As part of the Climate Desk partnership, this article was originally published by the Guardian and is being reprinted here.
It is well known that Ozzy Osbourne enjoys eating bats. However, it appears that the mammals are now also admirers of his.
Scientists have found that bats can vocally stretch much beyond most humans, and they can greet each other with death-metal growls.
They employ ventricular folds, which are thick structures in the larynx, to communicate at low frequencies in addition to emitting ultrasonic chirps to echolocate flying insects in the dark.
In the animal realm, the ability to produce sound through the ventricular folds, which are located directly above the vocal cords, is thought to be uncommon. With the addition of bats, this elite group will now include almost exclusively death metal and Tuvan throat singers.
According to Prof. Coen Elemans, who oversaw the study at the University of Southern Denmark, you can hear these sounds very clearly if you listen to a bat colony in the summer. Although the purpose of the sounds is unknown to us, they are made when the birds are irritated with one another, when they fly away, or when they decide to join a colony.
When the researchers started looking into how bats make high frequency noises for echolocation, they by chance made the discovery. The ventricular folds were found to be vibrating at low frequencies between one and five kilohertz while high speed video of bat voice cords in use was being recorded by the researchers.
According to Elemans, these vocal folds are solely used by humans for throat singing in Tuva and death metal. Death metal grunting results in oscillations that are incredibly erratic and harsh.
Black Sabbath’s Ozzy Osbourne made headlines in 1982 in Des Moines when he notoriously chewed the head off a bat while performing there. Until he bit down and noticed a strange sensation, he claimed he thought the bat was a rubber toy. When it was hurled on stage by a teenage admirer, the animal may have already been dead.
The only two well-known singers that have a vocal range of five octaves are Mariah Carey and Prince. The question of how bats reach seven is cleared up by the Danish research.
We’ve established that the range of the vocal membranes used for echolocation is three to four octaves, and this new structure expands the range below, according to Elemans.
A highly specialised larynx that has undergone changes to make it ideal for producing ultrasonic chirps up to 120 kilohertz has evolved in bats. Prior to the bat, these high frequency sounds serve as a spotlight to locate flying insects. The chirps, however, are very directed and only reach a few metres, thus the animals required a different way to produce low frequency calls to interact with one another across great distances.
According to Elemans, we believe that the selection pressure on these echolocation calls is so great that bats had to come up with a completely new method of communicating. Plos Biology has published the study.