From high-pitched echolocation calls to sounds of a cricket crawling, bats are great listeners.

05.07.24

By Alyson Brokaw

Ever wondered how bats pull off feats like dodging obstacles, catching bugs on the fly, or finding tiny insects on the ground, even when it’s dark? While bats can see, scientists call bats “auditory specialists,” relying primarily on sound to navigate the world. Millions of years of evolution and adaptations for hunting at night have made bats excellent listeners. But just how exceptional are they? And which bat has the best hearing? 

Spotted bat. Photo by Michael Durham/Minden Pictures.

Sound 101

Little brown bat call modified for human hearing range.

Before we determine which bat hears the best, let’s review how sound works. Sound moves through the environment in s-shaped waves and is primarily measured in two ways: frequency and amplitude. Frequency is a measure of how closely packed the peaks of sound waves are, determining pitch. Low pitched sounds, like a bass guitar chord, have long, stretched out soundwaves, while high-pitched sounds, like that of a whistle, have short, close waves. Pitch is measured in hertz (Hz) or kilohertz (kHz) for high pitched sounds. Human hearing ranges from about 20 Hz (slightly lower than the lowest note on a bass guitar) to almost 20,000 Hz (or 20 kHz). Depending on the species, bat hearing ranges from around 700 Hz to around 200 kHz. 

Imagine a sound wave again. The height of the waves is the amplitude of the sound, measured in sound pressure decibels (dB SPL) and indicating a sound’s intensity or loudness. From about 3 feet away, a whispered conversation measures around 20 to 30 dB, while a car horn registers at around 110 dB. How animals perceive loudness depends on distance from the source, with intensity decreasing with increased distance. Amplitude and frequency interact with each other and the environment to influence how sounds are perceived. To make it even more complicated, sounds in nature are rarely a single frequency or amplitude, instead consisting of a collection of different sound waves together. 

To Hunt You Better

Fringe-lipped bat. Photo by Christian Ziegler/Minden Pictures.

So who hears best? Bat listening abilities are closely linked to their ecology – what they eat, how they hunt, and their echolocation calls. Bats usually have two peaks in hearing sensitivity, one at lower frequencies and another at higher frequencies. The higher frequency peak usually corresponds to the frequency range of the bat’s own echolocation calls and is also highly sensitive to loudness. This is because bats use the intensity of sounds to calculate the distance and size of objects. The bat with the highest known echolocation call is Percival’s trident bat (Cleotis percivali), named for its trident-shaped nose leaf and found in sub-Saharan Africa. While their hearing range has not been measured, it is inferred to be somewhere between 110 and 200 kHz, based on the maximum and peak frequencies of their echolocation calls. 

Can You Hear Me Now? 

Gleaning bats, who capture prey from the ground or off vegetation are particularly skilled listeners. While these bats use echolocation to get around, they hunt by attending to the sounds made by prey, whether its rustling leaves or a mating call, and have low frequency hearing sensitivity to match. The fringe-lipped bat (Trachops cirrhosus) is more sensitive to frequencies between 3 and 6 kHz than similar bats, which closely matches the mating call of their favorite food, the túngara frog. Meanwhile, the white-throated round-eared bat (Lophostoma silvicolum) has extra keen hearing between 9 and 37 kHz, corresponding to the frequency of the calls of katydids. Bats that hunt by listening or have quiet echolocation calls often have really big ears. The spotted bat (Euderma maculatum), who uses low frequency echolocation to sneak up on flying moths, has ears that measure almost two inches when fully extended (that’s half of their body length). Large ears act like satellite dishes for sound, helping direct sound waves into the ear canal. But unlike satellite dishes, bats can change the shape of their ears in just a tenth of a second, letting them maximize their hearing sensitivity depending on the environment. 

Bats can change the shape of their ears in just a tenth of a second.

Fringe-lipped bat. Photo by Christian Ziegler/Minden Pictures.

But who has the best low-frequency hearing? That award goes to the common vampire bat (Desmodus rotundus). While most sensitive to frequencies around 70 kHz (the peak frequency of their echolocation calls), vampire bats can hear frequencies as low as 716 Hz. This means that common vampire bats hear the lowest frequency of any bat, even bats that don’t echolocate and other mammals like the Virginia opossum. It’s thought that hearing these low frequencies helps vampire bats tune into the breathing sounds of sleeping mammals while they sneak up to feed. 

Common vampire bat. Photo by Charles M. Francis

It is also important to note that bats have to listen for more than just echolocation calls or the sounds of insects moving. They also use a variety of social calls to communicate with each other, including courtship songs, aggressive buzzes and pup isolation calls. Most bats measured also show increased sensitivity at lower frequencies that correspond with the pitch range of these communication calls. 
From high to low, there is no doubt that bats are true masters of hearing. However, the specific hearing abilities have only been measured in a small fraction of the more than 1,400 species of bats worldwide. While the bats highlighted here currently hold the hearing crowns,  future discoveries could still shake up their reign.

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