Most members of the animal kingdom get sweet bonus stuff. Cats get retractable claws, monkeys get prehensile tails – and apparently koalas get extra vocal cords. Researchers have discovered that male koalas have an extra pair of vocal cords that gives their mating calls a pitch 20 times lower than it should be for a marsupial that size. To put that in perspective, it would be like a Chihuahua that can yap in the pitch of an elephant.
The key to the koala’s deep pitch is found in a special sound-producing organ outside its primary voice box. Normally, small mammals are high pitched because their vocal folds are constricted by their tiny voice box. But the koala’s extra vocal cords are outside the voice box, allowing their bellow to reach a much deeper pitch. “Koalas possess an extra pair of vocal folds that are located outside the larynx, where the oral and nasal cavities connect,” says Benjamin Charlton of the University of Sussex. He also says this has never been seen in a land-dwelling mammal before. “To our knowledge, the only other example of a specialized sound-producing organ in mammals that is independent of the larynx are the phonic lips that toothed whales use to generate echolocation clicks.”
These extra vocal cords don’t look different from any other mammals, described by Charlton as two long, fleshy lips in the soft palette. It’s their location that is so special and allows the koala to produce its irresistible mating call. This ‘charming’ call is created by a bellowing sequence of inhales and exhales, like a braying donkey. The inhale sounds like a really loud snore, and the exhale sounds like a really loud belch.
The researchers have published their study in Current Biology and hope to continue studying other mammals to see if koalas are really the only ones who possess a whole other organ devoted solely to producing sound.
Click here to see a video of those vocal cords in action!