This article is from the Fall 2000 AFRMA Rat & Mouse Tales news-magazine.
Colors & Coats
By Nichole Royer
Cindy Stratton, Ventura, CA, e-mail
Q A question that interested me has to do with Siamese mice. It talked about breeding Siamese to PEW to get Himalayans. Does that hold true for rats as well? Let’s say one breeds a PEW male (mother is a black Berkshire, father unknown; I was surprised to see this P.E. White in the litter because all the other rats were marked) to a Siamese. Would all babies be Himalayans or would one get some strange things from the P.E. Whites background?
A Yes, that’s the way to make Himi rats. Works exactly the same way. You would get all Himis . . . just like with the mice. The key though is you would get Himis that had little or no points on their feet and white on their tail (in other words you would not get show-quality Himis). PEW does not make a rat white, instead it “covers” whatever color is there. If mom was Berkshire and dad was unknown, chances are extremely good that the PEW male is actually marked. You just can’t see the markings because the white covers all the color. Thus, bred to a Siamese he will produce marked babies. Problem will be that the only color you will get is Himi, so they’ll be marked Himis. Since Himis have a white background, the only place you will actually see the markings is where they effect the points (mostly the feet and tail).
Actually, it’s fairly common for a PEW to show up in a marked litter. It is a simple recessive gene and a very common one within the pet trade. Since most of the marked rats we have around trace back to pet stores, it’s very common for both marked parents to be carrying that gene.
Q Does B.E. White work the same way as far as “covering” the marked color?
A Ahh, this is where it gets confusing. Let’s see if I can explain. First . . . white rats can be caused by two things. One is the albino gene that gives us normal PEW rats. The other is the marked gene which works very differently.
The marked set of genes cause patches of white to appear on the rat. Thus you get English Irish rats who have patches on chest and feet, Berkshire with patches on stomach and feet, Hooded with the white patch extending up to the spine, Bareback with the white patch covering all of the body, Capped/Masked with the white patch covering everything but the head, and white rats with the white patch covering their entire bodies. Technically, B.E. White is genetically a Capped/Masked that has been selected for as much white as possible. That’s why BEWs often have at least a few colored hairs behind an ear or on top of their head. In this same way it is possible to create a “mock” albino. If you take a color like Champagne and breed for as much white markings as possible, you will eventually get a pink-eyed rat who’s body color is white. It’s a PEW, but it’s not an albino (this is why we don’t use the term “albino” to mean a white rat with pink eyes . . . without breeding, there is no way to tell which you are dealing with). If you were to breed one of these PEW non-albino rats thinking it was an albino, you would be in for the shock of your life. Depending on what you bred it to, you could get everything from English Irish to Capped.
To put it a little more simply . . . albino “covers” whatever markings and color the rat has. BEW is caused by the markings and the color.
I always get a kick out of telling people that Dalmatian rats are not white rats with black spots. Instead they are black rats with lots of random white spots.