All about the White ASF rat!

(Pictures used with permission from Stefan K. from

I had the oppourtunity to discuss the amazing snow white ASF (vzm) rat with Stefan from Germany! Although he has since moved on to other endevours, he was gracious enough to answer some questions I had for him regarding the genetics and breeding for the elusive high-white ASF.

First, some explanatory remarks from Stefan:

I use this gene code:
Agouti: +
Cinnamon: b/b
Argente: p/p
Ruby Eyed: r/r
Silver Fawn: b/b p/p
I use these names for the different White variations:
Platinum: White rat with black eyes, black ears (B/B) or gray ears (B/b)
High White: White rat with black Eyes and white ears (b/B)
PEW: White rat with pink eyes and white ears (p/p)
I have no experience in breeding Ruby Eyed. I assume that this is a new variety based on a recessive dilution. If anybody has Ruby Eyed rats with b/b or p/p, please send me a picture!

Find more on Stefan’s website at

1. Can I get some of your background? What first interested you in the African Soft furred rat?

I needed some company for my single fancy mouse buck (male). Many German websites and forums recommended Mastomys as great fellows. So I got my first group from an [exotic animals expo] especially for reptiles in 2002.

2. How long have you been breeding small mammals?

I began breeding fancy mice in 2003. I met some people who wanted to build the first German community of mouse fanciers. We decided to found a club and agreed upon a breeding standard. A [little while] later I bought some fancy rats and started colour breeding. Rearing other exotic mice wasn’t something I would call “breeding”.

3. What other species do you own?

At the moment I am breeding Mastomys and Campbell’s Dwarf Hamsters. I also keep Deer Mice (Peromyscus maniculatus). Deer Mice are not often kept in Germany. I think I am the only fancier who has offspring for sale.

4. Let’s discuss the high white ASF. Are they your creation, or did you learn about them someplace in your readings?

I got my first platinum ASF rat in 2004 from a animal dealer in Netherlands. These have actually been the first white Mastomys I have ever seen (and they’ve been the last for three years). My specimen was very small and did not mate. In 2007 a friend of mine gave me a little group and I decided to breed with them.


5. How many generations did it take to get the high-white ASF?

When you mean the Whites with white ears? It took me two generations by using a Platinum male and a Headspotted Cinnamon female and inbreeding the F1.

6. Do you have any insight into the genetics behind the high white appearance?

In my opinion the Whites (regardless which ears or eye color) only evolve from two pied alleles and a special modifying gene, that is obviously only found in Europe. This modifier maximizes the white of the pied ASF so that the offspring are clean white, or with only little coloured spots in the neck. These spots are very insistent and appear on and off.

I believe that the platinum modifier is diluting the colored coat areas: A white rat that has one white eared and one black eared parent has grey ears. I would take the non-white counterparts of these (Agouti and Cinnamon) the offspring has black ears.

7. Can we discuss your opinion about a special gene? Do you believe it is easily identified just by looking at the rat that it is a carrier for the gene?

When you mean the special modifying gene of Platinum mice: I don’t know. I have never seen Solid Agouti rats with a platinum-gene.


8. Can you give an example of how you have bred the high-white into the other base colors? For example, a Fawn crossed with the H-W (high-white) to make essentially a Pink Eyed White rat?

In my case a Pink Eyed White came up in a litter randomly. I did not know that my mice had a heterogous Pink-Eyed-Gene. But it is very easy to combine Platinum/High White with argente or silver fawn. Just like I described it in question 5. It doesn’t matter if you take rats with or without bb (brown lightening/brightening). The results are simply snowy white rats with pink eyes.

9. Speaking of base colors, do you also share my opinion that there are 4 colors of ASF’s available? What are they named in Europe or your native language?

Yes I think we have four base colours. but I am not sure if the new “Ruby Eyed” are a new variety. I have never seen one and I don’t know if anybody did test breedings to find out how this colour behaves in combination with others. German breeders do not have a common nomenclature for the colour varieties and their genes. We call the wild type (very dark, greyish-brown looking, black ticking, black ears and eyes) “Agouti”.

The brightening/lightening (?) gene is mostly called “Cinnamon”. I don’t think the name fits but I don’t know a better word.

For the two red-eyed varieties (Agouti + pink eyes and Cinnamon + pink eyes) I do not know any popular name. Most breeders and keepers do not differenciate between these colours. Looking at the british nomenclature of fancy mice breeds I propose the symbol b/b for for the Cinnamon Gene and the symbol p/p for Pink Eyed Gene. The fancy mice with the gene code p/p are in europe called “Argente”. Fancy Rats with b/b p/p are in Europe often called “Silver Fawn”. So I would propose Argente (p/p) and Silver Fawn (b/b p/p) as declaration for the two pink eyed colors of Mastomys.

10. What are the names of the H-W on the different colors? I have heard of Platinum to describe the H-W on the wild Agouti color, is it different for Cinnamon?

The first whites in Mastomys came from Agoutis and have black eyes and black ears. I think a German breeder called them “Platinum” (named after the black eared white variety of pet pygmy hedgehogs) and this name is common in Germany and the Netherlands. But only for the black eared variety.

I chose the name “High White” to label the dark eyed whites with white ears (b/b). There was no other name known before (in 2009)… We know the term “High White” from snake varieties.

Between breeders and keepers of ASF rats this name is not well known and there isn’t agreement about the nomenclature of the different white combinations. I would propose the names:
      Platinum (for a White Agouti): white coat, black eyes and black ears
      High White (for a White Cinnamon): white coat, dark/ruby Eyes and white ears
      PEW (White Argente or Fawn): white coat, pink eyes and white ears.

I think there’s no need to differenciate the PEW with b/b and the PEW with B/-. They look the same. Breeders of other species (fancy mice) also call white mice with red eyes “PEW” (and there are many combinations that produce PEW).

11. Do you have any advice for other breeders working towards the H-W rat?

My advice is very simple: Take time and be strict: The main criteria for a good selection are healthy and friendly mice. The color is coming on their own.
I am ready to help if there’s any question. (I will answer much faster in German than in English).

There you have it! The high-white ASF should not seem so far fetched now ;). From Stefans explanations, it does appear that there is a European gene that can easily be bred for HW ASF. I’m always interested to know if anyone in the US has this variety, or what they believe may carry the gene. Perhaps we will be able to import this variety someday? Who knows!

Thanks again to Stefan for being so patient, since I took almost a full year to get this posted on our website!

Please feel free to comment or reply by email.

:: Connie