1200 km / h: this is the speed of sound in the air at 20 ° C. If we have to go to school to learn that number, bats have inherently integrated it, two researchers from Tel Aviv University (Israel) reveal in a new study.
Fluctuating speed of sound
Bats use echolocation to spot obstacles or prey in the dark. They produce sound waves that hit living and inert surfaces and then reflect back to their emitter. In this way, the latter can – taking into account the time elapsed between the emission and the return of the echo – locate their prey. But if at 20 ° C the speed of sound is 1200 km / h, these data may differ in other environmental conditions. So with temperature, but also with the composition of the air. Thus, sound waves propagate faster in hot air. Do bats learn to master the speed of sound in their lives or are they born with that ability? To this question Dr. Amichai and prof. Yovel responded in May 2021 in a journal PNAS.
The impression that the object is closer than it actually is
The researchers did not hesitate to play at the speed of sound not by changing the temperature but by changing the composition of the air: they injected helium into it. In this way, the propagation of sound waves was done faster. They placed young bats and adult specimens in this new environment. None of them managed to adjust: they all “saw” the object closer than it actually was. Then they performed flights with too short a route. This result therefore means that the echolocation of these mammals is innate and therefore cannot adapt to such a significant change in their environment, even if they grew up there. “They know the average values (speed of sound, editor’s note),, like range, he explains Science and the future Prof. Yovel. It seems that bats can cope with the natural speed of sound in the range of 7% variability.“.
“Animals rely on their senses to survive and reproduce, reminiscent of a study. Sensory systems are subject to a compromise between the advantage of flexibility that often comes with the cost of extended learning periods and the advantage of innateness that is less successful in coping with changed environments.“The expectations of bats in relation to sound waves are proof of that.
The researchers also believe that their research proves that the spatial perception of bats is not based on a unit of distance, but on time. “In reality, when we place a bat in a helium environment, we change the weather, but the distance is kept constant.“Professor Yovel says. Relying on echolocation, these mammals show that time is important to them.