American Fancy Rat & Mouse Association

This article is from the Winter 1998 AFRMA Rat & Mouse Tales news-magazine.

Breeding & Stuff

Creating Tailless Mice; Creating Tailless Rats
Creating Tailless Mice

Q I know that there is such a thing as a Tailless rat, but I’m very interested in having a Tailless mouse. Are there any breeders who have them? If not, how should I go about trying to create one?

A Tailless mice are nowhere near as common as Tailless rats, but they do exist. Most “Tailless” mice we have seen were purchased in pet shops. These mice have normal body shapes, and often a stump for a tail. When bred, these mice have produced babies with normal tails. Most likely these “Tailless” mice are simply normal mice who have accidentally had their tails “cropped” early in life, meaning it could have been bitten off, caught in something, etc. Therefore, they are not true Tailless.

A true Tailless mouse would look much like a Tailless rat. It would have no tail, or just a nub, with no evidence of a stump at the base. It’s pelvic structure would be changed leading to the familiar rounded hind end as seen in Tailless rats.

Tailless mouse
A true Tailless mouse owned and bred by Tina Shahroody

Though we have seen quite a number of supposedly Tailless mice, the only one that appeared to be truly Tailless was at a show held by the Rat, Mouse and Hamster Fanciers in northern California. It was bred and owned by Tina Shahroody.

Creating Tailless mice should be possible, though the question arises as to whether it is a responsible thing to do. Is it desirable to create mice who have a potentially damaging physical feature? Tailless mice will have the same physical problems that so many Tailless rats have. Eventually problems with fertility, paralysis, bladder and bowel control, etc., will develop. It is up to the individual breeder to decide whether this is a desirable mutation to pursue.

In order to create Tailless mice, you would first need to find mice who have genetically deformed tails. On occasion, mice are encountered (usually in pet shops) that are born with bent, kinked, twisted or shortened tails. These are not mice who have had their tails docked or damaged, but, instead, they are mice with a true deformity.

The trick is to find at least one mouse that has a genetically shortened tail. Take this mouse and breed it, then breed it back to its offspring. Keep any of the babies who have shortened tails, and breed them together. Continue close inbreeding with the shortest tails. Eventually you will get mice with little or no tails. They would probably not breed true and would, most likely, have many physical problems.

EDITOR’S NOTE: This is a very common question so we are going to answer it here. We do not, however, recommend purposefully creating mice which may have detrimental health problems.

The other way to get Tailless mice would be similar to what happened with Tailless rats. Someone would just simply have the mutation crop up in their mousery.

These mice wouldn’t be “created,” they would simply show up in a litter. They would also be likely to have the aforementioned problems, as seen in Tailless rats, but it might be worth working with them just to see the ramifications of the mutation.

Creating Tailless Rats

Q I live in a part of the country where there are no other rat enthusiasts. I have been very carefully acquiring an assortment of different fancy colored rats from the pet stores in the area. I am breeding these and selling them as pets. I am greatly enjoying working with the varieties, and, thanks to their beauty, I have recruited a new number of rat lovers.

Recently I obtained a Tailless male from one of the local pet shops. Based on his structure and what I have read about them, he appears to be a true Tailless. I would very much like to make more of them. How do I go about it?

A Ideally, you should attempt to find a female littermate of your male. If you are unable to do so, you will need to do a couple of breedings.

Tailless rat

First, find a female that is the color you would like to have in Tailless. Breed her to your male. This will produce a litter of babies with normal tails.

Now you have two options. The quickest way to get more Tailless would be to keep a female from this litter and breed her back to the father. You may get Tailless in the first litter from this breeding or it may take a couple of tries. This is the quickest way to produce more Tailless, but it involves very close inbreeding.

Another option, particularly if you want to create Tailless in your female’s color, is to keep two siblings (brother and sister) and breed them together. This may not produce quite as many Tailless as breeding a daughter back to the father; however, the babies won’t be quite as closely inbred.

If you are particularly concerned about inbreeding, you may consider breeding your male to two unrelated females. Keep a male from one litter and a female from the other, breed them together to get Tailless. Unfortunately, if you start with only one Tailless, there is no way to produce more without inbreeding. *

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Updated February 13, 2015