科学美国人60秒：飞蛾和蝙蝠的故事

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Moths Have an Acoustic Invisibility Cloak to Stay under Bats' Radar

飞蛾和蝙蝠的故事

Karen Hopkin: This is Scientific American’s 60-Second Science. I’m Karen Hopkin.

凯伦·霍普金:这里是科学美国人60秒科学栏目。我是凯伦·霍普金。

[CLIP: Audio of bat calls]

【音频：蝙蝠的叫声】

Hopkin: Bats use echolocation to hunt for their meals, and moths are often on the menu. But in the acoustic arms race between predator and prey, moths also have a trick or two up their sleeve—or, actually, on their wings, because a new study shows that moth wings are covered with scales that absorb sound, particularly the ultrasonic variety preferred by bats.

霍普金:蝙蝠利用回声定位来捕食，飞蛾也经常出现在它们的食谱上。但在捕食者和被捕食者之间的声音武器竞赛中，飞蛾也有一两个诀窍——实际上是在它们的翅膀上。因为一项新的研究表明，飞蛾的翅膀上覆盖着能吸收声音的鳞片，尤其是蝙蝠喜欢的各种超声波。

Thomas Neil: So moth and butterfly wings are covered in layers of scales. These are made of a naturally occurring polymer called chitin, which is a polymer you find in most insect and crustacean exoskeletons.

托马斯·尼尔：飞蛾和蝴蝶的翅膀上都覆盖着鳞片。它们是由一种叫做甲壳素的天然聚合物构成的，这种聚合物存在于大多数昆虫和甲壳类动物的外骨骼中。

Hopkin: That’s Thomas Neil of the University of Bristol. He started out by bombarding bits of moth wings with sound and seeing what bounced back.

霍普金:这是布里斯托尔大学的托马斯·尼尔。他先用声音“轰击“飞蛾的翅膀，看看有什么东西反弹回来。

Neil: We discovered that moth scales actually resonate in response to being hit with ultrasound. And they resonate at frequencies that pretty much perfectly match the frequencies that bats use for echolocation.

尼尔：我们发现飞蛾的鳞片在被超声波击中时会产生共鸣。它们共振的频率与蝙蝠用于回声定位的频率非常吻合。

Hopkin: That vibration converts sound energy to mechanical energy, which muffles the echo that gets back to the bats.

霍普金:这种振动将声能转化为机械能，从而抑制了传回蝙蝠的回声。

Neil: That probably hasn’t happened by accident, that these scales are such a shape and size that they’re resonating at just the right frequencies that they can absorb sound energy from hunting bats.

这可能不是偶然发生的，这些鳞片的形状和大小使它们能以合适的频率共振，从而吸收捕猎蝙蝠的声音能量。

Hopkin: Next, Neil and his colleagues modeled the sound-dampening capabilities of an array of different scales.

霍普金:接下来，尼尔和同事们模拟了不同程度的减声能力。

Neil: The really cool thing about moths is their scales are all different shapes and sizes. So what we found is that each individual scale will resonate at slightly different frequencies—and that, collectively, they actually absorb a really broadband range of frequencies.

尼尔：飞蛾最酷的地方是它们的鳞片形状和大小各不相同。因此，我们发现，每一个音阶都会在略微不同的频率上产生共鸣，而总的来说，实际上，这些鳞片吸收的声音频率范围很宽。

Hopkin: That range covers the frequencies of bat echolocation calls—findings Neil presented at the Meeting of the Acoustical Society of America.

霍普金:这个范围涵盖了蝙蝠回声定位呼叫的频率，这是尼尔在美国声学学会会议上提出的发现。

Neil: So it means that the moths should be pretty well protected from a whole host of bats that they might interact with out in the wild.

尼尔：所以，这意味着这些飞蛾应该得到很好的保护，免受在野外与蝙蝠互动的影响。

Hopkin: But does the strategy actually work?

霍普金：但是这个策略真的有效吗?

Neil: So we don’t actually know how effective these scales are at protecting moths in the real world. But from everything we can model and measure and predict, it seems like they would have quite a considerable advantage in trying to hide these moths from bats hunting at night.

尼尔：所以，我们并不知道现实中这些策略能多大程度上保护飞蛾。但从我们建模、测量和预测的一切来看，这些策略在帮助飞蛾躲避夜间捕食的蝙蝠有很大的优势。

Hopkin: For any bats that might be listening, Neil says there’s not much you can do to thwart this moth maneuver.

霍普金:尼尔说，对于任何可能在听的蝙蝠来说，你无法阻止这种飞蛾的行动。

Neil: The only real thing that they could do would be to call at higher amplitudes, so to increase the strength of their own echolocation calls such that the echo they got from a moth would be stronger.

尼尔：蝙蝠唯一能做的就是用更高的振幅发出叫声，这样一来，它们自己的回声定位叫声的强度就会增加，这样从飞蛾那里得到的回声就会更强。

Hopkin: In other words, you might catch more moths with a shout than with a whisper.

霍普金：换而言之，大喊比悄悄说话能捕捉更多的飞蛾。

Moths Have an Acoustic Invisibility Cloak to Stay under Bats' Radar

Karen Hopkin: This is Scientific American’s 60-Second Science. I’m Karen Hopkin.

[CLIP: Audio of bat calls]

Hopkin: Bats use echolocation to hunt for their meals, and moths are often on the menu. But in the acoustic arms race between predator and prey, moths also have a trick or two up their sleeve—or, actually, on their wings, because a new study shows that moth wings are covered with scales that absorb sound, particularly the ultrasonic variety preferred by bats.

Thomas Neil: So moth and butterfly wings are covered in layers of scales. These are made of a naturally occurring polymer called chitin, which is a polymer you find in most insect and crustacean exoskeletons.

Hopkin: That’s Thomas Neil of the University of Bristol. He started out by bombarding bits of moth wings with sound and seeing what bounced back.

Neil: We discovered that moth scales actually resonate in response to being hit with ultrasound. And they resonate at frequencies that pretty much perfectly match the frequencies that bats use for echolocation.

Hopkin: That vibration converts sound energy to mechanical energy, which muffles the echo that gets back to the bats.

Neil: That probably hasn’t happened by accident, that these scales are such a shape and size that they’re resonating at just the right frequencies that they can absorb sound energy from hunting bats.

Hopkin: Next, Neil and his colleagues modeled the sound-dampening capabilities of an array of different scales.

Neil: The really cool thing about moths is their scales are all different shapes and sizes. So what we found is that each individual scale will resonate at slightly different frequencies—and that, collectively, they actually absorb a really broadband range of frequencies.

Hopkin: That range covers the frequencies of bat echolocation calls—findings Neil presented at the Meeting of the Acoustical Society of America.

Neil: So it means that the moths should be pretty well protected from a whole host of bats that they might interact with out in the wild.

Hopkin: But does the strategy actually work?

Neil: So we don’t actually know how effective these scales are at protecting moths in the real world. But from everything we can model and measure and predict, it seems like they would have quite a considerable advantage in trying to hide these moths from bats hunting at night.

Hopkin: For any bats that might be listening, Neil says there’s not much you can do to thwart this moth maneuver.

Neil: The only real thing that they could do would be to call at higher amplitudes, so to increase the strength of their own echolocation calls such that the echo they got from a moth would be stronger.

Hopkin: In other words, you might catch more moths with a shout than with a whisper.