Not all cats purr. In fact, there are two kinds of cats, the ones that purr and the ones that roar. For instance, none of the Pantherinae subfamily of cats can purr. And this includes lions, leopards, jaguars and tigers. But they can roar.
Now the cats that can purr include our domestic common cats as well as big cats that can’t roar, like bobcats, cheetahs, lynxes, pumas and wildcats. And these are the ones we care about. Because it feels like they’re sharing their contentment with us when they’re happy.
How Do Cats Purr?
The most accepted idea is that a cat’s brain signals its laryngeal muscles in its voice box so that they vibrate. These muscles then act like a valve by opening and closing the glottis which is the space between vocal cords. And that allows air to flow past the cat’s voice box. Now one reason we’re pretty sure this is how purring works is that cats with laryngeal paralysis can’t purr. So what makes purring so distinctive, is that it works when cats are both inhaling and exhaling.
And while we have a pretty good idea of how purring works in the throat, scientists don’t 100% agree on how cats initiate purring. Some believe that it’s a voluntary act initiated by their nervous system. So this would mean that cats only purr when they want to. But other studies suggest that the purr signal comes from a neural oscillator in the cat’s brain. And then still another theory is that purring is caused by the release of endorphins when cats experience either pleasure or pain.
Reason Why Cats Purr
That’s right, cats don’t always purr when they’re happy. Sure, we mostly hear them do it when we’re petting them or feeding them. And nursing kittens purr to let their mothers know they’re well because they can’t meow and drink milk at the same time. So purring is a way to bond with their mothers and say hey cat mom, I’m A-okay. But purring communicates more than just happiness.
Upset, injured, sick or even dying cats are known to purr. And female cats sometimes purr when they’re delivering kittens. Animal behaviorists think that these cats are purring under difficult circumstances because they’re comforting themselves. Now it’s also possible that frightened cats purr to communicate peaceful intentions, to signal that they are not going to attack. And so older cats do this sometimes when they approach younger cats to say hey, younger cat, I am totally friendly.
Now there’s another pretty awesome hypothesis about why cats purr. The rapid opening and closing of their vocal chords creates a sound between 25 and 150 hertz. And these sound frequencies can both improve bone density and act as a natural healing mechanism. There is evidence, in fact, that shows that purring can repair bones, relieve pain and heal wounds.