Ocean.Giants.S01e03.Voices.Of.The.Sea
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00:30A giant sperm whale preparing to dive over a kilometre into the abyss.
00:51On its epic dive, it will hold its breath for longer than this programme lasts.
01:05And it will hunt, using the loudest sounds made by any animal on the planet.
01:20Hidden beneath the waves, whales and dolphins lead extraordinary lives.
01:42Travelling the world's oceans, we follow the scientists who have dedicated their lives
01:47to these incredible animals.
01:50They live in a world that's so foreign to us, and give us just a glimpse of their lives.
01:57I think we could talk with the dolphins within five years.
02:09Sharing these breathtaking encounters, two of the world's top underwater cameramen.
02:15It was certainly the biggest whale that I've ever seen.
02:18It just looked enormous underneath me.
02:21Fantastic.
02:22Today is the best day of my life.
02:27To survive in this alien world, whales and dolphins have developed unique powers.
02:36Killer whales use sound as a weapon.
02:42Whales sing their hearts out to the world.
02:49These strange creatures even see with sound.
02:59They are the voices of the sea.
03:13An estuary in Tasmania, Australia.
03:22Mighty sperm whales lie stranded.
03:38Something's gone wrong with their powers of navigation, and the consequences are deadly.
03:56Disorientated and without sufficient water to support its bulk, this great whale is slowly
04:03dying.
04:08Luckily, help is at hand.
04:19These rescuers use their boat to create a wave, trying to wash him into deeper water.
04:40They carefully cover up his sunburned skin.
04:46And finally, they use a net to tow him to safety.
05:09Free at last.
05:18Once clear of the shallows, he starts sending out loud clicks, using the echoes to form
05:26a mental picture of the world around him.
05:34Soon, he is back in the safety of deep water.
06:04Sperm whales don't just use sound to navigate.
06:09Their voices are central to their very existence.
06:21Sperm whales are regular visitors to the very deep waters of the Caribbean island of Dominica.
06:37Here, scientists are trying to understand how sperm whales use sound underwater.
06:52It's a source of endless fascination for biologist Shane Gero.
06:56I think I really like the sperm whales in particular, because they're deep divers.
07:02They live in a world that's so foreign to us, and give us just a glimpse of their lives.
07:07It's almost as if they have this big secret that they're not willing to share, and I just
07:11have to dig away and try and figure out what that is.
07:17The team head out into deeper waters, home of the sperm whales.
07:32But finding them won't be easy.
07:35Sperm whales spend most of their time at depth, only returning to the surface to breathe.
07:50Andrew Armour and his crew have been following these whales for over a decade.
07:58Today they're joined by underwater cameraman Didier Noirot and Doug Allen.
08:09The trick to finding sperm whales is to use an underwater microphone, or hydrophone, and
08:15catch them doing what they do best, making noise.
08:24Sound travels faster and further in water than in air, so the team will be able to hear
08:30any whales long before they see them.
08:36So what you want to hear is a series of clicks.
08:39The more you hear the better.
08:40If it sounds like popcorn or bacon frying, we're going to have a good day.
08:46I'm afraid the frying pan's empty.
09:10Sperm whales are the largest predators on the planet.
09:14There's the male.
09:15Wow, he's really well-harnessed.
09:16But even they have enemies, pilot whales.
09:25They will attack the sperms.
09:26They'll go out, eat the babies, and we've seen this interaction.
09:29The pilot whales will attack the sperm whales?
09:33Yeah.
09:35Confident that pilot whales don't usually attack humans, Didier is keen to take a closer
09:41look.
10:10Close cousins of the killer whale, pilot whales are only a third of the size of an adult sperm
10:16whale, but they have strength in numbers.
10:26Hunting in packs up to a hundred strong, they too will be listening out for the sounds of
10:32sperm whales.
10:51There is a chance that if we keep following these pilots that we'll end up tracking them
10:56as they track the sperms.
11:13At last the team begin to hear sperm whales, but these aren't clicks for navigation, these
11:20are clicks for communication, known as codas.
11:35It gets hard to count more than three, because after you get, it might be a click, oh, alright
11:54This is the chance to get close to the world's largest predator.
12:45Sperm whale families may contain several generations of daughters with their babies, overseen by
12:56a wise old grandmother.
13:08Shane believes that they communicate through a complex array of coda clicks, which vary
13:14from family to family.
13:21But they can also put these clicks to far more lethal use.
13:26It's time for the adults to feed.
13:33For the last 15 minutes, the adult whales have been deep breathing to store as much
13:39oxygen as possible in their huge muscles.
13:44Now it's time to dive.
14:14Doug and Didier can only hold a lungful of air, so their depth limit is around 60 feet.
14:40And with oxygen stored in their muscles, the sperm whales can go 100 times deeper and stay
14:47down for over an hour.
14:52Until recently, no one knew how sperm whales hunt in the abyss, but scientists now believe
15:00it happens like this.
15:07The reason sperm whales dive so deep is that there's lots of food down there, including
15:16giant squid over 30 feet long.
15:34A kilometer down, there's no light.
15:37The whale must find its prey through echolocation, interpreting the echoes of the clicks it makes.
15:47But these are no ordinary clicks.
15:50These hunting clicks are the loudest sounds made by any living thing, louder than a thunderclap.
16:03Induced in its five-ton nose, the whale's clicks travel backwards, then are reflected
16:08forwards through a series of oil-filled lenses, which focus them into a narrow sound beam,
16:16like a sonic laser.
16:24For the giant squid, there's nowhere to hide.
16:42While the adults are hunting, their infants are left at the surface, babysat by an auntie
16:49or sister.
16:52But even the best babysitters can lose track of their charges at times.
17:19Out of the blue, a baby heads straight for the boat.
17:26Unusually, it's all alone.
17:38It takes refuge between the hulls, maybe mistaking them for other whales.
17:57As Doug approaches, it calls out with a stream of loud clicks.
18:14It is said that when an adult sperm whale clicks at a diver, it's like being kicked
18:20in the chest by a horse.
18:26While this infant's coda clicks may not be as powerful, they will still carry for more
18:31than a kilometre, down to where the adults are feeding.
18:56From out of the blue, the baby's mother appears.
19:14Ignoring Doug and Didier, she gently shepherds her baby back to the family.
19:36It was super.
19:42We heard a lot of clicks.
19:44There was a lot of clicks.
19:45Yeah, a lot of clicks.
19:46Well, he was clicking at me.
19:47Yeah, he was clicking.
19:48He was calling her mom, you know, because he was without the boat.
19:51The mom came quickly to fetch him.
19:53She came right up and took him away.
19:55Through their remarkable manipulation of sound, sperm whales are able to communicate, navigate
20:12and even hunt in the pitch black abyss.
20:26For a whale, there's no tougher place to survive than here, in the frozen Arctic Ocean.
20:49It's home to the most bizarre looking of all toothed whales.
21:04The unicorn of the sea.
21:12The narwhal.
21:19To reach new fishing grounds, these whales must migrate huge distances through constantly
21:37shifting fields of ice.
21:49Unable to hold their breath for more than 20 minutes, they must find regular breathing
21:56holes in the ice.
22:00Or they risk becoming trapped, starving or drowning.
22:14So, how do they find these tiny air holes dotted across the vast sheets of ice?
22:31Like sperm whales, narwhals can echolocate.
22:44They fire off a series of sonic pulses and use the echoes to map the world around them.
22:54In this way, they can locate vital breathing holes from hundreds of feet away.
23:13As winter closes in, the sea around the narwhals begins to freeze over, leaving them with fewer
23:30and fewer holes in the ice.
24:13Only by using their sophisticated powers of echolocation can the narwhals find enough
24:30air holes to survive.
24:34But at least narwhal can see the fish they're after.
24:41One group of dolphins is not so lucky.
24:45They live in the last place you might expect to find a dolphin.
24:535,000 kilometers inland, in the heart of the Brazilian rainforest.
25:03Flowing through it, the mighty Amazon River.
25:10The planet's largest freshwater system.
25:20In some ways, it makes perfect sense for a dolphin to make its home here.
25:28There are more species of fish in the Amazon than in the whole Atlantic Ocean.
25:36But how can a dolphin catch fish in water so muddy that it can't see a thing?
25:56Cameraman Doug and Brazilian scientist Vera da Silva are on their way to investigate.
26:04It's very, very beautiful. I'm looking forward to going down there.
26:08But we'll be traveling everywhere by boat.
26:10Just rivers and water.
26:12And lots of dolphins.
26:14Lots of dolphins.
26:22This is the creature Vera is studying.
26:26Perhaps the strangest dolphin of all.
26:30The Boto, or Amazon River Dolphin.
26:52Doug is having trouble finding any Botos.
26:56For a better view, Vera must take Doug to a very special place.
27:04In the wet season, one of the Amazon's tributaries, the Rio Negro, breaks its banks.
27:12And floods an area of jungle the size of France.
27:16This unique water world is known as the Flooded Forest.
27:26The water is clearer here than in the main river,
27:32but it's choked with branches and leaves, and as dark as well-brewed tea.
27:50Finding these strange creatures is a challenge.
27:54Finding these strange dolphins hidden in the forest would be impossible
27:58if it were not for their natural curiosity.
28:02Come on, Botos.
28:04They are there.
28:06Yeah, they'll be there.
28:08Look, look, look.
28:10Right here, another one there.
28:12They start showing up.
28:14Having spotted some Botos, Vera uses her hydrophone to listen to their calls.
28:20Let's see how much noise these guys are doing now.
28:24Oh, OK.
28:32Do you want to listen?
28:34Yes, a little bit.
28:38Yeah, now I heard, yeah.
28:40Like a sergeant.
28:42Oh, no.
28:46I can't have it.
28:50Oh, yeah, yeah.
28:54The dolphins are very noisy, but what are these sounds for?
29:02To find out, Vera and Doug first need to attract the dolphins close to the boat.
29:08So is there a secret to bringing them closer?
29:12Yes, sometimes they will react to the noise or to some fish.
29:16If we give them some fish, they will come quickly.
29:22See, three at the same time.
29:30The bizarre-looking Boto shows off its slender, toothy body.
29:36It shows off its slender, toothy snout.
29:42And the enormous bulge on its forehead called the melon.
29:48But to find out how it uses them underwater, Doug will need to dunk himself in the tea.
30:06The Boto's are using two completely separate sound systems.
30:14The chattering noises are the sound of them talking to each other.
30:20The Boto's are using two completely separate sound systems.
30:26The chattering noises are the sound of them talking to each other.
30:30But they also appear to be scanning Doug with strange clicks and buzzes.
30:46This is their echolocation in action.
30:50This is their echolocation in action.
30:54This is their echolocation in action.
31:18He came up, took the fish and he swam backwards.
31:23He came up, took the fish and he swam backwards.
31:25I've never seen a dolphin swim backwards before.
31:37The Boto's lead Doug deeper into their underwater forest.
31:41Where echolocation allows them to navigate safely through this tangle of submerged vegetation.
32:01The Boto's clicks and buzzes are focused into a soundbeam by a fish.
32:07The Boto's clicks and buzzes are focused into a soundbeam by its bulging forehead melon.
32:19The beam works like a sonic head torch.
32:23Allowing the dolphin to build up a clear picture of its surroundings.
32:27It's as tangled and spiny under water as it is on the surface.
32:33Those Boto's are going to need all the maneuverability and all the sonar skills they possess to operate in this sort of under water environment.
32:43While all dolphins can echolocate, Boto's can't.
32:47While all dolphins can echolocate, Boto's clicks have a higher frequency and better
32:59resolution than any other dolphin, allowing them to distinguish objects as small as a
33:05pin.
33:16Even in zero visibility, catching fish is child's play.
33:33These are the weirdest dolphins that I've ever seen, absolutely, they're just fantastic.
33:43The world of Boto's is a noisy one, full of clicks and buzzes.
33:58There are others that use sound as a sophisticated weapon, including a remarkable population
34:05found off Iceland in the North Atlantic Ocean.
34:11On the Vestman Islands, a team of whale scientists is joined by cameraman Didier Noirot.
35:00Large numbers of killer whales have gathered to hunt the vast shoals of herring that come
35:08here to spawn each spring.
35:23But the coordinated and fluid movements of the shoals make them exceptionally hard to
35:28catch.
35:36So how do these huge predators manage to catch the herring, and in sufficient numbers, to
35:43make it worthwhile?
36:11Scientist Volker Diecker is an expert in killer whale acoustics.
36:16Volker, where do you think we'll find the killer whale?
36:19We've had really good success right in this area.
36:21Recently, Volker has been investigating how killer whales break through the herring's
36:26defences, and he thinks it is to do with sound.
36:40To prove his theory, he and Didier need to get right in close to the action.
37:00Having reached the area where the whales were last seen, Volker deploys his underwater
37:06microphones.
37:18A gathering of seabirds means the herring shoals must be close to the surface.
37:25Something must have spooked them.
37:30Seven or eight together came at the top of the wave.
37:35Killer whales.
37:38Volker is perfectly positioned to record the sounds of the hunting whales.
37:44It'd be great to see what the whales are doing underwater when they're making all these
37:52sounds.
37:54To capture the video evidence, Didier uses a pole camera.
37:59You are the ears and the eye.
38:03Getting in the water with feeding killer whales would be too dangerous in this poor visibility.
38:28Volker gathers his evidence.
38:49After two hours of intensive feeding, the killers have fallen silent.
38:57The attack is over.
39:02Back at HQ, the team analysed the killers' calls and revealed the whales' secret weapon.
39:09And what you're going to hear is a lot of echolocation clicks, but then you'll hear
39:12something pretty special.
39:14Here we go.
39:16Whistles echolocation.
39:21And now have a good listen.
39:31This high-pitched note is what's known as the herding call.
39:50The idea is that the whales may be using the sound to essentially cause resonance in
39:55the herring swim bladder that makes the herring's gut vibrate, and that makes the herring very
40:00uncomfortable.
40:01Panicked by the gut-wrenching noise, the herring bunch so tightly together they have no room
40:11for manoeuvre.
40:14The killer whales then deliver devastating tail swipes with the force of an exploding
40:25grenade.
40:40With the job done, the whales can relax over a leisurely feast of stunned fish.
40:56Whales and dolphins use their voices to keep the family group together, but there are times
41:03when talking just isn't enough.
41:17In the rich waters off New Zealand, hundreds of dolphins travel together in super pods.
41:33Moving in such large groups requires clear communication.
41:42But clicks and whistles only have a limited range.
41:52The only way to broadcast messages across the group is by generating louder, more explosive
41:58sounds.
42:04Different body smacks convey different meanings.
42:11It's thought dolphins may use such acrobatic leaps to signal the discovery of large shoals
42:49Body percussion is a key ingredient in dolphin communication.
43:04One enduring mystery surrounds the most celebrated musical event in nature, the songs of the
43:10humpback whale, currently playing off the islands of Hawaii in the middle of the Pacific
43:17Ocean.
43:33Before the singing can begin, the performers must give a masterclass in percussion.
43:46Forty-ton bodies hit the sea with an ear-splitting crash, and giant tail flukes thunder out a
43:57message to rival males.
44:12Didier makes sure to get a front row seat.
44:30The ocean reverberates with explosions of bubbles.
45:00And then the opera begins.
45:30The song of the humpback is something really beautiful.
45:42It's the most beautiful sound you can hear in the sea.
45:48You're the scientist.
46:02Jim Darling has spent the last 30 years trying to work out the meaning of these extraordinary
46:08songs.
46:11It's very close.
46:21Wow.
46:23There are a few of them, huh?
46:25Yeah, there's a few.
46:26There's one close, and three or four in the background.
46:28Okay.
46:29Yeah, we have a beautiful sound.
46:41With his mouth shut tight, shunting air back and forth through a larynx the size of a phone
46:47box, technically he's humming, not singing.
46:55Whatever it is, it's a voice that can travel thousands of kilometers across entire oceans.
47:10The male's recital may include half a dozen distinct themes which he's learned from other
47:34males.
47:38He may even add his own improvised variations.
47:46By copying sequences from each other, males constantly evolve their repertoire.
47:58But does it have a purpose?
48:01For a long time, it was presumed that the singers were singing to attract a female.
48:09And I think people like that idea because it's been written about a lot.
48:13But there's not a shred of evidence for it.
48:16We've never seen a female approach a male.
48:20If they aren't calling a mate, then why are they singing?
48:26Is it a way for males to size each other up?
48:31Could they even be making music for pleasure?
48:37The truth is that nobody knows.
48:56The enigmatic voices of whales and dolphins have captured our imagination for centuries.
49:07Scientists may one day find out the whole truth behind these extraordinary voices of the sea.
49:15But for now, the private life of these ocean giants remains wonderfully mysterious.
49:56Transcription by ESO. Translation by —