Bats are fascinating nocturnal creatures that actively navigate their environment using sound. While many of the sounds bats produce are beyond the range of human hearing, some vocalizations are audible and reveal aspects of their complex lives. They rely on an intricate auditory system for survival, allowing them to perceive their surroundings in darkness.
Echolocation: The Bat’s Sonar System
Echolocation is a sophisticated biological sonar system bats employ for navigation and hunting in the dark. Bats produce high-frequency sound waves, typically through their mouth or nose, and then listen for the echoes that return from objects in their environment. This process allows them to create a detailed sound-picture of their surroundings, determining the distance, size, shape, and movement of objects, including their prey.
The frequencies of these echolocation calls vary widely among bat species, generally ranging from 9 kilohertz (kHz) to over 200 kHz. Most of these calls are ultrasonic, meaning their frequencies are too high for the human ear, which typically hears sounds between 20 Hz and 20 kHz. Bats can adjust their calls, increasing the repetition rate as they close in on prey, a phenomenon sometimes called a “feeding buzz.” Different bat species also have distinct echolocation call patterns adapted to their specific hunting styles and habitats.
Some bats, like the spotted bat, produce echolocation calls that are faintly audible to humans with good hearing. The intensity of these calls can range from 60 to 140 decibels. Bats have specialized inner ears and a large auditory cortex to process these complex sound signals efficiently.
Other Bat Vocalizations
Beyond echolocation, bats produce a diverse array of vocalizations for communication, distinct from their navigation calls. These social calls serve various purposes, including territorial defense, attracting mates, and communication between mothers and their pups within a colony. They can also signal distress, leading to sounds that can resemble cries or whimpers.
These communicative sounds often fall within a lower frequency range compared to echolocation calls, making some of them audible to humans. Examples of social calls include chirps, clicks, squeaks, squawks, buzzes, and trills. For instance, some social calls can be loud and low in frequency, while others are short, rapidly descending sweeps or complex, song-like sequences. The ability to distinguish between echolocation and social calls is important for bats.
Identifying Bat Sounds
Distinguishing bat sounds from other nocturnal noises can be challenging for humans, as many bat vocalizations are ultrasonic. However, audible bat sounds, primarily social calls, often manifest as high-pitched squeaks, rapid clicks, or rustling noises. Bats communicating in attics may produce a series of chirps or squeaks. These sounds can be mistaken for those made by birds, insects, or rodents, which also produce chirping, clicking, or squeaking noises at night.
To confirm the presence of bats, specialized equipment such as a bat detector can convert ultrasonic echolocation calls into frequencies audible to humans, often sounding like clicks, chirps, or static. When a bat is actively hunting, the rapid increase in call repetition rate, known as a “feeding buzz,” can be translated into a distinct buzzing sound by these detectors. If audible sounds are identified as bats, remember that these animals are nocturnal and typically harmless. They play a beneficial role in controlling insect populations. In situations where concerns arise, particularly regarding bats roosting in structures, contact professionals.