Fur Type Genetics
Common Fur Types
NORMAL FUR
Normal fur is the wild type. It has longer, heavier guard hairs and a shorter, softer undercoat. When stroked backward, it will either snap back ("flyback") or gently roll back ("rollback") into place. Normal fur comes from the absence of any mutations in the fur genes.
Normal fur (flyback) - mature coat
L_ mm R_ Sa_
Photo credit: Dichrome Rabbitry
Normal fur (flyback) - immature coat
L_ mm R_ Sa_
Photo credit: Dichrome Rabbitry
Normal fur (rollback)
L_ mm R_ Sa_
REX FUR
Rex fur is characterized by an approximately 43% reduction in guard hair length and 20% reduction in undercoat length compared to normal fur, as well as a decrease in guard hair diameter and altered guard hair shape (Diribarne et al., 2011). Rex also have curly whiskers instead of straight. Simplified, the rex allele is r. This is recessive to normal fur, which is R. In order for a rabbit to have rex fur, it must have two rex alleles (rr). Normal furred rabbits can carry the rex allele (Rr). Rex
R: Normal fur
r: Rex fur
However, things are more complicated than that oversimplification above! There are actually three known rex alleles, r1, r2, and r3 (Diribarne et al., 2011; Castle & Nachtsheim 1933).. A combination of any of them (absent the R normal fur allele) will result in rex coat. The r1 mutation of the LIPH gene is the most common in rex coated rabbits, so it can generally be assumed that any rex rabbits are r1r1. The r1 and r2 mutations are on the same chromosome and are in linkage, whereas the r3 mutation is on a different chromosome.
R1: Normal fur
r1: Rex fur
R2: Normal fur
r2: Rex fur
R3: Normal fur
r3: Rex fur
R1R1, R2R2, R3R3, R1r2, R1r3, R2r3 combinations all produce normal fur. r1r1, r2r2, r3r3, r1r2, r1r3, and r2r3 combinations all produce rex fur.
The density of the coat is further influenced by mutations on the following genes: CCNA2, BMP2, IGF-1, TGF-β1, TGF-β2, and MMP2 (Chen et al., 2011a, Chen et al., 2011b, Chen et al., 2017).
Rex coat
L_ mm rr Sa_
Rex closeup of curly whiskers
L_ mm rr Sa_
Rex coats can sometimes appear a bit open or wrinkled in some places
L_ mm rr Sa_
WOOL/LONGHAIR
Wool is characterized by both the guard hairs and the undercoat being capable of growing much longer than normal. This is due primarily to a recessive mutation on the FGF5 gene (Zhao et al., 2018). Wooled rabbits may have wool or normal fur on their ears and face, depending on the breed. When there is wool on the ears and face, it is called "furnishing". The wool allele is l. This is recessive to short hair, which is L. In order for a rabbit to have wool, it must have two wool alleles (ll). Short furred rabbits can carry the wool allele (Ll).
L: Normal fur
l: Wool/Long hair
However, it is more complicated than this. Many other genes are also likely to influence the length of the wool Including WNT5A, WNT11, BMP4, BMP7, MSX2, PDGFA, and IGFBP5 (Zhao et al., 2018). These may all contribute to the final length of wool and account for differences between individual rabbits' capacity to grow longer or shorter wool.
SATIN FUR
hair shafts which are thinner and slightly translucent, allowing more light through to give a 'sheen' like satin fabric. The sheen typically intensifies the color. Satin fur is characterized by The satin allele is sa. This is recessive to normal fur, which is Sa. In order for a rabbit to have satin fur, it must have two satin alleles (sasa). Normal furred rabbits can carry the satin allele (Sasa).
Sa: Normal fur
sa: Satin fur
Satin coat
L_ mm R_ sasa
Photo credit
Satin coats
L_ mm R_ sasa
Photo credit
Satin coat
L_ mm R_ sasa
Photo credit
Satin kit already showing characteristic sheen
Photo credit
MANE
The mane mutation causes longer wool around the head and neck (like a lion's mane) and around the lower part of the body, especially near the haunches (called a "skirt"). The mane allele is is incompletely dominant to the non-mane allele. The mane allele is M. The non-mane allele is m. Rabbits without a mane at any time in their life are mm, and are called no-manes. Rabbits with a single allele for mane and a single allele for no-mane (Mm) are called single mane. Single mane rabbits may shed out most of their mane and skirt upon maturity. Rabbits with two mane allele (MM) are called double mane, and as young kits their sides remain hairless longer than the rest of their body. These hairless areas are where the wool will grow in for the mane and the body wool.
M: Maned
m: Normal (no mane)
Double Mane
L_ MM R_ Sa_
Photo credit
Double Mane kit showing the bald patches on the sides
L_ MM R_ Sa_
Photo credit
Single Mane
L_ Mm R_ Sa_
Photo credit
COMBINATION FUR TYPES
Rabbits can have combinations of different fur types. Below are different combinations.
Satin + Wool (Satin Angora)
ll mm R_ sasa
Photo credit
Wool and yarn from Satin Angora (wool + satin)
ll mm R_ sasa
Satin + Wool (Satin Angora)
Short regrowth and older longer wool
ll mm R_ sasa
Photo credit
Satin + Rex ("Reza")
L_ mm rr sasa
Images Credit: Rainy Day Satins
Rex + Wool ("Opposum")
ll mm rr Sa_
Satin + Lionhead
L_ M_ R_ sasa
Rex + Lionhead
L_ M_ rr Sa_
Wool + Lionhead
ll M_ R_ Sa_
Uncommon/Rare Fur Types
Astrex showing the 'bobbled' type of waves.
ASTREX/WAVY
Astrex rabbits are characterized by wavy coats (Pickard, 1941). Astrex/wavy appears to only show up in rex coats and may be specific to the r3 rex mutation. The combination which is proposed to produce astrex is r3r3 wawa. However, the mutation can pop up in different breeds, including those without rex coats. Likely this means the parents were carrying both r3 and wa. The coat can take two primary forms: bobbled or marcelled. It can vary from only mild wave to very wavy.
Wa: Normal fur
wa: Wavy fur
Note that some regular rex coated rabbits will have some wave to the coat when they are young. True astrex rabbits maintain some amount of wave to their coats into adulthood.
Astrex showing a 'marcelled' type of coat.
WUZZY
Wuzzy rabbits are characterized by are born appearing normal, but at about 10 days old, affected kits start to look unkempt (Crawry & Sawin, 1959). This is caused by the tendency of the tips of the hairs to clump together in a twisted manner. It is a recessive mutation, so two copies are needed for the rabbit to be Wuzzy.
Wu: Normal fur
wu: Wuzzy
The rabbit on the left is a Wuzzy and the rabbit on the right is a normal furred littermate.
FURLESS/HAIRLESSNESS/HAIR REDUCTION MUTATIONS
Rabbits with these mutations are characterized be reduced or completely absent fur. There are multiple mutations which can cause whole or partial furlessness (Geren et al, 2017; Botha et al, 2014; Boucher et al, 1996).
Furless
Furless rabbits are characterized by highly reduced or complete absence of fur. Patches of fur may still be found on the ears, muzzle, tail, and feet but are usually mostly or fully furless over most of the body. The Furless (AKA hairless) allele is f. This is incompletely recessive to normal fur, which is F. Rabbits which are Ff typically bald as kits but eventually grow in full fur. In order for a rabbit to be furless, it must have two furless alleles (ff). Furless allele carriers often have wiry fur, lose their fur easily (in clumps), and/or have bald patches. The Furless mutation often shows up fairly often in mini rex and rex.
F: normal fur
f: furless
Furless with normal fur
ff L_ mm R_ sasa
(If you know the original source of this image, let me know so I can credit)
Furless with normal fur
ff L_ mm R_ sasa
(If you know the original source of this image, let me know so I can credit)
Furless with normal fur
ff L_ mm R_ sasa
(If you know the original source of this image, let me know so I can credit)
Furless with rex fur
ff L_ mm rr sasa
(If you know the original source of this image, let me know so I can credit)
Nude/Naked
Nude is caused by a mutation on the forkhead box N1 (FOXN1) gene (Song et al., 2020). It is a recessive mutation, so all Nude rabbits must have two copies of the Nude allele (nunu). In previous literature, the mutation has been referred to as 'Naked', and it was denoted as N for normal and n for naked. Affected rabbits have sparse, curly hairs growing in until about 2-3 weeks old. Around 4 weeks old, severe hair loss begins. Around 6 weeks, hair begins to regrow, eventually stabilizing until the Nude presentation of a lack of hair around the neck and upper back plus sparse hair on other parts of the body is achieved. Nude rabbits also may have nai dystrophy and somewhat lower body weight than their normal furred littermates. Nude rabbits also have immunodeficiency due to reduced or missing lymphoid tissues such as the thymus, spleen, and lymph nodes. There are 3 different mutations on the Nu Locus: Δ5, Δ10, Δ11, so there are actually 4 alleles, including the wild type. Any combination of nu alleles results in hair loss, but some combinations result in more hair loss. See the images for different combination phenotypes.
Nu: normal fur
nu1: nude (Δ5)
nu2: nude (Δ10)
nu3: nude (Δ11)
Above figure shows Nude rabbits with different alleles, all at 5 weeks old. First is Δ5/Δ10 allele combination, second is Δ5/Δ11 combination, third is Δ11/Δ11 combination.
Nude rabbit (Δ5/Δ11 combination) nail dystrophy at 5 weeks of age.
Nude rabbit (Δ10/Δ10 combination) hair loss at different ages.
Nude rabbit (Δ5/Δ10 combination) hair loss at different ages.
Pelt Loss
Rabbits with the Pelt Loss mutation have hair follicles in the skin, but they fail to emerge from the skin, resulting in thickened skin. There are two genes involved, each with a normal and a mutated version. Variant 1 mutation makes an absence of fur, though less pronounced than the Furless mutation. Variant 2 causes lack of the undercoat hair only, so the coat is thicker than in Version 1.
Ps1: Normal
ps1: Pelt Loss variant1
Ps2: Normal
ps2: Pelt Loss variant 2
Wirehair/Hypotrichosis
Rabbits with the Wirehair mutation do not grow undercoat, only guard hairs (Geren et al, 2017). This causes a wirey appearance to the coat. The amount of hairs grown by each individual varies, but no affected rabbits have as much fur as a normal rabbit.
Wh: Normal
wh: Wirehair
There also appears to be another recessive type of hypotrichosis which reduces fur across the neck, head, and ears and is associated tooth defects and often tooth loss (Gruaz & van Praag, 2021). This tooth loss results in death around one month of age due to being unable to consume normal food, unless special considerations are taken.
Kit with wirehair/hypotrichosis.
(Botha et al, 2014)