Stumpy breeders refer to the types of tails as 'rumpy', 'typical', and 'LT' (long tail).
A 'rumpy' is a tail with the vertebre so short that in many cases, you cant even palpate the end of the last vertebra. All that exists is a tuft of hair over the anus. The 'typical' Stumpy can have a tail from a single vertebra to up to 4 inches. Everything after that is referred to as a longtail. It should be noted that even if the tail is only missing ONE vertebre from the column, genetically it is still an NBT animal.

This brings up the interesting question about can two Long Tails produce a NBT. The ACD has a requirment that the "tail should reach the hock." Yet in the 1980's, I had an ACD bitch who had a tail that was just short of reaching the hock.  Every now and then she would produce a 'typical' bob tail pup. Could it be that some of the ACD's out there are in fact carring an NBT gene? It would be very interesting to do a DNA on some of the ACD's that tend to have less than hock length tails.

If you have not read the article(the link to the article can be found below) in its is a short synopsis.

Of the 19 breeds of dogs (in this study of over 300 animals) that are born with Natural Bob Tails......all breeds showed the allele for the trait at the same location in the gene sequence.

Yes, it is possible for two NBT parents to produce tailed pups. The NBT is a single dominant trait . Since both parents carry one alelle for long tail and one alelle for the NBT, tailed pups can be produced.

Breeding two long tails together should only produce LONG tails

No, you can not produce a pup that is homozygous (carries two genes) for the NBT...a pup that carries two genes (one from each parent) is a lethal combination and the embryo is reabsorbed by

                                   the bitch, thus never born, or dies shortly after birth, if it at all.

The article about the NBT from the Finnish research can be found at  the link is broken.
Here is the shortened version.


Ancestral T-Box Mutation Is Present in Many, but Not All, Short-Tailed Dog Breeds

  1. Catherine André

+ Author Affiliations

  1. From the Medical Biochemistry and Developmental Biology, Institute of Biomedicine, University of Helsinki, PO Box 63, 00014 Helsinki, Finland (Hytönen and Sainio); the Institut de Génétique et Développement, UMR 6061 CNRS/Université de Rennes1, Faculté de Médecine, 35043 Rennes Cedex, France (Grall, Hédan, Dréano, Seguin, Galibert, and André); the Antagene, Research and analysis laboratory in animal genomics, 2 allée des séquoias, 69760 Limonest, France (Delattre and Thomas); the DNA Sequencing Laboratory, Institute of Biotechnology, University of Helsinki, PO Box 56, 00014 Helsinki, Finland (Paulin); and the Department of Medical Genetics and Department of Basic Veterinary Sciences, University of Helsinki and the Folkhälsan Institute of Genetics, Department of Molecular Genetics, PO Box 63, 00014 Helsinki, Finland (Hytönen and Lohi)
  1. Address correspondence to Marjo K. Hytönen at the address above, or e-mail:
  • Received April 17, 2008.
  • Revision received September 10, 2008.
  • Accepted September 15, 2008.


Dogs differ greatly in their morphological characteristics including various tail phenotypes. Congenitally short-tailed dogs are present in many breeds; however, the causative mutation located in the T-box transcription factor T gene (C189G) had only been described in the bobtailed Pembroke Welsh Corgis. We investigated here the presence of the T gene mutation in 23 other breeds (360 dogs, including 156 natural short tailed) in which natural bobtailed dogs exist. In the 17 breeds in which the C189G mutation was observed, there was a perfect correlation between this mutation and the short-tail phenotype. However, 6 breeds did not carry the known substitution or any other mutations in the T gene coding regions. No dogs were found to be homozygous for the C189G mutation, suggesting that the homozygous condition is lethal. In order to study the effect of the T gene mutation on litter size, we compared the number of puppies born from short-tailed parents to that born from long-tailed parents. In the Swedish Vallhund breed, we observed a 29% decrease in the litter size when both parents were short tailed. Given that the T gene mutation is not present in all breeds of short-tailed dog, there must be yet other genetic factors affecting tail phenotypes to be discovered.

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