Hey, if I can write about creatures that literally don’t exist, I’m allowed to do a cat colour variant.

Before any non-cat people roll their eyes and turn away, this won’t be a narcissistic deluge about my own. Tortoiseshells are interesting for reasons other than their latest antics, for instance at a genetic level. In fact they reveal something about us, and I don’t mean in a vomit-inducing, inspirational poster sort of way.

Near-East neighbour

Like all domestic cats, the tortoiseshell split off from Felis silvestris, or more specifically the Near Eastern wildcat, about 130,000 years ago.

Since our relationship was more a slow burner of mutual convenience, there aren’t as many records of cat and human interactions compared to, say, dogs (although for future generations, the internet has filled that gap about a trillion times over). So we made this discovery mainly thanks to a DNA study.

Being a keen and independent hunter, like its ancestor, is one of the characteristics commonly associated with the tortoiseshell. But is opinion as reliable as the science?

Or drawing from memory?


In a word, no. In a small 2012 survey by the University of California Berkeley, people reported several “tortie traits”: on the one hand, “aloof”, “intolerant” and “sassy”, but on the other, “easily trainable”. Unless it was sarcastically obeying, these don’t exactly match up. Then again, neither does its pattern.

X marks the blotch

You might want to top up your coffee, because we’re about to look at genetics.

Going back to high school biology, each cell has one pair of sex chromosomes – XX if female, XY if male. Cats have several genes that control fur colour, and one which has both a black and a ginger version, or allele, is only found on the X chromosome.

Since males have only one X chromosome, they can only carry one of the alleles, so will either be ginger or black. Females, on the other hand, can carry one of each, but their story doesn’t stop there.

For all female mammals, something called “lyonisation” happens very early on in their development. One of the two X chromosomes in a cell will be inactivated, and this can be random from cell to cell.

So in female cats, some of their cells will have the X chromosome with the ginger allele active, others, the black, resulting in a “mosaic expression” of ginger and black blotches. To further complicate matters, some cats have white patches as well, due to a lack of pigment.

Image by dmgreen44.

Said lack of pigment is due to another gene entirely, and this particular moggy mish-mash is known as “calico”. (Didn’t they make toys in the 80s?)

But going back to the tortoiseshell: a male can only exist if he has an extra X chromosome – XXY – or Klinefelter Syndrome. So when a rare male tortoiseshell was born in New Jersey in 2017, the rescue centre was swamped with hopeful owners. Such a bizarre pattern attracts its fair share of bizarre stories too.

Tall-toiseshell tales

I’m not sure which would impress the cat less, but rubbing the tail of a tortoiseshell – alive or dead – on warts was once believed to cure them. Stories from Scotland and Japan also posit that tortoiseshells could sense incoming storms at sea. (Purely anecdotal, but I suffer severe cat harassment when the wind is high.) And in one Danish tale, it was the cat that went under the radar. An amorous troll disguised himself as a male tortoiseshell to avoid his beloved’s angry husband. He remained in the lap of luxury until the latter died, at which point he changed back and ran off to service the willing widow.

So what does the tortoiseshell tell us about ourselves? Well, it’s plain for all to see – it’s a demonstration of what our own genes are doing, only with more blotchiness. And for at least some of you reading, more cuteness.


Latin: Felis catus

What? Colour of domestic cat with black and ginger blotches, caused by a genetic “mosaic expression”.

Where? Um, millions of homes worldwide, as well as the odd farm and feral versions.

How big? Can vary massively, as tortoiseshell is just a colour. However, the average domestic short hair is 25 centimetres / 9.8 inches high and 46 centimetres /  18 inches long, without the tail.

Endangered? Nope, domestication usually takes care of that.

Probable motto: I can be cute and camouflaged all at once. Win.

They look adorable. Do they need my help at all?

I’m sure you have one or two local cat charities or shelters you could help. But if you’re lacking in inspiration:

Cats Protection League

International Cat Care

Just to prove I’m not fibbing:

Andreassi, Katia. 2012. “Venus the two-faced cat a mystery“. National Geographic.

Ashliman, D.L. (translator). 2013. “The troll turned cat“, in Death of an Underground Person. University of Pittsburgh.

Burns, D.A. 1992. “‘Warts and all’ – the history and folklore of warts – a review“. Journal of the Royal Society of Medicine 85: 37-40.

The genetics of calico cats“.No date. Department of Biology, University of Miami.

Gosline, Anne. 2007. “DNA shows domestic cat had origins in Near East“. New Scientist.

Klinefelter syndrome“. No date. NHS.

Pelletiere, Nicole. 2017. “Rare male tortoiseshell cat attracts 100s wanting to adopt“. ABC News.

Sunquist, Mel, and Sunquist, Fiona. No date. “An excerpt from Wild Cats of the World“. University of Chicago Press.

University of California – Berkeley. 2012. “Don’t be so fast to judge a cat by its color, new study warns.” ScienceDaily.

Featured image credit: Mine! Feel free to use if compelled, but please link back to http://www.coffeeandcreatures.co.uk

Incidentally, if you are a cat person, feel free to wish my tortoiseshell Maisie a happy 11th birthday this month.