Bat larynx. Credit: University of Southern Denmark
Key Points:
- Bats can produce a range of frequencies that far exceeds vertebrates, including humans.
- When bats make low-frequency sounds, they use their “false vocal folds,” like human death metal singers.
- The normal vocal range for a bat is more than double that of most humans, with the exception of singers like Mariah Carey and Prince.
Researchers studying the diverse range of sounds bats make recently discovered an interesting fact: 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.
For the first time, researchers from the University of Southern Denmark, filmed what goes on in a bat’s larynx when it produces a sound like a growl.
"We identified what physical structures within the larynx oscillate to make their different vocalizations. For example, bats can make low frequency calls, using their so called ‘false vocal folds’—like human death metal singers do," said research lead and biology professor Coen Elemans.
False vocal folds are called so because they look like vocal folds but they are not used in normal human speech and song. Only death metal growlers and throat singers from a few cultures around the world use their false vocal folds like the bats. Humans move the vocal folds down so that they oscillate together with the vocal folds.
"This makes the vocal folds heavy and therefore they vibrate at very low frequencies," explained postdoc Jonas Håkansson, first author of the study.
The researchers say growling sounds are often produced when bats fly in or out from a densely packed roost. But, they do not know for sure what a growling bat intends to communicate when it uses its false vocal folds to produce low sounds in the range of 1 to 5 kHz.
"Some seem aggressive, some may be an expression of annoyance, and some may have a very different function. We don’t know yet," said biologist and bat expert Lasse Jakobsen, co-author on the study published in PLOS.
Altogether, the research team says the normal vocal range for a bat spans 7 octaves.
"That is remarkable. Most mammals have a range of 3 to 4, and humans about 3. Some human singers can reach a range of 4 to 5, but they are only very few. Well-known examples are Mariah Carey, Axl Rose and Prince. It turns out that bats surpass this range by using different structures in their larynx," said Elemans.
Information provided by University of Southern Denmark.