American Fancy Rat & Mouse Association

This article is from the Spring 1999 AFRMA Rat & Mouse Tales news-magazine.

Rex Rats

By Nichole Royer

Rex Rats

Rex Rat This adult male Agouti Rex shows excellent curl. “GH Rusty” owned and bred by Geri Hauser. At this photo he is only 6½ months old.

Oh! Its whiskers are curly! That’s one of the most common reactions we hear when someone sees a Rex rat for the first time. The Rex rat’s charming appearance and soft plush coat have made it a favorite among rat owners.


In England, Rex rats were bred by geneticist Roy Robinson in 1976. The National Fancy Rat Society standardized them in 1976.

In the U.S. we have had Rexes since before 1983. They were more than likely picked up from private parties, pet shops, or University’s. Karen Robbins got her first Rex (an Agouti Irish male) from Mary Sheridan, a fellow fancier, in the Spring or early Summer of 1983. Her first litter was born September 22, 1983. The first recorded Rexes being shown were at the October 8, 1983, show where Mary Sheridan showed two in the class.

On November 29, 1983, the first English Rexes were imported to this country. Out of 32 rats brought in, 3 of them were Rexes. There was a Black Berkshire Rex female which Joy Ely took, a Black Self Rex female from Mr. Anthony Bongiovanni of Himbridge Stud, which Mary Sheridan took, and a Cinnamon Rex male from Mrs. Jean Judd of Sakari Stud, which Karen Hauser (Robbins) took.

Geri Hauser, who consistently had some of the best Rexes we have seen, started her Rexes by taking the English Black Berkshire Rex from Joy and crossing with “Foxy” the first Chinchilla Berkshire. Out of the first litter born February 3, 1987, 5 of the 11 were Rexes. She then bred an Agouti Berkshire Rex daughter to a son of “Foxy” and “Lady” (the original Chinchilla Berkshires). The next generation she crossed them with the half wild rats she got August 21, 1986, from Liz Fucci in New York. Also, “GH Rusty” traces his background on his mom’s side to the Cinnamon Rex male from England.


Rex rats are distinguishable by one simple feature—their hair is curly. They can come in any color, and the density and extent of their curl can vary from barely noticeable to tightly curled.

Since AFRMA obtained some Rex animals from N.F.R.S. members in England, we adopted their standard to use. It says: “The coat to be evenly dense and not excessively harsh, with as few guard hairs as possible. Coat to be evenly curled and also to a lesser extent on the belly. Curly vibrissae (whiskers) are normal for Rex. Color to conform to a recognized color or color pattern (N.F.R.S.).”

There are Rex rats and then there are REX rats. Not all Rex rats are created equal. In fact, most people who own and even breed Rex rats have never seen a truly good example.

Most Rex babies start out with wonderful curly sheep-like coats. When they moult into their first adult coat at 6–7 weeks, however, their curl almost disappears. Instead of curl, they have kind of wavy hair.

For females and most males, this is about it. Though the coat may thicken/ tighten and then thin again, most Rex rats never regain their original “permed” appearance. For the rare male, however, this is not true. Once in a while you will get one that does regain that lush curly coat. Few and far between, these big males are really something to see.

Male or female, wavy or permed, all Rex coats have the unfortunate tendency to thin as they age. Often by the time they are 18 months old, their coat is very thin and patches are bald.

Breeding Rex Rats

The Rex characteristic in rats is somewhat unusual in that it is dominant (I will put a qualifier on this and say that the Rex rats we commonly have in the fancy are dominant Rex). This means that if you breed a Rex rat to any standard coated rat, half the babies in the litter will be Rex (if the genetics dice roll as they should). This makes it easy to produce more Rex babies. Keep in mind that standard coated rats produced out of Rex breedings do not carry Rex. Because Rex is a dominant gene, if it is there, you can see it!

Homozygous Rex Rat
This is a 7-week-old Homozygous Rex (Rex to Rex breeding). Note the patchy thin hair. Rat owned and bred by Karen Robbins.

When breeding Rex, it is not advised that two Rex rats be bred together. When a baby rat gets Rex from both its mother and father, its coat leaves a lot to be desired. Typically these “homozygous” Rex rats range from nearly hairless to haired with a very thin patchy coat. These rats, though often very sweet, can best be described as mangy looking. They are certainly not particularly attractive.

In order to breed really good Rex, you have to start with excellent stock. Ideally, find an adult buck who has a good tight curly coat and is a color which can be compatible with whatever color you would like to work with. Many breeders will not part with their best bucks; however, they often will offer stud service (they usually ask for pick of litter). This can be an excellent way for someone starting out with the variety to get excellent stock. Remember, the female you use for breeding should also be a good animal. She should have nice type and color.

Rex Kitten Rat
A 4-week-old Rex kitten (male) showing nice curl. Owned and bred by Geri Hauser.

Good Rex babies are very difficult to spot when they are young. As soon as you see whiskers on the babies, you can tell if they are going to be Rex (their whiskers will be curly). As they grow, some may appear a little curlier than others. These are usually the ones to keep; however, sometimes the less curly babies end up growing into their curls. Ideally, breeders will keep all of the best babies to grow them up and see how their coats turn out. Those that do not turn out curly enough at 6 months can be kept as pets or placed in non-show homes. This, however, requires a bit of space.

The Genetics of Rex

According to Roy Robinson in Color Inheritance In Small Livestock “The Rex is produced by a dominant gene Re. The Rex gene is inherited independently of those for color and pattern.” Essentially, what this means is that If you breed a Rex rat to any other rat, you will get some Rex babies in the litter. You can also combine the Rex coat with any color or marking.

The Rex gene is not the only mutation to produce curly coats in rats. In Genetics of the Norway Rat Roy Robinson sites 5 genes that cause curled hairs. Curly-1 (Cu1) is a dominant gene that causes curled coats at 2 weeks, the curl disappears after 10 days, and then slowly reappears starting on the rear of the rat when it is 7 months old. Curly-2 (Cu2) causes curly whiskers from birth and is also a dominant characteristic. It causes a reduction in the number and size of the guard hairs and produces a curled/rough undercoat. Kinky (k) is a recessive. It causes curly whiskers, a dense short coat in juvenile rats, and short rough coat in adults. Unlike Curly-1 and Curly-2, the effects of Kinky are more stable throughout the rats life. Shaggy (Sh) is also dominant and is similar to Curly-1 and Curly-2. It has been shown that the combination of C1 and Sh causes a more curled coat than just C1 alone. Finally, Robinson mentions Cowlick (cw), a recessive gene that causes a whorl of hair in the middle of the rats back.

Unfortunately, though known in laboratories, many of these genes are not known within the fancy. Cowlick in particular would be greatly sought after by fanciers. It is possible, however, that we do have more than one of these curly coat genes within our populations and just don’t know it because they produce similar results. I suspect that the combination of more than one of these genes is what produces the spectacular “show” Rexes and makes them so much more curly than the run-of-the-mill average wavy Rex. I could of course be wrong.

For a period of time I was in possession of a line of rats with wavy coats that were not our standard Rex. Unfortunately, without the space to do major test breeding, I’m not sure what they were. They were not distinctive enough from normal Rex to warrant breeding for show and the line has since died out; however, it stands as an example that the “other” curly genes are out there to be found.

Showing Rex

Showing Rex rats can provide the experienced fancier with a complex and very involved challenge. The effort to produce nice Rex rats that regain that truly curly coat, plus have the correct color/markings/pattern and conformation necessary to do well on the show bench can be a project spanning many years. Needless to say, this is not the variety for folks wanting quick gratification or numerous/frequent show ring wins.

Keep in mind that, while important, curliness of coat is not the only thing Rex rats are judged on. In fact, curliness and density of coat are only a part. Rex rats have to be a recognized color to be shown and if marked, they have to be marked correctly. They also have to be good examples of their color/marking. A poorly marked Hooded, light Siamese, or blotchy Silvered Black Self is never going to do well no matter how curly. This goes for the rats conformation as well.

Cinnamon Rex Rat
A Cinnamon Rex not showing much curl.

Though any recognized color/pattern/marking is acceptable for the Rex, some are better than others. For many of the marked varieties a curly coat will mess up the line of the marking. Self Rex rats are preferred. A good Pink-Eyed White Rex is beautiful (looks like a little sheep) and to be honest, the best I have ever seen have been Agouti.

Rex rats show beautifully as kittens. Planning for litters to be 5 weeks old the day of a show is ideal, since this is when their coat is at its best. After their first moult, young Rex rats should be taken home and watched. Most people will keep the best (curliest) several males from each litter simply because it is very difficult to predict which will develop into showable adults. The best females can be kept for breeding, but the girls are never curly enough to be shown.

At around 6 months of age those males who are going to develop a showable coat will do so. These are the ones to retain for breeding and showing.

Rex rats have an unfortunately short frustrating show life. Most Rex coats will begin to thin when they are a year old, and by the time they are 18 months they have bald spots, patchy areas, and must be retired. Even when their coat is in its prime, it will go through stages of moult that leave it unattractive.

Due to all the difficulties involved in dealing with them, Rex rats are really not a good choice for the novice fancier. For the experienced breeder, however, they provide one of the ultimate challenges. They require a certain amount of space so that you can grow out those males, however, they can be very successfully run in conjunction with whatever standard coated variety the fancier specializes in and thus make for a challenging offshoot to an already successful line.

Preparing the Rex for Show

Preparing Rex rats for show should be done as you normally would for whatever particular color, etc., you are dealing with. There are a few peculiarities, however. The Rex coat is rather thin so it is much easier to see under the fur and down to the skin. Nothing is worse than to see a beautiful coat with yellow, oily, dirty, scaly skin underneath.

A bath is a good idea before a show. Unfortunately, bathing tends to remove the oils from the rat’s coat and makes a Rex coat soft and less curly. Due to this, bathing before a show should be planned for 1–2 weeks before the event and lengths taken to assure the rat’s cage is kept clean and he doesn’t have the chance to soil himself again.

Buying Rex Rats

Rex rats make wonderful pets. Most people just love that soft coat and those curly whiskers. If you are interested in buying a Rex rat it is recommended that you follow the usual suggestions. If possible, buy from a responsible breeder so that you have a much greater chance of acquiring a healthy, well-socialized animal. Fortunately, Rex rats as a variety are not prone to any particular specific health problems that have to be looked for. Rex rats are fairly common, and even if you live where there is no access to responsible breeders, they do show up in pet shops with great frequency.

Female Rex Rat
This is an adult female Rex showing good coat for a female. Rat owned and bred by Geri Hauser.

Buying a Rex rat with intent to show is a different matter. If your numbers are small, and you want a Rex because you think they are cute and want to try your hand at showing one, by all means bring home a baby. They are cute, charming, and make great pets. With a little luck yours will be one of the few who turns out good enough to win. If it’s not . . . does it really matter?

On the other hand, if you are buying with intent to get into seriously breeding and competitively showing Rex rats, your best bet is to go to a breeder and see if you can talk them out of an older male with a mature coat. That way you will know what you are starting with and won’t have to waste 6 months waiting to see if your boy’s coat will pan out. You won’t get their best, but you may be able to get one that’s good enough to get you started. *

  • Color Inheritance In Small Livestock by Roy Robinson
  • Genetics of The Norway Rat by Roy Robinson
  • AFRMA Show Regulations and Standards
  • N.F.R.S. Handbook, “The Rex” by Beverly Bruges and “Genetics” by Ann Storey
  • The Proper Care of Fancy Rats by Nick Mays
  • With special thanks to Geri Hauser, Karen Robbins, and all the other fanciers whom I have discussed Rex rats with throughout the years.

For more photos of Rex of various ages and colors, see the Rex Rat Pics page.

Go to Rex Breeding
Rex and ‘Double’ Rex Rats

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Updated September 21, 2018