American Fancy Rat & Mouse Association

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

Tailless Rats

By Nichole Royer

Tailless rats are extremely popular right now. More and more are popping up, and a relatively large group of fanciers are breeding and promoting them. Often they are thought of as a fairly recent mutation, and many people are surprised to learn that they have been around for some time.

Tailless Rat Drawing

In 1915 and 1917 two scientific reports on Tailless rats were published by the Anatomical Record. These studies, titled “Taillessness in the rat” and “Further observations of Taillessness in the rat” were written by Sara Conrow of the Wistar Institute of Anatomy and Biology. In them she described nine anatomically Tailless rats which occurred in 71,500 animals produced over a 10-year period of time. (The Wistar Institute was, and still is one of the largest breeders of laboratory rats.)

In an article on Tailless rats in the “National Fancy Rat Society Handbook” (pp. 51-53) Nick Mays reports that in September of 1985 a Tailless rat appeared in one of his litters. At about the same time another English fancier, Jean Judd, discovered a Tailless in one of her litters. Since that time a number of Tailless have been produced all over the world. Interestingly, many (possibly all?) of these Tailless trace their ancestry back to a strain of Siamese bred by another English fancier.

Unfortunately, many of these early English Tailless had physical problems. Those reported include the absence of bladder and bowel control and deformed hind ends. Understandably, this led the Executive Committee of the NFRS to pass a motion that no Tailless rats could be exhibited at their shows since this “condition, being a defect, is contrary to the fancy’s aims of propagating top quality stock.” This idea is shared by many fanciers in the other European countries, as well as some in the U.S. Though it would be an interesting topic, I will not be getting into the argument as to whether Tailless rats should be bred and recognized. The argument on both sides is very persuasive and hotly debated.

When Karen Robbins, Joy Ely, and Mary Sheridan imported rats from England in November 1983, several Siamese were included. The first litter Karen Robbins bred from this Siamese stock included a little Tailless female. Born on February 14, 1984, she was the first AFRMA Tailless, and possibly the first Tailless bred by a fancier in the United States.

Though Karen’s female was never successfully bred, over the next few years a number of others appeared. The first Tailless to be shown at an AFRMA show (November 13, 1988) was Tiara Fantasia and Tiara Fan Male owned by Julie Borst-Willard. Over the next 5 years enough Tailless were shown to have them standardized. Since these Tailless were healthy, robust specimens with no signs of the serious problems experienced by English fanciers, AFRMA officially standardized them in November 1993.


Tailless rats are congenitally Tailless. They are born with no tail vertebrae and with modified sacral and/or lumbar vertebrae. This change in the rat’s structure allows the posterior of the pelvic girdle to sag, giving the Tailless its characteristic rounded rump and cobby appearance. Simply “docking” (cutting off) the tail of a rat will not cause this change in appearance.

Docked Rat
A “docked” rat hanging out in the water bottle holder. Note the stub of a tail and the normal long body length. “Docking” is considered unethical.

Docked Rat
A litter of “docked” rats. “Docking” a rat’s tail cannot eliminate all the of the tail vertebrae and they are left with a short stub.

Docked Rat
A litter of “docked” rats. The stubs of tails are noticeable on all the babies.

The AFRMA standard says that: “Tailless rats may be shown in any recognized color, marking, or variety. The distinct feature is the complete absence of a tail. Tailless rats may have a cobbier body and will have a rounded rump. Disqualifications: a small tail appendage or tail formation at the base of the body; any evidence of physical abnormality due to being Tailless, e.g. difficulty walking or climbing, skeletal problems, etc.”

Tailless Rat A true Tailless rat. Note the “dimple” where the tail would come out of the body and the shorter, cobbier body.

Tailless rats are also noticeable in their distinctive temperaments. Universally, Tailless rats are excessively outgoing, very personable (often kissy), very people oriented, and playful. Most often the adjective “bouncy” is applied to their personalities. Interestingly, they are also often the dominant rat within a group. Needless to say, Tailless rats make great pets. This distinctive personality could be attributed to the fact that most Tailless trace their lines back to the same animals (with close inbreeding); however, it’s interesting to note that their tailed littermates do not necessarily have the same temperaments.


Tailless rats are neither simple to produce, nor easy to breed. Anyone contemplating taking on this variety should do so only after careful contemplation of all the factors involved. Despite their attractiveness, THIS IS NOT A VARIETY FOR ANY BUT THE MOST ADVANCED AND KNOWLEDGEABLE BREEDER!!!!!!!!!!!!!! Breeding Tailless rats is not recommended for the novice.

Taillessness is not a simple recessive characteristic. If you were to breed two Tailless rats together, chances are you would still only get a few Tailless in the litter, or possibly none at all. This is complicated by the fact that Tailless females have many major difficulties in giving birth. Some Tailless females are sterile and never get pregnant. Others get pregnant, but because of the change in their pelvic structure they cannot give birth. This necessitates either a cesarean, or euthanasia. Most breeders believe that Tailless females should not be bred. Tailless to Tailless breedings have been done successfully by a few individuals; however, though it does appear to slightly increase the number of Tailless offspring, it also seems to increase the incidence of physical abnormalities.

This is not a variety for any,
but the most advanced and knowledgeable breeder!!

The method of breeding which most breeders report as highly successful is to cross a Tailless male with a tailed female whose father was a Tailless. This usually produces one or two Tailless in the resulting litter. Some litters contain no Tailless babies, while others may have as many as four or five. In the past few years the number of Tailless produced in each litter has been on the rise.

Not all Tailless rats are born completely Tailless. Some have a little “nub” of skin where the tail should be. Others may have a very thin (2mm thick) piece of pseudo tail. Ideally, breeders should be breeding for true Taillessness. The AFRMA standard disqualifies any rat with a nub, piece of tail, or lump where the tail would go. These animals cannot be shown. Some breeders may dock these nubs when the babies are a day or two old. This is undetectable in animals who had a skin nub (those with any sort of a tail containing vertebrae will have a small lump at the base of their pelvis as adults). The AFRMA standard, however, says that animals who have been changed in any way “designed to alter their natural condition” will be disqualified. Thus tail docking is technically unethical, though I suspect it often goes undetected.

Breeding Responsibility

Taillessness is a true mutation, the only one AFRMA recognizes which causes a dramatic alteration of the rat’s basic body structure. While these animals can be wonderful, healthy pets, they can also have horrible problems.

Because of their popularity, many people are breeding Tailless. When any type or breed of animal becomes popular, it is ruined by irresponsible breeders. It happened with Siamese and Blue rats, and now it is happening with Tailless. Breeders and pet shops have discovered that people will pay big bucks for a Tailless, thus Tailless are being bred indiscriminately for the sole purpose of making money. Often these irresponsible breeders got their original stock by purchasing tailed offspring out of Tailless lines from well-known fanciers. There are also those fanciers out there who breed Tailless with nothing in mind other than winning at shows. All of these people are responsible for what is now a serious problem.

When Tailless rats were first produced and bred, physical problems were almost unheard of. Within the last year however, thanks to the popularity of Tailless and the willingness of people to breed animals without a thought to their well-being, these irresponsible breeders have contributed to a dramatic increase of Tailless rats who have health problems.

So, what kind of health problems am I talking about? Well, let’s see. I have heard a number of cases of Tailless rats who have no bladder or bowl control. There are also a number who have died from bladder stones. Some have a fused pelvis, paralyzed back legs, and hind leg/foot deformities. I recently came across a Tailless female in my local pet shop who was totally lacking a pelvis (yes, the spine just ended, the hind legs attached to nothing). She was being sold, along with a male who had fused ankles (yes, a breeding pair) for $80. You bet I raised a stink!!!

This sudden (it’s been within the last year here in Southern California) dramatic increase in the number and severity of problems with Tailless are causing many fanciers great concern. Many of us are having to seriously reconsider our views on Tailless rats, and there are some who are calling for them to be stricken from AFRMA’s list of recognized varieties. Remember breeders, it is YOUR stock which has gotten out to the pet shops, YOUR grandbabies who are being bred with such horrible deformities, and some of YOU who are major contributors to the problem.

So, is it possible to breed Tailless rats responsibly? The answer is yes. Responsible breeders do not continue to breed any line of rats which produces detrimental physical problems of ANY KIND. For years fanciers bred Tailless rats with remarkably few problems. In an attempt to increase the number of Tailless babies in each litter, many lines of Tailless have been seriously inbred. This may be a major reason why so many problems are now cropping up. When harmful deformities do arise, a responsible breeder will be prepared to put down animals whose quality of life is seriously impaired. Responsible breeders will discontinue an ENTIRE line of rats if it produces babies with health problems. That goes for all varieties, not just Tailless!


Tailless Rats can be shown in any color or coat type, the major feature obviously being the total absence of a tail. This does not, however, mean that the lack of a tail is the only thing they are judged on. In order to win, a Tailless must have good type (the standard allows for a stockier build) and good color.

Currently, almost all Tailless are either Self Black, Siamese, Self Champagne, or Self Blue. Recently however, other colors and markings have been appearing, including Dalmatian Tailless.

A diligent judge will look and feel for any sign of a tail. This includes any sort of nub or tail vestige, and also any sort of a lump extending beyond the pelvis. In addition, judges have the rats move on the judging table, and they scrutinize them carefully. Any sign of abnormality in the rat’s movement, and it will be disqualified.

Buying The Tailless

This is one case where there is no question, buy from a breeder. Whether it’s for a pet or breeding stock, there is no way to find out what kind of problems a pet shop Tailless has in its lines. Go to every Tailless breeder you can find. Talk to them about the problems they have experienced. If they tell you that they have never had any problems, be suspicious! Ask around, find out which breeders other fanciers respect and recommend. Learn everything you can about Tailless, and if you are considering breeding them, think long and hard.

Once you have found a breeder, expect to put your name on a waiting list. Tailless rats are very popular, and most responsible breeders have a limited number of litters each year. Some breeders have babies sold a year or more in advance!

Authors Note: Over the last few years there have been many people asking for information on Tailless rats. Though I neither breed nor show them, the job of writing about them fell to me (for lack of any other volunteers). The information in this article is based on the sources listed below, as well as numerous conversations through the years with other fanciers who breed, show, and own Tailless rats. I am by no means an expert on the subject. If anyone has anything they would like to add, or has had other experiences with Tailless rats, please write ite to me so we can publish your information/views as well. *


Go to:
Taillessness in the Rat
Breeding Tailless Rats
Troubles With Tailless

Back to top

Updated September 21, 2018