Bats do make clicking sounds, but they are rarely heard because most are produced at frequencies well above the range of human hearing. These specialized vocalizations are the foundation of the bat’s entire sensory world, allowing these nocturnal mammals to navigate and hunt in complete darkness. This sophisticated biological system of sound usage allows them to create a detailed acoustic map of their environment in real-time.
The Purpose of Bat Clicks
The clicking sounds bats produce are the engine of a sensory system known as echolocation, a biological form of active sonar. To initiate this process, the bat emits high-frequency sound pulses, typically through the mouth or the nose, which can reach an intensity of up to 140 decibels in some species. These powerful sound waves travel outward until they strike an object, such as a tree, a cave wall, or a flying insect.
Once the sound waves hit a surface, they bounce back to the bat as an echo. The bat’s highly specialized inner ears and brain then precisely measure the time delay between the initial click and the returning echo. This time difference allows the bat to calculate the distance to the object with remarkable accuracy. Furthermore, by analyzing changes in the echo’s frequency and intensity, the bat can determine the object’s size, shape, texture, and direction of movement.
This mechanism is crucial for foraging, particularly when hunting aerial insects. When a bat detects a target, it rapidly increases the rate of its clicks, a phase often referred to as the “feeding buzz,” to gather continuous, detailed information about the prey’s exact location. Some species possess such fine-tuned echolocation that they can detect a target as thin as a human hair. The constant emission and reception of these clicks enable the bat to build a dynamic, spatial image of its surroundings, allowing for complex maneuvers and successful prey capture in the dark.
Understanding Ultrasound and Human Hearing
The reason most bat clicks go unheard by humans relates directly to the physics of sound frequency. Sound waves are measured in hertz (Hz), which represents the number of vibrations per second. The human hearing range typically extends from about 20 Hz up to 20,000 Hz (or 20 kilohertz, kHz). Sounds that vibrate at frequencies higher than 20 kHz are classified as ultrasound, which is where the vast majority of bat echolocation clicks reside.
Bat echolocation calls generally span a wide range, often beginning around 14 kHz and soaring to well over 100 kHz, with some species reaching up to 200 kHz. Since the sounds are ultrasonic, they are simply too high-pitched for the human ear to perceive, making the night seem silent even when a bat is actively clicking nearby.
While the high frequency makes the clicks inaudible to us, it is a necessary adaptation for the bat. Higher frequencies provide a much better resolution for detecting small objects, such as tiny insects, which is why bats use them. On rare occasions, a bat may produce a lower-frequency echolocation click that falls just within the upper limit of the human range. However, even these audible clicks are typically the exception rather than the rule for the navigation system.
Beyond the Navigation Click
While the high-frequency clicks are for navigation and hunting, bats also produce a diverse repertoire of other sounds that serve a purely communicative function. These are known as social calls, and unlike the ultrasonic echolocation pulses, they are often produced at lower frequencies that can sometimes be heard by humans. These audible sounds are usually chirps, squawks, squeaks, and buzzes that are used for social interactions and communication within a roost or during flight.
The purposes of these lower-frequency vocalizations are varied, including territorial defense, mating rituals, and maintaining cohesion within the colony. These communicative sounds are structurally different from the precise, rapidly changing pulses used for echolocation. Lower-frequency sounds travel farther than high-frequency sounds, making them more suitable for long-distance communication. Therefore, if you hear a bat-like sound, it is most likely a communicative call, which is a deliberate social signal, rather than the inaudible clicks of its personal navigation system.