Rat Resume:
Taillessness in the Rat

Linda Sinclair
From the Nov/Dec 1996 Rat & Mouse Gazette


My ratty fur people are part of me. Relationships and friendships come and go, so I put my fur people first. I had my first rats and mice at age 10-George, Windy, Teddy, Olive-Patches, and Louie. In 1984, I got Black and Agouti Variegated, and Nose Blazes-then I saw Odd-Eyes. It was love at first sight and I've been raising them ever since.

I study genetics and breed as much as I can. So far, I've gotten Odd-Eyes in most colors, and darker colors are less frequent, but possible. I am the current President of the Mouse and Rat Breeders' Association and judge rats and hamsters. I am still learning mice, but I breed all three species--mice, rats, and hamsters. I love my ratty fur people and I hope you enjoy my ongoing column, "Rat Resume," which is dedicated to Miss Mary Douglas, the mother of the rat fancy.


Many people are enjoying the mutation known as Tailless or Manx, and are involved in breeding them, yet I haven't read any articles about problems or Tailless origin, so here is what I discovered in my research, what I've experienced, and what I've been told by other breeders.

In the Wistar Institute of Anatomy and Biology, five Tailless rats were born out of 40,000 rats between 1915 and 1917. They were observed, and three were dissected so the vertebrai could be examined. The lumbar vertebrai were modified and the pelvic girdle was only attached by a small surface near the anterior end altering the angle of the hind legs , resulting in the lifted rump.

In England, Geoff Izzard had a strain of rats carrying the Tailless gene, and oddly enough, our rats in America go back to his, as the American responsible for the first Tailless here was Dorothy Pena of San Fernando, one of the retired presidents of M.R.B.A.. She told me that she had obtained a Siamese from San Diego when a group of rats had been imported from England, and had bred him to her Blacks and a Tailless showed up.

When I met Dorothy in 1985, she was well established with Black Chocolate (we may have lost) and Siamese (all of my own came from her stock through Bonnie Walters). I was present at the show when she gave breeding groups to Earnie, Bonnie, and Rosanne Rubino around 1987 or so, so I feel it is safe to say that most or all of our Tailless came from those animals.

The fact that this is a mutation that effects an elimination of a body part, alteration of spine and pelvis, can also present a problem: how do you prevent it from going any further?

  • I have heard of animals unable to walk, having splayed legs. Cause: Pelvis separates from the spine.
  • Animals that have still hind-quarters and cannot walk, they must hop. Cause: Fused vertebrai.
  • Animals with urinary and rectal messiness (incontinence). Cause: Celeste Robinson said her vet told her the second joint of the tail affects the bladder.

I have found Tailless females to often be sterile. Some may have problems with birthing due to spine and pelvic alteration.

As a breeder for ten years of Tailless rats, I have rules I follow. You may find them helpful, as I have only had three animals in ten years with urinary problems, and no other abnormal formations or disabilities.

  • Selective breeding: I use tailed females that had a Tailless sire and siblings, and breed to a Tailless buck. I never breed from Tailless females.
  • Outcrossing: I breed a Tailless buck to an unrelated (now Tailless) doe - then cross brother to sister from F1, or breed to another Tailless buck. This is a good way to start new colors or add new traits.
  • I use females who have partial tails, as the ovaries seem intact, and I fear a too extreme Tailless female may be also otherwise altered.

All in all, don't be afraid to breed the Tailless. Just be aware that it can involve malformation if Tailless to Tailless is used too often, or if lines are inbred too long.

Next time: New colors? Genes? SLATE, SAND, AND RED BROWN.