What causes a cat to have 4 ears?

We don’t know much about the genetic mutation which causes a cat to have 4 ears, which the experts describe as a “cosmetic anomaly”. The description “4 ears” is actually incorrect because ‘ears’ includes the whole ear: the ear flap, the ear canal, the middle and inner ear. The better description would be a domestic cat with “four ear flaps”. The scientific name for ear flaps is ‘pinnae’. Because these are non-functioning extra ears. The cat retains their normal, functioning ears incidentally.

That is something which The Daily Mail report did not mention. It’s a vital aspect of this genetic mutation. It is in fact a recessive mutation. The cat is unaffected in terms of health and therefore it is, as described, cosmetic. But note: the Wikipedia authors say that a 1957 study of 4-eared cats concluded that there were other anatomical anomalies such as smaller eyes and a slightly undershot jaw. The cats in the study were also inactive and lethargic.

The brain might also be affected they said. And breeding data indicated that the mutation is most often lethal with kittens dying in utero. This does not square up at all with my knowledge of this mutation and the story of Aslan is a good example as he is healthy as confirmed also by his owner. Wikipedia authors do go on to state that the majority of reported 4-eared cats have been healthy. Their reporting is confusing to me but I need to pass it on in this article.

Aslan the cat with four ears due to recessive genetic mutation
Aslan the cat with four ears due to recessive genetic mutation. Photo: TikTok account aslanthe4earedcat.
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Clearly, this genetic mutation affects the development of the embryo in the womb and programmes the embryo to create two ear flaps. It is basically an error in programming. A similar cosmetic anomaly is polydactylism, which describes cats with more than the normal number of toes (it affects humans and many other animals too). It is also entirely cosmetic which means there are no associated health problems. Polydactylism is quite common whereas extra ears are very rare indeed. Polydactyly in cats is the result of a single, autosomal dominant gene, which means that mutated gene overrides other normal genes. ‘Autosomal’ means not sex linked.

Cats with four ears do pop up from time to time and if you click on the link below you will be taken to a page about another cat with four ears.

Beautiful cat with four ears and one eye

Robinson’s Genetics for Cat Breeders and Veterinarians says that the Munchkin is an example of a genetic anomaly without medical issues. This is incorrect because the Munchkin is a dwarf cat and dwarf cats can inherit a couple of well-known medical conditions called lordosis and pectus excavatum.

Video of Aslan


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Note: This is a video from another website. Sometimes they are deleted at source which stops them working on this site. If that has happened, I apologise but I have no control over it.

The Wikipedia reference is: Little, C. C. (March–April 1957). “Four-Ears, a Recessive Mutation in the Cat”. Journal of Heredity. XLVIII (2): 57. doi:10.1093/oxfordjournals.jhered.a106682.


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