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Every summer evening 1.5 million bats emerge from underneath the Congress Avenue Bridge in Austin, Texas, on a search for their favorite meals of mosquitoes and other insects. To track their tiny flying prey(猎物), the bats make high-pitched(声调高的)sounds that deflect from an insect back to the bats’ large ears. The information from this process of echolocation(回声定位)tells the flying mammals the precise path of their fast-moving food. But how does any single bat in a crowd of thousands know that the ping it registers is not some other bats’ echo? Navigating this potential interference is not only the province of bats, however. Dolphins and other animals that rely on echolocation must also find ways around the maze of found waves around them.

People want to figure out how bats and dolphins do it because these animals are what Laura Kloepper, an assistant professor of biology at Saint Mary’s College in Indiana, calls “bio-inspiration” — helping us to find technological solutions to problems in our everyday life. The built-in biology of an echolocating bat holds secrets that would help human researchers develop better “active sensing” devices that imitate what bats do.

Kloepper highlighted the power of bats’ active sensing abilities in a presentation at the 176th meeting of the Acoustical Society of America that compared them with the powerful echolocating capabilities of dolphins. In her talk, Kloepper told of how her research group attacked a pair of dolphins with artificial dolphin-like clicks to try to confound them as they chose between two options. Her team challenged the marine mammals by pulling tricks such as adjusting the angle of speakers making the sounds to confuse them as they homed in on their targets of choice. What the humans learned was dolphins use two possible strategies to block out the nonsense noise. They either change the frequency of their calls — to a higher or lower pitch — or they change the timing. Either adjustment gives a dolphin a personal call, a signature it can recognize.

Kloepper has, of course, also studied bats. For this research she uses what she calls a “biological drone(生物无人机)”, a trained Harris’s hawk named Belle. Armed with a tiny camera and microphone, Belle wings into the midst of bat crowds and records their many calls for the sake of science. Kloepper says the reason she uses hawks, besides the fact “hawks are super-cool”, is that sending a regular drone with spinning propellers(推进器)into a dense bat crowd “wouldn’t be ideal.” Her team does use drones during night crowds, when the bats fly at greater distances from on another and are less likely to run into the machine.

A dolphin’s click is about a 20th the duration of a bat’s call. This difference, Kloepper says, leaves bats better able to make adjustments to their calls. Whereas a dolphin might change pitch, a bat has a slightly more nuanced repertoire(微妙的技能)to deal with the jamming. “Dolphins make impulsive signals that sound like clicks — sort of if you snapped your fingers together,” Kloepper says — whereas bat calls are more like human whistling. “Sure, we could slightly change some of the characteristics of our fingers snapping,” She notes, “but you could make your whistle go up or down in pitch or even jump between pitches, and you can control how long your whistle is.” Bats show a similar level of fine control over their echolocation, she says.

But the mystery of how bats pull off this jamming countermeasure remains. Researchers’ next step in solving this challenge is to focus on individual bats and their calls. Kloepper predicts “new electronic hardware to go on our drone and hawk that will allow us to really home in on which bat is making which call when it’s in the middle of this massive group.” The dolphins are not left out either. Kloepper plans to expand on her work by challenging the chatty marine mammals with even more interference to see if they can still echolocate.

每年夏天的晚上,有150万只蝙蝠出来觅食它们最爱的蚊子和其他昆虫。为了追踪它们微小的飞行猎物,蝙蝠发出高亢的声音,从昆虫转向蝙蝠的大耳朵。回声定位过程中的信息告诉飞行哺乳动物他们快速移动食物的精确路径。

但是成千上万个蝙蝠中的任何一只蝙蝠,真的知道它所注册的ping不是其他蝙蝠的回声吗?并且,导航模式这种潜在的干扰,称为声纳干扰,不仅存在于蝙蝠的领域。依靠回声定位的海豚和其他动物也必须找到绕过它们周围的声波迷宫的方法。

人们想弄清楚蝙蝠和海豚是如何做到这一点的,因为这些动物是印第安纳州圣玛丽学院的生物学助理教授劳拉·克莱珀(Laura Kloepper)所称的“生物灵感”,帮助我们找到解决日常生活中问题的技术方法。回声定位的生物学拥有帮助人类研究人员开发出更好的“主动传感”装置的秘密,该装置可以模仿蝙蝠的行为。

最初,人们使用主动感知来通过潜艇防御沿海水域或发现海洋深处的声音。但现在,克莱珀说,我们越来越多地转向像机器人吸尘器或自驾车汽车这样更普遍的需要。她说,问题在于“蝙蝠和海豚对我们来说仍然是个谜”。研究人员越能发现它们如何回声定位,我们就能收获越多的技术进步。在这些潜在的发展中,有传感器可以区分干扰回波与那些重要的回波。

克莱珀在美国声学学会第176次会议上的演讲中明确了蝙蝠主动感知能力的力量,这次会议比较了蝙蝠和海豚强大的回声定位能力。作为一名蝙蝠研究人员,克莱珀形容自己非常注重“团队蝙蝠”,尽管她依靠海豚来证明自己的观点。她说,她的工作是第一次研究海豚如何绕过声纳干扰。

在她的谈话中,克莱珀讲述了她的研究小组是如何用类似海豚的人造声波来轰炸一对海豚,试图在两种选择中混淆它们。她的研究小组向海洋哺乳动物发起了挑战,他们耍了把戏,比如调整发出声音的扬声器的角度,以便在它们回到自己选择的目标时迷惑它们。人类所学到的是海豚使用两种可能的策略来阻止无声噪音。他们要么改变他们的呼叫频率到更高或更低的音调,要么改变时间。要么,海豚可以在回声上识别出一个签名。

当然,克莱珀也研究蝙蝠。在这项研究中,她使用了她所称的“生物无人机”,一个训练有素的Harris鹰,名叫贝儿。佩戴着微型相机和麦克风,贝利飞着进入蝙蝠群中,为了科学的缘故,记录了他们的许多叫声。克莱珀说,她使用鹰的理由,除了“鹰太酷了”这一事实之外,就是把一个带有旋转螺旋桨的常规无人机“送入密集的蝙蝠群”并不理想。

海豚可能会改变节奏或音高,但是蝙蝠有一个稍微微妙的曲目来对付干扰。“海豚发出冲动的信号,听起来像咔嗒声,如果你把手指合拢,”克莱珀说,而蝙蝠的叫声更像是人类的口哨声。“当然,我们可以稍微改变一下手指啪啪声的一些特征,”她指出,“但是你可以让你的口哨在音高上或音高下或甚至在音高之间跳跃,而且你可以控制你的口哨有多长。”蝙蝠显示出对回声的类似水平的精细控制。她说。

北达科他州立大学生物科学副教授Erin Gillam说,结果就是蝙蝠不仅能够探测和跟踪移动的猎物,还能够感知不同物体的纹理,但他没有参与海豚的工作。她还站在蝙蝠队一边,因为动物“是最酷的,”她补充说,“海豚能够有一些灵活性,但不像蝙蝠那么多。”

尽管蝙蝠队有明显的偏见,克莱珀说,“蝙蝠有更长的叫声,而且众所周知,蝙蝠在大规模群体中回声定位,这就是我为什么认为当要避免干扰时,蝙蝠会赢的原因。


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