大卫·艾登堡：大自然的声音David Attenborough: The Sounds of Nature #生活记录 #艺术 #纪录片

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