Scientists solve the “cocktail party” mystery of bat echolocation

Every night, bats come out of the roost in large quantities, creating what scientists call the “cocktail party nightmare” of collision echocolocation.

No one knew how the bats managed this serious sensory challenge. Currently, Tel Aviv University scientists and Max Prinkk Animal Behavioral Research Institute (MPI-AB) track bats within groups of thousands to increase distance from the center of the group when the bat first emerges from the roost and adjust echolocations to safely operate in areas of highest bat density. The study was published in the minutes of the National Academy of Sciences on March 31st.

Aya Goldshtein, Omer Mazar, and Yossi Yovel spent many nights standing outside the Bat’s Cave. Still, it surprises scientists every time, seeing thousands of bats erupt from the cave, flapping wings at night, and sometimes densely densely to look liquid. But until recently, bat biologists were even more confused by what they didn’t see. “Bats don’t bump into each other,” says Goldstein of MPIAB.

“Nightmare” cocktail party

It was a scientific mystery that bats didn’t crash fatally every night when they squeezed out of the cave and foraged. Bats perceive their world primarily through echolocation. They release a call and hear the reflected echo. However, if many bats are echolocating at once – when the entire colony comes out of the cave for a few minutes, the call of others should erase the important echo information the bat needs. Scientists call this loss of acoustic information “disturbance,” and they expect bats to collide for it.

Still, air accidents outside a cave are extremely rare. “You’re almost excited when you see it,” Goldshtein says.

For decades, scientists have been trying to understand how bats solve this “cocktail party nightmare” and how ambient chat listens to the voices you need to hear. For example, they looked at how bats echo in groups. In the lab, scientists observed that each of the individual bats in a small group echoed slightly different frequency. Was this the solution?

Yovel says that such past research is an important stepping stone, but due to the important missing piece, it has not been able to provide a compelling answer to the mystery of cocktail party. “No one saw this situation in its appearance from the perspective of individual bats. Can you understand the behavior if you don’t study it through actions?”

Step into the Bat Cave

Goldstein and his colleague for the first time Data was collected from wild bats It appears from a cave at dusk. They used a combination of high-resolution tracking developed by Ran Nathan and Sivan Toledo, Ultrasonic Recording, and Sensorimotor Computer Modeling. All of this allowed animals to squeeze out of the cave opening and step into the bat sense world as they passed through the landscape.

A team led by scientists from Tel Aviv University studied larger mousetail bats in the Hula Valley, Israel. Over the course of two years, they tagged dozens of bats with lightweight trackers that recorded bat locations every second. Some of these tags also included ultrasound microphones recording auditory scenes from the perspective of individual bats. Each year, data was collected the same night the bats were tagged.

Warning: Tagged bats were released into emerging colonies from outside the cave. In other words, actual data was missing at the cave opening at the highest density. The team filled this gap with computational models developed with the advent of Omer Mazar and simulations. The model incorporates data collected by the tracker and microphone, recreating the complete action sequence that begins at the entrance to the cave and ends after the bat has flew two kilometers out of the valley. “This simulation allows us to test assumptions about how bats solve this complex task during their emergence,” says Mazar.

Avoid the sound dilemma

And the photos that appeared were amazing. When leaving the cave, the bat experiences a call dissonance, packed with 94% of the echocolocation. However, within five seconds of leaving the cave, the bats significantly reduced the clogging of echolocation. They also made two important behavioral changes. First, we incited from the core of dense colonies, while maintaining the group structure. Second, they released shorter calls and weaker calls at a higher frequency.

Researchers suspected that bats would quickly disperse the cave to reduce clogging. But why did bats change their echolocation to a higher frequency? Does calling not only increase the interference issues, but does it increase the risk of conflict? To understand the outcome, the author had to approach the scene from a bat’s perspective.

Mazar said: “Imagine you’re a bat flying through a messy space. The most important object you need to know is a bat directly in front of you. So you should echolocate it in a way that provides the most detailed information about that bat only.

In other words, bats change the way they echolocate to get detailed information about their neighboring neighbours. This is a strategy that will help you manipulate and avoid conflicts in the end.

The authors highlight this unexpected consequence of how bats solve the cocktail party dilemma by studying bats in their natural environments when performing related tasks. “Past theoretical and lab research has allowed us to imagine possibilities,” Goldstein says. “But only by putting yourself in the animal’s shoes as close as possible can we understand the challenges they face and what they will do to solve them.”