Bats raised in helium-rich air reveal the key to echolocation


It’s mature now Bats can use echolocation to show the mental picture of their surroundings. But we are still figuring out what this means-how bats absorb the echoes of their own sounds and use them to determine the location of objects.

in a paper Researchers released evidence on Monday that part of the reason bats participate in echolocation is because they have an innate sense of the speed of sound. How do researchers study this phenomenon?By improving bat In a helium-rich atmosphere, lower density air will increase the speed of sound.

In principle, echolocation is simple. The bat produces sound, which bounces off objects around it and then returns to the bat’s ears. For objects that are farther away, it takes longer for the sound to return, thus providing a sense of relative distance.

But bats can also use echolocation technology to identify prey in flight, or pick a location where they can land. For this, they need to have an absolute sense of distance. It is not enough to know that the branch to fall is shorter than the house behind it. You must know when to start the complex actions involved in latching to a tree branch, otherwise you may hit the tree branch or stop completely in the air.

The easiest way to get the absolute distance is to know the speed of sound. In this way, the delay between the utterance and the return echo will provide absolute distance. But how to test whether the bat has a certain sense of the speed of sound?

Eran Amichai and Yossi Yovel of Tel Aviv University decided to adopt a simple method: change the speed of sound. One of the factors that affect the speed of sound is the density of air. There is a simple way to change the density of air: use a lighter gas than air plus standard. In this case, the author chose helium and raised a group of bats in an environment filled with helium, thereby increasing the speed of sound by 15%.

(Whether a bat held up in this environment sounds interesting is sadly untested.)

The faster sound speed means that the reflected echo will return to the bat faster. In turn, this means that the objects producing these echoes will be closer than they actually are. Therefore, if we can somehow figure out how close bats perceive objects, we can measure their understanding of the speed of sound.

Fortunately, the species of bats used in these experiments changed their echolocation sounds as they approached objects. Therefore, by tracking the noise that bats make when they approach an object, we can understand how close the bat thinks they are to the object.

In order to conduct experiments, the researchers kept bats in a closed environment at a certain distance from the feeding station. One group was raised in ordinary air, and the other group was raised in helium-rich air. Then they changed the atmosphere into two groups. For bats raised with helium, the slower speed of normal air will make it take longer for the echo to arrive, making the feeding station appear farther away. For bats raised in normal air, the situation is the opposite.

It turns out that both groups of bats behave the same. They believe that the platform is closer in helium-rich air and farther in normal air. Therefore, it doesn’t matter what bats learn from the environment in which they grew up. Their views on the speed of sound are the same. This shows that this feeling is born of bats.

Given that the weather and altitude changes experienced by bats may also change the speed of sound, usually by more than 5%, this is a bit surprising. Therefore, it seems advantageous to be able to adjust the echo position according to the conditions. However, Amichai and Yovel put mature bats in a helium environment for several weeks, and they did not find that they could adjust their knowledge of the location of the feeding station. This is true even in an atmosphere with a helium content of 27%. Therefore, bats’ knowledge of the speed of sound seems to be locked in place.


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