*with an emphasis on Rex Rabbits

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

There is also an excellent description of rabbit coat colour 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

When it comes to coat colour, there are two Fundamental Pigments: Black & Yellow(red). The expressed colour 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 colour 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:

1. 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.
2. The coat has an amazingly plush feel - these really are velveteen rabbits.
3. The guard hairs carry the same amount of colour as a regular length hair but they are considerably shorter. This means that the colour of the hair appears more intense. Contrast that with long-coated rabbits like the angora when the same amount of colour is spread out over a MUCH longer hair; these rabbits always appear to have pale colours.

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

Agouti is the basic “wild” colour. Hairs on different parts of the body are coloured differently, but will have three-five different coloured bands on each hair. This pattern looks different on a rex because of the shorter hairs. The bands are smaller and the colours appear more intense. The Castor is the name given to the black agouti (the standard wild colour). Their hairs should have at least three rings: the undercolour should be slate grey; the intermediate colour 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 colour with a lighter undercolour (next to the skin). The underside (from chin through belly to tail) should be white on the surface with a grey undercolour, and there should be a redish line between the body colour and the undercolour. The insides of the ears, and around the nose and eyes should also be reddish (i.e. red or orange in full coloured [black or chocolate] rabbits and tan or cream in dilute [blue or lilac] rabbits).

The self rabbits should be exactly the same colour throughout right down to the skin.

A = Agouti [“wild” colour; multi-banded hair shaft]	at = Tan [giving tan or “otter” markings]	a = Self [solid colour]
agouti	otter	self (lilac)

There are only two alleles in this group: the “black” results in more intense looking colours 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

The shading (or colour) gene controls the amount of pigment in the hair; relative amounts shown as units of black 'B' and yellow( or red) 'Y' colour. 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 colours. The colour pattern of the chinchilla (c^chd) is essentially the same as that for the agouti except that is lacks the reddish colour in the mid-band.

C = Normal [BBBBYYY]
cchd = Dark Chinchilla [BBBBY–]
cchl = Light Chinchilla [shaded : seal & sable] [BB—–]
ch = Himalayan [BB—–]
c = White [Albino : absence of colour] [——-]

Dark chinchilla removes most of the yellow band. It makes the skin look brown but takes the red colour 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 (cchd-)	white (cc)

Controls the “intensity” of the colour: a diluted black is a blue, and a diluted brown is a lilac. The dilution affects the whole rabbit, not just the hair colour.

D = Full Strength
d = Diluted

Full Colour (Black)	Dilute (self Blue)
Full Colour (Black Otter)	Dilute (Blue Otter)

a black & blue (the same blue as below)	note the differences in eye colour
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 undercolour. 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.

Ed = Dominant [ not accepted in REX]
Es = Steel [ not accepted in REX; causes the black on the hair to be extended, often covering the middle band with dark.]
E = Normal
ej = Japanese [ not accepted in REX [excpet for tri-colour]; responsible for harlequin patterns]
e = Non-Extension [necessary for Red]

Normal Castor (E)	Steel Castor (Es)	Black-Orange Tri (Ej)

White markings are called “broken” in rabbits. This allele is influenced by various modifiers. In Rex, the ideal broken pattern allows for 10-50% colour. It can be a blanket pattern or spots, but the ears must be coloured and there should be colour 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 coloured parts are NOT desirable.

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

White markings fall into 3 categories:

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 coloured) rabbit produces even a single self baby, then the broken is not a charlie.

too much colour [Enen]	broken [Enen]	broken [Enen]
(broken calls for 10-50% colour)	(lilac)	(blue otter)
'almost' charlie [Enen]	Charlie [EnEn]	Charlie [EnEn]
(chinchilla)	(tri-colour)	(black)

All genes come in pairs. In the case where a dominant gene is evident (i.e. is the one whose traits are visible), then the second gene of the pair cannot be known [it's hidden, or masked] and is indicated with a '-'. That second gene might be the same as the dominant one or one of the “lower ranking” genes of that group.

The agouti group of colours carries the original (wild) colour pattern, where the body colour comes from hairs that are banded. The tip colour is determined by the B and D genes and is black in castors, chocolate in ambers, blue in opals, and lilac in lynxs. Next to it along the same hair shaft should be a red or orange colour in the castors and ambers (the redder the better), and a lighter fawn colour in the opals and lynxes, all allowing for a bluer hue in the blacks and a browner hue in the chocolates. Farther down the hair shaft is a blue colour (lighter in the dilutes) and at the base is a light dove grey or white. The guard hairs are typically the ones that are tipped. The belly colour is tan, off-white, or white (again, with the dilutes having the lighter colours).

Castor	Castor	Amber	Amber
opal	Opal	Lynx

Chocolate vs. Amber		Amber

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Black Otter	Chocolate Otter (on the left)	Blue Otter	Lilac Otter

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Note the differences between these two littermates in the nestbox: one is blue and the other lilac. Both are dilute, but the lilac (left/middle) has brown instead of black. The other babies in this group are all blue & blue otter.

Black	Chocolate
Blue	Lilac

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NOT A RECOGNIZED COLOUR

This is the colour you get when you combine the shaded gene (c^chd or c^chl) with non-extension (ee). The animal will look white but if you compare it against a true albino (rew) you will see that the eye has colour (albinos have NO colour so all you see is the pink from the blood vessels in the eye) and that there is a slight ticking on the coat. The colour of the eye and ticking will provide a clue as to whether or not it is black, blue, chocolate, or lilac, although it is difficult to distinguish black from chocolate and blue from lilac as so much of the colour is removed by the shading gene.

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The only colours in this group that is a recognized Rex colours are Red, and the Broken variety of Harlequin. In the Rex, the self version of harlequin (ejej or eje) results in bands of colour, ideally alternating, but when combined with the broken pattern (Enen) the coloured parts become orange with black or chocolate spots, or fawn with blue or lilac spots.

This is a blue-cream (or blue-fawn) harlequin
This one is black-orange

Only the Red is recognized in North America. It is the only rex colour to make use of the recessive WideBand gene (W) which fills the entire hair shaft with the mid band colour. Genetically speaking, the difference between a Red and a Tort is that the Red has the Agouti pattern, while the tort is a self.

These all have dark points (nose, ears, feet,…) and a lighter body. None of these are recognized in Rex. All carry the self pattern (aa).

Black Tort

Judith Graf, Color Basics 1991 (self-published booklet)

Glenna M.Huffmon, The Basics of Color Genetics in Rabbits (I have the 1995 third edition)

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