Bats in a traffic jam: This is how they manage to avoid colliding with each other during the mass exit from the cave

Aya Goldstein, Omer Mazar and Yossi Yuval They have spent many evenings at the entrances of bat caves. And yet, every time they see thousands of bats emerge into the night, in such high density that they almost look like flowing liquid – they are amazed anew. But until recently, what really surprised them was what they didn’t see.

"Bats don't collide with each other"", explains Goldstein from the Max Planck Institute for Animal Behavior. "Even when it comes to hundreds of thousands of bats all flying through a particularly narrow opening."

The mystery of how bats don't crash into each other every night when they leave their caves to forage has puzzled scientists for years. Many bats navigate primarily by Echolocation – That is, they emit calls and hear the echoes that return from the environment, which allows them to 'see' what is around them.

But when many bats do it together – as in a synchronized departure of an entire colony – the calls can interfere with each other and block out vital information. This phenomenon is called "Jamming", and the assumption was that this would cause conflicts.

And yet, air crashes outside caves are so rare that **"you almost get emotional when you witness one,"** says Goldstein.

Dive into the bat cave

For the first time, a team of researchers including scientists from Tel Aviv University collected data Bats in nature, just as they were leaving the cave at dusk. The researchers combined High-resolution tracking technology Developed by Prof. Ran Nathan and Prof. Sivan Toledo, Ultrasonic recordings, AndSensorimotor computational models – All of this allowed them to enter the sensory world of the bats at the moments of departure.

The study was published in the scientific journal PNAS (Proceedings of the National Academy of Sciences).

The study focused on Greater mouse-tailed bats in the Hula Valley and was conducted over a two-year period. During this period, dozens of bats were tagged with lightweight tracking devices that recorded their location every second. Some of the tags also included tiny microphones that recorded what was happening from the bat's personal perspective.

The researchers were unable to record the exact moment of exiting the cave (the most crowded point), so they supplemented the data using Computational model Developed by Omar Mazar, which simulates the mass takeoff process.

The computer combined the tracking data and sound from the bats to create a full simulation – from the moment they exited the cave to the flight of about two kilometers. “The simulation allows us to test our assumptions about how bats solve this complicated challenge,” explains Mazar.

Escape a sound trap

The picture that emerged was extraordinary. When the bats emerge from the cave, they experience tremendous noise – about 94% of their echolocation calls are distorted.

Yet, In just five seconds From the get-go, bats significantly reduce disruption. They make two behavioral adjustments:

1. they Disperse quickly From the dense core while preserving a group structure.

2. they Shorten and weaken the readings and transmit at a higher frequency.

   
   

But why a higher frequency? Isn't it expected that additional frequencies will exacerbate the jamming problem?

Mazar explains:
"Let's say you're a bat flying in a crowded space – the most important thing is to know what the bat in front of you is doing. Therefore, you need a reading that focuses specifically on it and provides as accurate information as possible. You may miss other details – but it doesn't matter, as long as you avoid a collision."

That is, bats Changing their echolocation So that you can adapt to crowded situations – and concentrate only on what is close to you.

Field research made the difference

According to the researchers, only thanks to Nature observations This behavior could be discovered. “Previous models and theories have given us the ability to imagine,” says Goldstein. “But it’s only when we get to observe actual behavior in real time that we can truly understand what the challenge is and how animals deal with it.”