Bats are a diverse group, with more than 1,400 species flitting across every continent except Antarctica. Researchers around the world are eagerly studying the airborne mammals, as they have adaptations that allow them to carry viruses that are deadly in humans and livestock while exhibiting minimal symptoms themselves. But one never knows how other behaviors and functions could eventually benefit mankind. not only to learn more about how pandemics 

Unlike humans who map the world in units of distance, bats map the world in units of time. What this means is that the bat perceives an insect as being at a distance of nine milliseconds and not one-and-a-half meters as was previously thought.

Animals rely on their senses to survive and reproduce. Sensory systems are subject to a trade-off between the advantage of flexibility that often comes with a cost of a prolonged learning period and the advantage of innateness, which is less successful in dealing with altered environments.

A new study at Tel Aviv University (TAU) has revealed for the first time that bats know the speed of sound from birth. To prove this, the researchers raised bats from the time of their birth in a helium-enriched environment in which the speed of sound is higher than normal. 

Their study was published in the prestigious journal Proceedings of the the [US] National Academy of Sciences (PNAS) under the title “Echolocating bats rely on an innate speed-of-sound reference.”

To determine where things are in a space, most bat species use sonar echolocation –emitting sound signals and analyzing the returning echoes that are reflected back to the bat. Bats can estimate the position of the object based on the time that elapses between the moment the sound wave is produced and the moment it’s returned to the bat. 

This calculation depends on the speed of sound, which can vary in different environmental conditions, such as air composition or temperature. For example, there could be a difference of almost 10% between the speed of sound at the height of the summer – when the air is hot and the sound waves spread faster – and the winter season. Since the discovery of sonar in bats eight decades ago, researchers have been trying to figure out whether bats acquire the ability to measure the speed of sound over the course of their lifetime or are born with this innate constant sense.

Now, researchers led by Prof. Yossi Yovel, head of the Sagol School of Neuroscience and a faculty member of TAU’s School of Zoology in the Faculty of Life Sciences and his former doctoral student Dr. Eran Amichai (currently studying at Dartmouth College in New Hampshire, US) have succeeded in answering this question. 

The researchers conducted an experiment in which they were able to manipulate the speed of sound. They enriched the air composition with helium to increase the speed of sounds and under these conditions raised bat pups from the time of their birth, as well as adult bats. Neither the adult bats nor the bat pups were able to adjust to the new speed of sound and consistently landed in front of the target, indicating that they perceived the target as being closer – that is, they did not adjust their behavior to the higher speed of sound.

Because this occurred both in the adult bats that had learned to fly in normal environmental conditions and in the pups that learned to fly in an environment with a higher-than-normal speed of sound, the researchers concluded that the rate of the speed of sound in bats is inborn and that they have a constant sense of it. “Because bats need to learn to fly within a short time of their birth,” explained Yovel, “we hypothesize that an evolutionary ‘choice’ was made to be born with this knowledge in order to save time during the sensitive development period.”

Another interesting conclusion of the study is that bats do not actually calculate the distance to the target according to the speed of sound. Because they do not adjust the speed of sound encoded in their brains, it seems that they also do not translate the time it takes for the sound waves to return into units of distance. Therefore, their spatial perception is actually based on measurements of time and not distance.

“What most excited me about this study,” concluded Yovel, “is that we were able to answer a very basic question. We found that in fact bats do not measure distance, but rather time, to orient themselves in space. This may sound like a semantic difference, but I think that it means that their spatial perception is fundamentally different than that of humans and other visual creatures, at least when they rely on sonar. It’s fascinating to see how diverse evolution is in the brain-computing strategies it produces.”