Bats Create Sounds Like Death Metal Singers, Study Says Their Octave Range Exceeds That Of Mariah Carey
Bats use "false vocal folds" to produce low frequency calls, similar to human death metal singers.
Bats can sound just like death metal singers in certain situations, a new study has found. A similar situation was shown in Stranger Things Season 4, where a character called Eddie played a thrash-metal song called "Master of Puppets" to attract bats in the Upside Down. It is a known fact that bats produce an extreme range of sound frequencies far exceeding human ability, mostly to communicate with each other. Now, for the first time, researchers have filmed how bats produce their extraordinary range of sounds.
The study describing the findings was recently published in the prestigious journal PLOS Biology.
The vocal range of bats far exceeds vertebrates including humans. However, the meaning of bats' sounds and songs is not known yet.
The new study, led by researchers at University of Southern Denmark, said that for some sounds, bats use the same technique as human death metal singers and throat singing members of the Tuva people in Siberia and Mongolia.
The research marks the first time scientists have filmed what goes on in a bat's larynx when it produces sound.
How do bats sing like death metal singers?
The team of researchers has identified what physical structures within the larynx oscillate to make their different vocalisations. Bats use "false vocal folds" to produce low frequency calls, similar to human death metal singers. Vocal fold is the other name for vocal cord. The vocal folds are the bands of smooth muscle tissue found in the larynx or voice box. The vocal folds vibrate, and produce the sound of one's voice as air passes through the cords from the lungs.
Bats are said to use false vocal folds because the cords they use look like vocal folds, but are not used in normal human speech and song.
Also known as ventricular or vestibular folds, false vocal folds are a pair of thick folds of mucous membrane that are located in a particular space in the larynx.
Death metal and throat singers from some cultures use their false vocal folds similar to bats.
In a statement released by the University of Southern Denmark, Jonas Håkansson, first author on the paper, said death metal singers use techniques to make the vocal folds heavy, as a result of which they vibrate at low frequencies.
When do bats sing like death metal singers?
When bats fly in or out from a densely packed roost, they produce growling sounds, similar to death metal singers. Bats, while growling, use their false vocal folds to produce sounds in the range of one to five kilohertz. It is not yet known whether bats use growling sounds with the intention to communicate.
Lasse Jakobsen, a co-author on the paper, said some growling sounds produced by bats seem aggressive, some may be an expression of annoyance, and some may have a very different function.
How do bats produce high frequency sounds?
Bats use echolocation when they hunt insects in complete darkness. When an animal emits a sound wave that bounces off an object, echolocation occurs. The phenomenon returns an echo that provides information about the object's distance and size. Apart from bats, toothed whales and some small mammals use echolocation.
Coen Elemans, one of the authors on the paper, said the researchers identified for the first time what physical structures within the larynx oscillate to make their different vocalisations.
Jakobsen said a bat can determine the shape, size and texture of echoing objects within milliseconds.
Not only do bats produce low frequency sounds, but they also create extremely high frequency sounds. For the first time, researchers have found how bats make their extraordinarily high frequency echolocation calls.
Bats create extraordinarily high frequency echolocation calls by vibrating very thin vocal membranes. Human beings once had these structures, but they were lost in evolution.
Study marks the first time bats’ vocal membranes were filmed
Håkansson said the team has directly filmed these vocal membranes for the first time. The researchers filmed the vocal membranes at extremely high rates, up to 2,50,000 frames per second, in order to show the vibrations of the membranes.
Several adaptations in the larynx are responsible for the bat's ability to make very high frequency calls very fast. These calls help bats catch insects while flying.
Bats have a high octave range
The study said that the normal vocal range for a bat spans seven octaves. An octave is a series of eight notes in a musical scale.
Elemans called this "remarkable", adding that most mammals have a range of three to four octaves, and humans about three. There are only a few singers who can reach a range of four to five octaves. Some notable examples are Mariah Carey, Axl Rose and Prince. Bats use different structures in their larynx to surpass this range.
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