BBC Natures Epic Journeys_3of3_Zebra
Transcript
00:00We're about to follow the world's greatest migrations and reveal their secrets in a way
00:08that's never been done before.
00:13All over the world, animals are on the move, embarking on vast journeys that they depend
00:20upon for survival, to find food, to give birth, or to escape danger.
00:29Travelling hundreds of miles through some of the world's most breathtaking wildernesses,
00:36that can turn against them at any moment.
00:39That rap is really picking up, they're just disappearing under the water.
00:43Groundbreaking technology allows our team to follow these migrations more closely than
00:49ever before, and understand them in unprecedented detail.
00:55We can track this ellie's movement in real time.
00:59Using the latest satellite tracking technology, we can monitor individual animals and witness
01:05first hand their struggles for survival.
01:08We've got a drama down here, we've got him, we've got the wolf, we've got the wolf.
01:14This time, we'll follow thousands of zebra as they undergo their gruelling annual migration
01:20in search of food.
01:22They must reach their grazing grounds just as the rainy season begins.
01:29Arriving too early, or too late, could spell disaster.
01:34For the first time, satellite tracking allows us to stay with individual mothers, foals,
01:42and dominant males as they brave drought, hunger, and ferocious predators.
01:49Below me, this wilderness has kept hidden a journey that's never been followed before,
01:55and about which virtually nothing is known.
01:58It's the longest land migration in all of Africa.
02:03This is the untold story of the Great Zebra Migration.
02:20Northern Botswana, a vast, parched wilderness the size of the United Kingdom.
02:29At the end of Botswana's brutal dry season, thousands of zebra gather on the Chobi floodplain
02:35as they prepare to travel 250 kilometres south to Naipan National Park.
02:48The journey takes them through one of the most punishing landscapes in southern Africa.
02:56Travelling in family groups, many of the females are heavily pregnant or supporting young foals.
03:03Each year, their goal is the same, to reach Naipan's fertile plains just as the rains
03:09produce the first flush of nutrient-rich vegetation.
03:13The timing of this journey is crucial.
03:17Leave too early, and they risk arriving at Naipan before the lush grass appears.
03:22Leave too late, and they'll miss out on the best food on arrival.
03:32Our first camp is on the edge of the Chobi River, the starting line for the migration.
03:41I've joined a team of specialist biologists and cameramen to attempt something that's
03:46never been done before.
03:50We plan to travel with the zebra on the ground, following their every move.
04:05Around 2,000 zebra are gathering across the vast Chobi River floodplain, dotted across
04:11the landscape in family groups of up to 20 animals.
04:16They won't be travelling en masse.
04:18Instead, each individual family will make its own decisions during the migration.
04:25I'm joining the scientists who are colouring the zebra, so that the team can track them.
04:32OK, Mike, Larry's getting ready to dart.
04:44Great shot.
04:45I didn't even recognise which one he was focusing on.
04:47Next minute, poof, done.
04:50The dart contains a sedative that immobilises the zebra within five to ten minutes.
05:03Once the zebra goes down, the team have to act as quickly as possible.
05:08You tell me when it's OK to get out.
05:09You can get out.
05:11A towel is put over the animal's eyes to help keep it calm.
05:21Well done.
05:22Check it.
05:23Is that all right?
05:27It's really thanks to this technology that we'll be able to stick with these zebra, getting
05:34readings every hour.
05:36That means for the first time, we'll be able to follow them.
05:40And that's not only going to give us insights into where they go when, but also into their
05:44behaviour, their decision-making process.
05:47And that's bound to reveal some unknowns into the lives of these zebra.
05:53The colouring data will not only help us to keep up with them, but we'll see for ourselves
05:58just how tough they need to be to take on this migration.
06:02It's only when you get really close to these animals that you realise just how sturdy they
06:05are, how hardy.
06:09They need to be.
06:10They're about to embark on what is the longest land migration in Africa.
06:16The hourly updates from the satellite collars will allow us to follow a number of different
06:20families, each with a collared animal in it.
06:24Awesome.
06:25That was hugely satisfying.
06:31One of the zebra collared is a very special nine-year-old female called Janet.
06:37She was the first zebra in this population to be collared way back in 2012.
06:45We first discovered this migration in 2012.
06:49Up until that point, people didn't know where the zebra moved.
06:52So in the dry season, you had zebra up here, and then in the rainy season, they disappeared.
06:57Exactly.
06:58So 2012, the first collars went out.
07:01And Janet, she was collared just up here on the floodplains.
07:04And it was very exciting.
07:05She didn't know where she was going to go or what she was going to do.
07:08And she moved 250 kilometres all the way down to Naipan, down here in the south.
07:14This is the longest mammal migration in the whole of Africa, which is amazing.
07:19The average round-trip distance is about 955 kilometres, which beats the wildebeest migration
07:25in East Africa.
07:27The first year she was collared, Janet's data completely changed our understanding
07:32of zebra migrations.
07:35It was assumed that the zebra travelled just 60 kilometres or so to the grassy plains of
07:40Savuti Marsh or Siloko.
07:43But Janet's collar revealed fascinating new information to scientists.
07:48She was travelling much further, all the way to Naipan.
07:54That year, Janet became the official record holder for the longest land migration in Africa.
08:02This huge journey takes the zebra through an area with virtually no food or water and
08:07plenty of cover for predators.
08:13So why do they leave Chobe at all?
08:16Chobe can sustain wildlife all year round.
08:20The rains obviously hit Chobe as well, the grasses get better.
08:23Why would zebra leave Chobe in the first place?
08:26The zebra there have competition with other animals.
08:29So they need a new resource and the vegetation that comes up in Naipan is very nutritious,
08:35the soils are very fertile and so the grasses are so much better.
08:40For the zebra, the potential rewards seem to outweigh the risks.
08:44But how exactly do they survive this immense journey?
08:48How do they navigate through a featureless landscape?
08:52How does it all even begin?
08:55We're down on the flood plains, we've been looking for Janet this morning.
08:58Cameraman Max Hug Williams' mission will be to follow the front runners all the way
09:03to Naipan, 250 kilometres to the south.
09:08Our other cameraman, Bob Hu, will hang back, following the families that are last to leave.
09:25Marking the journey are heavily pregnant females, as well as mothers with young foals.
09:36For them, the 250 kilometre migration will be particularly dangerous.
09:45Filming the zebra as they gather on the plain gives Bob the chance to familiarise himself
09:50with the collared individuals.
09:53If you look at these zebra, each one of them has totally different patterns on their stripes.
09:59And she's got some pretty distinguishing markings on her.
10:03She's got a beautiful sort of W on her left shoulder and so we've called her Winnie.
10:10And she's got a foal, it hangs right next to its mother almost all the time and they
10:15seem quite affectionate together.
10:23At six years old, Winnie may have already had three other foals and carried out six migrations.
10:32Although zebra foals can stand at less than an hour old, these babies won't have walked
10:38more than a few kilometres a day.
10:41You can see these little things can run.
10:45And I suppose all this behaviour is really important because you're going to have to
10:49go all the way south.
10:56These zebra are about to move in a mass exodus towards the south of Botswana.
11:02And one of the biggest mysteries is just what triggers this.
11:06One theory is that the start of the rainy season sets off an irresistible urge to migrate.
11:14Luckily, the team don't have to wait long before the first downpour.
11:40With the rains, everything changes.
11:45Very excited right now.
11:48I mean, we've been waiting for the rains and here they are.
11:52Pula. Pula they call it here in Botswana and that's the same word they use for money.
11:58In Africa, just add water and everything works.
12:04And it's not just Bob who's reacting to the change in the weather.
12:09Our satellite data shows that in the last few hours,
12:13all the zebra have crossed the Chobi River and have started to move south.
12:21The migration has started.
12:27250 kilometres to go.
12:30There's absolutely nothing on these plains anymore.
12:33There's just the last pocket of five or six.
12:37But otherwise, this plain is absolutely empty.
12:40Now the migration is underway.
12:43We'll have to keep up with them every step of this journey.
12:48The open floodplain offered some safety from predators.
12:52But now they face a new threat.
12:55The open floodplain offered some safety from predators.
12:58But now they face thick forest.
13:02And their first big challenge.
13:06A pack of African wild dogs.
13:09The continent's most relentless predators.
13:15Surrounded by trees, the zebra won't see them coming.
13:20Even without cover, wild dogs are a real threat.
13:24They may not be the biggest of Africa's predators,
13:27but their highly efficient method of hunting as a pack
13:30certainly makes them one of the most effective.
13:35During a hunt, each dog has a role.
13:42A leader drives the prey forward.
13:45While others act as flankers,
13:48corralling the prey towards the rest of the pack.
13:53The ultimate endurance hunters.
13:56Their ability to run up to 70 kilometres an hour
13:59and use sophisticated teamwork
14:01allows them to take down animals far larger than themselves.
14:08Meticulous coordination results in a kill more often
14:11than any other predator.
14:15In the forest, the wild dogs have already left Max far behind.
14:23You can see actually, dog tracks everywhere.
14:26They split out.
14:28There's one here.
14:32Look at that. That's a leopard track.
14:35I mean, on the plains they can see what's around
14:39and when one gets a sense of some danger, they all bolt.
14:42But in here, this is where leopards, wild dogs,
14:45have a chance of actually taking especially the foals.
14:48I mean, some of them were even struggling to cross the river this morning
14:52and you think, how are they going to make this epic journey of 250km?
14:56I have absolutely no idea.
14:58With so many predators about, Max needs to catch up with the zebra
15:02to see if they've managed to stay safe.
15:05Max, Max, Max, this is Rob at Base Camp.
15:08Just got some updated coordinates for you.
15:11The 1791 has moved south of the tyre road.
15:14In the forest just south of the wild dog tracks,
15:18the satellite data leads Max to his first collared zebra,
15:22who still has 230km to go.
15:25She looks heavily pregnant, you can see.
15:29A mini zebra with so few stripes on her front legs,
15:32it looks like someone's got an eraser and rubbed them up.
15:35Looks like she's got a pair of tights on.
15:38She's very relaxed though, that's great.
15:41What are we going to call her then?
15:43Because we've got Winnie, she's really easy to identify, the W.
15:47We've got to come up with something.
15:50She's definitely got a pair of socks on or something.
15:53Socks, OK.
15:56At only four years old, Socks is a young and inexperienced mother.
16:01This may even be her first pregnancy.
16:05She's in a small family of just seven animals.
16:09But these families, or hareems, can be up to 20 animals strong
16:14and are usually made up of unrelated females and their young,
16:18led by a single dominant male.
16:21The more experienced and powerful the stallion, the bigger the hareem.
16:25This male, he's got really obvious thick black bands on his neck
16:29and also on his right flank there's a marking
16:32which almost looks like a wishbone.
16:35We'll have to call him wishbone.
16:39Wishbone's job is crucial.
16:42He must protect Socks and the others from predators
16:45and protect his young.
16:48He must protect Socks and the others from predators,
16:51particularly now as they travel through this dense forest.
17:02Wishbone, Socks and the rest of the family are ahead of the other zebra,
17:08closely followed by Max.
17:11Bringing up the rear is Bob.
17:13He now has the chance to see how Winnie and the other herds at the back
17:17deal with the dangers of the forest.
17:20This is pretty exciting.
17:22There's a lot of zebra now packed together
17:24and they all seem to be on the move south.
17:27Winnie's in the middle there
17:29and she's travelling along with her foal and the rest of her family.
17:32But, you know, for the first time there's so many zebra.
17:37Amongst the large group at the rear are two other collared females,
17:42a pregnant mare called Spirit
17:45and a ten-year-old called Jewel.
17:53Travelling together for safety is a good idea.
17:57Just a few kilometres to the west,
18:00Max has found a young family who are on the move.
18:03Just a few kilometres to the west,
18:05Max has found a young family who haven't been so wise.
18:12As the wild dogs are well aware.
18:26Believe you me, when they get going, if they want to run something down,
18:30it's pretty much nothing that they can't take.
18:33But luckily for the zebra, it looks like these guys are fed
18:36and they're just relaxing in the shade.
18:48When the dogs' hunger returns,
18:50the pregnant females, or those with foals,
18:53will be particularly vulnerable to attack.
18:57If Socks gave birth, she's not a million miles away from here.
19:02I mean, that would be an easy prey for them.
19:11Meanwhile, there's been some worrying news about another collared animal.
19:18The satellite data shows that one zebra
19:21didn't travel far from the Chobe floodplain
19:24and it hasn't moved for the last two days.
19:31We've got a signal, Max.
19:32Is it strong? Are you getting something close by?
19:34Yeah, it's a strong signal. It's certainly around here somewhere.
19:37The team will have to home in using the VHF radio signal emitted by the collar.
19:42Newman Chuma, tracker and wildlife guide, leads us in.
19:48But if the zebra is dead,
19:50there may still be predators feeding on the carcass.
19:53If it is a lion on a kill,
19:55I mean, we've got to be pretty careful here, haven't we?
19:57Yeah. You need to spot the animal before the animal sees you.
20:01As they get closer, clues emerge as to what might have happened.
20:05You know, I can see quite a few tracks.
20:07A hyena.
20:08There's something dragging it this way.
20:12I can see something.
20:13Here's the carcass.
20:16It looks like this zebra may have fallen prey
20:18to one of the forest's many predators.
20:21Yeah.
20:25Look how many maggots there are already.
20:27It's only about two days old.
20:29Nothing lasts very long out here.
20:31You can see this. It looks like a puncture wound there.
20:35It's difficult to know exactly how it died,
20:38but this zebra's collar is fitted with a camera.
20:41It still looks intact, doesn't it?
20:43It does, yeah. OK, let's take this off.
20:46Once the footage is downloaded, it may reveal exactly what happened.
20:50So that's the last shot from the morning.
20:53So...
20:55Ah, look.
20:56Is that you?
20:57That's me, yeah.
20:58This is when the animal was collared on the 20th of November.
21:01The camera recorded in short bursts to extend its battery life.
21:09For the first few days, the zebra behaved normally,
21:12grazing and moving around the floodplain like Socks, Janet and the others.
21:16Then, four days later, it crossed the Chobe River again.
21:20All right, so it's back on the Botswana side.
21:23I think he's moving a bit faster there.
21:25I don't see many zebra around him, do you?
21:29Oh, you can see his shadow. Yeah.
21:31So he's swinging his tail.
21:33And now... Now he's lying down.
21:35It looks like he's on the ground.
21:37Zebra tend not to lie down, especially when they're by themselves.
21:41Yeah, that makes sense. It's not particularly safe to lie down like that.
21:45Yeah.
21:50The zebra stayed here for around 36 hours,
21:54moving about a little, but never leaving this location.
21:58Something was clearly wrong.
22:07Yeah, lots of flies. Yeah.
22:09And he's doing something with his mouth, but he's not grazing.
22:12We can't see if there's any blood or any sort of foam coming from the mouth,
22:16so we're not sure what's happening there.
22:20With no clear evidence of predation,
22:22our team thinks he may have been bitten by one of Botswana's poisonous snakes.
22:32It's down again, look.
22:34We don't know how long he stayed down for.
22:36Between the... Yeah, how long during the day...
22:38Before long, vultures begin to gather.
22:43And just a few hours later, the zebra is dead.
22:47Oh.
22:50That's it. That's it. Game over.
22:55Despite not being able to determine the exact cause of death,
22:59the collar data shows just how dangerous it can be out here.
23:04Our latest satellite data shows
23:07that many of the zebra are making steady progress south.
23:12But Socks, the four-year-old female that Max spotted in the forest,
23:16is pushing ahead of Winnie, Janet and the others, with her family in tow.
23:21I guess she's just a lot slinkier than we are.
23:23Helping Max get as close to them as possible is Duncan Rowles,
23:27an experienced photographer who's been following the zebra for years.
23:31Max, Max, Max, this is Rob at base camp.
23:34Max is Socks' latest satellite position
23:37and is trying desperately to catch up with her and her family.
23:43You can just see how far Socks has come.
23:4630km just yesterday, and now she's still in this really thick bush here.
23:52And the only way for us to have a chance of even getting close to her
23:56is carry on on this, which is as good as a road as you'll ever get,
24:01travel all the way round and then hope that she pops out somewhere near here.
24:10It's not clear why Socks' family has broken away from the others,
24:14but since she's heavily pregnant,
24:16she might be trying to reach Naipan before giving birth.
24:19Her incredible pace means that the hourly satellite data
24:23is not accurate enough to locate her precisely.
24:30So the team have to resort to another system.
24:35These collars allow scientists to track animal movements
24:38in two different ways.
24:40One is by using a GPS,
24:42and the other is by using a satellite.
24:45These collars allow scientists to track animal movements in two different ways.
24:49The first part uses a network of satellites to calculate its location
24:53in the same way as your phones and your cars use their navigation systems.
24:57But for real-time, on-the-ground tracking,
25:00the collar also emits a VHF signal
25:03that can be picked up with radio telemetry equipment,
25:06and every single animal will have its own unique frequency.
25:10With Socks fast disappearing into this vast landscape,
25:15it's the VHF radio signal that will give Max his best chance
25:19of catching up with her to see if she's OK.
25:27But in forest this thick, he might get close and still not see her.
25:32She's very close, we know that.
25:35The best chance is to just get the telemetry up
25:38and just see where that ping's coming from.
25:41She's super close now, she's just in these bushes.
25:44A really strong signal from here.
25:50That is zebra tracks.
25:53And that's completely fresh.
25:56That's a split second, she must have just crossed
25:59before we came around that corner.
26:02Having so narrowly missed Socks and her family,
26:05Max now has very little chance of spotting them
26:08as they head into the ever-thickening forest.
26:11And how are we supposed to follow that?
26:14I can't even see you from here.
26:17Socks has covered an amazing 50 kilometres in the last day and a half,
26:22but still has 200 kilometres to go.
26:27This migration is so new to science
26:30that every bit of data we gather helps scientists
26:33to understand the nature of this extraordinary journey.
26:36We need more data to really build up that picture.
26:40Then the satellite data shows something that stops us in our tracks.
26:44Within hours of each other,
26:46almost all the other zebra have made a U-turn
26:49and are heading right back to their starting point
26:52on the Chobe floodplain.
27:00You have a signal?
27:02Yes, I've got a signal. Let me just turn it up for you.
27:05Bob tries to intercept the zebra families as they return north,
27:08hoping to see them cross the only tarmac road in Chobe.
27:12The radio telemetry shows that Winnie's family are just about to cross.
27:19Where's Winnie? Where's Winnie? Where's Winnie?
27:22Shoot, there she is.
27:25Winnie and her herd are an experienced family,
27:28so what could possibly have made them turn back?
27:31Has some other cue in the environment told them they've left too soon?
27:36Or could the number of predators in the forest have driven them back?
27:42It seems like confusing times for these zebra.
27:45It's almost like they can't make up their mind
27:48whether they're going to go on this migration or not.
27:52They might not be comfortable yet with the amount of rain that's fallen
27:57to make the commitment.
27:59So they have to be very confident that there's enough water down there.
28:04Zebra need to drink pretty much every day
28:07and normally stay within 10 to 15 kilometres of water.
28:11Perhaps a lack of water further south has influenced their return.
28:15So there's a lot of fascinating behaviour going on, not only...
28:18Revealing as it is, the satellite data can only tell us so much.
28:23These are complex animals, aren't they?
28:25They certainly are, and it's not a straightforward migration.
28:28No, it's not like wildebeest just right go all together.
28:31Exactly.
28:32They make very different decisions.
28:34Exactly, and that's what we've observed so far.
28:36Different family groups will make different decisions
28:38and some groups will leave earlier, some groups will hang back and then move later.
28:42Combining the satellite data that's coming in
28:44with the information we're getting from the teams on the ground,
28:47that's going to build a much bigger and better picture.
28:51Whatever the reason, the majority of families have decided
28:55to head back to the food and water of the Chobe floodplain.
29:11With an entire 250 kilometres still to go,
29:15Bob finds that Janet, Winnie, Spirit and Jewel
29:19are showing no signs of restarting any time soon.
29:24So Bob will wait with them until they're ready to start the journey again.
29:31So there's Winnie coming down.
29:33God, that is great.
29:38Getting a nice drink.
29:41It must be hard for them to make the decision to move south like Sox has now.
29:48Why in the world would you want to leave this amazing paradise?
29:52But this paradise won't last forever.
29:56If too many zebras stay here, the food will run out.
30:01And they'll miss out on the more nutritious vegetation at Naipan.
30:09If our female zebra want to give their foals the best possible start in life,
30:13they'll have to leave here very soon.
30:18Sox and her family, however, are well on their way to having Naipan all to themselves.
30:24She's actually moved quite far south now.
30:2724.9818
30:30Sox is motoring 8km an hour.
30:33That's unbelievable. There's no way we can keep up with that.
30:36It's taken us an hour to do one and a half kilometres.
30:48Not only is Sox's family now well ahead of the others,
30:52they travel in a direct line to Naipan.
31:02In the flat wilderness of Botswana, the zebra somehow navigate perfectly,
31:07with no hills or landmarks for reference.
31:11Scientists still don't fully understand exactly how they do this.
31:16Until very recently, it was assumed these routes were learned
31:20and then passed down from generation to generation.
31:26But I'm travelling to meet a scientist who made a groundbreaking discovery
31:30that turned this theory on its head.
31:33In the 1950s and 60s, thousands of miles of fences were erected
31:38in an attempt to stop diseases being transmitted from wildlife to domestic livestock.
31:43But these fences stopped many animals from carrying out their annual movements.
31:49A few years ago, when some of these fences were removed,
31:52an ancient migration was seen to start up once more,
31:55following its exact same route.
32:00Dr Hattie Bartlem Brooks of the Royal Veterinary College made this discovery.
32:05So if the fence was up for 36 years and zebra lived to about 15 years in the wild,
32:10so there was no zebra that knew about this route that was alive when this fence went down?
32:15Yeah, I think that's the most exciting part about this story,
32:17is that everyone presumes that terrestrial migrations are taught, but in this case it can't.
32:21The mothers couldn't have taught the foals who couldn't have taught their foals,
32:24so I think there's a genetic urge to make them move.
32:27Something in the zebra's genetic code drives them to migrate.
32:31But what's even more fascinating about Hattie's discovery
32:34is that it seems their genes also tells them where to go.
32:38Something that zebra scientists didn't think possible.
32:41I think it just shows how complex they are, how...
32:44We completely take it for granted that it's just a zebra.
32:47It walks around, it eats grass. When it gets hungry, it walks to some more grass.
32:50But it's not like that. There's a huge complex interplay of things going on.
32:53They're not just a stripy donkey.
33:00For the zebras still in Chobe, something else is telling them to stay put.
33:05I believe we can get you out there. Great. OK, good luck.
33:08But they have moved off the floodplain to an area just south of the main road.
33:16Bob is catching up with them to try to understand what's going on.
33:21He finds them 240km from Naipan,
33:25in an area recently razed to the ground by a forest fire.
33:35Son, look at this, eh?
33:37All the ash on the ground is giving it nutrients.
33:41The result is amazing, isn't it?
33:43Suddenly you get this beautiful green grass coming up.
33:46And that's what they're eating right now. And they're loving it.
33:50Ash is an excellent source of trace elements that new vegetation thrives in.
33:55Seeing exactly what the zebra are doing on the ground
33:58allows a deeper insight into the movement data.
34:02So we know that our zebra haven't moved south yet
34:05and that there's a burnt area here now.
34:08How does it affect the migration, the timing of it?
34:11This could delay it, especially if there's not enough water or vegetation further south.
34:16They're going to stay in this area and take full advantage of this new growth of grass.
34:20So this is doing the zebra quite a big favour,
34:23giving them an extra source of food as they need to wait anyway.
34:26Next rains, you're ready to move down.
34:32Janet, Winnie, Spirit and Jewel are staying put for a very good reason.
34:41150km south, Socks and her family have stopped for the first time in six days.
34:51Socks is past the halfway point of the migration
34:54and now she's stopped in an area for over 24 hours.
35:00What does this mean, that even though she left really early,
35:03possibly to have her foal in the Nai Pan area,
35:07that she gave birth to the foal over the past 24 hours?
35:11It would be very, very good if Max could catch up with her and see for himself.
35:16Problem is, it's still extremely tough terrain to get through.
35:31She's so close, she's literally straight in front of us
35:36and that's as strong a signal as you get.
35:39I'm just worried that this is a really bad place on the journey to have a youngster
35:46because she'll be feeling weak, there's very little water next to no food
35:52and she's still got a third of this journey to make.
35:57As if that wasn't enough, it still hasn't rained.
36:09Scattered across this hostile wilderness are depressions on the landscape called pans.
36:15As long as there is rain, the water in these pans offers a lifeline for wildlife.
36:22Using data from the last 24 hours, Max searches the landscape.
36:30He finds a pan, but it's certainly not the oasis Socks needs.
36:34There's nothing to drink here.
36:36You can see they've been trying because these are zebra tracks here.
36:39Oh, zebs, yeah.
36:40And they've actually been into the mud,
36:42obviously just trying to suck whatever they can off the top there.
36:45That's definitely got to be Socks.
36:48She's come here and trying to get water from this mud wallow.
36:52I mean, she must be desperate.
36:54This elephant's come in to drink, there's nothing even for him.
36:57He's not even trying.
37:03With the light fading, there's little chance of finding Socks today.
37:11It's too dangerous for Max and Duncan to drive at night,
37:15but Socks could keep pushing south and leave them behind again.
37:22But there's nothing Max and Duncan can do till morning.
37:37Back at base camp, it's time to take stock of what we've discovered so far.
37:41As of today, here's what we know about our collared zebra.
37:45The majority of them are back in the floodplain.
37:48They've been moving between the burnt area and the floodplain.
37:51We've had a few showers, but it indicates that it's not quite the trigger,
37:56the environmental cue that these zebras need to actually embark on the migration.
38:01So why has Socks dashed towards Naipan?
38:06Is it that she simply misread the cues?
38:12It's becoming clear that their decision-making process
38:15is much more complex than we first thought.
38:20The following morning, Max might finally be in for a lucky break.
38:26Fire breaks are swathes cut in the forest to stop fires spreading.
38:31It looks like Socks' path might take her directly across one.
38:36Our best chance of catching her in the open and seeing what condition she's in
38:40is to try and intercept her as she crosses.
38:45With the data coming in every hour, they need to get in position before she arrives.
38:50We don't know what kind of state she's in, or even if she's had her full.
38:54You ready? This is five minutes old.
38:56Nineteen, two, four, two, five.
39:00You know, it's vital that we actually set eyes on her
39:03because we're starting to really worry.
39:07Shh, shh. Mind you, she's crossing.
39:10Sir, sir.
39:15There's only three of them, which is strange.
39:18I didn't see Wishbone near Stallion.
39:21It's only the briefest of glimpses, and of only three of them,
39:24but 90 kilometres from her destination, Socks is alive and well.
39:28We'll have to look at this footage again.
39:33The footage suggests that she hasn't had her full yet, which is good news,
39:37and information we'd never have gleaned from the satellite data alone.
39:41We're going to have to keep an eye on her.
39:44We're going to have to keep an eye on her.
39:47We're going to have to keep an eye on her.
39:51But the absence of Wishbone the stallion is a real concern.
39:55He should be protecting the herd from predators during this last push to Naipan.
40:07Then, out of the blue, Socks' satellite caller stops sending location updates.
40:13Without this essential data, we have no way of finding Socks in this vast wilderness.
40:20Her last known position is 40 kilometres from Naipan.
40:29Max's only option now is to continue south
40:32and hope that he can spot her emerging onto the open pan.
40:42Back in Chobe, Winnie, Janet, Spirit and Jewel have at last started to move south.
40:50This time, they don't stop at the burnt area.
40:53They keep going, and now they have 180 kilometres to go.
41:03At last, the main migration has started in earnest.
41:09It's time for the rest of the team to break camp and head south to Naipan.
41:20MUSIC
41:42Around 10,000 years ago, Naipan was an enormous lake.
41:47Now dried up, its soil is packed with potassium, calcium and magnesium.
41:54During the rainy season, these minerals produce lush and highly nutritious grass.
42:01But when Max arrives, things are not as he'd hoped.
42:06We've arrived expecting to see a flush of green grass,
42:10which is why the zebra are coming this way, but the rains have not hit here yet.
42:17MUSIC
42:27Even if the zebra make it through the forest,
42:30there'll be nothing for them to eat at the end of it.
42:34And that's not their only threat.
42:38MUSIC
42:41A pride of 14 hungry lions are lying in wait for the exhausted zebra as they arrive.
42:52Lions are the largest predators in Africa.
42:55They have explosive speed and power.
42:59Unlike African wild dogs, a single lion can take down a fully grown zebra.
43:08When there are lots of zebra around, the lions will kill frequently,
43:12feeding on the most nutritious parts and leaving the leftovers for scavengers.
43:19But the harsh dry season has taken its toll on the Naipan lions.
43:26These lions will have had a tough time.
43:28You can see they're quite skinny, but they've got through the dry season
43:32and they know that all the grazing animals are coming
43:35and their number one food choice will be zebra
43:38and all of our collared animals in a week or so are going to be here.
43:45Not only will the zebra find hungry lions waiting for them,
43:49they may also find themselves facing a complete lack of food
43:53if they arrive here before the rains.
43:57The changing of the seasons in Botswana could not be more dramatic.
44:02At the end of the dry season,
44:04temperatures soar as high as an unbearable 45 degrees C.
44:09The land is scorched and cracked until, on the horizon,
44:14a lightning bolt announces the beginning of the rains
44:17and everything is gone.
44:19As the heat soars, moisture builds in the atmosphere
44:23and enormous clouds appear, looming across the skies.
44:36For a while, the showers are still on,
44:39but the rain is getting heavier and heavier.
44:42The rain is getting heavier and heavier,
44:46For a while, the showers are localized,
44:50but then the heavens open.
44:53Here, as much as 12 centimeters of rain can fall in a single downpour.
45:13Here, as much as 12 centimeters of rain can fall in a single downpour.
45:23This is what the zebra have been waiting for.
45:27Several weeks later, finally, the rains have come
45:30and soon this dry, harsh salt pan is going to transform into a lush,
45:35green field full of protein and mineral-rich grass
45:40that the zebra rely on, especially now that they're foaling.
45:46The satellite data shows that all our collared zebra
45:50are now just north of Naipan,
45:52having averaged 30 kilometers a day for over a week.
45:56Somehow, they knew that all of this was about to happen.
46:00They have timed this to perfection.
46:08Now the rains have truly arrived,
46:11Now the rains have truly arrived,
46:13the nutritious grasses of Naipan will start growing.
46:17But the lions will be waiting.
46:25We've established our new base camp at the northern end of Naipan
46:30to catch the zebra as they come out of the forest and onto the plains.
46:35The morning after the rains,
46:37the satellite data reveals some great news.
46:40Janet, in the open.
46:42She's been giving us the runaround,
46:44but now we're going to finally clock eyes on her,
46:46see what condition she's in.
46:48She can't be very far.
46:50It's just about 3km from camp.
46:52We know she's here, but the data point is now an hour old.
46:57In this flat and open pan, radio telemetry should work well.
47:04The strongest signal is from this.
47:06This group here.
47:14Have a look, see, I think the second one's got a collar.
47:20That's her.
47:21Fantastic.
47:22Amazing, she's coming right through the middle of his spring butt.
47:26And this zebra, she was the first one down.
47:31And this zebra, she was the first one documented
47:34making this huge migration down here.
47:37And we're meeting up with her again.
47:39She's done it again. Amazing.
47:42In Chobe, Janet was part of a family of 15.
47:46But now there are only five of them.
47:51Hopefully the rest of her herd are also here somewhere
47:54and haven't succumbed to exhaustion or predation.
48:01Thankfully, the data shows that all the other families
48:05are also pouring into the park.
48:07Max, Max, it's Liz, do you copy?
48:09Hi, Liz, how are you doing?
48:1112 to 14km away from camp is Spirit.
48:16But when Max catches up with Spirit, he finds that all is not well.
48:24That's Spirit.
48:26Spirit was pregnant.
48:29We can't be sure what happened to her foal,
48:32but it looks like her family have had a recent run-in with the lions.
48:41Fresh wounds on three of the zebra in this group.
48:44I mean, it's the unmistakable marks left by a lion.
48:49There's a small foal and you can see his whole hind has been ripped open.
48:55That must have happened last night.
48:57The lions were around, we heard them roaring.
49:00You know, it's bumper season for them now that the zebra are here.
49:09We need to find out if Socks is still alive.
49:15Even though her caller's GPS has failed, it may still have a VHF signal.
49:20On the ground, the range is just a few kilometres.
49:23But from the air, it's closer to 40.
49:27It's only when you get up here that you really realise the vast expanse of this place.
49:31I mean, where could she be and how far do we have to look in every direction?
49:35She could be anywhere in an area up to 15,000 square kilometres.
49:39That is absolutely huge.
49:41So it really is needle in a haystack.
49:43We absolutely had no hope of finding her.
49:46If the telemetry transmitter is still working, we've got a very good chance of finding her.
49:53So, Liz, we've got a little bit of altitude now.
49:55I'm going to put this receiver on and you'll hear some static start to come through.
49:59This is set on Socks's frequency.
50:02And then we'll just listen through a lot of noise initially because all you can hear is static.
50:06And then you're just listening for a tiny, tiny little beep.
50:09And then we'll just listen through a lot of noise initially because all you can hear is static.
50:13And then you're just listening for a tiny, tiny little beep.
50:16And when we hear that, we start honing in, trying to zone in on where she is.
50:21OK.
50:22Keep your ears peeled.
50:24I am going to do my best for you.
50:28But finding a signal in an area this size seems next to impossible, even from the air.
50:35Max is standing by, ready to go in on the ground should we find anything.
50:50Do you hear that?
50:52There's the faintest, tiniest little beep through the static.
50:55I'm just hearing the static.
50:57Can you hear a beep?
50:59Yeah, but it's tiny. It really is very subtle.
51:03It's Socks!
51:05Oh my gosh, that's brilliant.
51:08That is definitely the unmistakable beep of a VHF caller.
51:14Socks is here. She's in Naipan.
51:18Now that we've picked up a signal, we have to fly in a search pattern until we pinpoint its exact location.
51:26Sir, it's her. The scooper's over there. It has to be.
51:33Max, Max, it's Lou. I've got some fantastic news for you.
51:37We've just located Socks.
51:39That's amazing news.
51:40Socks is a VHF caller who is flying out of Naipan,
51:54That's amazing news.
52:02If we're to see how Socks and her family are doing,
52:04Max will have to catch up with them on the ground.
52:07We'll head that way and let you know how we get on.
52:11Oh, I'm so happy about this. Good luck with it all.
52:19Last time we saw Socks,
52:20she was travelling without the protection of Wishbone the stallion.
52:24We need to know how she's doing and if she's had her foal.
52:29We're not far off now.
52:30I mean, we're almost parallel with them, so you start scanning a bit.
52:34It looks like there's some animals just...
52:37Oh, look. Amazing. Amazing. Look. That's Socks.
52:42She's got her unmistakable white socks on.
52:47She's with the stallion.
52:50Looks like they're all there.
52:52Then, Max spots something moving in the long grass.
52:56It's her foal.
53:03She's absolutely tiny.
53:04She must have dropped this foal in the last couple of days.
53:10How cool is that?
53:20When you look at Socks now and see what fantastic condition she's in,
53:24she made this journey really early on,
53:27but that's given her time to recuperate.
53:29And now she's given birth in the best possible place.
53:33She's found this little Garden of Eden here
53:35where there's more grass than we've seen anywhere else.
53:37So she's given this little fella the best possible start in life.
53:42The funny thing is her foal has stripes on his legs.
53:46And he's taking after Dad.
53:50As more and more zebra families pour into Naipan
53:54at the end of a gruelling migration,
53:57the plains come to life.
54:20The first green shoots are pushing up
54:23and the time to rest, give birth,
54:26and feed on the bounty has arrived.
54:34This little foal is only hours old
54:39and it's still so unsure on its feet.
54:44I mean, it is just the most beautiful scene.
54:48And the stallion is just standing by,
54:51being extremely protective of his mare and his new foal.
55:01And we know so little about these interactions.
55:04There's still so much to understand.
55:06But just seeing this scene today
55:09really does pay homage to the past.
55:12Really does paint a wonderful picture.
55:17And as much as I couldn't help but question
55:20why on earth an animal would decide to make
55:24such a ridiculously long and arduous journey,
55:29watching this now, it all makes sense.
55:33It's worth the journey, it's worth the trial and tribulations
55:38because as a mother, you have every instinct telling you
55:43we need to make it down here.
55:46This is going to make our family stronger,
55:48our foals will be stronger.
55:50Ultimately, that's what survival is all about.
56:03During our time in Botswana,
56:05we've had a privileged insight into Africa's
56:08longest and most recently discovered land migration.
56:16We've discovered the importance of each family
56:19making the right decision at the right time.
56:23And we've revealed that part of their ability to navigate
56:26is written in their genes.
56:30The discovery of this zebra migration is so important.
56:35It represents what ground-breaking science
56:38can reveal about the natural world
56:40in a way that simply wasn't possible before.
56:43And what surprised me the most is
56:46just how complex these animals are.
56:48A strong biological instinct,
56:50a drive to explore and to navigate,
56:53a constant adjustment to a changing environment,
56:56they're all at play here.
57:00As difficult as this migration is,
57:03these zebra achieve it perfectly.
57:07There is still so much to understand,
57:10but ultimately this research will help scientists
57:13to preserve this precious migratory route,
57:16but it will also provide invaluable insights
57:19that could help to save species
57:21and their habitats across the world.
57:30The best of David Attenborough's early ZooQuest adventures
57:33can be seen as never before in colour.
57:36Available to watch now on BBC iPlayer.
57:39Over on BBC Two next tonight,
57:42Sheila Hancock and Jeremy Clarkson
57:45join Stephen Fry for QI.
57:59.