Domestic cats don’t chew food they shear it

When you watch the domestic cat eating food you might think that they use their incisor teeth to grab food and then push it back to their premolars to masticate it into a form where it can be swallowed. But you would be mistaken. The domestic cat’s wild cat ancestor evolved dentition which is entirely suited to their lifestyle and predatory behaviour and the domestic cat has retained it in all its glorious efficiency.

It is often said that the cat is an engineering work of art in respect of a predatory animal. That describes every aspect of their anatomy and one of those aspects is their dentition and specifically a small wild cat’s third premolar which are highly specialised for cutting and shearing chunks of flesh into smaller sizes in preparation for swallowing. The flesh is not ground down as is the case with humans (and cows!).

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Unlike the human, wide, flat molars which are designed to grind food “the rear top and bottom teeth of small cats are used for shearing [slicing]. These upper and lower premolars are called carnassials and slide against each other like the upper and lower blades of scissors”. The quote comes from James Sanderson’s and Patrick Watson’s book Small Wild Cats.

Feline carnassials. These are from a common leopard. Image: Wikipedia (modified to make it square).
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I had difficulty in finding a picture of feline carnassials and eventually settled on those of a common leopard on the Wikipedia website. As you can see, they are nothing like the human molar which is more or less flat. The carnassials is sharp edged and the upper and lower carnassials work together to shear flesh like scissors.

Unlike ordinary scissors, the upper and lower carnassials are different. The upper carnassial is large with three “fangs” and one large crown. There are smaller crowns on either side. The lower carnassial is smaller and has two “fangs” and two crowns.

They act like self-sharpening scissors as the upper and lower carnassials on either side of the jaw wear against each other helping to keep the teeth sharp throughout the small wild cat’s life. I mention small wild cats but as you can see in the photograph the exact same teeth apply to the big cats as well. Although there will be variations.

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Millions of years of evolution has perfected wild cat dentition. Each wild cat species has slightly different dentition because they have different lifestyles and different prey animals. Evolutionary adaptation has created feline dentition which is highly tuned to the kinds of prey the particular species of cat consumes.

It even means that different populations of the same small cat species living in different places can have slightly different teeth, which, by the way, can lead to complications in classifying cat species by taxonomists because they use the teeth of animals and other morphological characteristics to classify the species.

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