The loud, grumbling bellow that emerges from a male koala sounds very unlike that of a cute, laid-back creature. Now scientists have discovered the anatomy behind the strange sound that males make during mating season.
Male koalas have very long vocal tracts – structures in their throats that produce the sounds. Their vocal tract anatomy is so unusually specialised, in fact, that they are able to make sounds that make them sound far larger than they are.
The study, reported in the Journal of Experimental Biology, used medical imaging to reveal that a male koala’s voice box, or larynx, sits very low in its throat. This “descended larynx” was thought to be a uniquely human feature – something that allows us to make the sounds we need for speech.
It was only in 2001 that scientists found that red deer also had a descended larynx. Its discovery in koalas now supports the theory that it evolved in even more branches of the evolutionary tree, probably to allow males to distinguish themselves vocally from females.