Aaaand it's out! New paper alert, today in @PNASNews #Bats #Echolocation #Bioacoustics

We (@YovelBatLab) found that echolocating bats rely on an innate reference to the speed of sound, and likely encode the world in terms of time, not distance.

Bats' brains calculate the distance to objects by the delay between an emitted pulse and the reception of its returning echo. For that calculation to work, there must be a reference to the speed of sound, and since this speed changes with temperature, humidity, and altitude,

we wondered if bats have to learn/experience to correctly couple a given delay to a specific distance, and if this is flexible.

So how do we check this? The trick was to change the speed of sound! we trained adults & pups to fly to a target, and enriched the air with helium

so sound traveled faster, creating a sensory error where the bat perceives the target to be closer than it actually is.

We expected the adults to learn from their mistakes, and that pups raised in heliox will not display an error. We were wrong...

We looked at performance, but mostly at echolocation parameters: call durations and interval *prior* to take-off that we identified in a previous study to give information on how far/near the bat perceives the target to be.

We also looked at echolocation and flight behavior during the flight, and all in all - we found that the reference to the speed of sound is innate and that adults were unable to adjust it.

We thought selection would favor learning or flexibility in this trait, so why not?

We think there are two reasons: 1. the error is not very costly: it decreases as the bat gets closer, and there is enough of a buffer for success even if ranging is a little off.
2. there is a strong selection pressure for new-born bats to have functional echolocation...

... as early as possible due to ecological constraints - they have to be independent quickly so that both pup and mother can prepare for winter.

We found that for a different species, but we think the same principle holds.

Even though bats had ample opportunity to learn from their mistakes, and even during successful flights, they always maintained a sensory error. This supports a hypothesis from Jim Simmons that bats encode the world in terms of time, not distance.

Last - perseverance: this is the last project from my PhD to be published. I started it in 2012!!
Failures, setbacks, 3 children, negative results (as in the opposite of what we expected), rejections, and revisions. In the end - it's out, I'm proud of it.
Don't give up

And, as usual, if you want to read the article but are blocked by paywalls - my DMs are open and I'll gladly share a pdf.

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