Unique organ gives koalas low-pitched call
19 Dec 2013 by Evoluted New Media
Koalas have an unusual mating call; its pitch is about 20 times lower than it should be for an animal of its size.
The cause of the extremely low-pitched bellow calls is a specialised sound-producing organ outside the larynx say scientists from the University of Sussex.
“We have discovered that koalas possess an extra pair of vocal folds that are located outside the larynx where the oral and nasal cavities connect,” said Benjamin Charlton. “We also demonstrated that koalas use these additional vocal folds to produce their extremely low-pitched mating calls.”
A koala’s bellow is produced as a continuous series of sounds on inhalation and exhalation, which sounds like snoring and belching respectively, explained Charlton.
The calls are more typical of an animal the size of an elephant; smaller species usually call with a higher frequency. The dimensions of the laryngeal vocal folds normally constrain the lowest frequency – and therefore pitch – an animal can generate.
Koalas have bypassed this problem by putting the vocal folds in a new location – just above the larynx at the junction between the oral and nasal cavities. The long fleshy lips in the soft palate may not look that different from the laryngeal vocal folds of other animals but their location is highly unusual and has never been seen in any other land-dwelling mammal before.
“To our knowledge, the only other example of a specialised sound-producing organ in mammals that is independent of the larynx are the phonic lips that toothed whales use to generate echolocation clicks,” Charlton said.
The study – published in Current Biology – represents the first evidence of a terrestrial mammal using an organ other than the larynx dedicated to producing sound. Charlton and his team will now look more closely at other mammals to find out if this vocal adaptation is unique to koalas.
Koalas use a novel vocal organ to produce unusually low-pitched mating calls http://www.cell.com/current-biology/retrieve/pii/S0960982213013444
