The genetics of rabbits involves things such as the breed, coat colors, size, shape, eye color, etc.
Most rabbit breeders are very clued up when it comes to genetics. The better the understanding of genetics, then the better the breeder.
Breeders use the word “genetics” to discuss the factors that make up the overall color of a rabbit.
Other factors that are important when looking at the genetics of rabbits include genes for dwarfism, albinos, the life-span, and even the behavior in rabbit breeds.
Rabbit colors are a crucial part of genetics and can be manipulated to produce a predictable outcome. Breeders have even been able to produce a luminous rabbit whose fur glows in the dark.
The genetics of rabbits that determine the color of the coat, the texture of fur, length of fur, and a variety of other physical characteristics are very complex. The math and formulas can get very complicated, but let’s try to simplify it.
Rabbit Genetics Explained
Genetics involves genes, the individual points on a chromosome which are long strings of DNA all coiled up together in the nucleus of the cell.
Genes determine the appearance or function of a body part. They may act all alone, or work together with other genes to produce a certain appearance or bodily function.
Chromosomes and the genes on them pair up in most cells. There are 22 pairs of chromosomes in each cell of a rabbit, not counting the sex cells or the red blood cells. These cells only have one half of the genetic material.
Each characteristic requires the participation of two genes, one from each chromosome. These genes must be located at the same spot on the individual chromosome to form a valid pair. Some locations on the chromosome may only hold the code for one type of gene, while other locations might contain multiple types of genetic information.
Locations that allow only one type of gene do so because any less would be harmful or fatal. An example of bad rabbit genetics would be the genes that control the shape of the teeth. If the chromosome location for teeth genetics had any other gene present, the teeth would not form properly and the rabbit would eventually starve to death.
Some chromosome locations allow more than one types of genes to be present, causing different non-harmful expressions of the same characteristic. For instance, a hair color gene may allow 2 genes of different types to occupy that location. One type of gene may be one that produces black hair, the other brown. Each chromosome may be either the black or the brown gene.
Some genes match their counterparts on the other chromosome exactly and some do not. If the two genes are exact matches, they are homozygous (the same). When two genes do not match, such as one black and one brown, they are considered heterozygous(different) or a hybrid.
When we speak of a gene location, we are actually referring to the same location on chromosome A and chromosome B – remember, it takes two sets of genetic information for this to work. When we talk about a location, we’re actually talking about the same spot on two different chromosomes.
Dominant & Recessive Genes
In genetics, when the two genes, found in the same location aren’t exact matches, one gene will express itself more than the other. The gene that is seen is called the dominant gene and is represented by a capital letter (i.e. “B”). The other gene is called the recessive gene. It is represented by a lower case letter (i.e. “b”).
If the dominant gene is the only thing expressed, this is complete dominance. This is what happens the majority of the time. However, there are times when the recessive gene alters how the dominant gene is expressed and this is called incomplete dominance.
Remember we said sex cells only have half of the chromosomes? Well, that’s because the buck’s sperm adds half of his genetic code, and the doe’s eggs add the other half. These sex cells are called gametes.
When the doe’s egg is fertilized by the buck’s sperm, the two chromosomes join together. The offspring are then born with 22 chromosomes.
The genes from the buck are matched with the genes from the doe. How these genes are expressed in the offspring is completely dependent upon dominance and recessiveness.
The determination of rabbit genetics is based on the law of probability. Here’s a simple explanation of what this looks like on paper.
Let’s take the black/brown color location which requires two genes. Rabbit X is black. We will use “B” as the black gene which in rabbits is expressed as complete dominance. Rabbit Y is brown. The recessive gene for this location, the brown gene or “b”, can only be expressed if the gene from both chromosomes is recessive.
Since there are two genes, there are 4 possibilities. For the black completely dominant gene, the gene code for the black rabbit could be either BB or Bb.
In order for the brown gene to be expressed, the only gene code for this brown rabbit is bb.
Because the B gene is completely dominant, both Rabbit X and Rabbit Y must have at least one B in their genetic code will present with black fur.
Unfortunately, the color of a rabbits fur is not quite this simple, there are other genes are work. For our discussion, let’s assume we have a solid black and a solid brown rabbit.
If we mate a black rabbit with another black rabbit, we can predict the color of the offsprings’ fur. Each black rabbit must have a B in their gene code. Since we don’t know what the other gene code is, we can leave a blank “_” to represent what we don’t know.
Each of the above rabbits now has a gene code of B_.
So, let’s match these genes up:
Rabbit X B _
Rabbit Y B
Matching each chromosome from Rabbit X with each chromosome from Rabbit Y, we get the following combinations: BB, B_, _B, and finally _ _.
The first three rabbits will all have black fur. It doesn’t matter that we don’t know what the unknown gene code is, black fur is completely dominant, so it only takes one dominant gene code for it to be expressed. But what about the fourth rabbit?
If the rabbit has black fur, we know that at least one of the gene codes was dominant – B, meaning either Rabbit X or Rabbit Y has the genetic code of BB. In this instance, all offspring between these two rabbits will always have black fur. Always. No exceptions.
But what if the fourth rabbit is brown? Well, the only way to get brown fur, the recessive trait, is if both genes are recessive – bb. In this case, the only way for this to occur is if both Rabbit X and Rabbit Y have the gene code of Bb. If this were the case, the laws of probability would tell us that 25% of the offspring between Rabbit X and Rabbit Y would have brown fur.
Since these pairings are entirely random, there is still no guarantee. It may take two, even three litters before the true genetic code can be determined with any certainty.
If you were trying to determine if a rabbit showing the dominant trait had the recessive gene, you would need to mate it with a rabbit showing the recessive trait. If you never saw the recessive trait expressed, it’s safe to assume the rabbit expressing the dominant trait has the gene code of BB. But again, this is genetics and nothing is absolutely certain!
The absence of a recessive gene being expressed isn’t a hundred percent sign that neither of the rabbits has the recessive gene, just that the probability of the recessive trait showing up is very slim.
Rabbit Genetics and the Dwarf Gene
What Is A Dwarf Rabbit?
Dwarf rabbits are small with compact bodies, short necks, and adorable rounded faces. They can vary in size and weight but a dwarf bunny usually weighs between 1.5 to 3.5 pounds. Any rabbit breed with a maximum accepted weight of 4 pounds or less is considered a dwarf rabbit.
There are several breeds of dwarf rabbits including Britannia, Petite, and the Dwarf Hotot. The most popular breed is the Netherland. Most dwarfed rabbit breeds have a significant Netherland Dwarf influence in their genetic background. “Nethies,” as they are sometimes known, are thought to have originated in Europe. They have become a popular choice worldwide because not only do they look adorable but they are easier to maintain and raise.
However, raising dwarf rabbits doesn’t always run smoothly. If you breed dwarf rabbits, there are a few issues that you may wish to research a little more…
The Dwarf Rabbit Gene
The dwarf gene is relatively easy to explain.
Each rabbit has two size genes, one dominant and one recessive.
When a male and female rabbit reproduce, each parent will pass one size gene to each of their offspring. The dwarf gene is a dominant gene so one dwarfing gene will create a dwarf rabbit.
However, if the rabbit baby gets two dwarf genes, one from each parent, it will die.
If this happens, it is commonly called a ‘Peanut’ – a dwarf rabbit with two dominant dwarf genes. There needs to be one normal size gene as a recessive backup for a dwarf rabbit.
Breeds Of Dwarf Rabbits
Dwarf rabbits are completely in proportion, they are just a lot smaller. There are several breeds of rabbit that carry the dwarf gene.
- Dwarf Lop – this is a dwarfed French Lop, also known as a Mini Lop in the US although some Mini Lops in America are much smaller than the Dwarf Lop
- Netherland Dwarf
- Mini Rex
- Mini Satin
- Holland Lop
- Dwarf Hotot (shown)
- American Fuzzy Lop
- Jersey Wooly
The following breed is very small but does not carry the dwarfing gene:
- Polish (Britannia Petite)
The Polish Rabbit (Britannia Petite in the US), shouldn’t technically be included as a dwarf rabbit although it often is due to its tiny size, however, it is not an official dwarf.
These rabbits have been selectively bred for their tiny size. Unfortunately, their bloodlines in the USA have been “corrupted” with genes from Netherland Dwarfs in order to obtain a desired color gene.
Dwarf Gene Explained
The dwarf gene works as a simple dominant gene. This means that just one dwarfing gene will produce a dwarf rabbit.
The dwarf gene is represented by the capital letter “D” as it is the dominant gene.
The recessive gene is represented by the lower case letter “d.”
All dwarf rabbits will inherit one dwarf gene (either D or d) from each parent.
Possible pairings can, therefore, be: Dd, dd, or DD.
- Dd = True Dwarf
- dd = Normal
- DD = Peanut
If you breed a True Dwarf with a True Dwarf on average, you will produce 50% true dwarf’s, 25% normals and 25% peanuts.
If you breed a True Dwarf with a Normal on average, you will produce 50% true dwarfs and 50% normals.
True Dwarf Rabbit
True Dwarfs (Dd) get one normal gene and one dwarf gene. These are the animals you want in your litters. True dwarfs match the standard of perfection for their dwarf breeds.
The Netherland Dwarf is a True Dwarf rabbit. It is round, short, and compact. The ears are short, and the feet are correct. True Dwarf Rabbits often do well in shows. They are much easier to judge for true characteristics with their short ears and smaller back feet. They normally weight between 2 and 4 pounds, which is a perfect show weight for a rabbit.
False Dwarf Rabbit
False Dwarfs (dd) or Normals are born with two recessive dwarf genes. They can be slightly larger, usually over 3 pounds. These are the Dwarf offspring that inherited 2 copies of normal size genes. They are also known as “Big Uglies.”
False dwarf bucks are sometimes called “Big Ugly Bucks” or BUBs and despite good bloodlines, they can’t compete on the show table as they are larger than 2.5 pounds. Their ears may also be too long and their proportions will not be correct. BUBs usually end up as well-loved pet rabbits.
False dwarf does are sometimes called “Big Ugly Does” or BUDs and can actually be an asset to your breeding program. She can’t be shown, but her slightly larger size may enable her to carry and deliver a bigger litter. She’ll probably lactate well and will pass a normal size gene to all her offspring, which when paired with a single dwarf gene from a True Dwarf buck, may create a show-stopping true dwarf bunnies.
Peanuts (DD) are born with two dominant dwarf genes. Although sometimes born alive, peanuts will not survive due to a compromised digestive system and brain complications.
Peanuts are excessively tiny and they have unusual cone-shaped heads which appear much too large for the body. They also have small deformed limbs. The ears are considerably smaller than the other kits in the litter with the difference being very noticeable.
If not stillborn, they usually last only 1-3 days past birth, but a few have lasted up to 3 weeks and a tiny percentage up to 4 weeks.
Sometimes peanuts can look normal and will last up to around 6 weeks before they die. This is preceded by a lack of eating or drinking and the rabbit will stop growing for the last 4 or 5 days before they die. Some breeders prefer to cull their peanuts at birth because of their probable suffering or some let them die on their own. It can be heartbreaking, but peanuts are part and parcel of breeding dwarf rabbits. You can avoid producing lethal peanuts by using “big uglies” (false dwarfs) in your breeding program. They have no dwarf gene to pass onto to their offspring.
Max Factor Gene
Back in the 1980s a group of breeders went through the complete process of documenting the animals that carried the Max Factor gene and followed the normal ratio procedure and proved the existence of the gene.
The name “Max Factor” was given to this gene after finding that an imported Dwarf buck named Max appeared to be the original carrier.
Max Factor acts like a normal recessive gene. The only way for it to be expressed in the offspring is if both parents have that gene code.
Max Factor kits (sometimes called “frogs”) are very odd-looking. They are born with their eyes open and feet all twisted inward. The eyes will usually be infected due to exposure in the birth canal. Many times the front feet will be just “flippers” with no toes and sometimes you will get one with extra toes. The hind feet usually are turned “upside-down” or turned inward. The double Max animals will have a different type of fur as well. Their fur almost feels like human hair rather than fur.
Most Max factor kits die shortly after birth but if they do survive, they take an awful lot of dedication and care. Most rabbits with the defects listed above will need constant cleaning as they urinate on themselves and can’t clean themselves properly. They also have severe eye problems which can be very costly and time-consuming.
If you have a Max factor rabbit we’d love to hear from you. You truly are a dedicated rabbit owner! Send us your story and some lovely photos of your unique little friend.
The Hippo Gene
This is a genetic defect in Dwarf rabbits that is thought to be either related to the dwarf gene, or it is possibly another expression of excessive dwarfism.
Hippo kits are usually born dead. They are small, short, and stubby, albeit very wide for their length. They have only a nub for a tail.
This is a defect thought to be associated either with the dwarf gene or perhaps with a digestive syndrome such as enterotoxemia.
Faders seem to not adjust to solid food. Instead, they don’t eat or drink. They hunch in a corner and grind their teeth.
Death usually occurs quite soon after birth. Onset of fading, also called wasting, is around 4 weeks, but could also be as late as 6-12 weeks.
Some Dwarf breeders believe there is at least a component of inheritance associated with faders.
Fur color in bunnies is dependent upon genes located at several places on the chromosomes. These genes work together and can produce a large variety of colors and patterns. The genes that control hair texture and hair length are located someplace else.
Basic Color Genes
The basic color genes in the rabbit are:
A, B, C, D, E, En, Du, Si, V, and W.
Here are the 5 basic genes:
- A: Agouti hair shaft pattern (or not)
- B: Black (or chocolate)
- C: Complete color (or shaded, or albino)
- D: Dense (or dilute) color
- E: Extension of color (or its limitation or elimination)
Some genes are nothing more than color modifiers, determining how dark or light the color will be expressed, or if a specific pattern will be present.
They include the rufus modifiers, the plus/minus (blanket/spot) modifiers, and the color intensifiers.
These modifiers are not single genes, but multiple ones that pool their effects.
Capitalized letters almost always refer to a dominant gene, and lower case to a recessive gene. Geneticists include a place marker in the spot of an unknown, second gene copy, represented by an underscore:
Since the capitalized code letters represent dominant genes, you cannot know by looking at the rabbit what the second code letter of the pair is. When the genetic blueprint is not fully known, the place markers are used.
Basic Rabbit Pigments
There are only two possible color pigments a normal rabbit can express: Dark Brown and Yellow.
The absence of both pigments results in white fur.
All the colors possible in rabbit fur are simple combinations of dark brown and yellow, or the absence of them. Rabbit fur color can show on the same, or different hairs, in different intensities, and in very specific patterns or none at all.
Long & Short Hair Colors
Both long and short-haired rabbits have the same color genetics, the number of pigment granules present is equal for both.
In general, rabbits that have long hair, such as Angoras, have diluted color expression.
In long hair, the pigment granules are spread further apart from each other, giving a less dense look and a more pastel color.
Rabbits that have short hair, such as the Rex, have a more intense color expression.
In short hair, the pigment granules are packed closely together, making the color dense and more intense.
Wild Rabbit Colors
Wild Rabbits brown fur called agouti.
Looking closely at this fur, you can see that it is made up of 3 to 5 bands of color.
The hair closest to its skin is gray. This is followed by yellow with black on the tips. These rabbits also have white bellies.
In domestic rabbits, this agouti pattern is called chestnut. There are several variations of this agouti pattern in domestic rabbits. These variations are caused by other genes and modifiers working together.
Color Gene Groups
We can actually classify the color genes in two groups.
- First, the color pattern genes. These genes determine which pattern will be expressed:
no pattern (self), agouti or tan.
- All the other genes are the color genes. These genes determine the placement and intensity of the color pigments on the hair.
Rabbit Color Pattern Groups
Taking the first gene above, that expresses color pattern, the colors can be divided into one of three groups. Colors vary in shade, base color, etc. but they all fit under one of three patterns:
(Just remember S.A.T)
A rabbit that’s one solid color all over its body. E.g.: black, chocolate, blue, lilac.
Note – REW (ruby-eyed white) and BEW (blue-eyed white) are not true self colors.
Self Color Group Explained
A self rabbit does not have markings on the underside. A self rabbit is essentially the same color all over. Blacks are selfs. So are chocolates, lilacs, and blues.
Tortoises are also selfs. So are Siamese sables and smoke pearls and sable points. These rabbits have some shading. For instance, the nose on a sable is darker than the back, which is darker than the sides of the body.
However, here’s the important thing: every single hair is only one color. There’s no banding on the hair shaft itself. The color might fade near the skin, but there’s no switching from black to red on a single hair-like there is on a Chestnut Agouti coat. If you take a square-inch patch of hair anywhere on the bunny, each hair will be about the same color as those around it. That’s the mark of a self.
Has bands of different color on each hair shaft. E.g.: chestnut agouti, shaded agouti, frosted pearl, lynx, opal
Agouti Pattern Explained
This is the original rabbit color pattern. Wild rabbits are agouti. The colors we call chestnut and chinchilla are agouti.
Agouti rabbits have white markings on the belly, chin, tail, eyes, nostrils, and ear-insides. Presence of those markings is your first indication that a rabbit might be an agouti.
The color of the rabbit’s back is not a solid color, but a blend of light and dark hairs mingled together. If you blow into an agouti’s coat, you will find that each hair shaft is banded with color and the hairs form concentric rings of color as they lay flat. Anytime you see rings of color, the rabbit is unquestionably agouti.
Has silver markings on the belly, underside of the tail, marking by the nostrils and circles around the eyes. E.g.: black otter, blue otter, tortoise otter, sable point marten
Tan Pattern Explained
Tan pattern colors have markings in all the same places that the agouti pattern colors do.
Tans, like agoutis, have light-colored markings (from orange to cream to white) on the belly, tail, chin, nostrils, eyes, and ears. They also have a light “triangle” marking at the nape of the neck.
The difference between tan and agouti is that a tan rabbit has a fully solid top color. There’s no blend of hair colors there. The top color might be black. It might be blue. It might be chocolate, lilac, tortoise, or sable. But it is not chinchilla or chestnut. Each hair is just one color, without bands. You’ll never see a ring of color on a tan pattern coat.
The Albino Color Gene
The Albino Gene isn’t so much a color as it is a color hiding gene.
An albino rabbit will be completely white since it’s missing the melanin gene which determines the color of their skin, eyes, and fur.
Not all white rabbits are albinos, so you’ll need to check their eyes. If their eyes are red or pink and their hair is totally white, they would be considered an albino.
Many animals with albinism lack their protective camouflage and are unable to conceal themselves from their predators or prey. The survival rate of animals with albinism in the wild is usually quite low.
The eyes of an albino animal appear red because the color of the red blood cells in the underlying retinal blood vessels shows through where there is no pigment to obscure it. An albino rabbit may not have the greatest eyesight due to their lack of eye pigment. Since their eyesight is not the best, they should be caged or kept inside since they may not be able to see predators.
REWs – Ruby-Eyed Whites
An albino rabbit, the REW or Ruby-Eyed White (sometimes known as Red-Eyed White), has two recessive genes, cc, in its gene code. Think of that like throwing a white sheet over the rabbit. The other genes for color are still there, but you can’t see them; they are not expressed. Even though the little “c” gene is recessive, if the rabbit gets two copies of it, the whole rabbit becomes an albino.
If the other rabbit has one small “c” gene, you won’t know until you breed it to a REW and you get REW babies. Your albino / REW babies will get a “c” gene from each parent. So you may get more REWs if the other parent carries a gene for it, too. If not, you won’t get any REWs.
If you have a pedigree for your rabbit, it can give you a clue as to what hidden color genes it may have. If your rabbit has a REW parent, you know that rabbit carries a REW gene, as it is the only gene for the C location that rabbit has to pass on to its offspring.
BEWs – Blue-Eyed Whites
The Blue-Eyed White is similar to En, but a little more complex.
V is the symbol for the BEW gene since the old name for BEW is Vienna White. Most rabbits are VV, non-bews, and non-carriers.
A vv will always be BEW, in this way it works like cc REW. (If a rabbit is both cc and vv the REW will show.)
So the BEW is often another color underneath. Breeding a BEW vv to a non-BEW VV will result in 100% Vv BEW-carriers. These carriers will often be marked with white.
Occasionally a Vv will not show any white and will look and can be shown like any other rabbit of its color. Still, it does carry BEW and this should be noted on pedigrees so future breeders know.