Benjamin Charlton of the University of Sussex reported the discovery of an additional vocalization organ in male koalas that accounts for the depth of male koala’s vocal range despite the relative size of the animal in the Dec. 2, 2013, edition of the journal Current Biology.
Male koalas make sounds that are as much as 20 times louder and deeper than the average size of the animal would indicate. The vocalizations made by koalas are more in the range of animals that are the size of elephants.
Charlton found a never before known vocal organ in male koalas located exterior to the larynx. Male koalas have an additional pair of vocal folds in the soft palate located at the juncture of the nasal and oral cavities. The location makes the difference in the depth of sound that male koalas can produce.
The discovery is unique in that male koalas are the only terrestrial animal found to date that has developed a vocal organ that is exterior to the larynx. The only other animals that possess vocal organs exterior to the larynx are some species of whales.
The male koala produces sounds as a mating call. The sound on inspiration is likened to loud snoring and the sound on exhalation is like a donkey’s bray.
Charlton plans further research to determine if this adaptation is truly unique to koalas only.