:23 | |
On the ground, the range is just a few kilometres, | 0:49:25 | 0:49:28 | |
but from the air, it's closer to 40. | 0:49:28 | 0:49:31 | |
It's only when you get up here | 0:49:32 | 0:49:34 | |
that you really realise the vast expanse of this place. | 0:49:34 | 0:49:36 | |
I mean, where could she be | 0:49:36 | 0:49:38 | |
and how far do we have to look in every direction? | 0:49:38 | 0:49:40 | |
She could be anywhere in an area up to 15,000 square kilometres. | 0:49:40 | 0:49:45 | |
That is absolutely huge, so it's needle in a haystack stuff. | 0:49:45 | 0:49:49 | |
We absolutely had no hope on the ground. What are our chances? | 0:49:49 | 0:49:52 | |
If the telemetry transmitter is still working, | 0:49:52 | 0:49:54 | |
we've got a very good chance of finding her. | 0:49:54 | 0:49:57 | |
So, Liz, we've got a little bit of altitude now, | 0:49:59 | 0:50:01 | |
and I'm going to put this receiver on. | 0:50:01 | 0:50:03 | |
You'll hear some static start to come through. | 0:50:03 | 0:50:06 | |
This is set on Socks' frequency. | 0:50:06 | 0:50:08 | |
We'll just listen through a lot of noise initially, | 0:50:08 | 0:50:11 | |
cos all you can hear is static, | 0:50:11 | 0:50:13 | |
and then you're just listening for a tiny, tiny little beep. | 0:50:13 | 0:50:16 | |
Beep. And when we hear that, | 0:50:16 | 0:50:18 | |
we start honing in and trying to zone in on where she is. | 0:50:18 | 0:50:21 | |
-OK. -You keep your ears peeled. -I am going to do my best for you. | 0:50:21 | 0:50:25 | |
STATIC | 0:50:25 | 0:50:28 | |
But finding a signal in an area this size seems next to impossible, | 0:50:28 | 0:50:32 | |
even from the air. | 0:50:32 | 0:50:34 | |
Max is standing by, ready to go in on the ground, | 0:50:40 | 0:50:42 | |
should we find anything. | 0:50:42 | 0:50:44 | |
STATIC | 0:50:44 | 0:50:47 | |
FAINT BEEP | 0:50:48 | 0:50:50 | |
You hear that? | 0:50:53 | 0:50:55 | |
There was the faintest, tiniest little beep through this static. | 0:50:55 | 0:50:58 | |
-I'm just hearing the static. -Yeah, yeah, so listen really... | 0:50:58 | 0:51:01 | |
-Can you hear a beep? -Yeah, yeah, but it's tiny. | 0:51:01 | 0:51:03 | |
-It really is very subtle. -FAINT BEEP | 0:51:03 | 0:51:05 | |
BEEPING | 0:51:07 | 0:51:10 | |
It's Socks! | 0:51:10 | 0:51:12 | |
BOTH LAUGH | 0:51:12 | 0:51:13 | |
Oh, my gosh, that's brilliant! | 0:51:13 | 0:51:15 | |
That is definitely the unmistakable beep of a VHF collar. | 0:51:15 | 0:51:21 | |
Socks is here, she's in Nxai Pan. | 0:51:21 | 0:51:23 | |
Now that we've picked up a signal, we have to fly in a search pattern | 0:51:25 | 0:51:29 | |
until we pinpoint its exact location. | 0:51:29 | 0:51:31 | |
BEEPING | 0:51:38 | 0:51:40 | |
-It's her, it's her. It's this group of zebra there. It has to be. -Yeah. | 0:51:42 | 0:51:46 | |
'Max, Max, it's Liz. I've got some fantastic news for you.' | 0:51:49 | 0:51:52 | |
We've just located Socks. | 0:51:52 | 0:51:54 | |
That's amazing news. | 0:51:54 | 0:51:57 | |
She's in a group of ten zebra. | 0:51:57 | 0:51:58 | |
Now, we couldn't get a visual on Socks herself, but... | 0:51:58 | 0:52:02 | |
'If we're to see how Socks and her family are doing, | 0:52:02 | 0:52:04 | |
'Max will have to catch up with them on the ground.' | 0:52:04 | 0:52:07 | |
We'll head that way and let you know how we get on. | 0:52:07 | 0:52:11 | |
Oh, I'm so happy about this. Good luck with it all. | 0:52:11 | 0:52:14 | |
Last time we saw Socks, she was travelling | 0:52:19 | 0:52:22 | |
without the protection of Wishbone, the stallion. | 0:52:22 | 0:52:24 | |
We need to know how she's doing, and if she's had her foal. | 0:52:24 | 0:52:28 | |
We're not far off now. | 0:52:29 | 0:52:30 | |
We're almost parallel with them, so if you start scanning a bit. | 0:52:30 | 0:52:34 | |
It looks like there's some animals just... | 0:52:34 | 0:52:36 | |
Oh, look. Amazing, amazing. | 0:52:37 | 0:52:39 | |
Look. That's Socks. | 0:52:39 | 0:52:42 | |
She's got her unmistakable white socks on. | 0:52:42 | 0:52:46 | |
She's with the stallion. | 0:52:46 | 0:52:49 | |
It looks like they're all there. | 0:52:49 | 0:52:51 | |
Then Max spots something moving in the long grass. | 0:52:53 | 0:52:57 | |
It's her foal. | 0:52:57 | 0:52:58 | |
He's absolutely tiny. | 0:53:04 | 0:53:05 | |
She must have dropped this foal in the last couple of days. | 0:53:05 | 0:53:08 | |
How cool is that?! | 0:53:11 | 0:53:12 | |
When you look at Socks now and see what fantastic condition she's in... | 0:53:21 | 0:53:25 | |
She made this journey really early on, | 0:53:25 | 0:53:28 | |
but that's given her time to recuperate | 0:53:28 | 0:53:30 | |
and now she's given birth in the best possible place. | 0:53:30 | 0:53:33 | |
She's found this little Garden of Eden here | 0:53:33 | 0:53:35 | |
where there's more grass than we've seen anywhere else, | 0:53:35 | 0:53:38 | |
so she's given this little fella the best possible start in life. | 0:53:38 | 0:53:42 | |
The funny thing is, her foal has stripes on its legs. | 0:53:43 | 0:53:47 | |
He's taken after Dad. | 0:53:47 | 0:53:49 | |
As more and more zebra families pour into Nxai Pan | 0:53:56 | 0:54:00 | |
at the end of a gruelling migration, the plains come to life. | 0:54:00 | 0:54:04 | |
The first green shoots are pushing up, | 0:54:23 | 0:54:25 | |
and the time to rest, give birth and feed on the bounty has arrived. | 0:54:25 | 0:54:31 | |
This little foal is only hours old | 0:54:36 | 0:54:41 | |
and it's still so unsure on its feet. | 0:54:41 | 0:54:44 | |
I mean, it is just the most beautiful scene, | 0:54:48 | 0:54:52 | |
and the stallion is just standing by, | 0:54:52 | 0:54:55 | |
being extremely protective of his mare and his new foal. | 0:54:55 | 0:55:00 | |
And we know so little about these interactions, | 0:55:05 | 0:55:07 | |
there's still so much to understand, | 0:55:07 | 0:55:10 | |
but just seeing this scene today | 0:55:10 | 0:55:12 | |
really does paint a wonderful picture. | 0:55:12 | 0:55:15 | |
And as much as I couldn't help but question | 0:55:18 | 0:55:21 | |
why on earth an animal would decide to make | 0:55:21 | 0:55:25 | |
such a ridiculously long and arduous journey... | 0:55:25 | 0:55:28 | |
..watching this now, it all makes sense. | 0:55:30 | 0:55:33 | |
It's worth the journey, it's worth the trial and tribulations, | 0:55:34 | 0:55:38 | |
because as a mother, | 0:55:38 | 0:55:40 | |
you have every instinct telling you, we need to make it down here, | 0:55:40 | 0:55:45 | |
this is going to make our family stronger, | 0:55:45 | 0:55:48 | |
our foals will be stronger. | 0:55:48 | 0:55:49 | |
Ultimately, that's what survival is all about. | 0:55:49 | 0:55:53 | |
During our time in Botswana, we've had a privileged insight | 0:56:03 | 0:56:07 | |
into Africa's longest and most recently discovered land migration. | 0:56:07 | 0:56:12 | |
We've discovered the importance | 0:56:17 | 0:56:19 | |
of each family making the right decision at the right time. | 0:56:19 | 0:56:22 | |
And we've revealed that part of their ability to navigate | 0:56:24 | 0:56:27 | |
is written in their genes. | 0:56:27 | 0:56:29 | |
The discovery of this zebra migration is so important. | 0:56:31 | 0:56:36 | |
It represents what ground-breaking science | 0:56:36 | 0:56:38 | |
can reveal about the natural world | 0:56:38 | 0:56:41 | |
in a way that simply wasn't possible before. | 0:56:41 | 0:56:44 | |
What surprised me the most is just how complex these animals are. | 0:56:44 | 0:56:48 | |
A strong biological instinct, a drive to explore and to navigate, | 0:56:48 | 0:56:54 | |
a constant adjustment to a changing environment. | 0:56:54 | 0:56:57 | |
They're all at play here. | 0:56:57 | 0:56:59 | |
As difficult as this migration is, these zebra achieve it perfectly. | 0:57:01 | 0:57:06 | |
There is still so much to understand, | 0:57:08 | 0:57:10 | |
but ultimately, this research will help scientists | 0:57:10 | 0:57:13 | |
to preserve this precious migratory route, | 0:57:13 | 0:57:16 | |
but it will also provide invaluable insights | 0:57:16 | 0:57:19 | |
that could help to save species and their habitats across the world. | 0:57:19 | 0:57:24 |