Why Do Cats Purr And Dogs Don’t? This Is The Reason Why!
If you have a cat, you know the soft, motor-like rumble it makes when you pet it or set down its food. Dogs never make that sound, and the reason comes down to anatomy.
Cats often purr when they are relaxed and content. Dogs show contentment in other ways, mostly through body language.
Why do cats purr and dogs don't? Dogs don't purr because they lack the specialized voice box mechanism that cats use. A cat's purr is produced in the larynx (voice box) as air moves in and out, and it is part of the normal cat vocal repertoire. Dogs simply aren't built to make that sound.
Below, we look at how purring works and how dogs show they are happy instead.
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Reasons Why Cats Purr And Dogs Don't
Cats and dogs are different species with different voice boxes and different ways of communicating.
Cats purr when they are relaxed, happy or seeking contact with you. They also often purr under stress, such as at the vet, while giving birth or when recovering from an injury. Purring may help cats calm themselves or ask for care.
How do cats purr? According to Scientific American, purring is produced through intermittent signaling of the laryngeal and diaphragmatic muscles. Cats purr while breathing both in and out, at frequencies between about 25 and 150 hertz.
A 2023 study by researchers at the University of Veterinary Medicine Vienna added a twist. Cat larynges removed for study could still vibrate at purring rates without nerve signals, possibly helped by pads of connective tissue in the vocal folds. The authors said muscle activity may still play a role.
Why can't lions and tigers purr? In the lion, tiger and jaguar, part of the hyoid apparatus (the set of bones that supports the tongue and larynx) is an elastic ligament. In the domestic cat and the cheetah, that part is bone.
Scientists long linked this difference to which cats roar and which purr. As National Geographic explains, later research found pads of fibro-elastic tissue in the vocal folds of roaring cats, so the full story is more complicated than the hyoid alone.
Dogs have a hyoid apparatus too, but their larynx and vocal folds are not built for purring.
You may notice your dog making a low grumble, groan or sigh when it's relaxed and being petted. Some owners think of this as a dog's version of purring, but it is a different sound.
Now that you know the reason why cats purr and dogs don’t, let's look at how dogs show they are happy.
Ways Of Dogs To Show Happiness
Relaxed ears. A happy dog's ears sit in their natural, relaxed position rather than pinned back or held stiffly forward.
A loose, wiggly body. A happy dog's whole body looks soft and relaxed, and it may wiggle when greeting you.
A soft, open mouth. Many content dogs have a relaxed, slightly open mouth, which people often call a smile. Bared teeth with a tense face is a warning sign, not a smile.
A loose, wagging tail. A broad, loose wag, often with the whole rear end moving, usually means a dog is happy and excited. A stiff, high, fast flick can mean the opposite, so read the tail along with the rest of the body.
Final Thoughts
Cats purr because their larynx can produce that sound, and dogs can't because theirs isn't built for it. Dogs show contentment mostly through body language.
Cats use body language too, just more subtly. Ear position, tail carriage, slow blinks and posture all tell you how a cat is feeling, and a purr is only one part of the message.
Sources
- Why Do Cats Purr?, Scientific American
- Domestic cat larynges can produce purring frequencies without neural input, University of Veterinary Medicine Vienna
- Hyoid apparatus and pharynx in the lion, jaguar, tiger, cheetah and domestic cat, Journal of Anatomy
- Why Margarita Can Purr, but Can't Roar, National Geographic
