The reason why some domestic cats meow silently is because it is a very close-range pseudo-vocalisation which has become a visual signal rather than a vocal one.
You’ll find that in the cat world there is an understandable difference in the quality and volume of the sounds that they make depending on distance that the sound has to travel to be effective.
The classic, well-known long distance feline sound is the tiger or lion’s roar. A calling sound. This can travel several kilometres. The domestic cat meow is a close-range sound which usually denotes a request.
The meow varies tremendously in its quality and intensity. You have the guttural Siamese meow which is quite demanding (in a nice way) and the delicate British Shorthair meow which can, in its delicacy, become silent.
My cat makes a silent meow. He produces this non-sound when he is very close to me and when we have made eye contact. For him it is a sign of pleasure. He is responding to my gentle petting at the back of his neck which he particularly likes. Each cat has their own pet likes and dislikes.
As there is no need to make a sound he doesn’t. It is more efficient that way. What should be a vocal signal meaning ‘I am content, and thanks by the way’, has become a visual one.
It is either entirely silent of the vestiges of a meow emanates from his mouth. His jaw might judder slightly. It is all very ritualistic.
I think it is fair to say that, as mentioned, of the purebred cats the British Shorthair is more predisposed to the silent meow than other cats. It comes down to individual characteristics at the end of the day and that cuts across random bred and purebred cats.
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