A new study has shown how Japanese horseshoe bats (Rhinolophus nippon) handle noisy environments at night.

For a flying bat, the night is not quiet. It is a blinding, chaotic wall of noise as they navigate and hunt within dense forest canopies. 

Every leaf, branch, and gust of wind bounces sound waves back to the hunter, creating a deafening acoustic fog.

Researchers from Doshisha University in Japan have found that the bat does not merely survive this sensory overload, but also actively manipulates its environment to overcome the clutter and locate its prey.

Outsmarting the noise

Many animals rely on echolocation — emitting sound waves and interpreting the returning echoes — to navigate and hunt. However, isolating signals in complex, noisy environments filled with background clutter and self-motion reflections poses a major survival challenge. 

To overcome this, bats have evolved ultrasonic echo-detection systems that filter out noise, enabling them to perceive their surroundings.

Bats are known to use Doppler-shift compensation (DSC).

As a bat flies, its own forward motion warps the frequency of its echolocation calls — much like how an ambulance siren changes pitch as it speeds past you. To prevent this shifting audio from overloading their sensitive ears, bats constantly adjust their outgoing vocalizations. 

Mostly, biologists viewed DSC as a defensive mechanism, a way for the bat to stabilize its own hearing during movement. The researchers suspected a deeper strategy.

“I have always been fascinated by bats’ ultrasonic sensing abilities and their use of physical phenomena such as the Doppler effect. This inspired me to explore whether bats use frequency control more strategically than previously understood,” said Soshi Yoshida, Doctoral Student at the Graduate School of Life and Medical Sciences, Doshisha University. 

To test this, the team conducted experiments on 11 wild-caught bats. Onboard microphones recorded real-time echoes during free flight alongside simulated “phantom” echoes. In addition, tethered live moths were used to analyze the faint acoustic signature of insect wing beating.

Bio-inspired radar

Bats manipulate their calls to lock the highest-frequency background echoes into a strict, unchanging reference frequency, known to scientists as constant reference frequency (fref). 

This precise control creates a clutter-free “silent frequency zone” just above fref, which physically carves out a quiet window in the acoustic environment.

Interestingly, the structural silence allows the bats to clearly detect the incredibly faint, distinct echoes produced by the wingbeats of flying prey.

To prove this silent window was vital for survival, the team artificially beamed a narrow strip of noise directly into the bat’s custom-made silent zone.

As a result, the bats failed their hunts. When noise was blasted outside of this frequency zone, the bats hunted with perfect accuracy. 

It was confirmed that this acoustic zone is an intentional, adaptive sensory strategy rather than an accidental biological side effect. 

The findings reveal that bats possess the intelligence to actively manipulate the physical properties of their acoustic environment to enhance perception, rather than just forcing the brain to work harder.

The strategy used by the horseshoe bat could advance human technology. Currently, radar, sonar, medical ultrasound, and wireless communication systems struggle in crowded, noisy environments.

Bat’s ability to actively manipulate and shape its signal environment can be mimicked to develop smarter sensing systems capable of extracting critical information from incredibly noisy and complex conditions.

 The study was published in the journal Communications Biology on May 19.