Question of the Day – The Long and Short of Tails

2011-12-13 (2)

Robyn Anderson of Love and Hisses has a new set of kittens. An interesting thing about this litter is that three of the four kittens are partially or completely tailless.  The above picture is from her blog – isn’t he cute?

This got me to thinking about the ways cats with short or missing tails are made.

There are several breeds of ‘tailless’ cats out there, and also a few ‘bobtailed’ cats.  The most well-known of the former are the Manx.  The most well-known of the latter are the Japanese Bobtail.  Interestingly, the two mutations that these breeds have are not related to each other.

Manx Cats

The Manx cat mutation is from a gene called, helpfully enough, the “Manx Gene”.  The gene is dominant, but not fully dominant.  Like White Spotting, having two copies of the gene in a kitten has a much increased effect.  In the case of the Manx gene, though, this effect is invariably lethal.  In most cases the double-dose kitten dies in utero and is reabsorbed by the mother, so Manx litters are somewhat smaller.

The Manx gene shortens and distorts the spine, starting at the tail. The effect is variable, again like White Spotting, controlled by other genes like a volume knob.  Modest ‘volume’ gives a short tail, more gives a short stumpy tail, even more gives a tiny knob or no tail at all.  Sadly, even with one gene the ‘volume’ can sometimes be even higher and cause malformations in the spine further into the back legs, or nerve and muscle issues.  These “Manx syndrome” kittens die at a very young age.

The preference for totally tailless kittens means that breeders are skating very close to producing these kind of kittens.  Breeders normally use one Manx and one non Manx to avoid the stillborn babies, much like the similar issues Scottish Fold cats have.  I’ve heard it said that if the Manx cats were not a historical breed, they might have had a lot of problems getting it accepted as a breed.  The ‘Ojos Azules’ breed was dropped when similar fatal side effects tied to the mutation were found to be linked to the mutation.

American Bobtail Cats

This breed is a relatively new breed, supposedly a new mutation much like the Manx, discovered in this country.  While the info I read was pretty cagey, from the sound of their breeder organization’s ethics rules it sounds like this mutation has problems similar to that of the Manx, if not identical to it.  Like the Manx, the effect runs the gamut from no tail to fully tailed.  From the sound of it, fully tailed cats are docked sometimes.

The intent of the program is to produce a lookalike to a bobcat.  The breed has no bobcat genes that have been detected, and I haven’t heard that bobcat tails vary much in length.  An advantage to these breeders is that the more risky tailless cats are forbidden to be used in breeding.   Since they want ‘stumpies’, the chance of fatal defects in the kitten are reduced.  But if you believe their ethics rules, not completely eliminated.

Japanese Bobtails

These cats have an entirely different mutation – the tail is short, but not missing.  I think I heard at a documentary that these cats have the same number of bones in the tail, they are just short.  This gene is a recessive, so both parents must contribute a bobtail gene.  I haven’t heard that there are any dangers associated with this mutation.

In Manx Circles, this would be known as an “Ultra Longie”…

About Oldcat

Engineer with Cats
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10 Responses to Question of the Day – The Long and Short of Tails

  1. Lurkertype says:

    The cat i had as a kid had a short tail with a knob at the end of it. He was half Manx and used that thing like a club. When he’d twitch his tail in anger, you heard it.


  2. kimkiminy says:

    Gracie has a very long tail. Probably helps explain why she so good in trees. We see a lot of bobcats up here, and I do believe their tail length can vary.


    • Oldcat says:

      Well I looked it up, and the agreement seems to be that a Bobcat tail ranges from 4-7 inches, which is less variation than the Manx gene’s effect of taking a 12 or so inch tail down to 0 or less. In the real world, the Manx gene tends to die out of the population unless mixing is restricted like on the Island of Man.

      I tend to be skeptical of the tendency to ascribe cat traits to ‘wild’ genes except in the cases where we know it was done. And even in those cases like the Bengal most traits in the breed are in the range of behavior of normal cats. The exceptions for Bengals are the rosette fur spot pattern and the reported immunity to Feline Leukemia.

      I’d say that the gene is more likely to be like the Japanese Bobtail version, which also can vary from very short to about half that of a normal cat tail.


  3. Kerry says:

    Oldcat, could you possibly talk about pixie-bobs, which are often polydactyl to boot? Many thanks.


  4. SC Amy says:

    Thank you for this! Other than knowing Manx cats didn’t have tails (or very short ones at the most) I never knew the potential genetic risks until I read some cat blogs that had lost kittens because of tail issues. In your research, did you come across any statistics about what percentage of cats without tails will have further complications?


    • Oldcat says:

      Well, not precisely that number, no. And that might not be the number you are looking for either, if you are wondering what the chance that a kitten that has reached the age Robyn’s have will have problems.

      Even counting kittens gives some selection bias, as some embryos that are very badly malformed will never survive to be born, and will only be ‘seen’ by a smaller average sized litter. Many of the issues are congenital, and thus could be seen already if present, especially the worst ones. But there is a possibility that the nerves in the spine will fail to keep up with the growth of the cat, and that weakness to the back limbs could start to develop with its subsequent problems.

      I did find some really detailed info that I’ll probably post in a future entry.


  5. Tammy says:

    We had two Manx cats when I was young. One was a tiger stripe with a 1-2 inch tail. The other was pure black with no tail at all. He did have some issues going to the bathroom, especially as he grew older, but managed pretty well overall. They were great cats. We named the black one Ewok because we adopted them shortly after the release of Return of the Jedi in 1983. I have a bit of a soft spot for Manxes and am very grateful that I live far, far away from Robyn. Oh, did you find anything in your research about the back legs being slightly longer than the front legs? Both of ours were slightly taller in the back.


    • Oldcat says:

      I don’t think it is the kind of thing that has a definite answer, but since all bobtail breeds and the Manx have the ‘back leg longer’ trait, even when the genetic cause is entirely different, I would guess that the reason the back leg is longer is that the ‘energy’ used up by the embryo in growing a tail has to go somewhere, so it goes to the back legs.

      So it is just a ‘side effect’ of the stunting of the tail growth, no matter how it is caused.


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