As well as house cats, cheetahs and cougars can purr but not roar. However, other cats like lions and tigers can roar but cannot purr, like jaguars or jaguars.
Although house cats can dominate the living room, one thing sets them apart from their jungle kin: their vocalizations. House cats can't roar as loud as big cats like tigers and lions, but they can still make their presence known by their gentle purrs and meows.
Why can't house cats roar, then? It would be a great way to help them navigate the house, even more than they already do.
This is due to the anatomy of the feline voice box and throat that creates these vocalizations. John Wible, Carnegie Museum of Natural History's curator of mammals, stated that cats can either purr or roar due to the way they are made.
Related: Why do cats meow when they are scared?
Purring is an unusual sound, because it can be made both when the cat breaths in and out. Wible stated that vocalization appears to have originated in cats first and is common in Felidae families. The purring cats include the house cat (bobcat), ocelot, lynx and cougar.
Wible explained to Live Science via email that roaring is a rare breed among cats. It evolved in a specific lineage of large cat species. These cats form the Panthera genus which also includes leopards, lions, tigers, jaguars, and tigers. Wible and a study published in the Journal of Anatomy suggest that the snow leopard may have lost its ability for roaring.
The voice box of cats, also called the larynx, is responsible for making the sounds they make, just like humans. Wible stated that the difference between purring cats or roaring cats begins here. However, it is not clear how cats make these sounds.
The throat is a bendy bone and roars are made from it
The throat houses the mammalian vocal box, which is where air passes through its structures to create sounds. Two essential components of the larynx produce vocalizations in cats: the vocal cords and the hyoid bone.
Wible stated that all mammals have bones in the neck near the lower jaw, which are the hyoid device. These bones connect to the base skull via either ligaments or directly. The hyoid is a key difference between purring and roaring species.
Wible stated that the unique arrangement of one pair of bones in the hyoid apparatus (the epihyoids) is what the roarers have. The epihyoid, which is not a bone, is an elastic ligament. Flexible cartilage allows animals to lower their voice box, resulting in a higher-pitched sound.
Variations in the voice box can produce purrs
Wible stated that purring is also possible by the difference in roaring and purring cats. "Purring occurs when the vocalis muscle is twitching rapidly in the vocal folds of the voice box.
Roaring cats have thicker, more dense, sturdier, and fleshier layers of tissue that make up their vocal chords. According to research published in PLOS One 2011, this tissue allows big cats to make a high-pitched roar. However, it does not allow them to purr.
Wible stated that whatever physiological changes led to the cat's purr "it must have provided an evolutionary advantage to continue in the cat lineage." Scientists don't know what the cat's purr is doing in the wild. Some theories suggest that purring may be a soothing or healing mechanism, or it may help protect kittens from predators.
Wible stated that "my house cats purr as an indicator of contentment as far I can tell." "But, I don't know whether that is the case for wild cats who purr."
Original publication on Live Science
