An Illustrated Guide to Rabbit Coat Color Genetics*

*with an emphasis on Rex Rabbits (see the Un-Official Rex Standard here)
Except where otherwise noted, content on this wiki is licensed under the following license:
(c) K.Becker, Mink Hollow Media, Ltd. (All Rights Reserved)

This guide assumes a knowledge of basic genetics. If you need a refresher, try: Dr. Dennis O'Neil, Behavioral Sciences Department, Palomar College, San Marcos, California

This site has a well-written introduction to genetics and to rabbit coat colors at Aurora Rabbits: Raising Rabbits.com

There is also an excellent description of rabbit coat color genetics by Laurie Stroupe Of The Nature Trail Rabbitry. It deals with Holland Lops and so skips over a few details that pertain to Rex, but is very thorough with lots of tables and pictures.

Another site full of great pictures & descriptions (with lots of Rex photos) by Pamela Nock

The Three Little Ladies Rabbitry has a great color chart.

When it comes to coat color, believe it or not, there are only two Fundamental Pigments: Black (eumelanin) & Yellow(red - phemelanin). The expressed color is a function of how much black or yellow pigment exists in the hair, which can change not only from hair to hair, but also along the length of a single hair. In rabbits, there can be as many as five bands of color on a single hair.

In addition, most animals have two types of hair: 'outer' guard hairs which are stiffer, thicker, and often straighter than the finer, wavier, and softer undercoat hairs. The outer coat consisting of guard hairs protects the animal, while the undercoat provides insulation.

Rex rabbits have the same double coat as other rabbits, it's just that their guard hairs are the same length as the undercoat (usually the outer coat is longer). This has several effects:

The outercoat does not hold the undercoat down and the entire pelt appears to stand on end. In fact, a coat that lies flat is a fault in a Rex.
The coat has an amazingly plush feel - these really are velveteen rabbits.
The guard hairs carry the same amount of color as a regular length hair but they are considerably shorter. This means that the color of the hair appears more intense. Contrast that with long-coated rabbits like the angora when the same amount of color is spread out over a MUCH longer hair; these rabbits always appear to have pale colors.

“The typical length of the single hair fiber of the Rex rabbit is 1.79–3.79 cm, with no statistically significant differences between hairs on various parts of the body (Tao 1994; Neirurerova et al. 2017). The diameter of the fiber is about 18–19 lm, and the hair density is 15 000–38 000 fibers/cm 2 (Tao 1994).”

Dorożyńska, K. and Maj, D. (2021), Rabbits – their domestication and molecular genetics of hair coat development and quality. Anim. Genet., 52: 10-20. https://doi.org/10.1111/age.13024

Tao, Y.R. (2010). Studies on the quality of Rex rabbit fur. World Rabbit Science, 2, 21-24.

LIPH Expression in Skin and Hair Follicles of Normal Coat and Rex Rabbits

Linkage Interrelations of Three Genes for Rex (Short) Coat in the Rabbit

A Case of Neighboring Loci with Similar Effects

All genes come in pairs. If both genes of a pair are the same, it is said to be homozygous for that trait.

Genotype refers to the gene itself, while phenotype refers to what we can see. Sometimes a phenotype will imply a certain combination of genes but the actual genotype is different. The best way to discover an animal's genotype is through test breeding with an animal whose genotype is known.

There are 5 main groups of color genes, each controling a different aspect of the color and markings. The genes within each group are listed in decreasing order of dominance. A Capital letter denotes a dominant gene.

A = agouti
a^t = tan (otter)
a = self

The pattern gene controls how the color appears on the hair. The dominance relationship for these genes is quite simple: each allele is completely dominant over the ones 'below it (as listed above). This means that the following pairs will all look exactly the same: AA, Aa^t, Aa. They will all look like agoutis. A tan (or otter) can be a^ta^t or a^ta, and a self can only be aa. Unless you know the genetic make-up of the parents, it is not possible to tell what the second gene is on an agouti or tan without test breeding.

Agouti is the basic “wild” color. Hairs on different parts of the body are colored differently, but will have three-five different colored bands on each hair. This pattern looks different on a rex because of the shorter hairs. The bands are smaller and the colors appear more intense. The Castor is the name given to the black agouti (the standard wild color). Their hairs should have at least three rings: the undercolor should be slate grey; the intermediate color should be as rich an orange or rufous red as possible, and the tips should be black.

The otter (called tan in most other breeds) should have a solid body top color with a lighter undercolor (next to the skin). The underside (from chin through belly to tail) should be white on the surface with a grey undercolor, and there should be a redish line between the body color and the undercolor. The insides of the ears, and around the nose and eyes should also be reddish (i.e. red or orange in full concentration [black or chocolate] rabbits and tan or cream in dilute [blue or lilac] rabbits).

The self rabbits should be exactly the same color all over their bodies right down to the skin.

A = Agouti [“wild” color; multi-banded hair shaft]	a^t = Tan [giving tan or “otter” markings]	a = Self [solid color]

agouti	otter	self (blue)

There are only two alleles in this group: the “black” results in more intense looking colors and the brown changes the black parts of the rabbit to brown. This means that in the Castor for example, the tips of the hairs become brown instead of black, making the rabbit look much redder.

B = Black
b = Chocolate

Chocolate (otter) vs Black (otter)	Castor (black agouti)	Amber (chocolate agouti)


Black	Broken Chocolate	Chocolate vs Amber

This gene affects the intensity of melanin production in the coat hairs. The normal or dominant form, C, is what might be termed 'full color' concentration. There are however a number of incompletely dominant alleles on this locus, with varying effects on color intensity. At least some of these variant forms are temperature sensitive - the higher the temperature, the more effective they are (i.e, the lighter the color).

The dominant form is C- and results in full color concentration.

The first variant is, c^chd, is (dark) chinchilla. This lightens most or all of the phemelanin with little or no effect on eumelanin. E.g. it turns black+tan to black+silver.

The next variant is shaded (or sable; sometimes also called light chinchilla) - c^chl. This one lightens most of all of the phemelanin, and some of the eumelanin. The effect is similar to that of the chinchilla variant, but further lightens the black turning it into more of a sepia color.

Second last is the Himalayan (or Californian) allele (c^h).This one has a profoundly temperature sensitive effect, resulting in hair growing from the warmest parts of the body totally white, and allowing color to develop only on the cooler parts of the body. This allele is also affected by external temperatures, so that colors tend to fade in the summer and become more intense in the winter. Any parts of the rabbit that are exposed to cooler temperatures will grow more colored fur, which can result in 'smuttiness', especially around the rear ruff or dewlap.

Finally, the most recessive allele in this series is c, true pink-eyed albino. This allele prevents ALL pigment from forming, and must be present in the homozygous state (cc) in order to be expressed..

Another Way to Look at It

The color concentration gene controls the amount of pigment in the hair; relative amounts shown as units of black 'B' and yellow( or red) 'Y' color. Imagine that the total amount of pigment in hair is the same for all hairs. As a result, shorter hairs appear darker (and also why long-haired varieties look faded). This explains the shading pattern found in seals, sables, torts, and the pointed colors. The color pattern of the chinchilla (C^chd) is essentially the same as that for the agouti except that is lacks the reddish color in the mid-band.

C = Normal [BBBBYYY]
C^chd = Dark Chinchilla [BBBBY–]
C^chl = Light Chinchilla [shaded : seal & sable] [BB—–]
C^h = Himalayan [BB—–] (with an added temperature-sensitive feature that prevents pigment from forming on the hairs when the follicles are warmest.
c = White [Albino : absence of color] [——-]

Dark chinchilla removes most of the yellow band. It makes the skin look brown but takes the red color out of the hairs. Note that a chocolate chin retains the brown hue in the tipping but has completely lost it from the midband.

normal (C-)	dark chinchilla (C^chd-)	shaded (C^chl-)	californian (C^h-)	white (cc)

Controls the “intensity” of the color: a diluted black is a blue, and a diluted brown is a lilac. The dilution affects the whole rabbit, not just the hair color. This includes the pigmentation in the skin and the eye color.

D = Full Strength
d = Diluted

We can look at the color (black vs brown) and the dilution genes together:
– B- – D- – = Black (where the – represent A, C, and E)
– B- – dd – = Blue
– bb – D- – = Chocolate
– bb – dd – = Lilac

Together, these two genes account for the four main color variations of all the other shades and patterns. For example in the agouti group we have: castor (black), opal (blue), amber (chocolate), lynx (lilac).

Full Color (Castor)	Dilute (Opal)


Full Color (Amber)	Dilute (Lynx)

Full Color (Black)	Dilute (self Blue)


Full Color (Black Otter)	Dilute (Blue Otter)

a black & blue (the same blue as below)	note the differences in eye color


both of these rabbits are dilute: the blue is Bb dd and the lilac is bb dd

These alleles control the presence, and extent of black on tips of hair and in undercolor. More extension causes the tipping to extend further down the shaft of each hair, and less extension keeps it at the tips. Non-extension gets rid of the tipping altogether, and the Japanese allele causes the black to appear in patches rather than on each hair, similar to the calico pattern of cats.

E^d = Dominant [not accepted in REX]
E^s = Steel [ not accepted in REX; causes the black on the hair to be extended, often covering the middle band with dark.]
E = Normal
e^j = Japanese [ not accepted in REX [excpet for tri-color]; responsible for harlequin patterns]
e = Non-Extension [helpfulfor Red]

Normal Castor (E)	Steel Castor (Es)


Black-Orange Tri (Ej)	Tort (ee)

The E-series has some partial dominances which can cause the second e-gene of a heterogygous pair to show through.

The Dominant Black (E^d) makes agoutis look like blacks. For this reason it is only 'useful' in solid colored rabbits (selfs).

The Steel (E^s) causes the darker undercolor to be extended. The ticking may also appear longer. This turns the short-haired areas dark and makes an agouti rabbit look like the top coat is too heavy. It also tends to turn the underside (belly) dark.

Next is normal extension (E) which allows the banding and colors to show through 'naturally'.)

The japanese extension (e^j) has a randomizing effect on the distribution of color. In a solid rabbit, it is responsible for the harlequins. It is the only e-series gene that is acceptable in harlequin rabbits. The black-orange and blue-cream carry C for full color concentration, and the magpies (black-white and chocolate-white) carry the chinchilla gene (c^chd). An agouti or otter with one full extension (E) and one japanese gene (e^j) will always show the randomizing effect which is most notable inside the ears and around the eyes.

In Rex, a self (no white: enen) harlequin and a broken (En-) is a tri-color and will show the dark parts as actual spots on an orange background. The full colors will have either black or chocolate spots on an orange background and the dilutes are similar only with blue or lilac and cream. Black spots on a cream background is undesirable.

The final allele is the non-extension gene (e) and is recessive to all of them. It eliminates all banding. On a self colored rabbit (aa) it will appear as a tortoiseshell (tort) and on an agouti (A-) it will eliminate the ticking which is necessary for reds and creams.

White markings are called “broken” in rabbits (en = english spot). This allele is influenced by various modifiers that can cause the white markings to vary from tiny amounts under the chin and on the chest to the markings on finds in a Hotot which has only a fine colored line around the eyes. In Rex, the ideal broken pattern allows for 10-50% color. It can be a blanket pattern or spots, but the ears must be colored and there should be color on either side of the nose. When the nose marking straddles the nose, it's called a butterfly marking. Spots on either side are also OK. Markings that look like they have single white hairs scattered through the colored parts are NOT desirable.

There's also a good article here (Nature Trail, Laurie Stroupe)

En = Broken Pattern
en = Self [Normal]
{there are others but they are not significant in Rex}

White markings fall into 3 categories:

enen	=	solid colored; no white
Enen	=	Broken, usually 10-90% color
EnEn	=	“Charlie”, usually < 10% color, typically around the eyes, ears, and down the center back

It is not usually possible to distinguish between an “undermarked” broken and a true (genetic) charlie. The only definitive means is through test-mating. If a cross between the undermarked broken and a self (solid colored) rabbit produces even a single self baby, then the broken is not a charlie.