As Stephen Mills explained in BBC Wildlife Magazine, only four "big cats" can roar: lions, tigers, leopards, and jaguars. These species, all of which belong to the Panthera genus, have a ligament in their voice box that can be stretched to create a "larger sound-producing passage and thus a wider range of pitch."

In "small cats" like cheetahs, the "fixed structure" of their voice box limits the range of sounds they can produce. While they can purr continuously, they cannot roar.