This article is from the WSSF 2007 AFRMA Rat & Mouse Tales news-magazine.

By Karen Robbins & Nichole Royer

Early in 1998, a male rat thought to be BEW appeared spontaneously in a strain of lab rats at the Edinburgh University in Scotland. These rats were used to demonstrate inheritance of color and were a mix of albino and “reddish Cinnamon” Hoodeds. This “BEW” (later named “The Milkman”) along with one of his “Cinnamon” Hooded litter sisters (later named “Crystal”) was given to a local breeder. The two were mated and produced a “BEW” and more “Cinnamon” Hoodeds. When the original “BEW” (The Milkman) was bred with Blue that had Siamese in the background, they produced Black Hooded and “B.E. Champagne” Hooded. Some of these kittens from both litters were bought by a fellow breeder. The “BEW” kitten, once moulted, turned into a dark-eyed Cream (pale buttermilk color). The “Cinnamons” turned into what was described as “milky-tea taupe” resembling the Stone color in mice (which are c^ec^e and what AFRMA calls Reverse Siamese; Coffee and Beige are the same genetically). The supposition at the time was the “reddish/bad Cinnamons” the University was getting was in fact these “taupe” rats that finally combined with the albino to create the “BEW.” Later it was determined the original “Cinnamon” Hooded sister to “The Milkman” was in fact this same “milky-tea taupe” color. Since the “taupe” resembled the c^ec^e “Stone” mice they gave them that name at the time, then the dark-eyed Cream could be referred to as c^ec (what N.M.C. calls B.E. Cream and AFRMA calls Ivory in mice).

A Color-point Beige, a.ka. B.E. Siamese mouse cech. Photo by Craig Robbins.

When the “B.E. Champagne” Hoodeds moulted, they developed points and their hood color went from a pinkish Beige to almost pure white, in essence turning into B.E. Himis (still genetically Hooded but you could no longer see the markings). Later, their points became barely visible which could be because the Siamese stock used in the area was very pale. The theory was that by breeding a “Stone Cream” with a dark Siamese, they would produce a better colored B.E. Himi/Siamese. In mice, the Color Point Beige/B.E. Siamese is one copy of the extreme gene and one copy of the Himalayan gene—c^ec^h.

Type in these initial dark-eyed Creams was described as “lousy” being small, narrow bodied, and with long heads. One positive feature was their nice big eyes. Big black eyes are one feature of the c^e mice.

One interesting thing noted in these early rats was the eye color—it was more of a brown with black pupil with a maroon tint to the iris when viewed in bright light (called “blackberry”). The babies appeared to be born with pink eyes with the dark color developing within a few days, to some not becoming fully black until they were several weeks old.

During the first couple years, they tended to have a high incidence of respiratory issues and inner ear disease, and they were vocal (squeaky), squirmy rats, but seemed to have few tumors. The females did make good moms with medium size litters.

Markings were obviously impossible to tell on the dark-eyed Creams since they looked like BEWs with a creamy tinge.

In most males of all three colors, as long as their markings extended to include color at the base of the tail, a dark gray freckle was observed on the tip of the testes.

In October 1998, a trio of the dark-eyed Creams out of the original dark-eyed Cream buck and a Cinnamon Hooded doe from pet shop stock, were picked up by a breeder in London (the litter consisted of Cinnamon, PEW, and dark-eyed Cream; later it was reported the trio was actually F2s from two dark-eyed Cream F1s from “The Milkman” and the unrelated Cinnamon Hooded bred together). This buck and one of the does were bred together and the litter consisted of 9 dark-eyed Cream and 4 PEW. Some test breedings suggested at this time were: Stone Cream x PEW, dark-eyed Cream x Stone Cream, dark-eyed Cream x Siamese (c^hc^h), Stone Cream x B.E. Himi and/or dark-eyed Cream x B.E. Himi.

Later, it was reported that the “Stone/taupe” rats appeared to be ticked—creamy white on beige—so it was thought the dark-eyed Cream and B.E. Himi to be “self” based (aa) and the “Stone/taupe” to be “agouti” based (A-). All breedings at that point of dark-eyed Cream to a Himi/Siamese produced B.E. Himi/Siamese. Breedings of dark-eyed Cream x Siamese and “Stone/taupe” x PEW never produced Agouti or other full color.

The presence of the cream gene appeared to reinforce the dilution more than the albino gene so the B.E. Siamese/Himis had smaller, paler points than their P.E. counterparts though that could have been because of the poor colored Siamese being used to cross with the “cream” and “Stone/taupe” rats.

An Ivory mouse cec. Photo by Craig Robbins.

A Beige mouse cece. Photo by Craig Robbins.

A Coffee mouse cece. Photo by Larry Ferris.

A Stone/Reverse Siamese Fox mouse cece. Photo by Karen Hauser.

One of the breedings at the time that questioned the c^e gene and the self vs. agouti base of these new colors, was of the F1 Blacks out of the dark-eyed Cream “The Milkman” and the Blue Hooded. When these were bred together, they produced what was called “blue-creams” and a Champagne. The thinking was a blue rat with the cream gene should look the same as a black rat with the cream gene. The other questionable litter was from a PEW to a “milk” with the entire litter being B.E. Himi. It was assumed that these were just a fluke, as the ratio you should get on paper doesn’t always mean that happens in actual litters.

A name change was proposed in 2000 to calling the dark-eyed Cream “milk” and the “Stone/taupe,” “biscuit.”

With some of the breedings they did, they found some of the dark-eyed Cream to be homozygous and some of the “Stone/taupe” carried albino. With these new findings, they looked into another gene causing these dilutions of color, this being the extension gene ee. In mice, the extension gene ee is what makes recessive yellow. This gene controls the amount and distribution of black and gold pigments in the fur. If the “cream” gene was not on the C locus, it would have to be dominant. With a breeding of a “milk” to a Silver Black from Siamese, the babies were B.E. Himi and Black proving it couldn’t be ee, otherwise all the babies should have been “milk” or “biscuit” or B.E. Himi. So that puts it back to being on the C locus. It was mentioned the possibility of these “creams” being the c^d ruby-eyed dilute gene. Its effect is supposed to bleach out the yellow pigment and to fade black pigment to sepia with ruby colored eyes. This theory wasn’t pursued (could be because the Creams had black, not ruby eyes).

In the summer of 2001 it was reported the first Sable (has two copies of the “biscuit” gene) appearing out of a Himi and “biscuit” breeding in Glasgow. This rat was described as having an agouti ticked-type undercolor—the body color was similar to “biscuit” but darker and grayer with black points.

At some point, the thinking changed from these rats being c^ec^e for the “biscuit” to c^b like in the Burmese cats. In Pro-Rat-A 147 (May/June 2005), it lists Burmese (taupe/Stone/biscuit) as c^bc^h, Cream (dark-eyed “dark” Cream) as unknown (these had not been mentioned in previous articles), Ivory (dark-eyed “light” Cream/milk) as c^e, Sable Burmese as c^bc^h, and Wheaten (Agouti) Burmese as c^bc^h or c^bc.

Since the initial introduction of the B.E. Creams into London, several people were breeding these new colors. However, it came a point where a lot lost interest (mainly due to temperament issues in the rats) and they were nearly lost in that area. The Scottish breeders had continued with the “biscuit” and the Burmese. Some of the English breeders were mainly breeding them with the Siamese rats to make the B.E. Siamese as it was easier to find homes for the dark-eyed ones rather than the red-eyed ones.

With more outcrosses being done, the thinking changed again on the possible genetics of these being on the C locus. They believed that the “black-eyed” gene was interacting with the C locus in a similar way as to how the pearl works with mink, or that the “black-eyed” gene was dominant to anything that didn’t have black eyes. Further breedings needed to be done to confirm either theory.

They had found three different shades from mixing the B.E.Cream with the Siamese/Himis. These ranged from nicely colored B.E. Siamese, B.E. Himis, and the Ivory. Most breeders at the time were only breeding with Siamese, Himi, and PEW. In their breedings, they found the black eyes to be dominant over the C locus.

The one litter that made people change their thinking on the genetics was from a Black that carried Siamese (with no black-eyed rats in the background) bred with an Agouti that had an Ivory parent. In the litter there were B.E. Himi (1) and R.E. Himi (3). Because there was both eye colors and three alleles are not possible, then the black eye seemed to be dominant and working with the C locus or dominant but hidden on the already B.E. rats, so “Be” was given for the black-eyed gene; this seemed to fit the results of this particular litter. More litters had similar results which pointed to this new theory.

One breeding noted was of a Russian Dove which was a great-granddaughter of the Agouti used in the above example, bred with an English Mink Roan. Both B.E. and R.E. Himis were in the litter along with all the babies being Mink based (U.S. Minks were thought to be different from English Mink and the results expected were all Black).

One thing that had not been tried by anyone at this time was seeing if you could make a B.E. Champagne or B.E. Silver Fawn. They found when a lot of dilutes were in the mix of the various point colors in the Siamese (Russian Dove Point, Mink Point, Blue Point), the eye color could change from black to ruby so they weren’t sure if you would be able to tell if you had a B.E. Silver Fawn or B.E. Champagne vs. a Topaz (Fawn) or Buff (Beige) which has dark ruby eyes.

It was at this point there is mention of the darker “Cream” color which they named “Cream.” They found that Ivory could be agouti based without affecting the light creamy color. These new dark “Creams” had darker cream ticking on a yellowy-beige color with demarcation lines like in agouti colors. They found the Ivory vs. Cream didn’t show up color differences until they did their first adult coat at 5–7 weeks of age. Most people had been working on the B.E. Siamese (black based aa) rather than the Ivory which may have been agouti based (A-). Breedings of the new “Cream” were:

• Ivory x PEW = some dark Cream (color first noted in this litter)
• Ivory x Cream = all B.E.
• Cream x Black = Agouti, Black
• Burmese x Ivory (had dark Cream sibling; from Ivory x PEW breeding) = Burmese, dark shade of Burmese Agouti, light shade of Burmese Agouti with no points, B.E. Himi, R.E. Himi, Ivory, PEW. One of the light Burmese Agouti with no points was bred with Cinnamon and produced Mink- and Cinnamon-based rats along with Black.
• Burmese (grandmother is sister to Ivory used in Ivory x PEW breeding) x dark Cream (from Ivory x PEW breeding) (U.S. breeding) = dark Cream, Ivory, B.E. Himi, Agouti Burmese (with and without points), Burmese (with and without points)

Breedings suggested at the time for the new Cream rats included: Cream x Ivory, Cream x Cream, Cream x PEW, Cream x Mink, Cream x Silver Fawn.

With these new colors (Cream and Agouti Burmese), more people became interested in breeding the new black-eyed varieties.

They found the best Burmese shade to be from using bad Siamese (too light)/bad Himi (too dark). As most people that bred Siamese was using the B.E. in the mix to make B.E. Siamese so it was easier to find homes for the kittens, the regular Siamese were being neglected in breeding their color for show and a lot of poorly/lightly colored ones were showing up.

By the end of 2005, the consensus was that a black-eyed gene and a separate Burmese gene had actually appeared in the original stock from Scotland that interacted with the C locus even though initial test breedings were pointing it to something on the C locus itself. The proposed genetics at that time if these new colors were on the C locus:

• Sable Burmese – 2 copies of the Burmese gene c^bc^h
• Burmese – c^bc^h or c^bc
• Wheaten Sable Burmese – A- c^bc^h
• Wheaten Burmese – A- c^bc^h or A- c^bc

One breeding was a Burmese with Mink (siblings; out of a Russian Blue that carried Siamese and a Burmese) that produced Sable Burmese, Siamese, Mink, and Black. This one Sable Burmese was then crossed with a Himi and all the kids were some form of Burmese (some were Russian Blue Burmese). When the first Burmese was later bred with Siamese, they produced Burmese and Siamese. These breedings seemed to disapprove the theory of these being the c^b gene on the C locus.

If the proposed genetics were instead one of a separate gene to make the Burmese (symbol given of Bu) that was working with the C locus which is what was causing the various shades and the fact some had points and some didn’t, then the proposed genetics were:

• Sable (with points) – c^hc^h BuBu or c^hc BuBu
• Sable (no points) – cc BuBu
• Burmese (with points) – c^hc^h BuBu or c^hc BuBu
• Burmese (no points) – cc BuBu
• Wheaten (Agouti) Sable Burmese (with points) – A- c^hc^h BuBu
• Wheaten (Agouti) Sable Burmese (no points) – A- cc BuBu
• Wheaten (Agouti) Burmese (with points) – A- c^hc^h BuBu or c^hc BuBu
• Wheaten (Agouti) Burmese (no points) – A- cc BuBu (no mention of the Ivory or B.E. Himi/Siamese proposed genetics were given)

If you apply these genetics to the Burmese to Mink breeding, it allows for the self colors in the litter.

Several other breedings seemed to follow these new lines of theory.

So that takes you to their thinking that when Burmese was bred to PEW, why the Himi or Burmese offspring had lighter colored points if you use the new genetics of BuBu. So even though most litters fit with the C locus theory, they also worked with the new separate gene theory and it explained the various anomalies breeders encountered.

With many different genes included in the mix such as Mink, Russian Blue, Blue, etc., plus the use of poorly colored Siamese and Himis, many variations and shades of Burmese were reported, sometimes making it difficult to tell what exactly the Burmese was. With the addition of Agouti to create the “Wheaten” variety, this made for even more colors to work with. When breeders used a good colored Siamese with dark shading, it made the Burmese almost Sable in appearance. Where on the other hand, the Burmese bred with very light Himis or PEWs produced Burmese that were too light in color with not as much contrast between the points and body color. For show, breeders have focused on the Burmese produced from using light Siamese/dark Himis to get the ideal medium shade. This means Siamese breeders should not use stock out of Burmese lines to further the R.E. Siamese rats. Interestingly enough, the show Sable Burmese are best created by also using poorly colored Siamese or Himis.

As with most “brown” rats, they tend to be patchy and rusty in color with lots of silvering in the bucks, making them hard to be in top show color.

With the Agouti version (Wheaten) Burmese, its color varies widely as well depending on the color quality of the Siamese/Himi used. Some dark Wheaten Burmese and the Agouti Sable Burmese look like bad Cinnamons with points.

One unique color that many breeders are pursuing is the Russian Blue Burmese. Most other color variations of Burmese are not unique enough to warrant a separate standard for.

Some kittens have been reported to have “marbled” or strange white patches in their color that had nothing to do with moult and was genetic based. This “marbling” tended to fade in the rats as they matured and breeders have selected against this. [One breeder I know here in the U.S. had an Ivory/B.E. Cream rat with a “beige” spot/mark on her side that was not staining or dirt and another had a litter of Burmese and B.E. Siamese with the “marbled” patches that stayed throughout adulthood.] One known feature of the c^e mice (Ivory), is their tendency to get “watermarks” or patches of darker beige color when they go through moult that can stay for months at a time.

An adult Burmese with “marbled” face. Photo by Karen Robbins.

An adult Ivory/B.E.Cream with beige colored hairs/patch on her side. Photo by Karen Robbins.

Breeders have worked hard to correct the temperament issues these rats have had and only breeding the ones with calm, even temperaments has this problem been greatly improved. Type has also improved when breeders included type in their list of things to breed for and not just concentrating on producing more of the new color.

Stock has been sent to other countries including the Netherlands, Belgium, and here to the U.S. From what breeders report back in their findings with their litters, it seemed to fit in with the new proposed theory of the genetics on these rats.

In the last article on the new black-eyed rats in Pro-Rat-A 151 (Jan./Feb. 2006), it is questioned on the theory of a separate cream coat color gene and a B.E. gene being involved and gives the suggestion of a possible incomplete penetrance of the black-eyed gene.

This now brings us to the U.S. involvement where in November 2004, several rats were imported to the U.S. from several breeders in England. Colors included Burmese, Sable Burmese, B.E. Cream, and B.E. Himi/Siamese. Babies from some of the first litters made their way here to southern California to breeder Carol Lawton. Which takes us to her questions regarding the genetics of these rats. Karen Robbins

References:

Pro-Rat-A 107, 111, 115, 124, 147, 149, 150, 151

Note: Poorly colored Siamese are used for show Himis in the NFRS.

Carol Lawton, e-mail
QHaving worked with the Burmese varieties for a little while, reading the AFRMA Mouse Genetics book, and talking to other Burmese breeders, I have several questions. Having some knowledge on the “extreme dilute gene” in Syrian hamsters and reading about the extreme dilute gene in mice (c^e), it sounds a lot like what the Burmese are. They seem to look, act, and breed like the extreme dilute gene.

Some of my questions:

• What is a Black-Eyed Cream mouse?
• c^e all on its own can/will create points on an animal?
• Does a c^e/c^e rat have points or have no points, partially depending on temperature (most of them do by the way)?
• Does c^e allow more (for lack of a better way of saying it) expression of color so the babies look like Siamese?
• Are the ones that have no points probably c/c^e, depending on temperature—this would explain why some aren’t showing points? I have a male with no points and one that the points come and go.

Answer by Nichole Royer
AWe have had 3 different alleles on the c locus in rats for some time:

C – normal
c^h– Himalayan
c – albino

It’s well known that:

CC – full color (Black)
c^hc^h – Siamese
c^hc – Himalayan
cc – albino

You will notice that the heterozygous c^hc (Himalayan) is halfway in color between the two homozygotes. That’s very typical of this series.

If you breed two Himalayans (c^hc) together, your expected litter will be one-quarter Siamese (c^hch), one-half Himalayan (c^hc), and one-quarter albino (cc). Thus, out of two rats you will get three different C gene colors. This is well known, well documented, and well established within the rat fancy (as it is within the mouse fancy). And this is no different than your Burmese example.

There is a lot of documented scientific proof of how the “c” locus works in mice. The mouse is the single most studied species on the planet as far as color genetics. The “bible” of mouse color genetics is The Coat Colors of Mice by W.K. Silvers www.informatics.jax.org/wksilvers/. In the third chapter, part 2 “The c (Albino) Series of Alleles” www.informatics.jax.org/wksilvers/frames/frame3-2.shtml, the first section is on extreme dilute gene c^e. It was discovered in mice in 1921.

Re: What is Black-Eyed Cream? If you go to the AFRMA website under the Standards section, look at the Self mice. Check out the Beige and the Coffee. Those are both aa c^ec^e. Genetically identical. Now go to the Tan and Fox section. Scroll down to the Fox mice. Both mice pictured are c^ec^e (genetically identical). Yes, the color varies that wildly. If you breed together two of the dark or two of the light Beiges, you will get mostly that shade and a few medium shade. If you breed dark to light, you tend to get a mishmash of everything. I’ve actually bred Beiges myself, so I can attest to the validity of that statement. Scroll down some more on the page and you will see “Ivory.” In mice, these are usually c^ec—light shade Beige + albino. Dark shade Beige + albino tends to give light Beige although you can get Ivory. You can breed the dark version into Coffee by selecting the darkest. You can breed the light version into Ivory by selecting the lightest, but you don’t really get intermediate stages.

Re: c^e all on its own can/will create points on an animal? Correct. I would expect them to not be as dark or distinctive as points caused by c^h.

Re: Does a c^ec^e rat have points or have no points, partially depending on temperature (most of them do by the way)? Correct. Most c^ec^e mice do not, but they have been selected not to have points. Most c^ec^e hamsters do appear to have points, some more distinct than others. [One interesting note: the c^e gene in hamsters was discovered in 1999. Ed.]

Re: Does c^e allow more (for lack of a better way of saying it) expression of color so the babies look like Siamese? Correct. Keep in mind the extremes, however, c^e varies from light to dark. Siamese varies from light to dark. Both sets of modifiers are going to affect how dark these animals are. Dark beige (Burmese) + dark Siamese are probably going to give you a Burmese looking animal with distinct points. Light beige + light Siamese are probably going to give you a Himalayan looking animal. Dark beige + light Siamese would likely give you a Siamese looking animal—with no shading. That’s one thing all the literature says over and over. You get shading with homozygous c^hc^h only. Any of the heterozygotes give you a solid colored animal with points.

Re: Are the ones that have no points probably c/c^e, depending on temperature—this would explain why some aren’t showing points? Quite possibly. I would also expect them not to be truly dark Burmese.

You have to understand the color varies so wildly with the c^e gene. Also, when you have a mish-mash of other genes in the mix, you can get unexpected results. Getting the gene isolated into animals with a very limited number of other possible genes and then doing some work with it is the first step.

Also, when you have other genes in the mix plus modifiers plus various shades of the same color (light vs. dark), the phenotype (what the animal looks like) may not be what it actually is genetically (its genotype or genetic makeup). You have to keep this in mind when looking at all these variations that are showing up. One classic example is the albino. What “looks like” an albino may not be what you expect an albino to be and that is cc, but may be a marked rat with all the markings bred off or from diluted color genes. In appearance it is a “pink-eyed White,” but in actuality something altogether different that is found out in the breedings produced. In mice “pink-eyed White” can be an albino cc, a pink-eyed Beige c^ec^e pp, or even a pink-eyed Himi c^hc pp.

The black-eyed gene—for the moment lets scrap the idea. The simplest explanation usually being the best: the c^e allele in combination with all the other alleles on the locus produces black-eyed animals who range in color from deep brown to off white— some of which have points. Why get more complicated than that?

Since poor Siamese/Himis have been used to cross into the Burmese, all the modifiers for light color and no shading have been selected for. Those same modifiers work on the other c locus alleles as well, which may be tweaking the results in a big way. Think how dramatically different in color a good Siamese is from a really bad one. Now put that variation into Burmese.

On one web site, it shows the various colors produced in a litter including a regular Siamese (Siamese, light Burmese, dark Burmese, and Sable Burmese, if I remember correctly). I was shocked. My Siamese babies are the same color as the dark Burmese—except at about 4 weeks they start coating out and turning into Siamese. I don’t think I’ve ever had a Siamese as light as what they called Siamese in any litter I’ve ever had (even way back when).

Lets just theorize for a second that Burmese = dark beige and B.E. Cream (BEC) = light beige—both actually being c^ec^e (just like in mice).

I ran across comments that breeding albino to Burmese does not seem to affect the color, it just gives you a slightly paler Burmese with no real visible points. But albino bred to BEC gives Ivory like it does in mice (in other words a slightly lighter BEC). With the two different black-eyed almost-white colors, I read they weren’t sure what caused the difference.

When dealing with PEW and any other c locus alleles, it will disguise any other genes you have hiding. So it really could produce all sorts of messes. By the way, in mice, you breed your PEW to Ivory to continue your line of Ivory. Breeding Ivory to Ivory gives you all 3 colors—PEW, Ivory, and light Beige.

Has anyone looked at the possibility of there being another c locus allele? One that doesn’t exist in mice, but one that causes BEC. That would open up a whole new world of possibilities.

In Syrian hamsters there are black-eared whites. Essentially Siamese, but without the points anywhere but on the ears—pure white otherwise. This is not a c locus allele that appears in mice or anywhere else.

So lets play what if by adding two new alleles on the C locus:

C – Normal
c^e – Extreme Dilute
c^h – Himalayan
cⁱ – Intense Dilute (lightens base color)
c – Albino

The way this series works is that each step down affects black more.

To me, this makes more sense than creating a whole new locus. I just know that it’s a lot more likely for two closely related mutations to appear on the same locus at the same time then for two separate things (Burmese and Black eyes) to turn up.

Look for the simplest solution:

1. would be a separate gene that causes the color on the c locus to intensify (Siamese into Burmese, Himalayan into B.E. Siamese, PEW into BEC). For that to work it would have to be dominant, and basically the breedings already out there prove that it’s not the case.
2. is for a single allele in its homozygous and heterozygous forms to cause the results seen. It’s possible here, but there is an awful lot of variation in color, and it’s not doing exactly what I’d expect. So I give that one a maybe.
3. would be for there to be two mutations close together on the same locus that are causing the different but rather similar results. It bears investigating.
4. would be for there to be a very complicated series of additional genes to have come into play here. Something that only affects the colors on the C locus, and that produce effects very similar to what is seen in c locus genes in other species. I will only go there if all other theories fail.

Some questions: are there examples of Burmese x Burmese breedings producing all Burmese? What about Sable Burmese x Sable Burmese? Are there examples of B.E. Himalayan x B.E. Himalayan breedings producing any Burmese? Are there examples of B.E. Cream x B.E. Cream breedings producing Burmese or B.E. Siamese/Himalayan? What about if you bred a B.E. Siamese to an albino, would you get B.E. Siamese and R.E. Himalayan? And if you breed together two B.E. Siamese, do you get any Burmese?

In going over your sample litter’s details and photos you sent on the Russian Blue Point Siamese x Burmese with points = Siamese Burmese, Himi Burmese, B.E. Siamese, B.E. Himi, is when the cⁱ theory occurred to me. Keep in mind you are thinking from the point of view of someone who’s been “instructed” in the current trends in Burmese. I’m a Siamese breeder who happens to know genetics. I’m coming from the standpoint of knowing Siamese and looking at your litter (at the time with absolutely no real background on the color). What I “saw” and what you “saw” may be two very different things. Truthfully, I did not see four different colors in there.

Mom is a Burmese with points. To me her color seemed washed out (you said that the points come and go). When I saw her I would not say her points were at all distinctive, so she would be c^ecⁱ. Being out of the English Siamese, it’s a good bet she’s “light” for color depth modifiers. Dad is my line Siamese. He’s easy – c^hc^h and “dark” modifiers. Bred together they should produce:

• 50% c^ec^h – Burmese with distinct points (some will have more “dark” modifiers and some will have more “light” modifiers)
• 50% cⁱc^h – B.E. Siamese (again, some with light modifiers and some with dark)

I have done a couple of “bad” Siamese-almost-Himi to “good” Siamese litters way back when. I expected to get something in between, but instead got poor Siamese and pretty good Siamese (totally shocked me). And lets face it, a poor Siamese sitting next to a good Siamese looks like a completely different color. So, with the Burmese, you have to keep in mind that those aren’t actually “Siamese” modifiers. They are c locus color depth modifiers.

My Siamese line has been known to throw Lilac. Not often, and I’ve obviously bred away from it since it screws up the Siamese (they have very light points—otherwise they look like Siamese). When you mix a whole lot of colors into the Burmese, it creates lots of variations in the color. All it takes is one recessive gene in common and you will get multiple shades of Burmese/Siamese.

Based on the info you sent on all the breedings, here’s my honest thought [Carol had also plugged in the new codes to more than 20 litters and they all worked with the new theory. Ed.]:

cece	Burmese
cech	Burmese
ceci	Burmese
cich	B.E. color point
cici	B.E. color point
cic	B.E. cream/Ivory

There may be some differences in shade, but so far based on what I’m looking at this works. When running through all those litters you sent, every single one works. This also all works out with that pedigree you sent me. The only piece that doesn’t work is there is a Siamese listed that has to be a bad Himalayan.

In double checking the codes, I ran back through the list checking what I’d assigned each animal based on what it produced against what each animal could be based on its parents. I did not come up with one single question mark.

What I do have is two litters that “should” have produced normal Siamese and didn’t. Both were small litters, however, so I can’t discount the fact that the dice may have just not fallen in such a way as to give Siamese. It’s a very small anomaly.

An Agouti Point Siamese out of Siamese with dark color-depth modifiers. At first glance it looks like a Seal-Point Siamese, but the light feet give it away as being an Agouti Point. Photo by Karen Robbins.

In the one example you sent of Burmese x Ivory = Ivory, PEW, black-eyed Himalayan, red-eyed Himalayan, Burmese with no points, Burmese with points, Wheaten (Agouti) Burmese with points, Wheaten (Agouti) Burmese with no points, the new codes do not allow for PEW but instead allow for Agouti Himalayan. Think about Agouti Himalayan. Think Agouti, now limit the color to just the areas where a Siamese has points. Then remove the brown band in the Agouti coat to white, and make the color of the black tips a pale brown. Then fade the color out to Himalayan instead of Siamese remembering the Siamese used had light color depth modifiers. Then think kitten coat (Himalayans look like PEW when babies and Agouti Point Siamese have almost no color on their feet). I’m betting that PEW, wasn’t, but without breeding tests there’s no way to know for sure. And without seeing that animal as an adult, there’s no way to guess (what do you bet it has a “dirty” nose?). [Read more about Agouti Point Himi Mice and how they look like PEW until grown up.]

A Sable Burmese rat cece. Photo by Karen Robbins.

A Burmese rat cech. Photo by Karen Robbins.

A B.E. Siamese rat cich. Photo by Karen Robbins.

An Ivory rat cic. Photo by Karen Robbins.

So, my answer on the genetics on the Burmese rats:

C Locus:

C	Full color (no dilution)
ce	Extreme dilute (produces black eyes on a beige animal in various shades)
ch	Acromelanism (Himalayan/Siamese)
ci	Intense dilute (lightens base color)
c	Albino (PEW)

Burmese Color Genetics:

CC	Black
cece	Sable Burmese
cech	Burmese (best color for Burmese)
ceci	Burmese (too light—looks like Himis as babies)
chci	B.E. Siamese
cici	B.E. Himalayan (white, then get points)
cec	Burmese (extremely light) or the dark Cream in N.F.R.S. (dark Ivory/B.E. Cream; may have hint of points)
cic	Ivory

Ed. Note: see below for a list of various breedings of the new black-eyed colors and the outcome.

Breedings listed of the new black-eyed colors:

original dark-eyed Cream (The Milkman) x sister “Cinnamon” (later determined to be “taupe/Stone”) Hooded = dark-eyed Cream, bad “Cinnamon” Hooded (some were “taupe”) original dark-eyed Cream x Blue Hooded (carried Siamese) = Black Hooded and “B.E. Champagne” Hooded (B.E. Champagne turned into B.E. Himis) original dark-eyed Cream x unrelated Cinnamon Hooded = 6 Cinnamon (4 Hooded, 2 Berkshire), 7 PEW, 5 dark-eyed Cream dark-eyed Cream x dark-eyed Cream = 9 dark-eyed Cream, 4 PEW (this litter was expected to have “Stone/taupe”) biscuit (Stone/taupe) x PEW = 4 biscuit, 3 PEW milk (dark-eyed Cream) x Siamese = 6 B.E. Himi, 4 P.E. Himi milk (dark-eyed Cream; assumed to be homozygous Cream) x pale Siamese = 9 B.E. Himi milk (dark-eyed Cream) x Silver Black from Siamese = 7 B.E. Himi, 8 Black Black Hooded F1 (out of original dark-eyed Cream & Blue Hooded) x sister Black Hooded = described as “blue-cream” “PEW” (mother Silver Fawn; littermates were Silver Fawn, Siamese/Himi, Agouti, Cinnamon) x “milk” = 12 B.E. Himi (the “PEW” could have been a Silver Fawn Point Himi and looked PEW but genetically was Himi; B.E. Himi babies looked like “milk” until smudges appeared on their noses and butts at 6 weeks; all the bucks had the “freckles” – dark marks on their testicles) Black (carried Siamese, no B.E. Cream in line) x Agouti (had Ivory parent) = some B.E. Himi and R.E. Himi Ivory x PEW = some dark Cream Ivory x dark Cream = all B.E. dark Cream x Black = Agouti, Black

Burmese x Ivory (had dark Cream sibling—from Ivory x PEW breeding) = Burmese, dark shade Burmese Agouti, light shade Burmese Agouti with no points, B.E. Himi, R.E. Himi, Ivory, PEW. One of the light Burmese Agouti with no points was bred with Cinnamon and produced Mink- and Cinnamon-based along with Black. Burmese (grandmother is sister to Ivory used in Ivory x PEW breeding) x dark Cream (from Ivory x PEW breeding) (U.S. breeding) = dark Cream, Ivory, B.E. Himi, Agouti Burmese (with and without points), Burmese (with and without points) Burmese x Mink (siblings; out of a Russian Blue that carried Siamese and a Burmese) = Sable Burmese, Siamese, Mink, and Black. Sable Burmese (from above litter) x Himi = all some form of Burmese (some were Russian Blue Burmese) Burmese (same one bred with the Mink above) x Siamese = Burmese, Siamese Burmese x Ivory = Ivory, PEW, B.E. Himi, R.E. Himi, Burmese (no points), Burmese (with points), Wheaten Burmese (with points), Wheaten Burmese (no points) Burmese (no points) x Cinnamon = Black, B.E. Siamese, Burmese, Wheaten Burmese Burmese (from Cream and Burmese) x Siamese Satin (U.S. breeding) = B.E. Himi, B.E. Siamese RBPS x Burmese (with points) (U.S. breeding) = Siamese Burmese, Himi Burmese, B.E. Siamese, B.E. Himi m Name Changes through the years: dark-eyed Cream to Milk to B.E. Cream to Ivory Taupe to Stone to Biscuit to Burmese Agouti Burmese to Wheaten Burmese

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