You will find various statistics on the rarity of tortoiseshell cats both in books and on the internet including in equally rare studies! The rarity factor varies as widely as 1 in 200 (Dr Desmond Morris in Cat World) to 1 in 400,000 by the Daily Mail! Where did they get that figure from? It seems that there is a difference of opinion.
**Having researched the matter my personal conclusion is a rarity factor of between 1:200 and 1:3000.**
Note: Male tortoiseshell cats are feminized male cats and sterile. They “act like a masculinized female rather than a true male” (Dr Morris). The male tortoiseshell is the result of a “minor genetic error”.
Rarity – how rare?
Here are some suggestions as to rarity:
Our dear Sarah Hartwell, Britain’s scientific cat lover, quotes figures of 1 in 1000 to 1 in many thousands with respect to the rareness of the male tortoiseshell cat. She doesn’t have a firm figure and if she doesn’t, there is no firm figure.
However, a Daily Mail reporter in an article about Eddie, a very dark male tortie (see photo), quotes a 1 in 400,000 chance of being born a tortie tom cat. The reporter also states that no more than a couple of these cats are born annually in the UK amongst the 8 million cats in the United Kingdom. Wikipedia quotes a 1 in 3,000 chance.
One reference a study: Leaman, T., Rowland, R., & Long, S. E. (1999). Male tortoiseshell cats in the United Kingdom. Veterinary record, 144(1), 9-12. Link: https://doi.org/10.1136/vr.144.1.9, concluded from a survey of veterinary practices in the United Kingdom that out of 4,598 male cats only 20 were tortoiseshells. This is 1 in 230. Or a rate of 0.43% of tortoiseshell cats being male.
The well-regarded book on feline genetics: Robinson’s Genetics for Cat Breeders and Veterinarians (fourth edition) states that male tortoiseshell cats occur at a very low frequency; one in every 3,000 male births. That’s probably a pretty reliable figure.
Eddie was adopted by a veterinarian, Karen Horne, who says it is genetically impossible for a cat to be born a male tortie. Clearly genetics go wrong sometimes which allows a mistake to occur. Karen says that she and her colleagues have never seen a cat like Eddie in 30 years of practicing veterinary surgery.
Harry, a rescue cat, who was at Lothian Cat Rescue, Scotland, recently (I wonder who adopted him) state that 99.9% of tortoiseshell cats are female. Harry was the first male tortoiseshell cat that they had dealt with in their 35-year history.
Sarah Hartwell makes the wise comment that rareness in this instance does not mean valuable. Male torties are almost always sterile and if they aren’t they don’t pass on their coat colour/pattern.
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However, there is a point that she overlooks (sorry Sarah). Because of their sheer rarity they are considered in some cultures to bring good luck. The rarity brings them a special kind of value which may translate to monetary value. For example, in Celtic countries tortoiseshell cats were considered a good omen if one lived in the home. And Japanese fishermen would pay HUGE sums of money to have one as a ship’s cat to protect the crew. There you are. Rarity is almost always associated with monetary value. Dr Morris says that the ancient Kymers of south-east Asia the first tortoiseshell cat was ‘created in a magical ritual’ during which ‘the cat sprang from the menstrual blood of a young goddess born of a lotus flower’.
Also, they don’t make good show cats. Rarity does not automatically mean a good show cat and they have to be shown in the “any other color” class. Good show cats have an appearance fitting the breed standard. Eddie and Harry are not part of a cat breed.
This brings me to calico cats – tortoiseshell and white. I presume the degree of rarity of male calicos is the same or similar to that of the tortie. I’ll await being corrected on that!
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