What percentage of calico cats are male?

Maine Coon Jennie - Calico

Maine Coon Jennie – Calico. Of course she is female. She is also beautiful.

About 0.033% of calico cats are male, we are told. I am not sure how accurate this figure is. Represented a different way it is one male calico cat for every 3000 female calico cats.

In fact, as their existence is theoretically impossible there has to be a genetic anomaly for a male cat to be a calico cat. The male calico cat is described as “very rare”. They are nearly always sterile because they have XXY chromosomes. This causes a condition called Klinefelter’s syndrome (in people), which is the result of additional X genetic material in males. In people, this syndrome can cause the person to be taller than usual with less muscle control and weaker muscles. I wonder if it affects cats in the same way. Update: please see Sarah Hartwell’s comment. The main cause of tortie male cats is a thing called “chimerism”. This is when two fertilised eggs fuse to become a single kitten. I’ll ask Sarah Hartwell to explain it in an article! There is a link to her site in the comments.

As they are very rare they are possibly more valuable than a typical pedigree cat if they are a pedigree cat. However the sterility prevents breeding, devaluing the cat.

Calico” is an American term meaning tortoiseshell and white. In the UK cat fancy the word “calico” is not used as far as I am aware.


  1. Dilute calico cat
  2. Calico cat behavior (some people think they have a certain character)


What percentage of calico cats are male? — 15 Comments

  1. yes,I saw one cat in China at CAA cat show .A male is very healthy.But the testicles are somewhat smaller。
    And the coat is tortoiseshell.

  2. Well in all the years I worked for vets we never had a male tortie (calico) in for neutering, yes some people brought them in thinking they were toms but they all turned out to be queens.

  3. Estimates of the frequency of tortoiseshell and calico tomcats range from 1-in-1000 to 1-in-many-thousands though many are misidentified classic tabby-and-white cats. Contrary to myth, tortoiseshell/calico tomcats are not valuable in financial terms (from here on, I’ll use to term tortie to include tortoiseshell, calico and torbie cats). Though many are fertile, they rarely pass on the tortie colouration to male offspring. And as pedigree cats, there may be no colour class for them to enter at shows.

    To understand what creates tortie cats, we must quickly look at the genes involved. The red gene is carries on the X chromosome. Normal male cats are XY and only need one red gene to make them a red (ginger) tomcat. Without a red gene, they will be black, grey, chocolate etc. Females are XX make-up. To be red, they need 2 red genes. If they only get one red gene they will be tortoiseshell females. If they get no red genes, they will be black, grey, chocolate etc. Cream is genetically “red + dilution gene” and behaves the same way. The scientific term for having patches of different colours is mosaicism.

    At first, scientists believed that tortie male cats must have accidentally inherited an extra chromosome: an X with red on, an X without red and the Y chromosome to make them an XXY (Klinefelter) male. As such they would be sterile and usually have physical anomalies such as an oddly formed pelvis/hips, unusual fat distribution and possibly giantism. Many Klinefelter males are a mosaic (jigsaw) of XY cells and XXY cells because the developing embryo does amazing things to ensure a viable infant.

    In the last 15 years, there have been many more studies of tortie tomcats and the XXY theory has been turned on its head. Many, or most, of the tortie tomcats studied were fertile. Tissue samples showed them to be normal XY males. Some of them had genetically impossible colour combinations such as black and grey patches or red and grey patches. It should be impossible to inherit a mix of normal colour and dilute colour patches. Though fertile, they only passed on one of those colours, not both, to their offspring. This warranted more detailed study and the surprising result was that many (or most) tortie tomcats are due to chimerism.

    A chimera is an organism that contains tissues from two different organisms. Unlike a hybrid, these cells keep their own genetic identity. It’s like conjoined twins that have joined so fully they have become one baby. Because female cats might mate with several males, the embryos that fuse into a chimera might have different fathers.
    Cat chimeras tend only to be noticed where they are “genetically impossible” according to normal Mendelian inheritiance. If a black XX embryo fused with a red XX embryo, the resulting tortie female kitten wouldn’t attract any attention. It’s mostly when the gender and/or colour combination is impossible that it gets noticed.

    If a red XY embryo bumps into and fuses with a black XY embryo, the result is chimera that contains some tissues or organs that are genetically red and some that are genetically black. The resulting kitten has a mix of black and red tissues and appears to be a male tortie (white patches are caused independently by another gene). There are many variations on this e.g. a red XY embryo that fuses with a grey XY embryo gives the impossible combination of a red-grey tortie male! An XY embryo could also fuse with an XX embryo to give a male kitten; in this case, the kitten turns out male only if the XY embryo builds the reproductive system.

    A third cause of tortie tomcats is somatic mutation. This is most easily explained as one or more large black birthmarks on a red or cream coat. It seems that during early embryo development, one of the cells might make a DNA mistake when dividing and this shows up in skin cells as one or more black blotches. This famously happened in a lion called Ranger born at Glasgow Zoo. Lions should never have the black colour, so when a lion with a black leg and black chest was born, the only reasonable explanation was a somatic mutation in the developing embryo.

    Finally there are “tortie mimic” conditions. Late colour-change genes (caused by the extension gene) turn a genetically black cat into a reddish or golden colour cat. The colour change take several months to complete and while the change is spreading over the coat the cat may appear to be tortoiseshell. Some of those colour change genes stop short of changing the colour of the whole coat; the end result mimics tortoiseshell. Unlike other tortie tomcats, these “tortie mimic” tomcats will pass on their colour to offspring.

    • WOW…..Sarah you’re too good, too nice. Fantastic comment. This has to be an article and I’ll make a donation to Chelmsford Cats Protection (a bit less than last time!). If you want to come to London sometime to visit just ask. Richmond is near by. It is a very nice place.

      I’ll comment on this properly after I have digested it for a while….. ;)

  4. Thanks Sarah for the comment here. I’m a longtime reader of your site and had learned from your articles on this. I would encourage anyone who wants to read more details to check out Sarah’s extensive treatment of the subject here http://www.messybeast.com/mosaicism.htm

    A lot of writings elsewhere need to be updated. We always used to hear / read that tortie male cats usually had extra X chromosome(s) and were nearly always sterile. but I kept hearing of fertile tortie males. So it makes sense that the usual cause is something different.

  5. Sarah had already posted one of the links to the article on chimeras. The one I posted was sort of an overview.
    There is a wealth of information on her site about these subjects. Here are some more:

    Early Reports & Studies of Tortie Males http://www.messybeast.com/mosaicism5.htm
    Klinefelter Syndrome cats http://www.messybeast.com/mosaicism3.htm
    ” A Torbie Dynasty?” http://www.messybeast.com/mosaicism4.htm
    Gender Anomalies in cats http://www.messybeast.com/mosaicism2.htm

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