Purr: What is it and how do cats do it?

I use the pun purrfect a lot on this website because cats purr, but what is purring? Why and when do cats purr? Do big cats purr? Let's delve into the world of cat purrs! 

What does cat purring mean?

Most people think that a cat that purrs is happy or at least content, but according to PetMD, cats also purr when they are frightened or in pain, so a purring cat is not necessarily a happy cat! 

Kittens start purring after only a few days according to NewScientist, but remain blind and deaf for around 2 weeks, so the first function of purring in cats is to communicate with their mother! The purring from the kittens lets the mother cat know where the kittens are and also when they are ready for some food which is one reason why your cat might purr at you too - to let you know it's time for some food! 

But why would a cat that is frightened or in pain purr? PetMD says a frightened cat may purr as a form a self soothing, kind of like how some people might repeat an affirmation or mantra to themselves when in a stressful situation. According to this article on the Journal of the Acoustical Society of America, purring has also been shown to create frequencies that are healing, particularly for bone growth or fracture healing! So, an injured cat would purr to help promote healing. PetMD even offers a suggestion for how purring became important for cats. They say that because of their unique hunting style of laying in wait for prey, purring might have developed to help keep them in shape during the relatively long periods of inactivity they experience while waiting to pounce! 

But don't worry, if your cat is snuggled up next to you and purring, it doesn't mean it is scared or in pain! A cat purring while interacting with you is a good sign that they are happy and enjoying their time with you! If you pet your cat and get some purrs, that's some positive feedback from your cat to keep up with the petting! However, if your cat has a change in behavior, you can't assume that it is happy just because it is purring. A cat who suddenly acts different might be scared or injured, so even if they are purring, it could be time for a trip to the vet to check it out! 

So, how does a cat purr? 

PetMD says when a cat purrs, it sends signals to it's larynx (or voice box) and diaphragm (which expands the chest when breathing) that cause the vocal cords to vibrate. Then, when the cat breathes in and out, the air moves across the vibrating vocal cords and makes a purring sound. This happens both on the in breath and the out breath, so you'll hear purring pretty much continuously. But, there may be even more to the story than that! Smithsonian magazine says it's unusual for a small sized creature like a housecat to be able to make such low frequency sounds because of their short vocal cords. They cite an article from Current Biology  where they found that cats have pads within their vocal cords that help make those sounds. They say the pads make the vocal cords denser, which allows the cat to make those lower frequency sounds. The Smithsonian article also mentions that more research is needed to see if a cat actively contracts and relaxes the muscles in the larynx in order to keep purring, or if they can initiate purring by pressing the pads together and from there stay on "automatic" until they want to stop purring. 

What about big cats? Does a lion purr? Can tigers purr? 

According to the Carnegie Museum of Natural History, lions and tigers do not purr like house cats do. This has to do with the hyoid bone. The hyoid bone in humans is commonly referred to as the adam's apple, it's U shaped bone in the throat, and in house cats, the hyoid bone resonates during purring. But tigers and lions have some tough cartilage that runs from the hyoid bones to the skull and prevents them from purring. That tough cartilage helps big cats like lions and tigers produce their load roar though! But, it's not just house cats that purr, other cats do too! PetKeen.com says that Cheetahs and Cougars are "big cats" that can purr, and also smaller wild cats like Ocelots and Bobcats can purr because they have a similar hyoid bone structure to our household felines. They also say these cats purr for similar reasons to our pet cats, to self soothe, heal or to signal that they are happy!

And I am happy that you joined me on this journey in to the purrfect world of purring! 


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