September 28, 2022

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Cricket Avoids Being Bat Food By Doing Nothing

[Sounds of the Panama rainforest]

“So what you’re listening to now, that’s a recording from the rainforest.”

That’s Marc Holdereid, of the University of Bristol in the U.K. He specializes in bioacoustics: how animals create seem and communicate with the seems they make. In the recording you just listened to, Holdereid removed the seems we people can listen to and minimized the frequencies of the seems we typically would not listen to so that they are audible to our ears.

“A rainforest is a extremely noisy natural environment. There is insect seems, bird seems, there’s leaves rustling. And all of this tends to make it tougher for you to detect one thing you want to listen to.”

Holderied is specifically interested in seems from the ultrasonic range—these are frequencies our ears cannot detect. But they come in loud and clear for a sword-tailed cricket in Panama. Here’s their house, slowed down so we can listen to it. [Forest seems]

Holderied and colleagues at the Universities of Bristol and Graz, in Austria, recently found the sword-tailed cricket has a novel survival method when it arrives to existence in their noisy natural environment. 

“Up there, it’s predominantly other bugs that create noises that stop you from detecting what you definitely want to detect—and that is a predator that could possibly attack you.”  

Each evening, hundreds of species of hungry bats fly about the rainforest and use echolocation to hunt for their meals. Which can contain the cricket.

“So we are chatting neo-tropical rainforests and they teem with different bat species and most of them, or quite a few of them, would be just after bugs. So the frequencies that they use to obtain the insect prey are masking pretty substantially a comprehensive echolocation frequency selection.”  

Echolocation is good for looking, but Holdereid states it’s also a possible weakness for bats—because in the ultrasonic globe, these calls are extremely, extremely loud.

“And after you have cracked that, after you have progressed an ear that lets you listen to these calls, you can just fly absent and escape into security.”

Which the cricket has realized to do. 

“Basically, they have a response threshold, that’s what we simply call it. So, they only react to seems that are extremely loud.”  

And how do they react? Nicely, they just stop flying—and plummet toward the floor. 

“Sometimes they don’t even fall all the way to the floor. So, if the calls are louder, they stop flying for a lengthier period of time of time, that signifies a lengthier fall. But if they stop for just a half a next, that could possibly not be plenty of time for them to hit the floor and just after this half a next, they get started flying yet again, but they are never ever in fact crashing, but they fall out of the bat’s strategy vector.”

The examine of the crickets’ novel survival method is in the journal Philosophical Transactions of the Royal Society B. [Heiner Römer and Marc Holderied, Decision creating in the deal with of a lethal predator: significant-amplitude behavioural thresholds can be adaptive for rainforest crickets under significant background sound stages]

“It’s a lovely case in point of this predator-prey arms race.”

In this situation, the passive prey has observed a way to dwell, and hear for, a different day.

—Emily Schwing

(The over textual content is a transcript of this podcast)