Koalas have a newly discovered extra set of vocal cords that allows males to hit notes 20 times lower than expected.
Because the sizes of an animal’s voice box and its flapping vocal cords dictate the range of pitches an animal can make, a typical 8-kilogram koala should stick near the soprano section. But the male’s sexy mating songs, which to humans sound like a string of belches and snorts, dip to tones usually only made by elephant-sized mammals.
By dissecting the voice boxes of 10 male koalas, Benjamin Charlton of the University of Sussex in Brighton, England, and colleagues found that the Australian marsupials possess a unique, extra set of vocal flaps outside of the voice box that lets them belt out sonorous sounds. The unusual vocal cords make the koala an anatomical as well as an acoustical anomaly, the scientists write in the Dec. 2 Current Biology.
The low-pitched rumbles and snorts of a male koala’s mating calls, heard here, come from the vibration of an extra set of vocal cords located outside the voice box.