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00:00The power of the sun drives the seasons, transforming our planet.
00:13Vast movements of ocean and air currents bring dramatic change throughout the year.
00:23And in a few special places, these seasonal changes create some of the greatest wildlife
00:29spectacles on earth.
00:32The most dramatic event in the world's oceans happens off the eastern shores of South Africa.
00:47These cool waters create the perfect conditions for a spectacle of epic proportions.
00:57And everything revolves around the humble sardine.
01:05Each year, millions of them are swept up Africa's coast on a desperate winter journey.
01:17Following them comes what will become the biggest army of predators anywhere on the
01:21planet.
01:29The climax to this chase depends on many crucial elements coming together for one brief moment.
01:35This can well claim to be the greatest show on earth.
02:05In the deep water off the southern tip of Africa lie the rich fishing grounds of the
02:16Agulhas Bank.
02:22It's home to billions of sardines.
02:24They live in immense shoals as defense against their many predators.
02:36Moving together as one in a shoal gives an individual sardine its best chance of survival.
02:47Sardines are so numerous, they're on the menu of most fish-eating predators here.
03:00It's summer and the sardines are lost in the vastness of the ocean.
03:05The shoals are so dispersed, they're hard to find.
03:26Common dolphins are specialist sardine hunters.
03:41Dolphins aren't the only ones on their trail.
03:43Gannets also rely on a diet of sardines.
03:48The best way for them to find the shoals is to follow the dolphins.
04:01When the fish are far out to sea, the dolphins need great perseverance to track them down.
04:15The dolphins use their own form of sonar, sending out a stream of clicks and whistles
04:20listening for returning echoes.
04:36At last, they've found what they're looking for.
04:50Working as a team, the dolphins isolate a group of fish and corral them into a tight
04:55ball close to the surface.
05:02The gannets can now make their move.
05:28The gannets can't dive deep, so they must rely on dolphins to keep the sardines near the surface.
05:46The feeding frenzy is short-lived.
05:49Most of the shoal escapes to the deep and the hunters are left still hungry.
05:57It's December, the height of the southern summer, and the sardines have the advantage.
06:02With the shoals dispersed, life is hard for all the predators.
06:14But in six months' time, if conditions are right, the scene will be set for astonishing
06:20and sustained drama.
06:27For a few short weeks each winter, cold ocean currents can sweep great shoals of sardines
06:33up the coast.
06:36Trapped close to shore, within this corridor of cool water, the fish are vulnerable and
06:42their predators will follow in droves.
06:47If it happens, this will be the sardine run, one of nature's great events, unique to these
06:53shores of South Africa.
06:58But for this epic event to take place, many elements have to come together.
07:02And with our changing climate, they're less predictable every year.
07:09For the predators, the winter sardine run, if it happens, can make the difference between
07:14life and death.
07:18Predators rely on the easy hunting during the run to wean their calves, but the omens
07:24aren't good.
07:25Last year, the sardines didn't run at all.
07:34Gannets follow the same pattern.
07:35They have their chicks in summer, so they too leave the nest in time for the sardine
07:40run.
07:52This is Bird Island, just off the Eastern Cape, the biggest gannet colony in the world.
08:04No less than 100,000 breeding pairs come here every summer to have their young.
08:18These incredible numbers show the wealth of life the annual sardine run can support.
08:29They also show how many lives may be in jeopardy if the sardines don't run.
08:42Right now, the African summer is taking its toll.
08:45With temperatures soaring and no cover on these exposed islands, the birds are in danger
08:50of overheating.
09:05The young are especially vulnerable.
09:09They have to be fed every day.
09:12Even with both parents taking turns, it's an exhausting task.
09:38In the summer, the sardines are a long way out to sea.
09:46The birds fly hundreds of miles in search of a meal.
10:02Once they've sighted their target, they plunge from heights of 100 feet, striking the water
10:12at 60 miles an hour.
10:26Every dive subjects them to enormous forces.
10:37The slightest miscalculation could be fatal.
10:47Gannets can dive no deeper than 30 feet, so once again they rely on the dolphins to keep
10:52their prey near the surface.
10:55But with so much traffic, there's always the danger of a collision.
11:18This one has broken her neck.
11:25Her death will mean that back on the colony, her chick will probably starve.
11:34The rest make the long flight home with their catch.
11:39One partner stays on the island to guard their chick.
11:47The pair welcome each other with a ritualized greeting.
11:51They have a strong bond and many couples mate for life.
12:16During the hours of daylight, the sardines stay deep in an attempt to avoid their predators.
12:29As the sun sets, the little fish themselves can begin to feed.
12:36They swim upwards to sieve the water for plankton, microscopic plants and animals.
12:56At daybreak, they sink once more into the safety of the jeep.
13:14It's not just dolphins and gannets that rely on sardines.
13:25There are other, more mysterious predators.
13:40The brooder's whale hardly breaks the surface to breathe and never so much as shows a tail
13:46fluke.
13:54For a 50-foot whale, they vanish with remarkable ease.
14:00We know little about these stealthy leviathans, other than they are sardine hunters too.
14:18Summer is a lean time for the brooder's whale.
14:23As it is for all the predators.
14:32Sharks follow the same patterns, tracking the shoals offshore through the summer, waiting
14:37for the winter sardine run, when the hunting will be easier.
14:44But being cold-blooded, they don't have the high energy demands of the whales, dolphins
14:49and gannets.
14:58All the predators have to endure the lean months, relying on the southern winter in
15:03June to bring a change in their fortunes.
15:10Now the changing seasons create a switch in the ocean currents.
15:16As summer gives way to autumn, the southerly-flowing warm current weakens and cold Antarctic water
15:22pushes further north, nearer to land.
15:27The sardines are carried along by these cool waters and pushed closer to shore.
15:38If these ocean currents continue to change, the sardine run should be only three months
15:43away.
15:49It's time for the gannet chicks to leave the safety of their colony.
16:04Gannets stop feeding their young when they're three months old.
16:07This forces the chicks to take to the sea.
16:13The young have enough fat reserves to survive for just ten days, and in this brief window,
16:20they must learn how to fly and hunt for themselves.
16:27This is the most critical time in a gannet's life.
16:31Hunger will mean starvation.
16:46To prepare for their maiden flight, they test their wings and strengthen their flying
16:51muscles.
17:05Eventually hunger drives them onwards and upwards.
17:27Some get up and away first time, but many don't make it past the crashing surf.
17:51Some bedraggled chicks struggle back to shore, but for others, the pounding has been too
18:21much.
18:50Fewer than half of all the chicks on this colony survive their first three months of
18:56life.
19:15The coast of South Africa is an unforgiving place.
19:24The baby dolphins are still dependent on their mothers.
19:28They suckle for six months before they, like the young gannets, have to start fishing for
19:33themselves.
19:41There is such an abundance of fish during the sardine run that even the calves can catch
19:46some and so begin to learn their hunting skills.
19:57But the sardine run might not even happen this year.
20:03For now, the dolphins will have to continue to scour the vast ocean.
20:30Back at the coast, other youngsters are getting ready to go it alone.
20:45Cape fur seals are also waiting for the sardines to come close to shore.
20:56But seals have a broad diet, so they can make the most of other feeding opportunities
21:02until the sardines come within range.
21:09Young seals are forced from the colony by the dominant males.
21:25Once they're cast out, the adolescents roam the coastline looking for food.
21:46They won't turn their noses up at a plump young gannet.
21:59Hungry seals patrol the surf, ready to pick off any birds that don't get airborne straight
22:04away.
22:07When the wind is light, the gannet chicks are stuck on the island.
22:20Surely they're safe here.
22:22But even on land, the seal is surprisingly fast on his flippers.
23:22In this one season, on this one colony alone, seals kill up to 10,000 fledglings.
23:39And as ever, it all comes down to sardines, for the seals are only after the fish within
23:45the stomach of their victims.
23:51For the young birds who do make it past the seals, there are fresh challenges, learning
23:56the skills of their parents.
24:04First they have to find their quarry, the sardine shoals, and the best way to do that
24:09is to follow the expert trackers.
24:24They're hungry.
24:25It's been days since their parents last fed them.
24:39As the search goes on, the chicks are learning the most sophisticated survival technique
24:44of all, how to harness the expertise of another species.
24:57After a long search, the dolphins have found a small school of fish.
25:06They drive the sardines to the surface and within range of the young gannets.
25:10Now, quickly, they have to learn the art of the plunge dive.
25:22But there's a problem.
25:23The opportunistic seals have found the fish too.
25:31The young gannets have a daunting choice, to risk diving with the enemy or to starve.
25:38If they don't take their chances soon, there will be nothing left.
25:56Even in luck, with sardines back on the menu, the seals ignore the gannets.
26:12As ever, the dolphins have done the hard work of rounding up the fish, and now a host of
26:17other predators take advantage.
26:22With the show diminishing by the second, competition is fierce.
26:27But there is still time for a mighty intruder.
26:44The brooder's whale devours the entire ball of fish.
26:50While the sardine run starts in earnest, these minor skirmishes are mere preludes to
26:55the main event.
26:58But winter is finally on the way.
27:01The cold current pushes further north.
27:04This cool water forces its way up the coast.
27:08If it continues to flow northwards, it will carry great shoals of sardines with it.
27:19The predators begin to gather in anticipation of a feast.
27:31Sardines can't tolerate water above 70 degrees Fahrenheit, so unless the cool water penetrates
27:37further up the coast, the fish won't move and the annual run just won't happen.
27:45Perhaps climate change has made its mark here.
27:48The waters have stayed too warm, stalling the movement of fish.
27:52There hasn't been a sardine run for the past two years.
28:04The entire fleet is becalmed.
28:24A winter storm rolls in from the Antarctic, battering the Cape, bringing cold water.
28:52Driven by their hunger, gannets still try to hunt in these dangerous conditions.
29:12In fact, this wild weather is just what all the predators have been waiting for.
29:18For them, it's a perfect storm.
29:23It has pushed a narrow tongue of colder water up the coast.
29:28This chilly current carries wave after wave of sardines with it.
29:32Hemmed in by the land on one side and warm water on the other, the sardines are being
29:38drawn into a trap.
29:44Nature is playing a cruel trick on these unfortunate fish, as they'll get no benefit from their
29:49mass voyage.
29:51They're slaves to the cold ocean currents.
29:58More than 500 million fish are swimming towards disaster, and yet this is just a tenth of
30:05the sardine population.
30:07The run is on.
30:15Ahead, an ambush is being prepared.
30:27As the seas begin to calm, the dolphins relocate the sardine shoals.
30:45As they track up the coast, the pods unite, combining forces.
30:59They form superpods of incredible numbers, up to 5,000 dolphins in one group.
31:12This is fast becoming one of the biggest groups of predators anywhere on the planet.
31:23The attackers spread out into wide hunting lines, stretching up to a mile across.
31:39Other divisions follow on, as ever, tracking the dolphins, shadowing them all the brooders'
31:53whale.
32:04They're all heading in one direction, towards a place known as Waterfall Bluff.
32:17It's an arc in the coastline which interrupts the flow of currents, trapping the water in
32:22a swirling eddy.
32:26And the dolphins know that the massive shoals often get caught in this bottleneck.
32:35But these sardines have managed to avoid the trap.
32:49The first shoals have been carried well to the north of Waterfall Bluff, ahead of the
32:54dolphin superpods.
33:03As the cool water is squeezed into an ever thinner band, closer to the shore, the shoals
33:09are forced up into the shallows.
33:23Only now do we get a real sense of the sheer volume of fish.
33:29This one shoal stretches along the coast for 15 miles.
33:39The water is 50 feet deep and packed with sardines from top to bottom.
33:47There could be more than a hundred million fish in this single shoal alone.
33:54As long as the sardines are in such shallow water, they're beyond the reach of the dolphins,
33:58who won't follow for fear of stranding.
34:03And the gannets can't risk diving into such shallow water either.
34:11But there are hunters who can follow.
34:14And they've arrived in their thousands... sharks.
34:39Heavy copper and ragged tooth sharks encircle the sardines.
34:48But for the little fish, there's safety in such vast numbers.
34:53The sheer volume of sardines, the way they twist and turn in harmony, confuses the sharks.
35:06Without dolphins to round up the fish, these sharks have to find their own solution.
35:23They try to trap the fish against the water's surface.
35:32But this boiling water is mostly sardines escaping.
35:36Few are actually eaten.
35:51Many fish triumph over the marauding sharks.
36:06The sharks continue to harry the shoal, pushing it ever northwards.
36:22Back at Waterfall Bluff, the dolphins and gannets are waiting for the next pulse of
36:26sardines to come up from the south.
36:31If there's another shoal, this kink in the coastline is the perfect place to ambush them.
36:36But if the fish don't come, these hungry predators face a long journey all the way back to the
36:42Cape.
36:48To the north, the survivors of the shark attack are nearing the end of their run at the beaches
36:53around Durban.
36:59These seem like the lucky ones.
37:02On their epic journey, they've evaded an army of hunters.
37:08But one final unexpected predator lies in wait.
37:25Fishermen can only net the sardines once they've swum this far north, within easy reach
37:30of the shore.
37:35Last year, no sardines were seen on this coast.
37:38So far this winter, the fishermen have landed only 50 tons, barely a tenth of what they'd
37:43expect in a good year.
37:52That's how unpredictable the sardine run has become.
38:09After such a long and hazardous voyage, it's a sad end for these sardines.
38:24At Waterfall Bluff, the dolphins and gametes have had to bide their time.
38:35Missing the first shoal, these predators are relying on the currents to sweep another big
38:40pulse of sardines up the coast.
38:45Now another great shoal is on the way, and it's heading straight for Waterfall Bluff.
38:58Trapped between the shore on one side and the warm water on the other, these fish are
39:03swimming straight towards the enemy.
39:19The sardines fall back on their instinctive defense, swarming into a huge mass that confuses
39:25a predator.
39:38But the dolphins have a strategy that turns this to their advantage.
39:46Working together, they separate off a pocket of sardines.
39:54In smaller numbers, the fish's shoaling defense now works against them.
40:01The dolphins corral the bait ball and herd it to the surface.
40:19This is what the other hunters have been waiting for.
40:25Now the sardines are within range of the gametes.
40:50The bait balls form and reform, seldom lasting longer than a few minutes each.
41:20The sharks pile in, taking advantage of the dolphins' hard work.
41:32The predators ignore each other.
41:34There's only one victim here, the millions of tasty little fish they've been stalking
41:39for so long.
42:02When gametes join the frenzy, in just six months they've become superb aerial hunters.
42:18Time after time, the dolphins round up another shoal for destruction.
42:47Frantically, the little fish try to get away from the seething surface of the water to
42:52dive beyond the range of the gametes.
42:59Now something truly astonishing happens.
43:06Diving takes the gametes down to 30 feet.
43:11Then the aerial squadrons become shoals of swimmers, as they pursue the fish down to
43:1760 feet.
43:23Sardines join with the predators in a beautiful yet macabre underwater ballet.
43:29There's little chance of escape for these fish.
43:53The stage is set for the biggest predator of all.
44:21The brooder's whale takes in 10,000 fish in one giant mouthful.
44:30But this time around, there are plenty of sardines for all.
44:46Each hunter amongst these millions plays its part in the drama, and each is dependent
44:53upon the other.
45:08The annual spectacle of the sardine run is undoubtedly the greatest gathering of predators
45:14anywhere on the planet.
45:22Surely one of nature's great events.
45:52Then, almost as quickly as it began, it's over.
46:23As the brief winter comes to an end, warm currents flowing south displace the corridor
46:31of cool water.
46:37Despite the massacre, more than half of all the sardines swept up on the great run survive.
46:48As the currents switch, the fortunate ones make good their escape.
46:56From here, they'll follow deep water currents, hitching a ride back to the cool waters of
47:01the Cape.
47:08The brooder's whale melts away to resume its secretive life somewhere out in the big blue.
47:21The dolphin's superpods break up and begin their long trek back to the Cape.
47:32Gannets, too, head south.
47:43As waterfall bluff falls quiet once more, no one can say whether this spectacular event
47:49will be repeated here in years to come.
48:01The sardine run may be unique to the coast of South Africa, but it's a vivid reminder
48:07of the riches that our oceans can still support.
48:32The amazing bait balls that characterize the sardine run are short-lived and very hard
48:44to find.
48:46was to turn into a two-year mission for the underwater team.
49:01To film the feeding frenzes, the team would need three key elements to come together.
49:06A huge shoal of sardines, the right mix of predators, and water clear enough to be able
49:13to see the action.
49:17The most important element to start with was being able to see underwater, and at the beginning
49:22of the first season, it wasn't looking good for underwater cameraman Didier Noirot.
49:28It looks like dirty water, but I'm going to check anyway to be sure.
49:36Didier was Jacques Cousteau's underwater cameraman for more than a decade.
49:41He knows that the sardine run is very unpredictable, and that some years it never happens at all.
49:50The predators were gathering, but the ocean currents weren't bringing any sardines.
49:58It wasn't a good start to the first season's filming.
50:05What's it like?
50:07No visibility.
50:12And the murky water held further risks.
50:15Poor visibility, you don't see what's coming, so it's not that we are scared of all the sharks,
50:21but we noticed that accidents, people get bitten always in dirty water,
50:27so why should we take the risk?
50:30If you go in dirty water to make bad pictures and get bitten by sharks, it's not worth it.
50:37I'd rather stay dry.
50:42After 20 days at sea with no sign of sardines, the crew kept themselves busy
50:47with some sound recording for the film.
50:52I didn't take my mask, you see, so I don't intend to dive.
50:58The team developed some ingenious techniques to get microphones close to the dolphins and gannets
51:03that were also waiting for the sardines.
51:07So what we're doing today is trying a radio mic and a Frenchman.
51:14The problem is he doesn't know when to stop talking.
51:19He's the quietest we've had him for days, but he's still rabid.
51:26No one was prepared for what happened next.
51:32The thing is, these aren't waterproof at all.
51:34Shark, shark! Quick, quick!
51:36Go, go! Quick!
51:50He bit me. Big copper.
51:53It's late, it's murky water, we cannot stay there too long, you see.
52:00And they come right underneath you.
52:01No, he bit my fins. I kicked.
52:04Seriously?
52:05Yeah, I told you, they are sharks, so come and fetch me.
52:11The sharks were definitely about.
52:14But the first season ended without Didier seeing any sardines.
52:24At the beginning of the second year, the pressure was on, but things were looking up.
52:32With the help of aerial spotter Eric Weber,
52:34Didier and the team could search a greater stretch of ocean.
52:42For the first time in three years, a huge slick of fish had been swept up the coast.
52:48The sardine run was well and truly on.
52:54And it was down to the eye in the sky to get Didier into the heart of the action.
52:59We've got thousands of sharks approximately 200 meters offshore.
53:03If you guys make your way out there, and if you're mad enough to go into the water,
53:07I'll talk you on to it, guys. It's really looking good.
53:10Just sharks, sards all over the place.
53:12Raven, we are in the area. Didier wants us to deploy on the highest concentration of sharks.
53:17Could you please guide us onto that area?
53:19Come 20 degrees left. You've got 40 meters to run.
53:2240 meters to run. I'm going to put you in the front of the sard.
53:27Seconds to run. Seconds to run. Divers ready.
53:299, 8, 7, 6, 5.
53:35Divers ready. 4, 3, 2, 1. Go. Divers away.
53:42The great tide was indeed living up to its name.
53:52At last, Didier had some action to film.
53:55He had good visibility and sardines in abundance.
54:03But without dolphins around, the feeding fences just weren't happening.
54:09The sharks were unable to feed on the vast walls of fish,
54:12and despite their impressive numbers, they were surprisingly wary of Didier.
54:19No, very quiet. Moving slowly. They are the lords of the sea.
54:25No, there was no frenzy, no attack. I think they get prepared for the big action.
54:32Didier had yet to even see a big bait bore,
54:35and there was only one week left for all the elements to come together.
54:39Clean water, lots of sardines, and just the right mix of predators.
54:45And if there was one place to find it, it was Waterfall Bluff.
54:51Huge numbers of predators were starting to gather.
54:57This was the most action the underwater crew had seen in two years,
55:00and again it was down to Eric to put them on it.
55:05John, this is Robert. We've got some major activity just off Combati.
55:11They were into the last week of filming, and the pressure was showing.
55:16John, this looks very, very good.
55:19Two o'clock, just yet. But it's moving quite fast.
55:22Because the dolphins are chasing us.
55:24Make it slow. Go right, 90 degrees.
55:27The tricky part is actually getting us onto the bait bore without breaking it.
55:36Hey, you've ridden over the bait bore.
55:40Just stop.
55:42I think you've just screwed that up.
55:44Don't get there. Move the boat. To the right.
55:49Below Eric. It's below Eric. Where's Eric?
55:52We shall go outside there.
55:57Now we have to go fast. We have to think faster.
56:01On the second to last day of filming, Didier finally got his chance.
56:06Go, Didier.
56:11Years of work had gone into putting Didier on the front line.
56:15Now it was down to him.
56:18After 90 days of filming, he had less than an hour in which to fulfil his dream.
56:25To film a bait bore in perfect conditions.
56:48Didier was at last amongst the greatest gathering of predators on the planet.
56:57He'd managed to get closer than anyone to the feeding frenzy.
57:02Without becoming part of it.
57:05Today was the day. We'd just found a bait bore.
57:08We were looking for months, years.
57:12And we finally found it.
57:15Only one problem.
57:17The sharks were too much aggressive.
57:19We were very... We got bored.
57:22We were very angry.
57:24We were very angry.
57:26We were very angry.
57:28We were very angry.
57:30We were very angry.
57:32We were very... We got bumped a few times by sharks.
57:35And that was just a bit, you know, serious.
57:41All that action came and that was just an amazing spectacle.
57:44All those birds diving together.
57:49Like real cannon explosion.
57:53And all those sharks and their following and the dolphins.
57:57That was just magical. Magical.
58:03The feeding frenzy they filmed that day ended as quickly as it had begun.
58:08After two long years, Didier and the crew
58:11had managed to be in just the right place at just the right time
58:15for one of our ocean's greatest events.