It is rare to see a particular pattern of striping in tabby cats. Tabby is not a breed, just a kind of feline coat which has stripes on it. Of the various striped possibilities the configuration we refer to is called a "blotched," or marbled, or classic tabby pattern. You may recall this blog disdains Wikipedia, and that is because if you quote Wikipedia, you are just saying you know nothing about a particular point. Even so, I did find out the names of this pattern from that source.
The pattern is a swirl, and typically appears on the sides of a cat with this marking. The cat often looks like it has a oval or spiral circling in it's striping. The effect is quite beautiful and as I said, not so common as most make it out to be. The pattern is referred to variously as marbled tabby, classic tabby, or blotched tabby. All point to the same swirl.
Most includes John Bradshaw who discusses the distribution of this pattern in his book,
Cat Sense: How the New Feline Science Can Make You a Better Friend to Your Pet (2013).
Apparently now in Britain there are more of this marbling striped cats than there are the regular striped ones (which have vertical--like a tiger's-- stripes). His research suggests that until two thousand years ago, and maybe even more recently, all tabbies had this vertical striping. "The mutation for the blotched tabby pattern probably first took hold sometime in the late Middle Ages and almost certainly in Britain where it is the commonest pattern today."
Here's an interesting part:
Despite... [the fact gene for blotching is recessive] in Britain and in many parts of the United States blotched tabbies outnumber striped tabbies about two to one, meaning that more than 80 % of cats carry the blotched version of this gene.
But his point is intriguing. The gene for the classic tabby must provide some benefit to the cat over the rest of the cat population or that gene would not have spread, especially so far and so fast. But nobody knows WHAT benefit that is. There was a theory relating the gene to the survival of cats after Britain was industrialized. At a point when British cities were covered in soot, the marbled cat and the black cat both found it easier to hide. Still our author discards this idea, at least for now.
We see the rise of the blotched tabby gene in Britain reflected in the proportions of blotched tabbies in former British colonies all around the world. In the northeastern United States, New York, Philadelphia, and Boston, settled in by Europeans in the 1650's , only about 45% of cats carry the blotched tabby gene, but this is considerably more than in originally Spanish settled areas, such as Texas, at around 30%, - where cats look much like those in Spain today.
So the more recent the arrival of the British blotched tabby, the larger its numbers in the general cat population in their new home, since a more recent date indicates a larger number of cats with that gene in the home country, arriving on foreign shores. This is part of Bradshaw's argument that the number of British cats with the gene for blotched tabby coats has steadily grown in Britain.
...the Atlantic Provinces of Canada, settled some 100 years later, have more blotched tabbies. European colonies settled in the nineteenth century are more variable: Hong Kong, in particular, has fewer than it should, probably because there was already a striped-tabby population of Chinese origin there, thus diluting the effect of British immigration. Australia on the other hand has more than it should, possibly the result of later waves of British immigrants in the 20th century bringing their cats with them. The proportion in Britain was over 80% in the 1970s, and have continued to rise since then.
Bradford's whole statistical argument would fall apart were it not for the Atlantic Provinces statistics, falling where they do chronologically. But we should all be grateful for Canada. It is always exciting to find out about a real mystery: in this case, what is the evolutionary advantage for blotched tabbies, which advantages relate to their thriving so, in their British setting.
Oh, and today, July 1, is Canada Day, so it is nice we have some glorious facts to celebrate it with. O Canada.