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AnimalsTranscript
00:00The natural world is filled with sound, but so far, we've been hearing nothing.
00:29We've been hearing only part of it.
00:34The most advanced audio technology can now record sounds that we can't even hear.
00:52For some animals, sound is the key to survival.
00:59They use sound to hunt...
01:05and escape.
01:14Sound can make the difference between life and death.
01:24It's time to open your ears to life as you've never heard it before.
01:54Dawn on the African savannah.
02:17It's the best time of the day for lions to broadcast their message.
02:41As the sun rises, cold air is trapped near the ground.
02:53Because it's denser than warm air, it allows sound to travel further before dissipating.
03:04It's a declaration to other prides of his ownership of these hunting grounds...
03:11and the key to his and his pride's survival.
03:18It's one of the greatest acoustic displays of power in nature.
03:39It can be heard up to five miles away.
03:46But even this isn't far enough to reach the boundaries of their territory.
03:53It spans over 150 square miles.
03:58To defend an area as immense as this, the pride must roam and roar.
04:10Some members are too small to get very far.
04:20This pride is protected by three brothers.
04:26Together, they head off on patrol.
04:34A lion's roar sends a clear message to other prides.
04:43The sound can also be used in more subtle ways.
05:09This garden is filled with the sound of the buzzing of bees.
05:14It's a sign that the plants have been successful in attracting pollinators...
05:19with their brightly colored flowers and seductive smells.
05:28The buzzing sound we associate with bees is a by-product created by the beating wings as they fly.
05:41But some bees take advantage of their buzz and use it in a surprisingly sophisticated way...
05:48to a supply of food that others can't reach.
06:00One such bee lives underground.
06:10These are buff-tailed bumblebees.
06:15For the colony to survive, each worker must collect as much pollen as she can with which to feed their young.
06:25Searching for it is a constant preoccupation.
06:50It's spring in England.
07:03And she is not the only one in search of food.
07:09Competition for pollen and nectar is high.
07:14And poppies are putting on a show.
07:20Packed full of pollen, they flaunt it at the top of long filaments called anthers.
07:29These flowers are a free-for-all, and everyone is seeking a share of the bounty.
07:54But she doesn't need to compete with other species if she can find a particular kind of flower.
08:11She's found what she's been looking for...
08:16a type of nightshade.
08:25Its flowers are less striking, and unlike poppies, its pollen is locked up inside long yellow anthers.
08:36The only way for it to escape is through tiny holes.
08:44The bumblebee holds the key that unlocks this treasury of pollen.
08:50Sound.
08:53Locking in her wings, she uses her flight muscles to vibrate her whole body, buzzing up to 370 times a second.
09:09This sonic assault blasts the pollen loose.
09:25She then grooms the pollen down into sticky sacks on her legs and flies off to the next flower.
09:39Very few species can buzz-pollinate in this way, so bumblebees have nearly exclusive access to the nightshade's pollen.
09:55The bee's pollination buzz is higher-pitched than that made during flight.
10:03It's the same frequency as the musical note D.
10:14She's like a living tuning fork.
10:18Some buzz-pollinators can vary their pitch, fine-tuning it to suit different flowers, so pollen is released in the most efficient way.
10:33Fully loaded, she returns to the hive.
10:44She has successfully used sound to help secure the pollen her colony needs.
10:56We tend to take bees for granted, but it's not just plants that depend on them, we do too.
11:05Many of our crops rely on pollinators like bees and other insects.
11:12Worryingly, bee populations, together with those of many other insect pollinators, are in serious decline around the world.
11:23And with their numbers plummeting, both the natural world and our own food supplies are in danger.
11:32Bees need our help, and without them and the sound of their buzz, the future for us all would look bleak.
11:48Sound provides the key to this partnership between bumblebees and plants.
11:56But not all relationships in nature are as harmonious.
12:05The Bahama Islands in the Caribbean.
12:15The sand flats here are the home of garden eagles and razorfish.
12:30But there is trouble in paradise.
12:36The sound of approaching danger.
12:43There's a queue to hide.
12:55A mixed group of spotted and bottlenose dolphins.
13:04Their whistles and squeaks are part of their continuous conversations.
13:10Their range of frequencies seven times greater than ours.
13:26To hunt for food, they must split up.
13:31Each dolphin needs 15 kilograms of fish a day.
13:39But thanks to their rowdy arrival, there isn't a morsel in sight.
13:47The hunt is on.
13:51The bottlenose dolphins now switch from whistles to bursts of fast clicks, up to 200 per second.
14:19These high-frequency clicks are sent out like a sonar beam through an organ in the forehead called a melon, with which they can scan the ocean floor.
14:39When the beam of sound hits a fish hiding beneath the sand, it's reflected back, revealing its location.
14:48Using echolocation, the dolphins are able to create a visual map of what is hidden under the sea floor.
15:07Some of these clicks are ten times higher than the sounds our ears can detect.
15:16High-frequency sounds are most effective at close range, enabling the dolphins to pinpoint their prey with great precision.
15:32But there is more to these pirouettes than meets the eye.
15:39Scientists have recently discovered that bottlenose dolphins favour their right side when scanning the seabed.
15:49The right side of the head usually produces the sonar clicks, and the right side is also better at detecting the returning echo.
16:10The only evidence that there has been a sonar search here are small craters in the sand.
16:19Dolphins use sound with great effect to find their food, but in other places, a quieter approach is the key to a successful hunt.
16:50In the forests of Manitoba in Canada, the great grey owl is a master of silence.
17:03Specially adapted flight feathers allow him to approach silently.
17:18His prey is hidden under a blanket of snow.
17:43Voles.
17:47Finding them in this vast snow-covered landscape seems an impossible task.
17:57To combat the extreme cold, he must catch seven voles a day.
18:04His ears will be his most effective weapon.
18:13Voles need to feed continuously, or they will freeze to death.
18:24They constantly dig tunnels to find new food supplies, unaware of the danger above.
18:38Hidden under a face covered by feathers, the owl's ears are positioned at slightly different levels on either side of his head.
18:49Sound will hit one ear before the other, allowing him to pinpoint his prey with great accuracy.
19:01His acoustic arsenal doesn't stop there.
19:08The large facial ruff, formed from feathers that are particularly stiff and dense, help to amplify sound and funnel it towards the ears.
19:31Through half a meter of snow, the sound of scampering feet is inaudible to us, but it's loud enough for him.
19:48With the help of a specialist camera equipped with 60 highly sensitive microphones, we can reveal what the owl is hearing.
20:00The camera visualizes where the vole is beneath the snow.
20:19And he's off.
20:31This time, he's missed.
20:50Despite his acute hearing, hunting in snow is a challenge.
20:56The snow not only muffles sound, it bends it, too.
21:04While it appears as if the vole is here, it's actually over there.
21:10The only way to defeat this acoustic illusion is for the owl to get directly above the vole, where sound is no longer distorted by the snow.
21:24As he flies, he tracks the sound as it changes.
21:36The closer he gets, the less the sound is bending.
21:41Directly above the vole, he can pinpoint his target.
21:46The closer he gets, the less the sound is bent.
21:56Directly above the vole, he can pinpoint his target.
22:16The great grey owl's hearing is its key to securing a meal.
22:24For others, it's crucial to avoid being eaten.
22:31In the Arizona desert, it's the height of summer.
22:37Daytime temperatures are over 40 degrees Celsius.
22:43So it's best to be active at night.
22:48Filming under infrared lights with a specialist camera, we can see everything.
22:59But to a kangaroo rat, it's nearly pitch black.
23:06In the dark, her most valuable ally is sound.
23:13Sound
23:19Her mission tonight is to collect as many seeds as she can.
23:26But food is scarce and competition fierce.
23:36And in the dark, it's hard to spot danger.
23:43Sound
23:49Her ears are 90 times more sensitive than ours,
23:53and hollow spaces in her skull act like an echo chamber,
23:57amplifying the faintest of sounds.
24:06But she has another problem tonight.
24:13Wind.
24:23She might not hear a predator until it's too late.
24:32This time, it's just a stick.
24:36But in the darkness, she's right to be cautious.
24:43Snakes can pick up the sounds of scampering feet through their lower jaw.
24:57She's made it to her favorite feeding spot.
25:01But she's not alone for long.
25:13She warns him to stay away by drumming her foot on the ground.
25:25He can decipher her size and strength from her signal.
25:35He comes back.
25:40It's a battle of beats.
25:51Stalemate, there's only one way to resolve this.
26:10Sound
26:22Dinnertime at last.
26:26Sound
26:36She hears something.
26:45Just out of striking range, she drums again.
26:52This time to alert the snake it's been spotted.
26:58But just to be sure.
27:11Message received.
27:15Sound
27:20While kangaroo rats use the ground as a drum to drive their enemies away,
27:26others are summoned by seismic sounds.
27:34Sound
27:39Sound
27:45Sound
27:50Amboseli National Park in Kenya.
27:55It hasn't rained here in nearly a year.
28:01And the dry season has turned into a severe drought.
28:07Sound
28:12For elephants, the situation is desperate.
28:19With no food or water for miles around, the matriarch must wait for a message.
28:25A sound that will travel through the ground.
28:31Sound
28:37If it arrives, it will guide them from disaster.
28:44The young calves are especially vulnerable.
28:50Sound
28:52Their mother's milk will dry up if rain doesn't arrive soon.
28:58Sound
29:03Sound
29:11A hundred miles away, a storm has broken.
29:17Sound
29:21And the elephants have heard.
29:26Sound
29:29Not with their ears, but with their feet.
29:35Sound
29:38The sound of the storm sends low-frequency vibrations through the ground.
29:44Sound
29:48The herd picks up the vibrations through a network of nerves in the fatty pads of their feet.
29:57Sound
30:02By lifting one foot, they can make better contact on the ground with the other.
30:09Sound
30:12It's the message the matriarch has been waiting for.
30:18She gives a low, let's-go rumble.
30:25It's echoed by her sisters.
30:34The journey ahead is treacherous.
30:38But the sound of the storm will be their guide.
30:44Sound
30:55Finally, after two days on the move, they've made it.
31:03Sound
31:05Their ability to detect sound a hundred miles away has saved the herd.
31:12Sound
31:16Elephants aren't the only ones who respond to the sound of rain.
31:24But sometimes sounds can be deceptive.
31:30In Vancouver, in Canada, it's also raining.
31:36Sound
31:54Sound
32:07Underground, the soil is teeming with earthworms.
32:13Some rise to the surface in search of food or mates.
32:21But if the ground isn't wet enough, they risk drying out.
32:27Sound helps them pick the opportune moment.
32:33As the rain hits the ground, it creates vibrations that travel down into the soil.
32:42Sound
32:45They're picked up by sensitive nerve cells in the worm's skin.
32:51As they rise, the tumultuous pitter-patter is music to their senses.
33:01But it is also a sound that conceal their fate.
33:07The worms aren't the only ones on the move.
33:14Outside the city, a flock of gulls are coordinating their morning departure from the roost.
33:22Sound
33:26Sound
33:32Thanks to the rain, they've got a special meal on the menu today.
33:38Worms.
33:41But by the time they arrive, the downpour is over.
33:47Sound
33:49And the worms are already retreating.
33:55Dining options look scarce.
33:59But the gulls have a crafty trick.
34:04For it to work, they must find their rhythm.
34:09Sound
34:15Paddling creates vibrations that likely mimics the sound of rain.
34:22Sound
34:25It's a dance of deception.
34:30The worms rise once again.
34:35Sound
34:39They can't resist the rhythmic rain dance.
34:46Sound
35:02Another shower brings an acoustic climax.
35:08Sound
35:15The rainy season will last all winter, so worms are on the menu until spring.
35:24For these gulls, the cunning use of sound helps them win an easy meal.
35:33But in other parts of the world, the stakes are higher for both predator and prey.
35:42Sound
35:50Sound
35:53As night falls on the African savannah, the air is filled with sounds of a formidable hunter.
36:02Sound
36:15On the other side of the territory, the females of the pride are preparing to hunt.
36:22Over 30 strong, they must make a kill every night.
36:27Sound
36:32Close by a hyena den.
36:36Sound
36:39The adults must also head out to find their next meal.
36:44Sound
36:47Hyenas will often steal if the opportunity arises.
36:53Even from their deadliest foes.
36:57But separated from the males, this pride is vulnerable.
37:03Sound
37:06For a successful heist, the hyenas rely on sound.
37:13First, the lionesses need to make a kill.
37:18With a noisy family in tow, that can be tricky.
37:23Sound
37:26Wildebeest have gathered together for safety.
37:34In darkness, they have to rely on their hearing.
37:39Sound
37:51The lioness makes a stealthy approach.
37:56Sound
38:03But there is a problem.
38:08The porcupine is a playful distraction for the youngsters.
38:13The sound of shaking quills is a warning.
38:18Sound
38:22And the wildebeest have heard the commotion.
38:26Sound
38:29Sound
38:35They have blown it for her.
38:39Sound
38:41But they will take the rattle of shaking quills more seriously next time.
38:46Sound
38:49Sound
38:54The pride have detected another opportunity.
38:59Sound
39:01The warthog burrow.
39:05Sound
39:09Sound
39:21The sound of their feast carries far in the cool night air.
39:27And the hyenas have heard.
39:31Sound
39:38But there are too many lions here to steal this meal alone.
39:44Sound
39:47She will need the full force of her clan.
39:50Sound
39:53She sends a message to rally her troops.
39:56Sound
40:00Sound
40:05Directed at the ground, her message resonates further and faster than it would through air.
40:11Sound
40:21Even with numbers now on their side, sound is critical if they are to steal this meal.
40:27Sound
40:33Calling unites the clan.
40:35They must approach as a tight-knit group, making as much noise as they can.
40:40Sound
40:43Sound
40:46Sound
40:50Sound
41:11The noise of the battle has alerted more lions.
41:16Sound
41:25It's game over for the hyenas.
41:28Sound
41:31The brothers have returned.
41:34Sound
41:47Sound
41:50After a successful night, the pride is well fed.
41:55Sound
41:58Some will spend the day dozing.
42:03But for others, it's time to reaffirm the pride's ownership of their territory.
42:09Sound
42:17Sound
42:24We are only just beginning to understand the many ways that animals use sound.
42:29Sound
42:32For us, the sound of the natural world is a source of peace and tranquility.
42:38Sound
42:40For other animals, it's a tool they have to master in order to hunt and survive.
42:48Sound
42:57Sound
43:01Sound
43:08It's so cold out here.
43:10I think just over here to the left looks pretty good.
43:14Okay.
43:15We have a picture.
43:16Our film crew have come to Manitoba in Canada in search of the great grey owl.
43:23Yeah, that looks like a promising spot.
43:26Okay.
43:28I think there were some owls here last week.
43:32But like many of our shoots, we rely on the work of others who've come before us.
43:39For years, scientists have wondered exactly how the owl penetrates the layers of snow that conceal its prey.
43:51Biologists Chris Clark and Jim Duncan are on a mission.
43:56This is excellent.
43:57There's a plunge hole right here where the great grey hit the snow.
44:02They are armed with a special tool.
44:05I'll grab the battery.
44:06Okay.
44:07An acoustic camera.
44:09This version has 40 sensitive microphones that pinpoint sound while a tiny camera films its exact location.
44:19It should allow them to see exactly what the owl is hearing.
44:24This camera is wonderful because it actually visualizes where the sound is coming from.
44:28And so I'm actually able to look and see how does the environment affect the sound.
44:38Snow is a formidable barrier.
44:45For the vole, it's a cloak of invisibility.
44:50To the owl, it's an obstacle that must be overcome by hearing alone.
44:59The researchers bury a speaker under the snow.
45:02It will play the sound of a foraging vole.
45:08They will bury it at different depths and use the acoustic camera to see how the snow affects the sound.
45:16The speaker is now visible in the camera view.
45:18This black thing right here, that's the speaker.
45:20And the acoustic camera, that blob of color, it's localizing the sound coming right from the speaker itself.
45:28But the playback from the snow-covered speaker reveals a surprise.
45:32The snow dramatically alters the location of the sound.
45:39That meter stick is above the speaker and there's a blob of color where the acoustic camera perceives the sound to be coming out of the snow.
45:47It's amazing.
45:48The snow is actually bending the path that the sound is taking.
45:52As a result, if an owl were to try to localize the sound of the vole from where it hears the sound, it would miss.
45:58It would hit the wrong spot.
46:01But Chris realizes there is a way for the owl to overcome this problem.
46:07As the owl is coming in, it's listening to pinpoint the location of the vole.
46:13Because of the snow, it sounds like the vole is here, when it's actually there.
46:22But as the owl gets closer, it starts to overcome the effect that snow has on the sound.
46:29For the first time, Chris realizes why, at this point in its attack, the great grey owl hovers.
46:38The acoustic camera reveals that it's now in the perfect position.
46:45The sweet spot for the owl is when it's right above the prey, directly above the prey.
46:51Directly above the vole, the snow doesn't bend the sound, so the owl can pinpoint exactly where the vole is.
46:59Only then does the owl plunge.
47:05Wow.
47:06It's completely amazing that these owls can localize their prey just by listening.
47:11I love doing this kind of research, and through that, understand the natural world
47:15and the amazing things that species like the great grey owl are doing.
47:21For decades, researchers had believed that there was more to discover
47:25about the great grey owl's acute hearing.
47:29But now, it's time to find out.
47:33For decades, researchers had believed that there was more to discover
47:37about the great grey owl's acute hearing.
47:42Now, they've finally uncovered the complex ways it uses sound to hunt its prey in snow.
47:52Alrighty.
47:54As the story of sound continues,
47:59we reveal how animals use sound to fight off competition
48:07and use songs in their quest to win a mate.
48:53www.nasa.gov
48:55NASA Jet Propulsion Laboratory
48:58California Institute of Technology