Today we are going to look in detail at the characteristics that make one pet rat look different from another. These include color, shading, marking, coat type, and ear type.
Find out what type of rats you have and why they look the way they do? What makes a brown rat black – or blue? And, did you know that all rats have a Mini-Me!
Are Pet Rats All One Species?
Pet rats – also called fancy rats – are the species rattus norvegicus (the Norway rat/brown rat). The brown rat is the dominant wild species in many countries, thriving in close quarters with humans.
Another species of wild rat, rattus rattus (the black rat/ship rat/roof rat), is also kept by some rescuers and specialists. Black rats are the dominant wild species in some countries, like South Africa.
However, even in these countries, the pet rats (even the black ones) are brown rats. The name may seem odd to us because there are so many types of fancy rats, who come in a rainbow of colors. But most wild rats are brown.
Are There Different Breeds of Rats?
No, there is only one breed of rat, because a breed refers to a group within one species of domesticated animals that have been bred to be distinctly different in physical appearance and behavioral traits.
All pet rats are essentially the same in terms of their conformation (physical shape) and behaviors. There are gender differences and individual differences but there are not specifically different sub-groups.
Rats who differ from each other in terms of coat color, markings or coat type are referred to as different varieties.
We might also say “different types of rat”, but this can be confusing because they are really all the same type of rat, just different colors.
There is even more confusion because “type” means something completely different when speaking about rats. Rat type refers to the physical conformation of an individual rat and how closely it matches the “ideal rat”.
This ideal was decided on when people first began to breed and exhibit (show) varieties of fancy rat – and the rat fancy was born. The first recorded exhibition worldwide was in 1901 at a mouse show in Buckinghamshire, England.
Now there are rat clubs and societies in countries around the world where the many varieties of rats are exhibited and judged. The interpretation of the “ideal rat type” does vary to a degree in different countries.
The American Fancy Rat and Mouse Association lists:
- 42 color varieties
- 2 ear types
- 12 markings
- 4 coat types
- Plus, tailless, hairless and odd-eyed rats
The UK National Fancy Rat Society has standards for 57 varieties, some of which have multiple color variations, and all of which can present in one of two ear types and 3 coat types. They also list 13 new varieties that are not yet standardized.
Looking at these figures and the number of variables, our best guess of total possible varieties of fancy rat must be close to a thousand! However, many varieties are rare, and some will never yet have been bred even though they are currently possible in theory.
So, let’s look at the common groupings and some of the individual varieties that you are most likely to come across.
How Does All This Variation Happen?
In a word – genes!
The default color of a wild brown rat is agouti, which is a lovely rich brown background that is evenly ticked with longer black guard hairs. The undercoat is dark grey to black and the belly fur is pale grey.
The eyes are black, the ears are up on top of the head and the coat is smooth. There are no patches of white fur. All unmutated wild brown rats are this color (and ear type, coat type, etc) and every variation from this is a genetic change caused by a mutation in the genes.
How Different Types of Coat Color Occur
The agouti color is called a ticked variety because it is a background color (brown) with a second color ticked through the coat (black). This is a dominant coat color gene which is why so many wild rats are this color.
However, each dominant gene has a recessive alternative, and when a rat inherits two recessive genes – one from each parent – the effect of the recessive gene is shown (as a different color/marking/coat type/ear type option).
Agouti is dominant. Its recessive alternative is black. This is why there are also some black Norway rats in the wild. A black rat is black throughout the entire coat, including the belly fur and undercoat. This type of “all one color” rat is called a self.
So, we have our first two groupings of rat types (varieties):
- Ticked varieties
- Self varieties
Unlike agouti, most of the genes that change a rat’s appearance are recessive genes, so rarely appear in nature, because to show the change two random carriers must come together to mate. Even then only about one-quarter of the babies will have the recessive characteristic (e.g. a new coat color).
The other factor preventing this is the color itself. A rat who isn’t well camouflaged soon becomes dinner for a predator, so is less likely to live to reproduce. New color mutations can occur at any time, but in wild rats, they tend to disappear just as quickly.
Self Rat Varieties – Single-Colored Coats
These varieties are all modifications of the black rat. So, a beige rat is a black rat whose coat color has been diluted by another gene – in this case, the red eye dilution gene.
Common types of self-colored rats include:
Black – black throughout the entire coat, including the belly fur and undercoat. Black eyes.
Chocolate – rich, dark brown with black eyes.
Beige (Buff UK)
Beige (Buff UK) – warm, greyish tan with ruby eyes.
Mink – mid greyish brown with a distinct blue sheen. Black eyes.
Champagne – warm beige with pink/red eyes.
Blue (British Blue UK) – Dark slate blue with black eyes.
Russian Blue – Very dark slate blue (UK describes as soft blue with a metallic sheen). Although this is a self variety there is a subtle speckled/ticked effect to the coat. Eyes are black.
These are descriptions from club standards which show judges use to assess the rats, however, it’s important to realize that there is huge natural variation in some of these colors.
This variation is often exploited by selective breeding to create new varieties. One example is the blue gene. In practice, blue can be anything from very pale through to very dark, and there is a standard for sky blue (mid blue) and powder blue (pale blue) as well as blue (dark blue) in the USA.
Another common self-colored rat is the pink eyed white. This is a true albino, caused by a gene that strips all pigmentation from the coat and eyes. A pink eyed white can be any type of rat genetically but the albino gene pales the color to white.
Ticked Rat Varieties – Multi-Colored Coats
All the ticked varieties are simply the agouti version of the self colors. A rat who has been ‘modified’ by color genes to produce any of the self varieties would be a black rat if they didn’t have the effect of the other color genes.
However, if the rat is a modified agouti, we end up with the ticked varieties. Using the list of self-colored rats above, the equivalent ticked varieties are:
Agouti – rich brown background with black ticking. The undercoat is dark grey to black and the belly fur is pale grey. Black eyes
Chocolate agouti – bright chestnut background with dark chocolate ticking. Looks like a bright agouti and is not different enough to have its own show standard.
Fawn (topaz UK) – rich orange background with silver ticking. Blue-grey undercoat. Paler creamy belly. Ruby eyes.
Cinnamon – warm russet brown background with chocolate ticking. Medium slate undercoat. Silver grey belly. Black eyes.
Amber (silver fawn UK) – bright fawn background with white ticking. Off white undercoat and belly fur. Pink/red eyes.
Blue agouti (British blue agouti UK) – yellow-tan background with blue ticking. Mid slate undercoat. Sliver blue belly fur. black/ruby eyes.
Russian blue agouti – fawn background with dark blue ticking. Dark blue undercoat. Silver belly fur. Eyes black.
The color of a rat’s coat usually makes little or no difference to a pet rat, it’s just appealing to us to see a variety of colors. However, some colors do have noticeable effects on the rat.
- pink eyed rats have poor vision;
- fawn rats can have blood clotting issues;
- blue rats (not Russian blue) are often less robust in terms of immune system function.
Shaded Rat Varieties
Rats, like cats and rabbits, have the potential to express shading genes such as Himalayan, Siamese, and Burmese. This group of genes results in temperature-sensitive paling of the coat.
What this means is that coat over the center of the body (where it‘s warmer) is paler, while the coat at the extremities (cool points) remains dark. The result is a striking contrast of the pale body with the dark nose, ears, feet, rump, and tail.
The type of body color and shading vary depending on the different genes and results in:
Himalayan – white body color with dark neat points on the nose, ears, feet, and tail of the rat but no shading over the rump. Eyes can be black or red depending on other genes that affect eye color only.
Siamese – warm beige body-color with very dark points and lots of gradual shading into the body color. Black or red eyes.
Burmese – warm toffee body color with dark points and shading. Black eyes.
Once again, the actual color varies a great deal depending on other color genes that are affecting the rat and whether the unmodified rat is an agouti or a black. You can also get a Siamese who is blue or Russian blue, which are distinct varieties.
Any other types of rat color (mink, fawn, etc) can, in theory, be mixed with the shaded genes but this will just dilute the shading down to create a creamy rat with a slight smudge of darker color on their nose!
Marked Rat Varieties With Different Types of Pattern
This variation looks dramatic and therefore is common in rats born in rodent farms, who end up in pet shops. This makes marked rats very common, but markings can vary a great deal.
Marking refers to any amount of white pattern on an otherwise colored rat. So, all of the self, ticked and shaded rats listed above can also be marked. Markings are highly variable, and many don’t have a specific name.
However, there are several reproducible markings which are caused by specific genes. These are standardized (so that they can be judged at rat shows) but it is very rare to find a marked rat that fits the “ideal”.
Some common types of marked rats are:
Irish – a colored rat with one white marking on their underside. In the UK this needs to be on the chest and in the shape of a large triangle. White front feet and part white back feet.
Berkshire – a colored rat with a white marking covering the whole of the underside, but not extending up the sides. White socks and a half white tail.
Hooded – a colored rat with extensive white markings that leave only a colored hood down to the shoulders and a single solid stripe down the back to the tail.
Variegated – the head and shoulders are colored with a white spot or blaze on the forehead. The rest of the body of the rat is covered in distinct small patches of color, giving a spotted effect. The belly is white.
Down Under (downunder UK) – a colored rat with a recognized marking that has the corresponding colored area (stripes or spots) on the belly. So, a Berkshire downunder would ideally have solid color over the belly as well as the head, shoulders, and back, with two marked (white) stripes along the area where the top meets underbelly on each side.
Roan (husky) – roaning describes a gradual whitening of the coat beginning with the face but often ending in an almost white rat. The effect is very gradual and leads to a lovely salt and pepper effect in young adults. The head has a wide inverted V-shaped blaze and the jawline and underside of the head and belly should be white.
Markings come in many degrees and patterns and most marked rats are simply mismarked. This results in rats who are best described as an over marked hooded or an undermarked Berkshire (examples only).
The results are often striking visually, and these kittens are very popular with new pet owners.
It is possible to be completely marked (i.e. all white) from a specific gene mutation and this results in a variety called back eyed white.
Sadly, despite attempts to improve this type of rat, black eyed whites often have hearing loss and epilepsy. This variety is now banned from shows in the UK.
Rat Varieties With Different Types of Coat
The standard coat for a rat is short, soft, and smooth with a good sheen. Long guard hard (part of the rat’s sensory system in terms of touch) run throughout the coat over the shoulders, back and sides.
There are a number of potential coat altering genes in the rat genome, the commonest of which is a dominant gene that gives a curling effect called rexing.
One copy of the rex gene gives a lovely wavy coat especially over the back of the rat. Most of the guard hairs are missing and the whiskers are also curled.
A rex coat can occur on any color, shading and/or marked type of rat. This is true of all the coat, ear and body variations.
Two copies of the rex gene produce a double rex which is a somewhat hairless rat with extremely curly whiskers. These rats often have random patches of hairlessness that come and go throughout life. They look like threadbare teddies!
Satin is another, less common, coat variety that gives a high gloss finish to the rat’s hair. The satinization effect also makes the color of the coat look very intense.
The American Fancy Rat and Mouse Association also allow one other type of rat coat to be exhibited at its shows. This is a rough-looking, messy, harsh coat called bristle.
Rat Varieties With Different Types of Earset
Pet rats have two possible ear positions:
- Standard – on top of the head.
- Dumbo – on the side of the head.
Dumbo rats are essentially top eared rats with a gene mutation that affects the development of some features of the skull in the growing rat embryo.
Research in 2009 found structural shortening of some of the bones in the dumbos face, and along with the low set ears, this gives dumbos their characteristic soft, wide-brow appearance.
Dumbos have been extensively bred and are generally thought not to be negatively impacted by this mutation. They are in all perceptible ways the same as top eared rats other than their ear position, and their hearing seems unaffected.
In other words – they have the same character traits, growth rates, end size and behaviors as top eared rats. Dumbos can be bred in all of the same varieties as standard rats too.
Rat Varieties With Different Eye Color
The standard (unchanged) eye color for a rat is black.
Some of the genes that dilute the coat color also dilute the eye color to ruby or red. The palest pink eyes are only seen in albino rats where all pigment has been removed.
As well as the effect of the coat color dilution genes, a rat’s eye color can sometimes be affected by a separate gene that creates black eyes.
This affects the shaded varieties (creating black-eyed Siamese and black-eyed Himalayan) and albinos, which become black-eyed white rats – a variety called Ivory. These white rats with black eyes do not have the health issues of the fully marked rats known as black-eyed whites.
Rat Varieties With Different Body Type
There are two possible changes to body type:
Research has shown that there are a few hairless rat genes which can give slight differences in appearance. Hairless rats can be completely naked or have a small amount of fuzzy hair around the face.
Hairless rats can have issues maintaining body temperature in cooler climates and need significantly more food than standard rats. They may also suffer associated health problems, such as eye issues because they lack eyelashes and early-onset chronic kidney failure.
In some countries like the UK, hairless breeding has stopped amongst reputable breeders, because of failure to improve these health issues. Hairless rats are also banned from rat shows.
Taillessness in rats is a recognized mutation, but it is widely considered a welfare issue because a rat uses their tail for balance and temperature regulation.
For this reason, reputable breeders will not intentionally breed tailless rats. And in some countries, the mutation has more or less disappeared.
Rat Varieties With Different Body Size
Dwarf rats are readily available in some countries like the US but are still rare worldwide. They are around ⅓ to ½ the size of standard rats and do not grow large due to a lack of growth hormone. They are proportionately the same as standard rats.
Although small, they are very active, so, still need a big habitat with plenty of running, climbing, and digging opportunities.
How Do We See So Many Different Types of Rats?
We estimated at the beginning that there were around a thousand potential varieties of pet rat (probably more), and now we near the end of our article having described less than 35 of them! So how can there be so many?
Firstly, a rat can have several color dilutions in play at the same time. So, for example, a black rat can be diluted by the blue gene and the mink gene at the same time, creating a variety that is very pale silvery blue.
They could even have the blue gene, the mink gene, and the red eye dilution gene. This would create a pink/red eyed rat of a pale blue-toned magnolia color.
All these myriad of potential color combinations also have the possibility of occurring alongside all the potential markings – a blue hooded, a fawn variegated and so on.
Shaded rats can also be any color and any marking, so, you can see how the numbers quickly mount up. Then for every possible combination of colors, shading and marking the rat could either be the standard coat, rex, satin or bristle.
They could also be standard ears or dumbo, hairless – which may look different depending on markings (because the skin can be pigmented) – and which hairless gene is involved. And finally, all the above possibilities also apply to dwarf rats.
If you were wondering “what type of rat do I have?” we hope that you have managed to work it out through reading this article. However, just remember that many rats don’t hit the ideal for color or marking.
You may need to just choose one that you feel is “close enough” and call them a pale chocolate hooded rex or a dark mink dumbo. Whatever you decide you’ll still be able to be sure of calling them one thing – and that’s cute!