Why Your Cat Can Purr, But Cannot Roar November 09 2018

The little purring ball of fluff in your living room has a lot more in common with a tiger stalking the jungles than you might think. They share about 95.6% common DNA. They both rub their faces on objects (and each other) as a sign of affection. They both hunt live prey (and sometimes bring it back to the ones they care about.) And yes, big cats and small cats alike both really, really dig catnip. There are many similarities between big cats and our fluffy felines at home, but why can big cats roar and domestic cats can't? And why can domestic cats purr, while big cats can't?

It all comes down to a small bone, called the hyoid. Cats that roar can't purr, and cats that purr can't roar. 

The big cat family is split up into four species of big cat that can roar: lions, tigers, leopards, and jaguars. These big cats can roar thanks to the construction of their hyoid bone, which is a U-shaped bone in the throat that sits above the larynx.

Without getting too technical, the hyoid provides structure for parts of the sound-producing section of the throat, making it central to sound production in cats. Lions, tigers, leopards, and jaguars all have a special flexible ligament that connects the hyoid bone that is able to withstand the force of a roar: A lion or tiger can roar as loud as 114 decibels. That’s the same level of sound a jet airplane makes during takeoff. A male lion's roar can be heard from five miles away. Just for comparison, the little lions in our living rooms purr at around 25 decibels.

In domesticated cats and other wild cats that can’t roar, the hyoid bone is completely ossified. Because it’s non-flexible and hardened, these cats produce a less intimidating and comforting purr. Their vocal cords have specialized folds that are divided and vibrate during inhaling and exhaling. But it limits their range of pitch and prevents the ability to roar. 

When it comes down to it, it's probably a good thing our cats at home can't roar - imagine being woken up at 2 am to a hungry cat roaring into your ear!