BBC Natures Epic Journeys_2of3_Caribou
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 they depend upon
00:21for survival, to find food, to give birth and to escape danger.
00:29Travelling hundreds of miles through some of the world's most breathtaking wildernesses
00:34that can turn against them at any moment.
00:39That rapids 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 depth.
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.
01:09We've got him, we've got the wolf, we've got the wolf.
01:14This time, we're following caribou as they migrate through Canada and Alaska, joining
01:19them for the final and most dangerous stage of their journey.
01:23As they race to get to their calving grounds before giving birth.
01:29For the first time, we can stay with them as they brave ice-strewn rivers, challenging
01:35mountain passes and starving predators.
01:39This is the setting for the longest land mammal migration anywhere on the planet.
01:46Over 100,000 caribou will come pouring through these mountains on an extraordinary journey.
01:52And we're here to follow them every step of the way.
02:05Ivavik National Park in the Western Arctic.
02:12A wilderness so remote, it has fewer visitors each year than the summit of Everest.
02:23Our home will be Sheep Creek, an abandoned goldmine-turned-research station.
02:33It's taken four days of solid travel to reach it.
02:39Oh, wow. So good to be here.
02:41It was really touch and go there for a while with the low cloud cover, but we're finally here.
02:47Using this as base camp, a hand-picked team of specialist biologists and camera crews
02:52will join local experts to study the caribou migration as it happens.
03:03Every spring, these distant coastal plains are the goal of almost 100,000 pregnant caribou
03:11and their offspring as they walk 500 kilometers to give birth.
03:16Incredibly, at the same time every year, all the females give birth within days of each other.
03:24This is what they come for.
03:26Cottongrass, the perfect nutrient-rich food for nursing mothers.
03:31And the timing is critical.
03:33The grass is at its best for just a matter of days.
03:36But first, the caribou must come together from across their winter range.
03:41We're waiting for them at a spot that's 350 kilometers from their calving grounds.
03:49Here, as they enter the treacherous valleys of Ivavik National Park,
03:53the landscape should funnel them into one vast group.
03:58They now have just 22 days until peak calving season.
04:03Thanks to the satellite collars, we can see exactly where the herd is at any one time.
04:11Caribou biologist Mike Suter is helping me to interpret the data as it comes into base camp.
04:20We're starting to learn still lots of new things with this new technology.
04:23But we have a small sample, you know, 50 satellite GPS collars on our herd.
04:28We have a small sample, you know, 50 satellite GPS collars on our herd
04:32that's numbering, you know, in the ballpark of 200,000 caribou.
04:35So, you know, that's one of the really interesting things about the satellite GPS collars
04:39is the more we have out, the more we're going to learn.
04:45Earlier in the year, wildlife cameraman Max Hugg-Williams
04:48joined the team collaring our caribou in their wintering grounds.
04:53He was accompanied by scientist Jason Cykowski,
04:56who needs to get as close as he possibly can with his net gun.
05:01But caribou have a top speed of nearly 80 kilometres an hour.
05:05The whole operation requires an enormous amount of skill.
05:11Our team of scientists believe that this is the fastest way to do the job,
05:15stressing the animal as little as possible.
05:19Netting may be a bit of a challenge,
05:21but it's a way to keep the animal in the right place at the right time.
05:26The caribou have a top speed of nearly 80 kilometres an hour.
05:35It may appear intense, but without the use of tranquilizers,
05:38the caribou can rejoin their herd as soon as the collar is on.
05:42I've just got to pin her down here while you're putting this collar on.
05:45Yeah, and just keep your leg up behind those hawks and she can't kick back then.
05:49It's incredible being this close to a caribou.
05:52Even through a glove, you can feel she's got such thick fur.
05:56You can see they're perfectly adapted for these crazy temperatures,
06:00which in winter drop to minus 50.
06:02And when you look at the hooves, I mean, they're bigger than my hand.
06:05It's almost like a snowshoe.
06:06Yeah, these animals are built for this.
06:11The collar will provide Jason's team with information on their exact movements
06:15for the next four years,
06:17giving them detailed insight into the animal's birth rate, behaviour and survival.
06:26She seems really chilled out now.
06:28She's just looking for the rest of the herd.
06:33We're going to try and keep up with the herd on foot.
06:36On foot? No chance.
06:44Max's plan to follow in their footsteps is incredibly ambitious.
06:50Caribou are the Arctic's most specialised species of deer,
06:54able to withstand temperatures down to minus 60 degrees Celsius
06:58and survive on vegetation that no other mammal can.
07:03The porcupine herd, named after the Porcupine River,
07:07spend their lives roaming over an area the size of Great Britain,
07:11feeding, breeding and evading predators.
07:15Key to their success is getting the timing of the spring migration just right.
07:21But they can get it wrong.
07:24The last time they were late to their calving grounds, 20,000 newborns died,
07:30their exhausted mothers too weak to feed them.
07:35Today, the data from their collars suggests they could be late again.
07:40I'm not sure it's the best time for camping.
07:43Max and biologist Peter Sinkins are trying to find out why they're moving so slowly.
07:54Look how deep it is.
07:56It's really crusty on the top as well.
07:59No wonder the caribou are not coming this way yet.
08:03Trudging through this snow saps energy and takes time,
08:07for caribou and humans alike.
08:12But exhaustion and starvation aren't the only killers here.
08:18We've got a grizzly bear, and it's quite a big male.
08:22And he's following the river towards us now.
08:27Yeah, I wouldn't be surprised if he's over 600 pounds, that guy.
08:34Yeah, I'm not sure whether he'll have actually smelt us yet,
08:37because we're downwind, but he's...
08:39I don't think he'll smell us.
08:42Yeah, I'm not sure whether he'll have actually smelt us yet,
08:45because we're downwind, but he's...
08:48clearly just come out of hibernation, and he's probably pretty hungry.
08:54Having just woken from six months of hibernation,
08:57the grizzlies here are starving.
09:02They're badly in need of protein
09:04to supplement their main diet of roots and berries.
09:08When the caribou pass through,
09:10they must make the most of this short-lived but vital food source.
09:16Right now, during the spring migration,
09:18these mountains are home to one of the highest concentrations
09:21of grizzlies in the world.
09:26Yeah, he's definitely spotted us.
09:28He's now eyeballing me straight down the lens.
09:31But bears aren't the only predators the caribou need to avoid.
09:39Wolves are formidable pack hunters,
09:42but this Arctic environment supports only small packs,
09:46so they often have to hunt alone.
09:50Their lives are desperately hard.
09:53Most wolves won't live beyond four years,
09:56and nearly 80% of pups die before they're a year old.
10:00If they miss the caribou migration, they will pay dearly for it.
10:04Starving wolves have even been known to eat their young.
10:14Using the satellite data and observations on the ground,
10:17we'll see exactly how the herd cope with the threat of predators.
10:23But first, we need to find our caribou.
10:26We'll look at the last week's worth of movement,
10:28and this will give us a sense of how fast they're moving.
10:32So they've continued a little further to the east.
10:35Yes, yes, yes. I mean, they're tantalisingly close.
10:38I can't believe how excited I am at just coloured dots on the satellite image.
10:47With just 13 days to get to the coastal plains,
10:50the caribou still have 300 kilometres to go.
10:54Delayed by unseasonally heavy snow,
10:57they're finally drawing close to the spot where Max and the team have been waiting.
11:01Max, it's Liz. Do you copy?
11:05Hi, Liz.
11:06Max, where are you going?
11:08Got some really good news for you.
11:10There are basically three lines of caribou on a trajectory to your camp.
11:18Max!
11:19Come on, we've got our first group.
11:20We've finally got the caribou.
11:22Where about?
11:23On the edge of the mountains.
11:24They're here.
11:28Come over here.
11:31If you look at the ice straight in front of us...
11:33Oh, my God. Oh, my gosh.
11:34And there are loads of them.
11:41At last, after a long, hard winter,
11:45the landscape comes alive with caribou.
11:58Our Inuvialuit host, Lee John,
12:01who was born on the edge of the Calving Grounds,
12:04already had an idea that the caribou were about to arrive.
12:08Lee John actually spotted them.
12:10Tell us again, what is it?
12:11When we see the ravens flying by,
12:13I would say,
12:17meaning, raven, raven, where are the caribou?
12:20And then when they flew over,
12:22I would say,
12:23meaning, raven, raven, where are the caribou?
12:26And then when they flew over,
12:27and we started scanning the area,
12:29we spotted them.
12:30I'm so delighted you have no idea.
12:34The stage is set for one of nature's greatest events.
12:54One, two, three, four...
13:00Using a feed from the helicopter's camera,
13:02I can see just how many caribou have arrived,
13:05and they're all heading north to the coastal plains.
13:16There are lines of caribou descending hillsides,
13:20lines of them crossing the waterways.
13:25Something triggers this coordinated movement
13:28that we still don't fully understand.
13:31It really is so thrilling to watch them.
13:41Now that they've all been funneled onto the same route,
13:44we can join them and study them in their entirety.
13:48Max will now try to stick with them to the calving grounds
13:51as they embark on the most dangerous leg of the migration.
13:57The first one's just come.
14:06It's amazing.
14:07We've just caught the first front runners.
14:09They're making a beeline down the valley,
14:11and everyone is following that leader.
14:15The caribou are so determined to push on
14:18that they completely ignore Max
14:20as they pass through in huge numbers.
14:24But the calm atmosphere doesn't last for long.
14:31Something just spooked them.
14:35It may be a bear that spooked them,
14:37and now they've come together in a tight herd,
14:40and they're just looking around.
14:43From the air, it's clear that they're reacting to something.
14:49The caribou are sat on the ice over there,
14:52and they're bolting this way.
14:54There's a wolf in the distance moving over the ice,
14:57and it's coming towards the herd.
15:03That's ridiculous. It's like a stampede.
15:06I can't see the wolf at the moment.
15:08Where's the radio?
15:11Hey, guys, did you see the wolf?
15:20In the open, the wolf is easy to spot.
15:26Caribou are a big prize for a pack with pups to feed,
15:30but weighing up to twice that of an adult wolf,
15:33they are dangerous.
15:35This lone wolf has no choice.
15:37It desperately needs to feed.
15:40SIREN WAILS
16:11SIREN WAILS
16:14SIREN WAILS
16:39Having panicked the herd,
16:41the wolf looks out for weaker or slower individuals.
17:02As the herd splinters and reforms,
17:05some of the caribou lose sight of their attacker,
17:08giving the wolf the advantage.
17:11SIREN WAILS
17:26The wolf needs to grab the caribou by the throat,
17:30but one well-aimed hoof could end the battle.
17:41SIREN WAILS
18:12SIREN WAILS
18:20This time, the wolf has won.
18:29The game of survival is finally balanced up here.
18:33But a fresh kill won't be kept secret for long.
18:42GROWLING
18:47They've just been spooked by something over there.
18:50Just six minutes after the wolf made its kill,
18:53grizzly bears are already homing in.
18:56I can't quite believe what these guys are up against.
18:59A wolf coming from that side, now we've got a bear over here.
19:02I've never seen anything like it.
19:05Bears are not as fast as caribou,
19:08so they need to use the element of surprise
19:11or scavenge kills from other predators.
19:14But they are much faster than humans.
19:20This guy's spotted us and he's coming straight for us now,
19:24which is a little bit unnerving, to be quite honest.
19:32What do we do now?
19:34OK, let's back off a little bit.
19:39He's off.
19:42Yeah, he was just curious there.
19:44We were standing still,
19:46and as soon as we started moving, that's when he backed off.
19:49He's not expecting a camera crew,
19:52and so it's very likely he was just coming to check us out,
19:56was that a caribou, and then backed right off, so that's good.
20:02Within moments, another bear has determined
20:05the dead caribou.
20:08Grizzlies can smell food from miles away.
20:11The wolf took a huge risk, but for very little reward.
20:19Max's bear has also turned its attention to the carcass.
20:26This bigger grizzly is running in.
20:30He's chasing off this smaller bear.
20:45Hey, Liz, Max here. Can you hear us?
20:48Yes, I can hear you, Max.
20:50Several bears have been sort of fighting over this carcass
20:53for a long time now.
20:56Several bears have been sort of fighting over this carcass
20:59and displacing each other.
21:01We got him, Max, we got him. There's a bear on the carcass,
21:04and he's dragging the carcass at the moment.
21:12While the predators in the area remain focused on the kill,
21:16the caribou can press on towards their calving grounds,
21:19leaving the bear to his spoils.
21:22This bear is making light work of this caribou.
21:26There's hardly anything left.
21:28When this bear is done with it, the eagles will come in,
21:31the grey jays, the foxes.
21:33Nothing will be left, and it just goes to show
21:36how important a source of food the caribou are
21:39for so much of the wildlife here.
21:44All the predator activity has now pushed large numbers of caribou
21:48to the west of the Firth River.
21:52But 30 kilometres ahead, their path is blocked by a sheer cliff face.
21:57They'll have to decide whether to cross the river
22:00or negotiate huge mountain peaks.
22:03But for now, they have more urgent problems to deal with.
22:07There are more bears around now than at any other time of the year,
22:11even around our camp.
22:16So you can see there's a track right there.
22:18Is this back foot?
22:20It's quite a bit larger than the front foot.
22:22He's a big fella, right?
22:24That's a reasonable-sized bear, yeah.
22:26Grizzlies mostly scavenge kills from other predators.
22:30But could they catch and kill an adult caribou?
22:35I have an interesting one that's on the website.
22:37Can you see that OK? Yeah.
22:39OK, he's got a grizzly bear there.
22:41And running pretty good, obviously.
22:43That's a full caribou.
22:46You can see he's got the bigger antlers.
22:48Look at the cubs.
22:49That's a female with her cubs, and she's going for it.
22:54Yeah, this female thinks it's worth the risk
22:57of tackling an adult bull caribou.
23:10He looks like a younger bull.
23:12He's not extremely large, so I don't think he's terribly...
23:15He's still a fair size.
23:17Oh, my gosh.
23:21She is really going for it.
23:23That's extraordinary.
23:27Oh, my good Lord.
23:29Grizzly bears are just so powerful.
23:39That was amazing. She was fearless.
23:42So that caribou is going to provide a lot of food for her
23:45and will obviously transfer that to her cubs,
23:47so that's important for the cubs' survival.
23:52Given the chance, grizzlies pose a real threat to our caribou herd.
24:05With just 12 days to calving,
24:07the caribou push on around the clock in the 24 hours of daylight.
24:12It's time to go.
24:22Max, Max, it's Liz. Do you copy? Over.
24:25Hey, Liz. Morning, morning. How are you doing?
24:28I've got a data update for you.
24:30The pace has picked up.
24:32The fastest pace is about 30km a day.
24:35The majority of the herd are moving north.
24:38I was actually going to say we saw a collar last night,
24:41number 88, so it would be really interesting
24:44if you can track that female down and see how far she's gone.
24:48OK, we'll take a closer look at number 88 from the data
24:51and we'll get back to you ASAP.
24:59The herd is moving fast
25:01and Max and the ground team are finding it hard to keep up.
25:05Max needs to stop, eat and sleep,
25:08but the caribou's specially adapted body clock
25:11allows them to keep going, taking short naps along the way.
25:15Max and his team are in for a gruelling few days.
25:19The satellite data shows the caribou are hardly stopping at all.
25:35Meanwhile, the data provides Mike and I with an insight
25:39into the female that Max saw the night before.
25:42I was shocked when Max told us that it was 88.
25:45I took a look and I was blown away
25:47because she does have quite a bit of history for all of our collars.
25:51She's actually an older cow, so she's going to be 10 years old this June.
25:55Caribou 88 has been collared for the whole of her life
25:59and her data has revealed something quite remarkable.
26:03Year after year, she has travelled with the rest of the porcupine herd.
26:09But earlier this year, she left
26:12and joined a completely separate one, the Central Arctic herd.
26:18Is it possible that she bred with a member of this different herd?
26:22It's entirely possible, yes.
26:24She would have been down in the mountains here
26:26where the Central Arctic herd is during the rut.
26:28The one thing we can say with some certainty
26:30is it looks like she's going to calve with the porcupine caribou,
26:33not the Central Arctic.
26:34She's back to her own herd.
26:35She's a porcupine caribou.
26:37Exactly why she left is a mystery.
26:40But the herd are lucky to see the return
26:43of one of their older and more experienced females.
26:46She had been bringing up the rear.
26:49Now she's straight to the front and is helping to lead the entire herd.
26:55This is an incredibly important role,
26:58especially as this wilderness presents a new challenge at every turn.
27:05Whilst frozen, rivers are safe and easy to cross.
27:11But as the temperature rises,
27:13they can quickly turn into raging, deadly torrents.
27:18This is unbelievable.
27:20We were up at camp and heard the change in the noise of the river.
27:27Huge, bold waves.
27:32This is incredible!
27:34This is unbelievable.
27:38This is fantastic!
27:40This is fantastic!
27:43This is incredible!
27:46huge boulders of ice have broken free further upstream and are rushing past here.
27:54The river has gone up by at least a couple of meters.
27:59There is no way a caribou can get across this right now but this is what they have to deal with.
28:08Last year as the Porcupine River broke up locals saw just how dangerous it can be.
28:17Caribou crossing the river were caught out as the ice broke carrying them unstoppably downstream.
28:24So
28:41with just 10 days left to calving our caribou on the western side of the river
28:47are forced to make a crucial decision.
28:55The majority of the herd passed through the hills back there but there's a small group
29:05that have come down to this dead end. There's a huge cliff face here so there's no way they
29:10can pass on this side of the river. So that lead female, I don't know whether it's an inexperienced
29:14leader but now she's got to make a massive decision. Either they've got to swim across
29:18that river or head up this really steep slope here and we just saw a grizzly bear go up there
29:24so it's not looking good either way. They're all going for it. A female enters the water
29:34the others follow.
29:43That looks like the worst part of the river.
29:44The force of the melt water has created a powerful set of rapids
29:57but the caribou plunge in regardless.
30:03That rapids really picking up they're just disappearing under the water.
30:07The power of the water is simply too much.
30:28I mean one I saw disappear under the water I don't know if he if he came back up
30:35As the drama unfolds I take to the air to join Max.
30:48I think they've finally seen sense and doing a U-turn
30:53just goes to show the experience you need to navigate through these mountains.
30:59With nowhere left to turn the caribou opt for the mountain route.
31:05Hey Liz we've got drama down here we've just had a big group that was stuck in this dead end valley
31:11half of them nearly got swept away the other half wouldn't get in the water and have taken
31:16on this massive peak in front of us. Okay Max there's a bear in the vicinity as well.
31:23And it's not just the bear that spots an opportunity as the caribou change course.
31:28See it moving in the trees see him moving about halfway up.
31:33He's just spotted a wolf on the hill.
31:36He seems to be going up and to the left as if he's kind of checking out these guys but he's
31:39gone quite a bit of ways up that slope. We got him we got the wolf we've got the wolf.
31:46I mean we knew that there were going to be predators here but I didn't quite imagine it
31:53would be so busy and they're all looking to get their share of the caribou.
32:04The caribou now have no choice but to come back down to the river.
32:12And from here there's only one option.
32:22Despite being further upstream the current is still strong.
32:30The more experienced females lead the way.
32:43Suddenly a yearling starts drifting away from its mother.
32:52And soon even the adults are struggling.
33:14The yearling is out of its depth separated from the herd and heading towards the rapids.
33:22But caribou fur is hollow to insulate against the cold which means the calf floats.
33:42There's no time to rest. The herd must keep moving
33:46if they're to reach the coastal plains before calving.
33:53The more we observe our caribou the more apparent the challenges and dangers they face.
33:58Their survival hangs in the balance every step of this astonishing journey.
34:16Although porcupine herd numbers are currently stable
34:20other herds have decreased by as much as 85 percent in just a few years.
34:29Our data backed up by our observations on the ground will contribute to the bigger picture
34:35of caribou survival across the arctic and will hopefully provide clues to these sudden declines.
34:41Eight days until calving and the relentless pace of the migration
34:45has now left Max and the ground team far behind.
35:12The caribou are already 25 kilometers ahead of Max's position. It's time to catch up.
35:24Max's mission to keep up with the caribou on foot has proved impossible.
35:30The animal's extraordinary strength and stamina
35:33and their relentless urge to push north to the coastal plains has beaten him.
35:42There's only one way to catch up.
36:01The caribou have walked nearly 400 kilometers from their wintering grounds and yet have barely eaten.
36:09Their reserves are running dangerously low.
36:17Number 88 is still with the other trail breakers leading the way.
36:24She and the others have only 50 kilometers to go but they're each burning nearly 6,000 calories a day.
36:32They need to conserve as much energy as possible.
36:35We have to remember that these caribou are running on empty now. Of course they're pregnant too and
36:40they're running low on all the reserve they stored up in the previous
36:44summer and autumn for this extraordinary migration to the coastal plains.
36:50What's more, the calves they carry are now making their greatest demands.
36:5580% of all foetal growth happens during this final stage and if that wasn't enough,
37:03and if that wasn't enough, they must now cross a vast array of snow-filled plateaus.
37:12It takes seven times more energy to break a trail through deep snow than it does to walk on bare
37:18ground but the caribou have an ingenious solution. They walk in single file. It really is fascinating
37:30how precisely they follow each other in a single file. It's all about conserving energy. Every
37:37calorie that you can save by not breaking your own trail, by following in the footsteps of another
37:45caribou, means you've got a bigger chance of succeeding at the other end. There's clear
37:52evidence that caribou have been walking like this in these valleys for over 12,000 years.
38:00Using the very same paths for millennia, this ancient migration has etched its story on the land.
38:19Max and the ground team have been following the caribou relentlessly and have hardly slept.
38:30But the pace is taking its toll on the caribou too. These caribou have been going all night.
38:36They're so focused on their destination at this point. They're so close to getting to the north
38:40slope that they just keep going. Their drive is so strong they're even prepared to leave
38:47behind their yearlings to get there on time. These guys don't get to sleep. You look up there,
38:56you see the snow patch. The yearling just looks absolutely knackered, wiped out. He's just
39:03sort of given up, lying down while the rest just moved on. I mean, it's just tough love, isn't it?
39:10Even though his mum's probably in that group. I mean, she's not waiting for him. It looks like
39:15he's given up. No, he's trying to get up now, actually. There's no way he's going to catch
39:21and they're on a mission and he's stumbling along. The pregnant females are like a week away from
39:28giving birth at this point, right? So, you know, they've started this migration as early as
39:33January and so they've come a huge distance. Well over 5,000 caribou die during each spring
39:43migration from sheer exhaustion or predator attacks. A bear can't catch a full-grown
39:50caribou unless they catch them by surprise, but that is what they're looking for.
39:55Stragglers on their own. That's just easy pickings for a bear.
40:00Yeah, especially when the yearling's already exhausted.
40:10One last push and the lead caribou are finally heading out of the mountains
40:15and onto the coastal plains.
40:19After nearly 500 kilometres, barely feeding, they've arrived just in time for the early
40:26growth of highly nutritious cotton grass. But even now they can't afford to relax.
40:35We've got a big grizzly bear just started with this group of caribou.
40:41I mean, they're quicker than him but it looks like he's tried to ambush them
40:45and we just want to get in position so we can see something.
40:54We saw him definitely in these bushes. He startled them.
40:57There's caribou all around us. There's a group that are calm here which
41:01hopefully suggests the bear's not just in front of us, but that group over there got
41:07completely spooked. They just ran for it and he is somewhere in front of us, probably about
41:13100 metres. They are faster than any bear but if he can play his cards right and catch
41:20them by surprise then he'll have a tasty dinner. But it looks like they've got away this time.
41:31Do you see anything? There's nothing down by the river there.
41:36Not seeing anything but the willows are thick down there.
41:43He's big.
41:58These caribou haven't seen him at all.
42:02They're so fixated on just eating after this long journey that
42:07it's like they haven't even seen him. He's just wandering up and they're not even responding.
42:13In such open landscape the bear has little chance of catching a caribou.
42:23This leaves Max and Pete at risk. He's now closer to us than he is the caribou.
42:29What's the plan here then Pete?
42:33Staying calm is essential. Bear bangers are at hand if they need to startle the bear.
42:39He's coming close now. And if it charges and gets too close,
42:43as a last resort, Pete would have to use his gun.
42:50He's charging. Okay, let's not run. Running can actually trigger an attack.
42:56This is not the best terrain for us is it? We don't want to trip up now.
43:00That was a little bit too close for comfort. That bear was clearly going for the caribou but
43:06they're a little quicker than us. And as they started to run off,
43:11he decided to change his attentions towards us. He gave us a bluff charge, let us know who's boss and
43:20that gets your heart rate going. They're so quick. They'll be on you before you know it if they want
43:25to be. They can run as fast as a racehorse. You didn't tell me that before. He's still coming.
43:29He's still coming. He's coming with purpose now. The bear is coming towards us by the chopper up
43:37quickly and get ready to pull us out of here. He's coming pretty quick now guys. No running? No.
43:48Okay. It's a close shave and a powerful reminder of what the caribou are constantly up against.
44:04We're finding out so much more about the harsh realities of this epic mighty bear hunt.
44:09Helped of course by the invaluable satellite data. The collars themselves form the basis for
44:15all of our sampling that we do. But even though we've been studying them for as long as we have
44:20and they are one of the better researched herds in the world. No and still there's so much you
44:23don't know yet. Absolutely. And of all of the behaviours that you have observed, what has been
44:29the most surprising to you? I think the most surprising to me has been the fact that we've
44:34And of all of the behaviours that you have observed, what has been the most surprising so
44:39far? I think just the synchrony of movement is what blows me away. So here's a great example.
44:45This was back at the end of August last year and we had caribou that were spread all across
44:50all the way over towards a clavic 200 kilometers away from each other. And on the same day it was
44:57like a switch went off. All those caribou started moving and they all went in this exact same
45:02location. It was amazing. We're talking hundreds of thousands of caribou here and they're all on
45:10the same day starting to move. They're all going to the exact same location and then they're all
45:15moving together as one pretty much cohesive group at that point. How do they know? Like you're at
45:24one end of the range, I'm at the other end of the range. How do we both know that that's the day
45:28we're going to move and we're all going to go to this one spot?
45:33Typically this type of thing might have gone unnoticed in the past. That's one of the beautiful
45:36things about our satellite GPS columns is that it actually allows us to see this as it occurs.
45:44The more we study this migration, the more we can reveal about these remarkable animals.
45:49With just five days left to calving, the herd is spreading out across the coastal plain.
46:02There are huge numbers that have already come down these plains and it's such a difference
46:06in landscape from those rugged hills to flat open plains. The last leg of the journey.
46:14Yeah, great. Full stretch.
46:19Somewhere in this vast landscape, the caribou will give birth. Despite the endless challenges
46:27and obstacles, their relentless pace and stamina have got them here on time. The caribou aren't due
46:34to calve here for another few days, but we don't want to risk distressing them when they're at
46:39their most sensitive, which means that this is Max's last chance to catch up with the herd
46:44before leaving them alone to give birth.
46:55Wow, it's so different here, isn't it?
47:01They seem so much more relaxed here. It's like they know they've made it.
47:07Look at them coming in now. They're curious. Yeah, they will do that.
47:15They're just checking us out here. They're just munching away on this grass. Yeah, like the little
47:21flower on top there. As you can see, it's new growth. Very critical to the caribou at this
47:27time of the year. So those fresh shoots have just come out. That is fresh shoots. This ground is
47:32covered with cotton grass. So it's that that they've come all this way for? Right, yeah, it's fresh stuff.
47:45In the two weeks after the snow melts, the cotton grass sprouts and flowers.
47:50This is when it's at its most nutritious.
47:54It's this narrow window that the caribou have raced here for.
47:58Not only can they now replenish their reserves, but scientists have shown that eating the grass
48:04at this specific time helps mothers to produce a richer milk for their newborn calves,
48:10greatly improving their chances of survival.
48:17And it's earned this place a special name with the Inuvialuit.
48:21Now that we've followed the caribou from the southern part of the park to the northern part,
48:28now we leave the caribou in peace to have their young ones.
48:38We may have had to leave the caribou for a long time, but it's been a long time since we've seen
48:45We may have had to leave the caribou for a while, but the satellite data continues to tell their story
48:51as they move along the plains into Alaska. The pregnant females finally stop to give birth in
48:57the area with the most nutritious and abundant cotton grass on the plains. And at last, we can rejoin them.
49:06Here they are, here they are. It's so good to see them again.
49:10Here they are, here they are. It's so good to see them again.
49:15After all their efforts, I'm keen to know how successful this year's calving has been.
49:22I wonder if I'm setting eyes on any we saw at the beginning of the migration.
49:27Seeing them in such huge numbers, almost each adult accompanied by a calf, is just...
49:36Yeah, it's a little bit emotional actually. It's so lovely to see.
49:41There must be thousands of caribou.
49:47This time, our base camp will be in the Alaskan part of the Porcupine Caribou Range.
49:55I've been joined by Eric Wald of the U.S. Fish and Wildlife Service, who will guide us through the area.
50:01Eric is the head of the Alaskan Fish and Wildlife Service, and Eric is the head of the Alaskan
50:06Porcupine Caribou Range.
50:11I've been joined by Eric Wald of the U.S. Fish and Wildlife Service, who will guide us through the area.
50:17What direction and distance from our current location are they?
50:21Being so remote, we have to get the most recent data by satellite phone.
50:26What did he say?
50:27Well, they're headed our way, about 17 kilometers to the northwest of us.
50:32We saw them from the air as far northwest as there?
50:35Yes.
50:36Using this information, Max is moving into position.
50:42There's maybe up to 200,000 caribou, and they're all about to pass directly in front of us.
50:51They're so quick, it's ridiculous.
50:58With new calves alongside, the females molt into their thinner summer coats.
51:06That satellite collar number 25 is right in front of us.
51:14I think back to when we saw these guys for the first time in Alaska and put those collars on,
51:22and they've gone so far since then.
51:25To think what that lady's been through.
51:29It's mind-blowing.
51:31Having survived an immense and arduous journey, our caribou got the timing just right.
51:40Over 70,000 pregnant females gave birth within five days of each other.
51:48That's one calf born every eight seconds, day and night, for five whole days.
51:54Nourished by the rich milk from the best cotton grass,
51:57the calves have doubled in size in just 10 days.
52:02But they've got a lot to learn.
52:09There's a calf right in the middle of the herd calling.
52:13Clearly lost his brood.
52:16How you begin to find your mum when there's 200,000 caribou.
52:23She could well have already moved on.
52:28He's found her.
52:31You could see his relief.
52:33He suddenly must have heard his mum and he ran forward and just saw her.
52:40He could see his relief.
52:41He suddenly must have heard his mum and he ran forward and just —
52:46straight to her side and tried to get some milk, and that's so good to see.
52:57Despite having only just calved,
53:00our satellite data shows that the herd are soon on the move again.
53:04So May 25th through the 28th.
53:07OK that's when we left them.
53:09And when was the majority of the calving, then?
53:12Calving is from June 8.
53:14And they move very quickly away from the calving location,
53:18don't they?
53:19Yeah, after two, three days, the calves
53:21are able to keep up with their mom.
53:25And keep up, they must.
53:29Soon, the whole herd comes together and can move as one,
53:35joined by another 70,000 males and youngsters.
53:40This time, it's not bears or wolves
53:42that are driving them together.
53:47It's a creature a million times smaller,
53:50but a billion times more numerous than the caribou.
53:57Mosquitoes.
54:00A single caribou can lose half a pint of blood a day to them.
54:04They have even been reported to die from asphyxiation
54:08as thousands of tiny mosquitoes clog up their airways.
54:14The relentless attack creates waves of panic through the herd.
54:26Walking up to the herd, the caribou
54:29and the other calves are in a state of panic.
54:34Walking constantly into the wind gives some relief,
54:41as does herding together as closely as possible.
54:47This gives us our best chance to see how they fare this year
54:51and how their numbers are holding up.
54:57It's good news.
54:58The porcupine herd is now bigger than ever recorded.
55:03And it's an incredible sight.
55:29During our time here, the satellite data
55:32and our team on the ground have captured the critical decisions
55:36made by this herd.
55:38When to move, how fast to travel, which routes to take,
55:43and which rivers to cross.
55:46We've discovered the importance of experienced females,
55:50and the importance of their ability to adapt.
55:58Like number 88, leading the herd out of danger.
56:02And we've seen how sheer stamina, determination,
56:06and ingenuity help them to time this journey faultlessly.
56:11In a punishing wilderness where their lives constantly
56:14hang in the balance and little else can survive,
56:18these caribou have adapted perfectly.
56:23This has been a journey of epic proportions.
56:28And what struck me the most is just what caribou are capable of.
56:35Not only do they carry out the longest land migration
56:38in all of the animal kingdom, but they
56:40have found ways to survive countless threats
56:43and obstacles that are thrown at them at every turn.
56:47And next year, the new cows will have
56:50to learn just what it takes to make it out here.
56:54Their mothers will pass on all of their knowledge
56:56and all of their experience as the race to the calving grounds
57:00begins all over again.
57:15Next time, in a world first, we join a newly discovered animal
57:20migration.
57:21Thousands of zebra migrate hundreds
57:23of miles across one of Africa's harshest scrubland.
57:27Failure could end in disaster.
57:33Another of nature's epic journeys on BBC One
57:36next Wednesday at 9.
57:38After the news, a tribute to a footballer, pundit,
57:41and pioneer, Jimmy Hill, a man for all seasons at 10.45.