2016-4-20

English

http://www.chinavoa.com/show-8469-236216-1.html

Eavesdrop on Echolocation to Count Bats

窃听蝙蝠回升定位

"What you're listening to is what I like to call the beautiful chaos of the bat echolocation stream." Laura Kloepper, a bioacoustician at Saint Mary's College in Indiana. "So you're listening to the sound of probably a couple hundred bats emerging per second from the cave and there's a microphone that we have suspended in the middle of the bats to record the sounds. These are the echolocation sounds the bats make when they're flying and this is what they use to help navigate and find prey."

你所听到的是我称之为天籁之音的蝙蝠回声定位流。劳拉`科柏是印第安纳州圣玛丽学院的生物声学家。“你听到的是每秒钟从洞穴中出来的数百只蝙蝠发出的声音，我们在蝙蝠当中安装了一个麦克风，来记录这些声音。这是蝙蝠在飞行中发出的回升定位流，蝙蝠利用回声定位帮助自己进行导航和寻找猎物。”

The sounds—slowed down 10 times so we can hear them—were recorded at a network of lava tube caves in New Mexico. Kloepper and her colleagues camped out there to study how Mexican free-tailed bats echolocate in huge swarms without jamming each other's signals. And they noticed that the intensity of the “bleeps” seemed to correlate with the number of bats fluttering out of the cave. Meaning, maybe you could survey their populations with audio. "One night we were sitting around the campfire at our field site and we said, I wonder if this would actually work?"

这些声音——经过10倍减慢处理，我们人类才能够听到——是在新墨西哥州的很多熔岩洞中记录的。科柏和同事们在熔岩洞外露营来研究是蝙蝠是通过何种方式在大群蝙蝠中不干扰同伴的信号的情况下，进行声波定位。他们注意到声波的强度和飞出洞穴的蝙蝠的数量有关。这也就意味着，也许可以利用声音来计算蝙蝠的数量。“有一天晚上，我们围着篝火聊天，我猜想，这个办法可行吗?”

So they set up a new experiment, capturing audio and GoPro video at the cave site. They counted the bats in each video frame, and correlated that to the zips and zaps, to create predictive models. They then tried the method at another cave—and found that their models could indeed estimate the number of bats emerging using acoustics alone. The study is in the journal Royal Society Open Science.

所以，他们制定了新的实验计划，在洞穴处捕捉音频和视频。他们计算了每个视频帧数中的蝙蝠数量，并将此与声波相关联创建了预测模型。然后，他们将这种方法应用于其他洞穴——结果表明，这些模型利用声学可以估计出现的蝙蝠数量。该研究结果发表在英国皇家协会《Royal Society Open Science》。

"Historically what has been used to estimate bats has been photographic estimates, visual estimates, mark-recapture estimates, and those have been highly prone to bias." Newer technology, like thermal imaging cameras is accurate, but expensive. So at a time of epic bat mortality—due to, for example, the fungal white nose syndrome that’s wiping out bats in Canada and the U.S.—Kloepper says her method might be a cheap, reliable way to determine the most critical caves to save.

“过去人们利用照片、视觉、标记捕捉方法来估计蝙蝠的数量，但是这些方法都存在着很大的误差。”热成像相机等先进的技术测量的很准确，但价格昂贵。所以，蝙蝠大量死亡时，如真菌白鼻综合症肆虐了加拿大和美国的蝙蝠，科柏表示，自己的方法将会是决定拯救最重要洞穴的最低廉、可行的办法。