From the subtlest cream to the deepest black, rabbit coats come in a kaleidoscope of colors. But what hidden factors control this diverse palette? The genetics behind rabbit fur colors involves a complex interplay between multiple genes and pigments. Take a hop down the rabbit hole to explore the science of coat color inheritance. Learn how dominant and recessive genes produce vibrant solid tones or stunning agouti bands. Discover how modifiers transform expected red eyes into ruby or sapphire. Whether breeding giant Flemish Giants or tiny Netherland Dwarfs, understand the genetic wizardry behind a Technicolor bounty of bunny fur.
Basic Color Genes
The genetics behind rabbit fur colors and patterns are complex, involving multiple genes interacting to produce the final coat color and pattern. At the most basic level, there are genes that control the production of the two pigments that contribute to rabbit fur color – eumelanin which produces black/brown pigment and phaeomelanin which produces red/yellow pigment. The main genes involved are:
Agouti Gene – This gene controls the distribution of eumelanin and phaeomelanin across the hair shaft, producing different patterns of banding. The dominant allele (A) results in the agouti pattern of alternating bands of eumelanin and phaeomelanin across each hair. The recessive allele (a) turns off agouti banding, resulting in solid eumelanin or phaeomelanin color across the hair.
C Gene – The C gene controls the production of full color (both eumelanin and phaeomelanin) versus dilute color (paler version of the pigments). The dominant C allele allows full color while the recessive c allele dilutes the color.
B Gene – The B gene controls the production of black eumelanin. The dominant B allele allows black pigment while the recessive b allele restricts black pigment, resulting in brown instead.
D Gene – The D gene controls the density of pigment granules produced. The dominant D allele results in dense/dark pigment while the recessive d allele produces dilute pigment.
E Gene – The E gene controls the production of yellow phaeomelanin. The dominant E allele allows the production of phaeomelanin while the recessive e allele restricts phaeomelanin, resulting in default white/gray color.
En Gene – The En gene intensifies phaeomelanic pigment, resulting in deeper red/orange tones. The dominant En allele intensifies phaeomelanin while the recessive en allele does not intensify the pigment.
The combination and interaction of these main genes are what produce the wide variety of colors and patterns seen in rabbit coats.
Typical Rabbit Pigments
There are two main pigments that contribute to rabbit fur colors:
Eumelanin – This dark brown/black pigment is produced by melanocytes in the skin/fur. The production of eumelanin is controlled by the B gene and D gene. The B gene controls the switch between black or brown eumelanin. The D gene controls the density/intensity of eumelanin with the dominant D allele resulting in very dark black/brown while the recessive d allele causes a lighter dilute brown.
Phaeomelanin – This red/yellow pigment is also produced by melanocytes. The production of phaeomelanin is controlled by the E gene and En genes. The recessive e allele blocks the production of phaeomelanin resulting in default white/gray. The En gene intensifies phaeomelanin shifting it from pale yellow to rich red/orange tones.
The C gene controls whether full coloration (both eumelanin and phaeomelanin) is allowed or whether a dilute pale version of the pigments is produced. When combined, eumelanin and phaeomelanin interact to produce a spectrum of fur colors in rabbits ranging from whites to grays, browns, and orange/red tones.
Long and Short Hair Colors
While all rabbit breeds have the same pigments and genetic controls over color, there are some key differences between typical colors seen in long-haired angora type breeds versus short-haired breeds.
Black – Solid black is common, produced by dominant B and D genes allowing full black eumelanin.
Blue – Dilute version of black caused by double recessive dd that lightens the eumelanin.
Chocolate – Rich brown caused by double recessive bb restricting black eumelanin.
Lilac – Very pale brown from double recessive bbdd diluting the brown eumelanin.
Reds/Oranges – Varying shades caused by phaeomelanin production allowed by dominant E with En intensifying the shade.
Agouti – Banding pattern caused by dominant A with alternating eumelanin and phaeomelanin bands across each hair shaft.
Chestnut agouti – Darker agouti pattern with black eumelanin bands.
Chinchilla – Paler agouti pattern with gray eumelanin bands.
Opal – Dilute version of agouti with pale color banding.
Solids – Caught in a loop trading recessive aa allows solid eumelanin or phaeomelanin color across the hair.
While long hair favors solid eumelanin colors, short hair displays more agouti banding which interacts beautifully with the different pigments.
Wild Rabbit Colors
In wild rabbit species, more natural selection pressures have shaped the common coat colors and patterns seen:
Agouti – Most common pattern, provides camouflage with background matching bands. Varies from gray to brown tones.
White winter coat – Seasonal coat allows white/very pale agouti blend for winter camouflage. Molted off for summer.
Black tones – Some wild species exhibit blackish tones rather than browns, allowing concealment at night.
Bright white underside/tail – Helps conceal rabbit from overhead predators when seen from below.
Disruptive patterns – Broken coloring with spots/stripes help break up the body outline. Seen in snowshoe hares, Amami rabbits.
Warm brown tones – In species inhabiting dry desert or sandy areas, coats match the surroundings.
Seasonal variations – Lighting & temps can trigger partial molts from summer brown to winter white.
The wild ancestors of domestic rabbits evolved these colors and patterns through natural selection to aid their survival in the environment.
Color Gene Groups
To simplify the wide variety of potential color combinations, rabbit colors are often grouped based on the gene pairs involved:
1. Self Group
The self group requires the recessive aa genotype which switches off the agouti pattern. This allows a solid coat color of either eumelanin or phaeomelanin across the rabbit. The exact self color depends on the other genes present. Examples include black, blue, chocolate, lilac, and red.
2. Agouti Group
The agouti group requires at least one dominant A allele to produce the characteristic banded hairs with alternating eumelanin and phaeomelanin. The specific type of agouti depends on modifiers like the C and D genes. Chestnut agouti has darker banding while opal has diluted pale bands.
3. Tan Group
The tan group is produced by the recessive at alleles in combination with recessive ee restricting phaeomelanin production. This results in a solid eumelanin base color with lighter phaeomelanin ("tan") only at the points of the rabbit (ears, nose, tail, feet). Examples are black otter or blue otter.
Color Pattern Groups
In addition to the color genes, other genes control the distribution of color across the rabbit's coat, creating distinct patterns:
The self pattern is full coverage of the self color across the entire rabbit. No white spotting or other markings are present.
The agouti pattern results in the namesake banding of the hairs across the entire rabbit. Solid coverage with the agouti hairs.
The tan pattern is characterized by solid eumelanin on the main body but lighter "tan" phaeomelanin color restricted only to the points.
The Albino Color Gene
The albino, or "c" gene is responsible for producing albino rabbits. This is one of the few rabbit color genes that is not fully dominant or recessive. Instead, it displays incomplete dominance:
- CC or Cc – Normal pigment production
- cc – Albino coloring, blocking most pigment production
One copy of the recessive c allele carriers some minor dilution effect, but two copies are required for the full albino phenotype of white fur and red eyes. The albino gene overrides all other color genes since it severely reduces pigment production.
REWs (Ruby-Eyed Whites)
The REW or ruby-eyed white rabbit exhibits the albino coloring. However, instead of the typical red eyes associated with albinism, the REW has deep pinkish-red eyes that appear ruby in color. This eye color results from a genetic modification that reduces normal eye pigments. REW is the result of two gene pairs:
- cc – homozygous recessive c alleles causing the albino phenotype
- siam gene – this modifier restricts pigment production in the eyes, altering the color
So REW rabbits have white coats due to the albino c gene, while the siam gene modifies the expected albino red eye color to produce the unique ruby tone.
BEWs (Blue-Eyed Whites)
The BEW or blue-eyed white shares the same albino genetics as REW, carrying two copies of the recessive c gene to inhibit pigment production, resulting in the white coat. However, instead of the siam gene, BEWs have the Vienna gene modifier, which works similarly to produce blue eyes rather than the expected red albino eyes. So BEW is the combination of:
- cc – homozygous recessive albino genotype
- Vienna gene – restricts pigment in the eyes, changing the color to blue
The Vienna gene modifier arose later than the siam gene, first documented in Vienna in the early 1900s. So while REWs and BEWs share the same albino background, different secondary genes interact to produce the different colored eyes.
This covers the key genes and major concepts that control rabbit fur color genetics. From the basic pigments of eumelanin and phaeomelanin to the complex interactions between multiple genes, this helps explain the diverse palette of colors and patterns seen across domestic rabbit breeds. An understanding of the genetic factors allows breeders to plan color outcomes and continue refining the rainbow beauty of rabbit coats.