Why Koalas Have Bizarrely Low-Pitched Calls
The discovery of a novel organ explains the mystery.
The koala's mating call sounds nothing like what you'd expect from such a cuddly-looking creature. The deep rumbling and snorting is 20 times lower than what's expected for an animal weighing fewer than 20 pounds—it's more typical of what you'd hear from an elephant. They get their remarkable bellow from a novel organ never before seen in a land mammal, scientists report today in Current Biology.
"Koalas possess an extra pair of vocal folds that are located outside the larynx [or voice box], where the oral and nasal cavities connect," Benjamin Charlton of the University of Sussex said in a statement.
To see if they could reproduce the sounds, Charlton's team ran tests on three male koala cadavers (no animals were killed expressly for the purpose of this study). They used a pump to suck air through the pharynx and larynx via the trachea, mimicking the bellows live koalas make when they inhale.
The only other similar example of an animal with organ specialized for sound production other than the larynx is the toothed whale, which has phonic lips used to generate echolocation clicks.
The calls of these solitary, nocturnal animals may attract far-off mates. Karen Black, an evolutionary biologist at the University of New South Wales in Sydney, Australia, told Nature's Brian Owens that it's not surprising that koalas have a unique anatomy for sound production.
The low-frequency bellows allow koalas to communicate over long distances in their open forest habitats, she says. She notes that they also have extremely large auditory bony structures called bullae in their middle ear, which could be an adaptation for picking up low-frequency sounds.
Next up, Charlton will investigate whether any other marsupials share this remarkable adaptation, or whether koalas alone are the Barry Whites of their kin.