Ann Storey MSc FIBMS - published in Pro-Rat-A No 143
The NFRS has a show regulation which states;
‘Any mutation that the society deems harmful to the health of the rat shall not be shown in any class, including New Varieties & pets’.
The NFRS currently has two varieties held under this regulation, the hairless or sphinx and the tailless or Manx. I have written this article to make it clear why these decisions where made and what they mean, as there appears to be some confusion about this.
Several mutations are responsible for hairless, most dominant but some are recessive. Some of these mutations are very harmful and produce rats with persistent skin infections etc while most only appear to affect the coat. The commonest one in the UK is the double or homozygous rex, which you get when you cross two rexes together. In this case approx 25% of the kittens will have a very weak coat, which grows through and then breaks off. Most hairless mutations are like this. Another recessive mutation turned up via imported stock. The hairless mutations I have seen all had whiskers (curly ones) but at least one mutation does not have them. Some are prone to ingrowing eyelashes.
This variety is showable in the US (especially in the warmer states) but not in the UK at shows with NFRS support. These rats are much more sensitive to cold than normal rats and are more prone to injuries due to their lack of a protective coat. Both of these things makes them unsuitable for showing.
tailless rats are due to the interaction of several genes and possibly environmental factors as well. Some strains are prone to produce them. For instance the Siamese which went to the US in the ‘80s, but in my experience they are just as likely to appear from the crossing of two unrelated strains. Some tailless have a small stub of tail but most that I have seen have none at all or perhaps a very tiny finger-like projection. Most tailless are perfectly healthy, however some have problems with nerve impairment to the bowels and the bladder and a few lack hip sockets and are missing some pelvic bones.
The main problem is that tails are necessary for heat regulation and therefore tailless are more prone to heat exhaustion. This makes them unsuitable to show, especally in the summer months.
Contrary to popular belief, the NFRS does not ban the keeping, breeding or selling of these varieties, we really don’t have that power. However, apart from the controls on showing, neither variety can be advertised on the Breeders' List.
There are no plans to add any other variety to that list at the moment.