Natural Bobtail

Quick Summary

Natural bobtail is a naturally occurring mutation in the T-box transcription factor T gene resulting in a shortened tail.

Pembroke Welsh Corgi displaying bobbed tail
Natural bobtail in a Pembroke Welsh Corgi

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Phenotype: Dogs with natural bobtail have naturally bobbed (shortened) tails. Length of the bobbed tail is variable; some individuals may have nearly full-length tails while others may have virtually no tail.

Mode of Inheritance: Autosomal dominant

Alleles: N = Normal (no natural bobtail), BT = Natural bobtail

Breeds appropriate for testing: Australian Cattle Dog, Australian Shepherd, Austrian Pinscher, Bourbonnais Pointer (Braque du Bourbonnais), Brazilian Terrier, Brittany Spaniel, Catahoula Leopard Dog, Croatian Sheepdog, Danish/Swedish Farmdog, Jack Russell Terrier, Karelian Bear Dog, McNab, Mudi, Pembroke Welsh Corgi, Polish Lowland Sheepdog, Pyrenean Shepherd, Savoy Sheepdog, Schipperke, Spanish Waterdog, Swedish Vallhund

Explanation of Results:

  • Dogs with N/N genotype do not have this natural bobtail variant. They will most likely have normal length tails, though other genetic factors may affect tail length. They cannot transmit this natural bobtail variant to their offspring.
  • Dogs with N/BT genotype are expected to have a natural bobtail. They may transmit this natural bobtail variant to 50% of their offspring. Matings between two N/BT dogs are expected to produce 50% puppies with natural bobtail, 25% puppies with normal length tails, and 25% puppies with the embryonic lethal BT/BT genotype (an expected 25% reduction in litter size).
  • Dogs with BT/BT genotype are expected to terminate development in utero (embryonic lethal); this genotype is not expected to be seen in live dogs. If a BT/BT genotype puppy is born alive, it may display severe developmental defects, including spinal deformities, that are incompatible with life.


$50 one test per animal
$70 two tests for coat color/fur type/bobtail (same animal) 
$90 three tests for coat color/fur type/bobtail (same animal) 
+ $15 each additional test if ordering more than three coat color/fur type/bobtail tests on the same animal

Turnaround Time
At least 15 business days; may be delayed beyond 15 business days if sample requires additional testing, or a new sample is requested.
Additional Details

Jack Russell Terrier puppy with naturally bobbed tail
Natural bobtail in a 3-month-old Jack Russell Terrier puppy

Natural bobtail (NBT) is a naturally occurring mutation in the T-box transcription factor T gene that results in a shortened tail. The mutation, a single nucleotide variant (c.189C>G), is inherited in an autosomal dominant fashion with both sexes equally affected. This mode of inheritance means that the presence of one copy of the variant will produce the bobbed tail phenotype in males and females. The length of the bobbed tail is variable and under the influence of other as-yet-undetermined genetic factors that cause some NBT individuals to have nearly full-length tails while others may have virtually no tail.

While heterozygous individuals (N/BT genotype, possessing one normal and one affected T gene) have shortened tails, data suggest that the homozygous condition (BT/BT genotype, possessing two copies of the affected gene) is lethal in utero in most cases. Breeding of two heterozygotes (a N/BT x N/BT mating) is predicted to produce 25% N/N puppies with normal length tails, 50% N/BT puppies with natural bobtail, and 25% homozygous affected BT/BT offspring. Most BT/BT genotype offspring are predicted to terminate in utero and therefore represent a potential 25% reduction in litter size.

One report in the veterinary literature identified two tailless Pembroke Welsh Corgi puppies with BT/BT genotype that survived to term but displayed severe developmental abnormalities incompatible with life, including anorectal atresia and spinal defects. Both puppies were from the same parents but different litters, and neither survived long after birth. This small sample size and lack of further reports suggests that it is rare for BT/BT puppies to reach full term.

Genetic testing is recommended to verify and validate the natural bobtail status of dogs, especially if docking is allowed, and to help with breeding pair selection to decrease the risk of reduced litter size and lethal deformities. Testing for natural bobtail assists owners and breeders in identifying dogs that have this trait.


Type of Test
Results Reported As
Test Result Natural Bobtail
N/N Normal. No copies of the NBT mutation.
N/BT Natural bobtail. 1 copy of the NBT mutation.
BT/BT Natural bobtail. 2 copies of the NBT mutation.*

* Result unlikely to occur for live dogs; NBT is considered a homozygous lethal in utero.


Haworth, K., Putt, W., Cattanach, B., Breen, M., Binns, M., Lingaas, F., & Edwards, Y.H. (2001). Canine homolog of the T-box transcription factor T; failure of the protein to bind to its DNA target leads to a short-tail phenotype. Mammalian Genome, 12(3), 212-218. doi: 10.1007/s003350010253

Indrebø, A., Langeland, M., Juul, H.M., Skogmo, H.K., Rengmark, A.H. & Lingaas, F. (2008). A study of inherited short tail and taillessness in Pembroke Welsh corgi. Journal of Small Animal Practice, 49: 220-224. doi: 10.1111/j.1748-5827.2007.00435.x

Hytönen, M.K., Grall, A., Hédan, B., Dréano, S., Seguin, S.J., Delattre, D., Thomas, A., Galibert, F., Paulin, L., Lohi, H., Sainio, K., & André, C. (2009). Ancestral T-box mutation is present in many, but not all, short-tailed dog breeds. Journal of Heredity, 100(2), 236-240. doi: 10.1093/jhered/esn085