How Japanese Horseshoe Bats Solve Noisy Echolocation in Crowded Colonies

When greater Japanese horseshoe bats hunt in crowded colonies, their high-pitched echolocation signals overlap to create background noise, but according to a study published in the Journal of Comparative Physiology A by Doshisha University researchers, these bats gradually adjust their calls to share nearly identical frequencies, helping them receive clearer echoes and detect prey.

How Bats Use Echolocation to Navigate and Hunt

Bats rely on echolocation to move through the dark and hunt insects, sending out high-pitched sound waves that bounce off nearby objects and return as echoes, helping them judge distances and locations. Because many species are active at night, they cannot always rely on eyesight, according to Science X.

They produce ultrasonic calls that are too high for humans to hear. These sound waves hit insects, trees, cave walls, and other objects before bouncing back. By listening to these returning echoes, bats can work out where an object is, how far away it is, and whether it is moving. Scientists also study bat echolocation because it has inspired improvements in sonar systems and sensing technology used in robots and other devices.

Adjusting Frequencies to Create a Silent Spectral Window

The Doshisha University researchers wanted to understand what happens when many horseshoe bats with slightly different call frequencies live together. To find out, they studied wild greater Japanese horseshoe bats brought into captive colonies of the same species, measuring their echolocation frequencies before they entered the colony and again after spending about one month living with other bats, utilizing data collected from 2008 to 2024 across 15 different capture events.

According to the study, the bats did not spread out their call frequencies to avoid interference. Instead, they slowly moved toward a shared frequency. This adjustment was especially prominent for bats whose calls started at lower frequencies. Those bats increased their call frequencies after joining the colony, while bats already using higher frequencies hardly changed. Furthermore, when wild and captive bats already shared similar call frequencies before joining, this adjustment did not occur, suggesting bats only change calls when noticing a distinct difference between individuals.

Overcoming Background Noise for Better Prey Detection

Researchers believe this shared frequency helps create a “silent spectral window.” When many bats call together, background sounds stay below a certain frequency, leaving a quiet range where important echoes from moving insects stand out more clearly, according to the findings published in the Journal of Comparative Physiology A.

Scientists compare this phenomenon to trying to hear someone speak in a noisy room. If the voice you want to hear occupies a sound range with less background noise, comprehension becomes much easier. For horseshoe bats, this quieter frequency range allows them to detect echoes from fluttering insects more reliably. Lower-frequency bats benefited the most by shifting upwards, reducing conflict with higher-frequency bats while keeping prey echoes within a clear listening range.

Frequently Asked Questions

How do greater Japanese horseshoe bats’ echolocation calls differ from other species?

While most bat species use sound calls whose frequency changes during each call, greater Japanese horseshoe bats use calls featuring both changing frequencies and a long section staying at a nearly constant frequency, paired with highly specialized hearing.

Why do lower-frequency bats shift their calls upward in colonies?

According to the Doshisha University study, lower-frequency bats shift their calls upward to match colony members, avoiding signal overlap and creating a silent spectral window that improves prey detection.