The answer is both Yes and No.
- Yes, when a Manx cat has no tail or a short tail this is how he/she was born and there is no change throughout the cat’s life.
- No, because not all Manx cats are born without a tail. Such is the variety of tail length that breeders have created a language to describe the various types of tail possessed by Manx cats: rumpy (no tail), riser (bump), stumpy (vestigial tail), stubby (short tail), longy (half to normal length tail).
There is an extra point to make about Manx cats being born without tails. It seems that breeders may dock the tail of a Manx cat when it is long or short (as opposed to not existing).
They say that this is for health reasons (to stop it becoming arthritic) but I would suggest that one reason is to sell a Manx cat that complies with the breed standard and which is more valuable. A Manx cat with a tail looks somewhat like a random bred cat and is considered pet quality to breeders who show their cats. Buyers of a Manx demand a tailless cat. The best show cats have no tail whatsoever, ‘Taillessness: appearing to be absolute in the perfect specimen’.
For health reasons Manx cat breeders mate Max cats with non-Manx cats. The result is a litter of kittens of which half carry the Manx gene and of those there will a range of tail lengths from no tail to a short tail.
I think I have answered the question in the title. If you want more detail, the following links to further pages and sections of pages on PoC may assist: