Researchers from a large international team, including scientists from the National Museum of Natural History, Sofia, have discovered that bats can quickly adjust the loudness of their calls in response to sudden increases in background noise, also known as the Lombard effect. When flying in the dark, bats rely on the echoes of their own calls to navigate and locate prey. However, noise from natural or human-made sources can interfere with these echoes, making it harder for bats to “see” their surroundings.
In this study, the researchers observed how greater mouse-eared bats from Orlova chuka cave, Ruse, Bulgaria, respond to loud noise while flying. They found that these bats can increase the volume of their calls within just 20 milliseconds after detecting noise. This rapid adjustment helps ensure their echoes are still strong enough to be heard over the background sounds. What’s remarkable is that this response happens 10 times faster than Lombard effect reactions seen in other animals, including birds and mammals. This unprecedented speed ranks the Lombard reflex of bats among the fastest reflexes of the mammalian nervous system. The discovery once again highlights the amazing adaptation of bats to the extremely dynamic environment in which they live and hunt, making them some of the most successful predators on the planet.
The researchers also explored whether bats would time their louder calls to periods when the noise stops briefly, allowing them to save energy. However, they found that bats do not adjust their call timing in this way. Instead, they react immediately and instinctively to the noise, without waiting for a quieter moment. This suggests that the bats’ response is an automatic reflex rather than a deliberate choice.
This study sheds light on the sophisticated ways bats cope with noisy environments. Their ability to quickly and automatically adjust call volume ensures that they can continue to navigate and hunt effectively, even when conditions are challenging. The findings not only enhance our understanding of bat behaviour but also help us expand our knowledge of how mammalian reflexes and more broadly — musculoskeletal and neurological systems work.