More on cat genetics

From the readers’ comments on yesterday’s cat-coat post, there’s clearly some interest in the genetics and evolution of house cats (Felis catus).  This is a huge topic, too large to cover here (in my younger and impecunious days, I thought of writing a popular book on the topic).  I just want to make two points:

1. We know an enormous amount about the genetics of cat coat color and pattern. Wikipedia, for instance, has a good summary, and if you want a dose of photos with your genetics go here.  Note that much of what was written about the genetics of ticking and tabby patterns before this year is likely to be wrong: a recent paper by Eizikir et al. (2010) shows that there are at least three loci responsible for the variation (everybody used to think that there was one), and probably at least two developmental pathways involved in producing the familiar patterns of spots, stripes, and swirls.

Here’s a nice photo from their paper showing a cross between two parents (“P”), their offspring (F1), and the backcrosses, obtained by crossing F1 individuals to one of the parents.  Note the re-establishment of the striped “mackerel” pattern in the backcross offspring.  These crosses helped Eizikir et al. disentangle the genetic interactions involved in coat pattern.

2.  Why is there such variety in the coats of domestic (and stray) cats? Surely because people have bred for those colors and patterns, and most feral cats are recent descendants of pets.

It’s my theory that all feral cat populations will eventually revert to the tabby pattern; this comes from observing long-time populations of strays, and seeing the pattern of the “Scottish wildcat”, which I firmly believe is not a native species but a descendant of feral domestic cats.  (Populations of feral dogs seem to revert to a yellowish, dingo-like color.)  Why this reversion, if it’s indeed the case?  Perhaps selection for camouflage, although I’m not sure what preys on feral cats, and whether those cats live in habitats where a tabby pattern would camouflage them to both predators and prey.  Another explanation is that the tabby pattern is linked to genes that help domestic cats survive when forced to live ferally.

__________

Eizirik, E., V. A. David, V. Buckley-Beason, M. E. Roelke, A. A. Schaffer, S. S. Hannah, K. Narfstrom, S. J. O’Brien, and M. Menotti-Raymond. 2010. Defining and mapping mammalian coat pattern genes: Multiple genomic regions implicated in domestic cat stripes and spots. Genetics 184:267-275.

31 thoughts on “More on cat genetics

  1. Although I do not have a background in this, I have been admiring the feral cat populations in the Middle East for some years now and in particular noting the naturally spotted (Egyptian Mau througout the region) descendants, the striped cats and the ones crossed in between with stripes AND spots. Always curious if the spots are just converting to stripes in the populations.

  2. “Perhaps selection for camouflage, although I’m not sure what preys on feral cats”

    It should be obvious: camouflage not only conceals prey from the predator, but helps the predator sneak up on the prey. Duh! Why do duck and deer hunters wear camouflage?

      1. But cats are natural nocturnals (those extra-wide opening irises et al). Wouldn’t the ‘tabby’ colouring be good for a nocturnal, no matter where it lives ?

        1. That is a valid point. In Europe the domestic cat has predators, among them large birds of prey, the fox and most important, the domestic dog; especially in areas where the dog is allowed to run round in packs, they revert to instinct and will hunt small animals like cats. On two occasions I have watched dogs dodging traffic to consume a road kill cat. Many dogs used to be left out during the day when owners were at work. Fortunately strict legislation has dealt with that situation.

      1. When I lived on a farm in Sweden, our (young) cats had to survive common buzzards and red kites. If a cat takes cover in a bush, kites will reportedly land and pursue it on foot.

        We also lost a large number of kittens to badgers. At one point, one had raided the carport (catport?) and left behind a dozen or so bisected kittens for later consumption. Pattering would probably not be of much use in that situation, but it did help us determine that some half-kittens were missing.

    1. Coyotes are a big one. One of my friends had a farm in Michigan with a lot of barn cats, and they always lost a good chunk of the cat numbers when it got colder and the coyotes suddenly had less food.

      1. Also, great horned owls and eagles (in North America).

        Here in the UK, perhaps a fox occasionally gets a cat, but my guess is that’s not very often.

  3. This is interesting.

    There was an article in PNAS last year on domestication that includes an analysis of Felis silvestris –
    http://www.pnas.org/content/106/suppl.1/9971.figures-only?related-urls=yes&legid=pnas;106/Supplement_1/9971

    Plus this in Science –
    Science 27 July 2007:
    Vol. 317. no. 5837, pp. 519 – 523
    DOI: 10.1126/science.1139518

    & on Scottish Wildcats –
    http://onlinelibrary.wiley.com/doi/10.1046/j.1365-294X.2001.01196.x/abstract

    No time to read them now!

  4. On Okinawa the feral cats are preyed upon by mongoose(s?), especially the kittens. On Cape Cod, coyotes are known to take cats so I suppose they also take the feral variety.

  5. Is it not at least possible that the tabby coat is sexually selected for? That females prefer males with the tabby pattern?

  6. “seeing the pattern of the “Scottish wildcat”, which I firmly believe is not a native species but a descendant of feral domestic cats.”

    OK, now your going to have the BBC Springwatch and Autumnwatch people — and most of Scottish nature lovers — after your hide.

    Although the Scottish wildcat interbreeds readily with the domestic cat, my understanding is that they are impossible to domesticate, even if reared by humans from a very young age. But perhaps this is just anecdotal?

    The wildcats are identified by distictive markings on their rather thick tails. Perhaps this is rather smaller difference genetically.

    1. And here is one!

      Saw this on a Google alert and had to comment, Scottish wildcats are well established in fossil records, cultural accounts and genetic research as a native species, 2 million year old fossils have been found of wildcat bones in Scotland and domestic cats only emerged 12,000 years ago around the Middle East; they only got to the Highlands of Scotland in big numbers in the last few centuries, hence we see spots and stripes on domestic tabbies (from Asian and African wildcat populations, their ancestors) but only stripes on pure, unhybridised, European and Scottish wildcats (the original wildcat population and design). Unfortunately most wildcats you see in the media or photos or even wildlife parks are cross bred feral hybrids so have many domestic traits, the real deal that you only get to see in the middle of nowhere makes even a Norwegian Forest Cat look rather tame and feeble, they’re documented killing golden eagles, making a real mess of German Shepherd Dogs and pet cats or ferals that stray into their territory don’t get to limp home afterwards, these are a very seperate species designed over millennia to survive Scotland.

      The lineage began with European wildcats in Martelli’s wildcat something like 10 million years ago, that became the modern European wildcat (of which the Scottish wildcat is a sub species) and successive ice ages pushed parts of that population south to evolve into African and Asian populations some of which domesticated into our pet cats.

      I entirely agree that true ferals (ie cats living in the wild and not necessarily alley cats) will ultimately revert back to tabby patterns; ferals have to survive by hunting and hiding just as wildcats do and nature has found the tabby pattern to be ideal for acheiving that. I would assume Asian ferals were more likely to be spotty tabbies and European ferals more likely to be stripey as well.

      1. PS Ray
        Correct, no one has ever got close to domesticating a pure Scottish wildcat (or European as far as I know), a few people have “habituated” hybrids to them being around (wildlife photographers, breeders) but the wildcats still won’t allow them to touch or even get very close to their vicinity. I would guess an evolved response to the amount of persecution they’ve had from humans over the years, the only ones that survived were those that went out of their way to avoid people.

      2. “these are a very seperate species designed over millennia to survive Scotland.”

        Sorry: “designed”?

        I’m surprised how much I see this word even in formal, biological, contexts where there’s no religious agenda. But reifying evolution like this, even if it’s a useful shorthand, only confuses the issue and weakens arguments against those who see evolution as the handiwork of a “real” Designer, intelligent or otherwise.

        Words like “design”, “belief” and “faith” should be deprecated in scientific and other rational discussions.

        That’s what I believe.

  7. About reversion to tabby coats.

    What about sexual selection?

    Human selection of breeding pairs may force certain coat colors and other human-desired characteristics, but it (human breeding pair selection) will be neutral in its effect on the instinctive mating preferences of the females (there may be some drift in mating preferences, but nothing to force significant change). In the absence of human interference, sexual selection would rapidly force reversion to any traits preferred by females, even in an environment not selecting for camouflage. Even in an environment that selects for a completely different camouflage than tabby coloration, sexual selection may dominate coloration patterns in the short to mid term.

    Just a hypothesis… but if I were a betting man…

    Might not be too difficult of an experiment to see, after controlling for traits like size, strength, athleticism, and temperament, whether female cats prefer tabby coats.

    In wild species that seem to have the ‘wrong’ camouflage for their environment, perhaps those populations were somewhat recently forced into a new environment or their environment changed around them, and sexual selection pressures are slowing or preventing evolution to a more suitable coloration pattern.

  8. “(Populations of feral dogs seem to revert to a yellowish, dingo-like color.)”

    Earnest Thompson Seton considered “yaller dogs” to be atavistic, “the mongrelest mixture of all mongrels, the least common multiple of all dogs, the breedless union of all breeds.”

    He published a story about one in 1898 in his book Wild Animals I have Known.

  9. Two books well worth reading over:

    “The Cat” by Muriel Beadle, ISBN 0-671-22451-4

    “The Cat’s Mind” by Bruce Fogle, ISBN 0-87605-795-4

    Fogle in particular mentions the dubious temperament of crosses between the Scottish wildcat and the domestic cat (p. xiv).

    1. To this list, I will add Paul Leyhausen’s “Cat Behavior” It’s not easy going unless you’ve done some study in ethology, but it’s definitely worthwhile. He explains, among other things, why cats can bond more closely with humans than with other cats, and why cats “play” with their prey.

  10. Very interesting article! As an owner of Maine Coon cats, I’m used to folks thinking they are all brown tabbies. The breed developed in mother nature, and all colors are possible. Though, the Brown Tabby is most famous (perhaps better-suited to outdoor hunting?)

    Interestingly, you’ll never see ticked patterns or pointed patterns, as those require “in-breeding” practices. Lots more on their many natural colors here: http://www.maine-coon-cat-nation.com/maine-coon-cat-colors.html

  11. cupla points here:

    1. Regarding camouflage; I have a standard grey Kliban tabby. It never ceases to amaze me how hard he is to see, especially if he is not moving. I go out at night and call him. Next thing I know he is standing next to me but I never see him coming.

    2. I visited the Croatian island of Vis. Small stable community. Lots of feral cats there and they all look alike. Solid mousy grey color, kind of frizzy hair (ugly actually – maybe that’s why they’re feral, nobody wants ’em.)

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