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.
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.
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 tortie 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.
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!
Some pages on calico cats: