American Fancy Rat & Mouse Association

This article is from the WSSF 2009 AFRMA Rat & Mouse Tales news-magazine.

Propagation of a New or Rare Variety

By Ann Storey, N.F.R.S., England

From Pro-Rat-a, No. 124 July/Aug. 2001, the N.F.R.S. journal. Permission given to reprint article.

This article is not just about new varieties; those varieties that have just been discovered by the fancy or have been hanging around for a bit with no development, it is also about those varieties that have just got their standard and also old varieties that have been rediscovered or are on the brink of extinction. In most cases the work that must be done is similar.

The only difference between a neglected variety and a new variety is that the old one already has a standard and can be shown in breed classes as soon as it is sufficiently improved. Otherwise, the techniques used are the same. The genetics are also usually known, which they may not be in the new variety.

I will start by being controversial on two fronts. One, I do not believe that these varieties are a job for the novice. They should cut their teeth on the more established varieties as they are unlikely to get anywhere with the new or rare varieties. Good stock for these is usually in short supply and therefore should not be wasted on practice attempts! Also, most of the results are disappointing and it may take several years’ work to get anything remotely showable. This often disheartens new fanciers. It is also necessary to be ruthless about culling unfit stock and most beginners object to this. Point two is that only those varieties that have real promise should be developed. It is very easy to find a new variety to work on. At any one time there are many that have the potential to become standardised. However, you must consider who will breed them after standardisation. It is an advantage if the variety can be developed by more than one person at a time as this will provide important outcross material and increase the chances of the variety’s success.

All new varieties must be distinct from already standardised varieties (for example, there would be no point in working on one of the other available rex-type coat mutations), must be attractive enough to attract new fanciers, must be a mutation that can be passed on, and must not carry any harmful side effects that cannot be bred out. The NFRS has a rule prohibiting the exhibition in any class (including pets and new varieties) of any mutation that it considers to be inherently harmful. At the moment this includes tailless and hairless rats.*

The number of varieties that should be standardised are limited by the number of fanciers there are to breed them, although there are some varieties that are so attractive that they would find breeders whatever.

Starting Out

The approach taken to develop your variety depends on whether it is a coloured or a marked variety and on its origins. You may, for instance, have found it in a pet shop, obtained it from overseas or a laboratory or found it in your own or another fancier’s stud. Alternatively you may decide to modify an existing variety. I will deal with each in turn.

Pet Shop

It is always worth checking out pet shops just in case. Varieties that have originated from them include the Blue and now the black-eyed Cream. The problem is that most pet shop rats come from poorly bred and maintained stocks. They tend to be small and runty and may carry many faults including health and temperament problems. Most pet shop rats are this way because they are bred for quantity and not quality and in the worst cases are bred by mixing all the rats together and removing the offspring as required.


Until recently, most overseas rats were imported by the NFRS as we have a special fund to deal with this. If you hear of a new variety, it is advisable to approach the committee first as importing and quarantining can cost a lot of money. Varieties that have arrived from overseas include the Siamese, one strain of the red-eyed group (Buff* and Topaz*), the Chinchilla, the Russian Blue, and the Dumbo. These rats are usually better than the pet shop rats as they have been bred to some sort of a standard. However, deterioration usually occurs in quarantined rats, especially in litters that are bred there. It is better to import a couple of bucks instead, does are usually too old by the time they get out. It is now possible to import rats from the European Union under the terms of the Balai directive without them going through quarantine. In this case, rats must be imported from a breeder who is registered with their local equivalent of the Department of the Environment, Food, and Rural Affairs. There are several other requirements and anybody thinking of doing this should contact DEFRA and also someone with experience of this type of importation.

You must never consider smuggling rats in or ask anybody else to do it for you. There have been a couple of cases in the NFRS of visitors from the Continent smuggling rats in unasked for, but this should be severely discouraged. The penalties for getting caught are considerable and in most cases the animal will be destroyed.


It is quite difficult to get rats out of laboratories (unless you know someone) except as implanted frozen embryos. This has not been done in the rat or mouse fancy as yet but it is possible. Also, while colour mutations of mice are kept, it is rarer to find stocks of colour mutant rats maintained unless they also have some other mutation useful in research. Like pet shop rats, these tend to have problems. Varieties that have been obtained this way include the Siamese, some of the red-eyed rats, and the Rex. The black-eyed Cream is said to have originated from laboratory stocks held by Edinburgh University.

The Fancy

Rats obtained within the fancy should have fewer problems. However, in my experience this is not so as mostly the owners select for the mutation only for a few generations. This leads to inevitable deterioration in every other department. They include; Pearl, Cinnamon Pearl, Black-eyed White, Capped, Variegated, Opal (Blue Agouti), Lynx (Lilac Agouti), and Lilac.

The Bad News

All new varieties are difficult to develop and it normally takes years to get them on the show bench and out of the new varieties class. It really does require a lot of patience. Once they get onto the bench, be prepared for constant sniping and back-stabbing. Your rats will be accused of general bad temperament and health problems whenever one of them bites someone or dies. This reputation will last for years. Do not let any go unless it is someone you would trust with your life and they swear on the Bible not to let any pet shops have them. If they do let them go, then you can guess that the rats will turn up in a pet shop in the Outer Hebrides before the week is out! Any breeding problems will be blamed on ‘genetic’ difficulties in your stock. It is also probable that while you are slaving away trying to make silk purses out of your bunch of sows’ ears, the rest of your stock will go completely down the toilet. If you are really unlucky, you will also be taken as responsible for any perceived deterioration of stock in general!

The other important point, perhaps the most important, is this: YOU MUST BE PREPARED TO CULL*, and cull very hard. There are nearly always health problems with unstandardised rats and it is completely unreasonable to pass your throwouts on as pets or sell them to a pet shop. This can lead to a lot of expense and heartache amongst their unfortunate owners, especially if these are kids. Just because they may look fit when you sell them, does not mean that they will stay that way for long.

Don’t make the reputation of new varieties any worse than it already is!


Colour Varieties

If possible, obtain two or three bucks of your chosen variety and mate them to the fittest, typiest agouti does you can lay your hands on. “Why agouti?” I hear you say. The reason for this is that their genetics are simple, they are usually fit, healthy, and fertile and they usually have good type. If you intend to specialise in rare and unstandardised varieties, then I recommend you maintain your own line of agoutis. Sometimes, where the genetics are known, another variety will be seen as being more appropriate. However, size, type, fitness, and temperament must also be taken into account.

Never mate a pair of the new variety together as this will just perpetuate a lot of faults. Don’t bother with any does either as these are usually inferior breeders to the agouti outcrosses. If possible, mate up about four agouti does. This may seem like a lot of rats, but it is important to widen the gene pool at first, not restrict it, so that you have plenty of material available to correct faults.

Procedure for a Recessive Gene

If the gene is recessive, then the kittens of this Fl generation will all be agoutis. Leave each doe with about three does and one buck. Run on your bucks and does until they are about 4 months old. Now keep the typiest and fittest six does and two of the bucks. Keep the second best buck and two of the does (not the best ones!) in reserve just in case. Mate up the four best does with the best buck. If the gene is inherited as a simple recessive, the colour should turn up in the second generation. If this is the case, you will get a mix of agoutis and the new variety in the F2 litters. If the agoutis are carrying other colours (most do), you will probably get a lot of other things as well. I suggest that for now you ignore all these ‘red herrings’ and keep to the task in hand. Cull all the rats except for the new variety. Let these rats run on but do not expect any great improvement yet, they may even be worse. Discard the Fl parents, do not breed back to them. Keep the best new variety does from the F2 litters and mate them to the best agouti buck you can find—if necessary, borrow one. (Alternatively you could do this using agouti does instead with a new variety buck. However, very good does may not be available. It is easier to borrow a top stud buck, although you can use the original agouti does if they are still fertile.) It is better if he is related to the original agouti does. As before, all the litters will probably be agouti, but cull as you did for the Fl generation. This is the F3 generation. It is possible that some of the does will be poor rearers. If this happens then, providing you have other stock, you should cull this doe and her litter and not foster it or rear it by hand. Likewise, if any rat fails in health or temperament during the programme, then it should be culled as well. Things that are especially important to avoid are respiratory disease, weight gain or loss not linked to diet, tumours, general poor health, barbering, and reproductive problems.

When your F3 rats are old enough, they can be mated together as before to produce the F4 generation. This should contain your new variety. Cull all the other colours. Hopefully these rats should be showing an improvement. If they are, it may now be possible to start to breed them together to improve colour and so on. You will still need the odd outcross back to a good (preferably related) agouti from time to time. If the F4 is not showing an improvement, it may be necessary to repeat the agouti mating again. It is important not to embark on a heavy inbreeding programme until you are sure that the variety is healthy and has most of the points in the stock that you will require in the finished variety. Fanciers worry about the agouti outcross because, unless the mutant gene is dominant or incompletely so, it is ‘submerged’ for a generation and this makes people nervous. Agouti is nearly always the best outcross. If the new colour is non-agouti; such as Blue, agouti is still better than its non-agouti counterpart, black, as agoutis usually have better type. It does mean that the number of Blues you get out of the F2 generation are fewer (1:9 instead of 1:4), but instead there will be Blue Agoutis from which Blue can be bred. Failing the availability of good agoutis, almost any fit and typy unmarked variety can be used. All the current Cinnamon Pearls on the show bench are there due to a dose of Siamese!

Propagating a Dominant Gene

If the new gene is dominant or incompletely so, then its presence will show up in all the generations from the Fl onward. Rats not showing the colour are not carrying it and can thus be discarded. While the procedure followed is the same, it does mean that typy heterozygotes (carriers) that would normally get discarded in the F3 generation, can be identified from non-carriers and used if they are any good.

General Points

The problem with using colours other than agouti is that you will probably get many more strange coloured rats turning up due to different combinations. While this may be interesting, it will not help you to concentrate on the variety you are trying to develop. Sometimes the new colour may link to the outcross colour. This means that it can be very difficult to get the new colour out as linked genes do not separate easily. Eventually they will separate, but this is a tedious and time consuming business.

You may have noticed that the original mutant buck was only used once. This is quite correct. You only want his colour, not his faults!

Marked Varieties

The recommended procedure depends on whether we are talking about a new marked gene or modifying an existing pattern. The hooded locus, the best known major white spotting locus of the rat, seems to mutate with monotonous regularity. Some of these new mutations are attractive, while some too closely resemble marked rats already available. Some of these mutations, apart from affecting the amount and position of the white, will also affect colour. There are also a few other white spotting genes available now, again some can resemble other mutations.

New marked gene – For example, if a Dutch mutation turned up in a litter, it could turn up in any litter, self or otherwise. It would be recognisably a Dutch, but would need to be worked on. It would be all right to use this with the agouti outcross as the gene would still come through. Once type and general fitness have been established, work to improve the pattern could commence. With all marked varieties there is a tendency to ignore everything except the pattern. In mild cases, this leads to ‘patterns on legs’ where the rat has a good pattern and nothing else. In severe cases, it can lead to extinction due to a build up of health and infertility problems.

Modifying an existing pattern – If, for instance, you decided to breed a Dutch by modifying a capped or a Berkshire (something which has been attempted) then it is more difficult to maintain vigour. It is necessary to continuously mate together those rats that have the markings closest to the ideal and it is inevitable that problems of poor type and fertility will crop up. Although it is important to develop the pattern, you must be aware that it is going to be very difficult to introduce an outcross, therefore, it is very important to develop two or more lines to provide you with outcross material if problems occur. The Black-eyed White occurred as a result of a mutation, but it was developed by breeding the least marked rats together. Little attention was paid to other points and the early rats were poor, weedy, and often infertile. It took a long time to sort these problems out. In a case like this where outcrossing is inevitable to save the breed, it is safest to go back to the parent variety, in this case Capped and Variegated. Otherwise, go for broke and use a good self.

If the new variety has occurred in your or another fancier’s stud and already is fit and typy, you are very lucky as you will be able to work on the colour/pattern as soon as you have bred some more. Mate the rat back to her father (if it is a doe) or his mother (if a buck), failing that, a brother, sister, or other close relative. There should be a proportion of the new variety in the litter.


Once you have bred a few litters and the rats are recognisably of the variety you wish to standardise, it is advisable to exhibit some in the new varieties class. First you should contact the Standards Officer who will give you advice about naming the variety and writing a standard. Once this has been done, the proposed new standard will be passed onto the committee for approval. They will then give you a date from when you can start to show them in the new varieties class. Names should conform to recognised fancy usage. Standards must not describe what you have, but should be the ideal that you are trying to attain. They should be GENETICALLY possible but practically very difficult to breed to. Showing them will get other people’s ideas on them and may also attract other fanciers into helping you and taking up the variety. Once your rats are close enough to the standard to have a reasonable chance of holding their own in the guide standard class, they can be standardised. As standardisation is in the hands of the committee, you will need to be advised by them as to when this should be done. Once a guide standard has been granted, the rats can be shown in the guide standard class. From then on it is important that work continues and that they are shown regularly. The minimum time between getting a guide standard and a full standard is two years. If, however, they are not shown or worked upon, then that standard can be rescinded. The guide standard period can be extended for rats that make only slow progress. Full standardisation is only granted when it is felt that the rats can hold their own amongst the standardised varieties.

Often, new varieties become intensely fashionable after standardisation. Rather like a dog winning Crufts, this often does nothing for the variety. Good stock is in short supply and the temptation to fill orders with substandard stock is strong. This stock is sure to disappoint and can quickly lead to the new variety losing out and being vilified. This was most severe with the Cinnamon Pearl that was reduced to one buck within 2 years of standardisation.

Re-establishing Old Varieties

Re-establishing an old variety can follow the same pattern. However, in this case the rat can be shown directly in the breed classes. They can have problems catching on with other breeders and judges in that while new varieties tend to have a honeymoon period, during which it is likely they will win several best in shows and become fashionable, this does not generally happen with the oldies, who frequently became rare in the first place because they did not attract anyone.

The Good News

You may think that this article is generally negative, but if this puts you off, then I would have to say development is probably not for you. However, it is enormously satisfying to see a variety you have wept blood over for many years suddenly come right and go on to win, and I have to say that one of my most treasured wins was the first BIS won by a Blue Agouti, a variety I was instrumental in getting standardised. I also bred the first champion. Then there is the thrill of the litters, where you never quite know what is going to turn up. I am telling you, it is quite addictive!

Good luck, you will need it!

* Note:
AFRMA has accepted Tailless and Hairless rats.
Topaz = U.S. Fawn
Buff = U.S. Beige
Cull health and temperament issues = euthanize
See AFRMA’s bylaws or Unstandardized page on the web site for info on standardizing new animals in AFRMA. *

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Updated March 19, 2014