It is a common misconception that bats are deaf. These nocturnal mammals possess an advanced auditory system. Their ability to perceive sounds is specialized, allowing them to thrive in environments where vision is limited. Bats exhibit an exceptional range of hearing.
Bat Hearing Beyond Human Range
Bats possess an extraordinary auditory range, extending far beyond what humans can detect. While the average human ear perceives sounds between approximately 20 Hertz (Hz) and 20,000 Hz (or 20 kilohertz, kHz), bats can hear frequencies as high as 120,000 Hz, and some species even up to 200,000 Hz. This ability to hear in the ultrasonic range allows them to perceive sounds inaudible to humans.
This acute hearing serves various purposes, such as detecting the subtle movements of prey or identifying obstacles in their flight path. While humans rely heavily on vision, bats use their sophisticated hearing to navigate and locate objects in complete darkness.
Echolocation and Its Importance
The most well-known application of bats’ superior hearing is echolocation, also referred to as biosonar. This process involves bats emitting high-frequency sound pulses and then interpreting the echoes that bounce back from objects in their environment. By analyzing these returning echoes, bats construct a detailed “sound map” of their surroundings, much like a sonar system.
Echolocation is important for a bat’s survival, especially for navigation in dark conditions and locating prey. For instance, an insect-eating bat produces a rapid series of calls, often termed a “feeding buzz,” to precisely pinpoint an insect’s location before swooping in to capture it. Different bat species employ varied echolocation strategies; some “shouting bats” emit loud calls, around 110 decibels, suitable for open spaces, while “whispering bats” produce quieter calls, around 60 decibels, to glean insects from foliage in cluttered forest environments.
Specialized Ear Structures
The specialized hearing and echolocation capabilities of bats are made possible by unique anatomical adaptations within their ears. Their external ears, known as pinnae, are often large and complex. Many species can rotate them independently to precisely capture returning echoes, allowing for highly accurate sound localization.
Inside the bat’s ear, specialized structures process high-frequency sounds and rapidly changing echoes. The cochlea, a snail-shaped tube in the inner ear, is often enlarged in echolocating bats, containing more turns than in non-echolocating mammals. Research has also revealed differences in a bony canal called Rosenthal’s canal within the inner ear, which houses neurons that transmit auditory signals to the brain. In some echolocating bats, this canal may be partially absent or have larger openings, supporting their sophisticated echo interpretation.