Bats are creatures of the night, known for their unique ability to navigate in darkness. These vocalizations are fundamental to their survival, allowing them to thrive in environments where vision is limited.
The Sounds Bats Make
Bats produce a variety of sounds, predominantly high-frequency calls (ultrasound), but also some audible to humans. These sounds are primarily created in the larynx (voice box) and emitted through their mouth or nose. Some species can also produce clicks by snapping their tongues or using their wings. These high frequencies have shorter wavelengths, beneficial for creating detailed acoustic pictures of their surroundings. The pitch of these sounds can vary, with some calls maintaining a constant frequency, while others sweep across a range of frequencies to gather different types of information about their environment.
Echolocation: Bat’s Primary Use of Sound
Echolocation, also known as biosonar, is a sophisticated biological system bats use to “see with sound” in the dark. This process involves bats emitting rapid pulses of high-frequency sound and then listening for the echoes that bounce back from objects in their environment. By analyzing these returning echoes, bats can construct a detailed “sound map” of their surroundings. By interpreting information from echoes—such as the time it takes for the sound to return, its intensity, and changes in frequency—bats determine an object’s distance, size, shape, and texture. This allows them to navigate complex landscapes, avoid obstacles, and locate prey with remarkable precision, even detecting objects as thin as a human hair. When hunting, bats can rapidly increase their call repetition rate, creating a “feeding buzz” that helps them pinpoint the exact location of their prey before capture.
Beyond Echolocation: Social Communication
Beyond their primary use for navigation and foraging, bats also employ a diverse array of vocalizations for social communication; these social calls differ from echolocation calls and serve various purposes within their colonies and interactions with other bats. Bats use distinct sounds to convey intent, mark territory, and coordinate group activities. Examples of social calls include chirps, squeaks, and screeches used for mating, warning signals, and recognizing individuals. Mother bats, for instance, can identify the calls of their own offspring among many others in a large colony. Some research even suggests that certain social calls, such as distress signals, can be more audible to humans due to their lower frequencies compared to echolocation calls.
Human Perception of Bat Sounds
Most bat sounds are inaudible to humans because their ultrasonic frequencies exceed the upper limit of human hearing. The human ear typically perceives sounds between 20 Hz and 20 kHz, but bat calls often range much higher, sometimes up to 200 kHz. This difference means that the majority of the sounds bats make for echolocation remain a mystery to our ears. While most echolocation calls are undetectable by humans, some lower-frequency social calls or sounds produced by larger bat species can occasionally be heard by sensitive human ears. To overcome this auditory limitation, specialized “bat detectors” or ultrasonic microphones convert high-frequency ultrasonic sounds into audible frequencies, allowing researchers and enthusiasts to study bat activity and identify species by call patterns.