Horseshoe bat echolocation study finds colonies tune calls together

A horseshoe bat echolocation study from Doshisha University reports that greater Japanese horseshoe bats can bring their call frequencies closer together inside a colony. The researchers say the behavior may help the animals reduce acoustic interference when many bats are listening for echoes in the same space.

The work by Haruhito Matsumoto, Soshi Yoshida and Shizuko Hiryu was published in the Journal of Comparative Physiology A. Doshisha University said the findings add to research on how bats sense prey and obstacles, a field that has also informed sonar and autonomous robotic systems.

How do horseshoe bats avoid echolocation interference?

Bats use echolocation by sending out ultrasonic calls and reading the returning echoes to judge objects around them. Greater Japanese horseshoe bats, or Rhinolophus nippon, use calls that include both frequency-modulated and constant-frequency parts, according to the researchers.

The constant-frequency portion is especially useful for detecting prey through changes in reflected sound. The bats also have an acoustic fovea, an anatomical feature tuned to a narrow band around the second-harmonic constant-frequency component, known as CF2.

As a bat or its target moves, the frequency of a returning echo can shift, a phenomenon known as Doppler shift. The researchers say these bats adjust the constant-frequency portion of their calls so the returning CF2 signal remains in the range their hearing system is most sensitive to.

Yoshida and colleagues connect the new findings to earlier work on a “silent spectral window,” a relatively uncluttered band of frequencies that can make prey signals easier to detect. Their interpretation is that colony members align their calls in a way that helps preserve that window for detecting Doppler-shifted echoes from fluttering prey.

What did the researchers measure?

The team captured wild greater Japanese horseshoe bats at 15 time points and recorded their CF2 frequencies. The bats were then placed with a captive colony of the same species, and their CF2 frequencies were measured again after one month.

Doshisha University said the data span 15 capture events from 2008 through 2024. That long record let the researchers compare wild and captive bats and look for frequency convergence after the groups were mixed.

The pattern was uneven. According to the study, bats that began with lower CF2 frequencies, typically the wild-caught individuals, shifted their calls upward more strongly during convergence.

When the wild and captive groups did not differ in frequency at the start, the researchers did not see the same convergence. Yoshida said the observation depended on years of careful call records kept by current and former laboratory members.

Why did lower-frequency bats shift upward?

The researchers propose that lower-frequency bats faced a conflict because their prey-related echo “glints” could fall near the higher-frequency calls of other colony members. By shifting upward, those bats could reduce that overlap while helping the colony maintain a shared clearer band above CF2.

Higher-frequency bats had less reason to change because their glints were already in a clearer range, according to the team’s interpretation. The study says acoustic overlap is a problem for bats living among members of the same species, but mixed same-species groups have received limited attention in research on echolocation interference.

The authors conclude that greater Japanese horseshoe bats can adjust echolocation at the colony level, not only as isolated individuals. Doshisha University said the finding offers a closer look at how animals coordinate sensing when their own signals could otherwise get in one another’s way.

This story draws on original reporting from Phys.org.