Science & Technology

Helium-rich air-fed bats reveal the key to echolocation

Now has a good reputation Bats can use echolocation to create an image of their environment. But I still don’t understand what that means, how bats receive echoes of their vocalizations and use them to locate objects.

so paper Researchers, published on Monday, provide evidence that bats are involved in echolocation because they were born with an essential sense of speed of sound. How did the researchers study this phenomenon?By raising Bat In a helium-rich atmosphere, low air density increases the speed of sound.

Echolocation is fairly simple in principle. The bat makes a sound that bounces off an object in its environment and returns to the bat’s ear. For objects that are far away, it takes time for the sound to return, giving a relative sense of distance.

However, bats can also use echolocation to identify in-flight prey and choose where to land. To do that, you need an absolute sense of distance. It is not enough to know that the branch you want to land on is closer than the house behind it. You need to know when to start the complex movements associated with latching to a branch. Otherwise, you may hit a branch or stop completely in the air.

The easiest way to get the absolute distance is to sense the speed of sound. This allows the delay between the vocalization and the return echo to provide the absolute distance. But how do you test if a bat has a sense of speed of sound?

Eran Amichai and Yossi Yovel of Tel Aviv University have determined that there is an easy way to change the speed of sound. One of the factors that affect the speed of sound is the density of air. There is also an easy way to change the density of air. Spikes a gas that is lighter than air. In this case, the author chose helium and raised the group of bats in an atmosphere that contained enough helium to increase the speed of sound by 15%.

(Sadly, it wasn’t tested if bats raised in this environment sounded interesting.)

The faster speed of sound means that the reflected echo returns to the bat faster. In other words, the objects that create these echoes are perceived to be closer than they really are. Therefore, if we can somehow understand how close the bats perceive an object, we can get a measure of their understanding of the speed of sound.

Fortunately, the bat species used in these experiments change the sound of echolocation as they approach an object. Therefore, by tracking the noise that occurs when a bat approaches an object, you can see how close you think the bat is to the object.

To do this experimentally, researchers raised bats in an enclosure with a feeding station at a distance, one group in normal air, and another in helium-rich air. I grew up. After that, we exchanged the atmosphere of the two groups. For helium-grown bats, slow normal air velocities will increase the time it takes for the echo to arrive, making the feeding station visible in the distance. The opposite is true for bats raised in normal air.

After all, both groups of bats behaved the same. They recognized that the platform was close in helium-rich air and far in normal air. So it doesn’t matter what you learned from the environment in which the bats grew up. Their perception of the speed of sound was the same. This suggests that perception is unique to bats.

This is a bit surprising given that bats experience changes in weather and altitude, and the speed of sound can change by more than 5%. Therefore, it may seem advantageous to be able to adjust the echolocation according to the conditions. However, Amichai and Yovel did not find any indication that mature bats could be placed in a helium environment for several weeks to adjust their perception of where the feeding station was. This was true even in an atmosphere that was 27 percent helium. Therefore, the bat’s knowledge of the speed of sound appears to be fixed in place.

Helium-rich air-fed bats reveal the key to echolocation Helium-rich air-fed bats reveal the key to echolocation

Back to top button