Rabbit Color Calculator (coat colour genetics: A, B, C, D, E loci)

Understanding the rabbit colour calculator — concept and principle

This calculator predicts the coat colours of rabbit kits from the genotypes of the buck and doe at five main colour genes: A (agouti), B (black/chocolate), C (colour series), D (dense/dilute) and E (extension). It gives the most likely colour, its chance, and the probabilities for pattern, base colour, colour series, extension and albino kits. Rabbit breeders and genetics students use it.

How it is calculated

• Each parent passes one of its two alleles at each gene to a kit, with equal chance, giving four equally likely combinations per gene.
• The five genes are treated as independent, so their probabilities multiply.
• A kit shows the most dominant allele it received at each gene. Dominance orders: A agouti > aᵗ tan > a self; B black > b chocolate; C full colour > cᶜʰᵈ chinchilla > cʰ Himalayan > c albino; D dense > d dilute (black → blue, chocolate → lilac); E normal > eʲ harlequin > e non-extension.
• Two copies of c give a red-eyed white (albino) whatever the other genes are.

The principle

Coat colour in rabbits follows Mendel's laws: each kit inherits one copy of each gene from each parent, chosen at random. Dominant alleles mask recessive ones, so a rabbit can carry colours it does not show. The combination of genes then builds the colour: B and D set the base pigment, A sets the pattern, C controls how much pigment is made and E controls where black pigment appears.

Worked example

Default inputs: buck Aaᵗ Bb CC Dd Ee; doe Aa Bb Cc Dd EE.

1. A: three of four combinations carry A, so agouti pattern 75%, tan pattern 25%.
2. B and D: B_ D_ = ¾ × ¾ = 56.3% black base; blue 18.8%; chocolate 18.8%; lilac 6.3%.
3. C: the buck is CC, so every kit has full colour (100%); chance of albino 0%.
4. E: the doe is EE, so normal extension 100%.
5. Most likely colour: black base, agouti pattern, chance 0.75 × 0.5625 = 42.2%.

How to read the result

The probabilities apply to each kit independently; a litter of eight will not show the exact proportions. Unknown hidden alleles in a parent change the odds, so test matings or pedigree records improve predictions. Show names for colours vary between breeds and clubs.

Common mistakes

• Assuming a rabbit's visible colour reveals its full genotype.
• Expecting litter proportions to match the percentages exactly.
• Forgetting that two c alleles override all other colour genes.

Frequently asked questions

Can two black rabbits have a blue kit?

Yes, if both carry the dilute allele d.

Why does albino override everything?

Two c alleles stop pigment production, so the other genes have nothing to colour.

What is agouti?

The wild-type banded hair pattern controlled by the A gene.

Are these genes really independent?

The model treats them as on different chromosomes, which is the usual simplification.

Sources: Oregon State University Extension Service, M. Stern and J. Cruickshank, "Understanding the genetics behind rabbit coat colors: Part 2 — coat color genes" (2022, updated 2023)