Imagine searching for a gemstone in a dark cave; you use a flashlight, looking for a rainbow-colored glint in the darkness. Now, imagine ten other people in the cave with you, using different colored flashlights at the same time. Suddenly, you can no longer tell which light is coming from your gemstone, which light is from another flashlight, or which light is coming from a reflection of another unknown object. That is what echolocation with multiple, overlapping frequencies would be like. But now, imagine if every person in the cave was using a flashlight in the same color. The glint from the gemstone would be much easier to see. A new study reveals that greater Japanese horseshoe bats use a similar strategy; they align their echolocation call frequencies within a colony to avoid interference and better ‘see’ their surroundings.
Bats are an ecologically important species, responsible for pest control, pollination, and seed dispersal. They use echolocation to ‘see,’ emitting ultrasonic sound waves that bounce back off objects and give them an idea of what, where, and how fast these objects are. Understanding bat echolocation is essential for revealing how animals perceive and navigate their environment. Moreover, the sophisticated sensing strategies of bats have inspired advances in bio-inspired sensing technologies and autonomous robotic systems. For example, sonar technologies are constantly being improved based on observations from echolocating species like bats.
Most bats use frequency-modulated (FM) acoustic pulses, i.e., they vary the frequency of single sound waves in their calls. However, some bat species, such as the greater Japanese horseshoe bat ( Rhinolophus nippon ) use unique pulses that include both FM components and constant-frequency (CF) components. The bats detect and identify prey through ‘glints’, periodic modulations in the amplitude and frequency of the reflected CF component of the echolocation call. Additionally, these bats have a special anatomic feature called the acoustic fovea that shows exceptional sensitivity to a narrow frequency band that is centered on the second harmonic CF component (CF2) of the echolocation pulse. CF-FM bats adjust the CF component of their echolocation calls to ensure that the CF2 component falls within the acoustic fovea to compensate for a phenomenon known as ‘Doppler shift,’ where the frequency recorded by a moving observer or emitted by an object in motion changes based on their speed and direction of motion.
Now, what happens when you mix a group of bats with overlapping CF2 frequency bands? This was the driving question behind a new study, published in Journal of Comparative Physiology A . The study, authored by Haruhito Matsumoto, Soshi Yoshida, and Shizuko Hiryu of Doshisha University, describes how, when wild greater Japanese horseshoe bats are mixed with captive colonies, they modify their CF calls in an unusual way. “ Unlike some other echolocating bats that separate their call frequencies to avoid interference, these horseshoe bats appear to converge on a shared frequency. Building on our previous study showing that they use a ‘silent spectral window’ to detect Doppler-shifted echoes from fluttering prey, we propose that this convergence allows colony members to maintain and share that window ,” explains Dr. Soshi Yoshida.
Elucidated in a previous work, ‘silent spectral window’ refers to a clutter-free band of frequencies above a given threshold that allows for more effective sensing of prey. Here, the horseshoe bats adjust their echolocation frequencies so that most background acoustic interference remains below the threshold. Since Doppler-shifted acoustic glints from fluttering prey occur within this clutter-free frequency band, the silent spectral window enables reliable detection of these prey signals.
For their study, the researchers captured wild horseshoe bats across 15 different time points and measured their CF2 frequencies. The bats were then introduced into a captive colony of the same species of bats, and their CF2 frequencies were measured again after a month. From 2008 to 2024, data was collected from wild and captive bats across 15 capture events to obtain information on convergence. Significantly, the researchers observed an asymmetric pattern to the convergence; lower-frequency individuals (typically, wild-caught bats) strongly shifted their frequencies upwards during convergence. When there were no initial differences in frequency between the wild group and the captive group, no such convergence occurred. “ This observation was only possible because past and present laboratory members carefully recorded the calls of individual bats over many years. It highlights the scientific value of long-term data accumulated through sustained effort ,” says Dr. Yoshida.
The upward shift displayed by lower-frequency individuals supports the idea that convergence is a strategy employed by horseshoe bats to share a silent spectral window above the CF2 frequency. Essentially, when lower-frequency bats received their echolocation bounce backs from prey (i.e., glints), they were in the same range as the higher-frequency calls of other bats in the colony. By shifting their frequencies higher, the lower-frequency bats could avoid that conflict. At the same time, the higher-frequency bats already enjoyed a clear window for their glints and so had less of a driving force to adjust their calls.
Overlap in echolocation frequency is a major challenge to sensing in same-species colonies of bats, but research on acoustic interference in mixed populations of same-species bats is scarce. This study helps fill that gap and provides new insight into how bats interact at an individual level and achieve high-sensory performance in echolocation.
Profile
About Soshi Yoshida from Doshisha University, Japan
Dr. Soshi Yoshida received his Doctor of Engineering degree from the Graduate School of Life and Medical Sciences at Doshisha University, Japan, in March 2026 and is currently affiliated with the American Museum of Natural History as a JSPS Overseas Research Fellow. His research focuses on bat echolocation, bioacoustics, sensory ecology, and neuroethology, especially how bats use Doppler-shifted sounds for navigation and prey detection. In recognition of his contributions, he received the prestigious JSPS Overseas Research Fellowship, awarded by the Japan Society for the Promotion of Science.
About Shizuko Hiryu from Doshisha University
Shizuko Hiryu is a Professor in the Department of Biomedical Engineering, Faculty of Life and Medical Sciences at Doshisha University, and Director of the Acoustic Navigation Research Center.
Her research interests include ultrasonic engineering, bat bioacoustics, and sensing technologies. She has published extensively in these fields, with a particular focus on bat echolocation and acoustic simulation.
In recognition of her pioneering research on bat echolocation and bioacoustics, she has received numerous awards, including the Young Scientists' Prize from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) and the JSPS Prize from the Japan Society for the Promotion of Science (JSPS).
Journal of Comparative Physiology A
Experimental study
Animals
Greater Japanese horseshoe bats (Rhinolophus nippon) gradually converge their echolocation call frequency to colony members
23-Jun-2026